Buildings

2024

Jump to: 2023, 2022

13 pages, 6275 KiB

Open AccessArticle

Investigation of Desiccation Cracking Behavior of Waste Carbon Fiber–Reinforced Clay Material

by Fei Chen, Yang Chen, Ling Li, Changde Yang and Binbin Yang

Buildings 2024, 14(7), 2081; https://doi.org/10.3390/buildings14072081 - 7 Jul 2024

Viewed by 889

Abstract

Carbon fiber is a common waste building material, but its effect on the drying and cracking properties of clay materials is unknown. In this paper, crack rate and fractal dimension are used to characterize the influence of waste carbon fiber materials on the [...] Read more.

Carbon fiber is a common waste building material, but its effect on the drying and cracking properties of clay materials is unknown. In this paper, crack rate and fractal dimension are used to characterize the influence of waste carbon fiber materials on the development of soil cracking. With the rise in carbon fiber content to 0.2%, 0.4% and 0.6%, the crack rate of soil cracking decreased by 7.9%, 17.3% and 23.3%, respectively, while the fractal dimension of soil cracking decreased by 2.4%, 8.7% and 21.2%, respectively. Accordingly, the critical moisture content of the soil samples increased by 33.2%, 110% and 151%, and the time of the soil constant evaporation stage decreased by 5.1%, 13.8% and 34.5%, respectively. When carbon fiber is combined with soil, carbon fiber will increase the interface bonding strength, friction and interlocking force, effectively inhibiting the cracking of soil, and it provides a channel for water transport in the soil in the early stage. Full article

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15 pages, 5054 KiB

Open AccessArticle

Study on the Properties of Belite Calcium Sulfoaluminate Cement–Ordinary Portland Cement Composite Cementitious System

by Xiangyu Xin, Guangbin Duan, Jiang Zhu, Pengkun Hou, Piqi Zhao, Peng Du, Shoude Wang and Yongbo Huang

Buildings 2024, 14(4), 890; https://doi.org/10.3390/buildings14040890 - 26 Mar 2024

Viewed by 994

Abstract

Due to low early strength and high shrinkage, ordinary Portland cement (OPC) has difficulty meeting the actual needs of modern construction projects, while belite calcium sulfoaluminate cement (BCSA–OPC) composite cement provides a new solution. The mechanical and the drying shrinkage properties of the [...] Read more.

Due to low early strength and high shrinkage, ordinary Portland cement (OPC) has difficulty meeting the actual needs of modern construction projects, while belite calcium sulfoaluminate cement (BCSA–OPC) composite cement provides a new solution. The mechanical and the drying shrinkage properties of the BCSA–OPC mortar were determined, the hydration heat of the BCSA–OPC was studied, and the pore size distribution of the mortar was investigated. In addition, the hydration products of the BCSA–OPC were analyzed by X-ray diffraction (XRD) and simultaneous thermal analysis (TG-DSC), and the microscopic morphology of the BCSA–OPC mortar was observed by scanning electron microscopy (SEM). The results show that with the increase in BCSA dosage in the BCSA–OPC, compared with OPC, the flexural strengths of the mortar of 50% dosage of BCSA at the hydration age of 1 d, 3 d, 7 d, and 28 d are improved by 33.3%, 36.6%, 23.6%, and 26.8%, and the compressive strengths are improved by 50.8%, 35.7%, 13.4%, and 27.7%. The drying shrinkage and total porosity of the mortar at the hydration age of 28 d are reduced by 117.4% and 21.55%, respectively. It is attributed to the filling effect of a large amount of ettringite (AFt) and intertwined with the fibrous C-S-H gel to form a network. This study will provide a theoretical basis for the application of the BCSA–OPC engineering. Full article

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15 pages, 2804 KiB

Open AccessArticle

Evaluation of Deformation and Settlement Properties of Cement-Stabilized Silt Mixed with EPS Beads of Various Sizes

by Sharafat Ali, Feng Yong, Farhad Jamil and Mudassir Mehmood

Buildings 2024, 14(2), 334; https://doi.org/10.3390/buildings14020334 - 25 Jan 2024

Viewed by 979

Abstract

The expansion of China’s highways and railways, as well as the growing demand for them, has focused attention on the impact of traffic loads on foundation settling, uneven deformation, and ground cracking. These effects have garnered considerable research attention, with particular emphasis placed [...] Read more.

The expansion of China’s highways and railways, as well as the growing demand for them, has focused attention on the impact of traffic loads on foundation settling, uneven deformation, and ground cracking. These effects have garnered considerable research attention, with particular emphasis placed on integrating innovative materials into the soil matrix. This investigation involved loading experiments utilizing a combination of lightweight soil, expanded polystyrene (EPS), and cement. Consolidation tests assessed the extent of deformation and settlement, incorporating varying proportions of EPS and cement. The test results show that when subjected to confined conditions, the stress–strain relationship curve assumes a hyperbolic shape closely linked to the e-p curve. This shape effectively captures the unique structural characteristics exhibited by lightweight soils. As the size of the EPS particles and the applied stress increase, a corresponding rise in the strain of the specimens is observed. Simultaneously, as the strain magnitude increases, the elastic modulus experiences a decline. Additionally, it is noted that this trend further increases as the doping of the cement with EPS particles increases. When the EPS volume ratio and cement mix ratio remain constant across different specimens, there is a decrease in structural strength as the size of the EPS increases. In lightweight soil, settlement can occur rapidly, with approximately 95% of total consolidation deformation happening within a few minutes, which suggests that the settlement is instantaneous and primarily consolidation settlement. The structural strength of lightweight soil shows a negative correlation with the size of EPS, implying that larger EPS size may lead to a reduction in strength. Therefore, it is recommended to consistently use EPS beads with a diameter of 3–4 mm during construction. Full article

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2023

Jump to: 2024, 2022

15 pages, 8369 KiB

Open AccessArticle

Thermo–Solid Coupling Analysis of Bionic Piston for a Mud Pump in Tunnel Engineering

by Hongjie Tian, Dongzhuang Tian, Pei Ju and Jinxuan He

Buildings 2023, 13(11), 2770; https://doi.org/10.3390/buildings13112770 - 1 Nov 2023

Viewed by 1216

Abstract

With the development of mud shield tunnel construction technology, the demands on the working performance of a mud pump are becoming higher and higher. As one of the critical components of a mud pump that is easy to wear, the performance of the [...] Read more.

With the development of mud shield tunnel construction technology, the demands on the working performance of a mud pump are becoming higher and higher. As one of the critical components of a mud pump that is easy to wear, the performance of the piston directly affects the operational efficiency and lifespan of the mud pump. The bionic shape of the piston was designed under the guidance of non-smooth surface characteristics of natural organisms to enhance friction and wear performance as well as longevity. The stress field and temperature field characteristics of the pistons with three bionic structures (pit, stripe, and prismatic) were analyzed based on finite element simulation. The stress field analysis results indicated that, for the prismatic shape and pit shape pistons, the maximum stress was concentrated in the lip regions, and both of them bore large stress at the root. For the stripe-shaped piston, the stress was dispersed on both sides of the stripe structure, the stress at the root was small, and the stress gradient along the axial direction was relatively gentle. The stripe-shaped bionic structure can significantly improve the stress distribution state on the piston surface, and the optimal stripe width was recommended to be between 1 and 1.5 mm. The temperature field analysis results indicated that, for the stripe-shaped piston, the surface temperature and heat flux were the smallest, and the temperature gradient was relatively smaller than that of pit-shaped and prismatic-shaped pistons, so it was easier to dissipate heat. When the stripe width was 1.5 mm, the temperature distribution was the most uniform, and the heat flux in localized areas was the smallest, so the heat generated by friction was relatively easy to discharge in the unit area. Full article

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15 pages, 6667 KiB

Open AccessArticle

Study of Mechanical Properties of Saline Soils under Different Stress Paths

by Shukai Cheng, Qing Wang, Jiaqi Wang and Yan Han

Buildings 2023, 13(9), 2347; https://doi.org/10.3390/buildings13092347 - 15 Sep 2023

Viewed by 1062

Abstract

The stress path is a critical factor affecting the mechanical properties of saline soils. In order to study the mechanical properties of saline soils under different stress paths, in situ saline soils in the Qian’an area of western Jilin province were selected for [...] Read more.

The stress path is a critical factor affecting the mechanical properties of saline soils. In order to study the mechanical properties of saline soils under different stress paths, in situ saline soils in the Qian’an area of western Jilin province were selected for this study, and triaxial shear tests under six different stress paths were conducted, including the consolidated undrained triaxial test under the conventional stress path under the isobaric consolidation condition; the consolidated drained triaxial test under the conventional, equal p, reduced p, and increased p stress paths under the isobaric consolidation condition; and the consolidated drained triaxial test under the conventional stress path under the K₀ consolidation condition. The effects of the consolidation conditions, drainage conditions, and stress paths on the mechanical properties of in situ saline soils were investigated. The results reveal that the stress–strain relationship curves of soil samples decrease continuously in the order of increased p, conventional, equal p, and decreased p, and they all show the characteristics of strain hardening. The stress path curves have the same slope under the same stress path. For different confining pressures, only the relative positions of the curves are different. Under the conventional stress path, the slope is 1; under the increased p stress path, the slope is 1/3; under the equal p stress path, the slope is 3; and under the decreased p stress path, the slope of the curve is −1. For the same confining pressure, the magnitude relationships of shear strength under the different stress paths are as follows: increased p > conventional > equal p > decreased p. For the cohesion c and internal friction angle φ, the consolidation condition has a greater effect on the cohesion c and a smaller effect on the internal friction angle φ; the drainage condition has a smaller effect on the cohesion c and a larger effect on the internal friction angle φ; and the stress paths have a greater effect on both cohesion c and internal friction angle φ. Full article

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12 pages, 3200 KiB

Open AccessArticle

The Impact of Freeze–Thaw Cycles on the Shear and Microstructural Characteristics of Compacted Silty Clay

by Jia Jia, Hongying Wei, Dehuan Yang and Yuancheng Wu

Buildings 2023, 13(9), 2308; https://doi.org/10.3390/buildings13092308 - 11 Sep 2023

Cited by 3 | Viewed by 1160

Abstract

The shear strength characteristics and weakening effect of soils under freeze–thaw (FT) cycling are the key problems that should be solved to ensure the integrity of infrastructure construction in seasonally frozen soil areas. Thus far, however, the research on the mechanism of strength [...] Read more.

The shear strength characteristics and weakening effect of soils under freeze–thaw (FT) cycling are the key problems that should be solved to ensure the integrity of infrastructure construction in seasonally frozen soil areas. Thus far, however, the research on the mechanism of strength deterioration resulting from microstructural changes induced by FT cycles remains insufficiently comprehensive. To investigate the deterioration characteristics of the shear strength of seasonally frozen soils in FT cycles, a series of laboratory experiments were conducted using compacted silty clay subjected to a maximum of five closed-system FT cycles. The stress–strain curve, secant module, shear strength, and microscopic structure were measured for specimens before and after the FT cycles. The stress–strain curves of the unfrozen and thawed specimens demonstrated a strain-hardening behavior, indicating an increase in resistance to deformation. Moreover, the shear strength and secant modulus of the unfrozen specimen surpassed those of the thawed specimen significantly. As the number of FT cycles increased, there was a gradual decline observed in the strength, stiffness, cohesive properties, and internal friction angle of the thawed specimen. The nuclear magnetic resonance technique was employed to interpret the experimental findings. It was demonstrated that the micro-pores undergo continuous enlargement and transformation into medium-sized and large-sized pores, leading to FT deterioration. Based on the experimental results, a modified Duncan–Chang model was developed to simulate the mechanical behavior of compacted silty clay while considering the influence of FT cycles. Full article

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21 pages, 2546 KiB

Open AccessArticle

Evaluating the Reactions of Bridge Foundations to Combined Wave–Flow Dynamics

by Xian Xiao and Jianwei Nie

Buildings 2023, 13(8), 2030; https://doi.org/10.3390/buildings13082030 - 9 Aug 2023

Viewed by 979

Abstract

As the ongoing development of national infrastructure progresses, we see an increase in the construction of deep-water bridges, specifically cross-sea bridges. This paper uses Stokes’s wave theory to simulate and analyze how a bridge foundation dynamically responds to wave–fluid interactions. Firstly, the governing [...] Read more.

As the ongoing development of national infrastructure progresses, we see an increase in the construction of deep-water bridges, specifically cross-sea bridges. This paper uses Stokes’s wave theory to simulate and analyze how a bridge foundation dynamically responds to wave–fluid interactions. Firstly, the governing equations, boundary conditions and initial conditions of fluid motion are derived, expanded and solved via Stokes’s wave theory, and a spectral model is simulated and plotted. Based on the P-M spectrum and equal frequency method, a method of wave height attenuation during wave propagation is proposed. Using an SSTK-ω turbulence model, a numerical wave flume is established considering the fluid model, the selection of element type and the boundary conditions set, and the influencing factors of wave propagation (attenuation) are analyzed. Waves with different wave parameters (period, depth and height) are numerically simulated and compared with the theoretical values. Finally, we perform an analysis of the dynamic response under wave–current coupling conditions. We establish different operational scenarios and obtain the following results: under a load duration of 200 s, the peak transverse displacements for spans 1, 2 and 3 measure at 0.84 m, 0.63 m and 0.62 m, respectively. The peak transverse displacements under operational scenarios 2 and 3 show reductions of 25.0% and 25.7%, respectively, when compared to scenario 1. However, large transverse displacements remain. This suggests that the influence of waves and water flow on the transverse displacement of the main span should not be overlooked. Full article

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18 pages, 4005 KiB

Open AccessArticle

Research on the Non-Planar Deformation Behavior of Reinforced Concrete Components Based on Size Effect

by Zhihan Peng, Binglei Xie, Yongqian Feng, Jun Teng and Zuohua Li

Buildings 2023, 13(7), 1716; https://doi.org/10.3390/buildings13071716 - 5 Jul 2023

Viewed by 983

Abstract

The section deformation distribution of reinforced concrete components is nonlinear due to the size effect. Existing analysis models such as the plastic hinge and the truss element are based on the plane cross-section assumption. The nonlinear deformation distribution of the section cannot be [...] Read more.

The section deformation distribution of reinforced concrete components is nonlinear due to the size effect. Existing analysis models such as the plastic hinge and the truss element are based on the plane cross-section assumption. The nonlinear deformation distribution of the section cannot be accurately simulated. Therefore, in this paper, non-planar strain distribution functions of sections are established. The law of the influence of geometrical characteristics and load characteristics on the nonlinear deformation distributions of the sections of the beam ends is analyzed. The quantitative method is established between the section size, position, and shear span ratio, and the nonlinear deformation distributions of sections. The finite element simulation and test results show that the non-planar strain distribution shape functions of sections given in this paper can accurately describe the axial strain distributions of different sections along the height and width of the sections. The non-planar deformation behaviors and mechanical properties of the components can be simulated. The interface connection accuracy is improved in the structural multiscale simulation. Full article

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13 pages, 3371 KiB

Open AccessArticle

Accuracy of Non-Destructive Estimation of Length of Soil Nails

by Yonghong Wang, Jiamin Jin, Qijun Zhang, Ming Zhang, Xiwei Lin, Xin Wang and Peiyuan Lin

Buildings 2023, 13(7), 1699; https://doi.org/10.3390/buildings13071699 - 3 Jul 2023

Cited by 1 | Viewed by 1292

Abstract

The effective length of soil nails is one of the critical parameters ensuring the reinforcing effect, and its accurate estimation is of great significance for the safety of the slope and deep foundation pit supporting projects. Traditional quality insurance methods, such as nail [...] Read more.

The effective length of soil nails is one of the critical parameters ensuring the reinforcing effect, and its accurate estimation is of great significance for the safety of the slope and deep foundation pit supporting projects. Traditional quality insurance methods, such as nail pullout tests, suffer from a series of drawbacks including being destructive, high cost, and time-consuming. In contrast, non-destructive testing (NDT) has been increasingly applied in various engineering fields in the past decades given its advantages of not damaging the material and easy operation. However, the current application of NDT in soil nail length measurement is relatively limited, and its accuracy and reliability are yet to be quantitatively evaluated. This paper introduces three methods for estimating soil nail length based on guided wave theory and collects 116 sets of NDT data for nail length. The accuracy of the NDT in soil nail prediction is statistically analyzed using the model bias method. The results show that those methods can accurately predict the nail length with an average error of less than 3% and a low dispersion of 12%. The accuracy of the NDT methods is not affected by the hammer type or estimation method. Furthermore, this paper proposes a model calibration to the original NDT method, which improves the model’s average accuracy by 3% and reduces dispersion by 4% without increasing computational complexity. Finally, the probability distributions of the model biases are characterized. This study can provide practical tools for fast estimation of in situ nail length, which is of high significance to supporting slopes and deep foundation pits. Full article

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13 pages, 2178 KiB

Open AccessArticle

Study of Improved Grey BP (Back Propagation) Neural Network Combination Model for Predicting Deformation in Foundation Pits

by Xu Ouyang, Jianwei Nie and Xian Xiao

Buildings 2023, 13(7), 1682; https://doi.org/10.3390/buildings13071682 - 30 Jun 2023

Cited by 2 | Viewed by 1224

Abstract

Deep excavation engineering is a comprehensive discipline that involves multiple fields such as engineering geology, hydrogeology, and foundation engineering. With the improvement of the utilization rate of underground space, the demand for the construction of large-scale underground structural engineering is growing, making the [...] Read more.

Deep excavation engineering is a comprehensive discipline that involves multiple fields such as engineering geology, hydrogeology, and foundation engineering. With the improvement of the utilization rate of underground space, the demand for the construction of large-scale underground structural engineering is growing, making the excavation of underground soil become increasingly frequent, which also brings about the safety problems of deep foundation pit engineering and the surrounding environment. Prediction of foundation pit deformation is an important research direction with diverse historical developments, but it is also facing a series of difficulties and challenges. In order to solve these problems, this article proposes an improvement plan, establishes a prediction model based on the combination model of grey BP (back propagation) neural network, and verifies its effectiveness through experiments. The results show that the average error of the new model’s prediction of horizontal deformation is about 0.31, which is about 32% lower than the traditional model’s prediction error. The difference between the vertical deformation prediction and actual monitoring results is also controlled. The vertical deformation predicted by wavelet transform is 7% to 9% larger than the actual monitoring results, meeting the prediction requirements. Finally, this article explores the research on the prediction of foundation pit deformation in deep excavation engineering, An improved grey BP neural network combination model was proposed and its effectiveness was verified through experiments. This article has important reference value for the study of deformation prediction in deep excavation engineering. Full article

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16 pages, 8100 KiB

Open AccessArticle

Experimental and Numerical Study on Tensile Behavior of Double-Twisted Hexagonal Gabion Wire Mesh

by Yu-Liang Lin, Peng-Fei Fang, Xin Wang, Jie Wu and Guo-Lin Yang

Buildings 2023, 13(7), 1657; https://doi.org/10.3390/buildings13071657 - 28 Jun 2023

Cited by 4 | Viewed by 2185

Abstract

Double-twisted hexagonal gabion wire mesh is a type of reinforced soil material that is used in gabion retaining walls to stabilize the soil slope in geotechnical engineering. In this study, a series of tensile tests were conducted to investigate the tensile behavior of [...] Read more.

Double-twisted hexagonal gabion wire mesh is a type of reinforced soil material that is used in gabion retaining walls to stabilize the soil slope in geotechnical engineering. In this study, a series of tensile tests were conducted to investigate the tensile behavior of hexagonal gabion wire mesh. Meanwhile, numerical models of gabion wire mesh were built to investigate the whole tensile loading-strain process. The influence of wire diameter, mesh width, and mesh length on the tensile strength of hexagonal gabion wire mesh were evaluated based on laboratory tests and numerical simulation. The quantitative relationship of tensile strength versus wire diameter, mesh width, and mesh length was typically fitted by a quadratic function, linear function, and monotonically decreasing exponential function. The numerical result presents a good consistency with those obtained from the experiment. The result of the loading-strain curve obtained by both experiment and simulation exhibits an “S” shape with a distinct serrated characteristic. The loading-strain curve can be divided into the following four stages: mesh distortion stage, wire stretching stage, overall yield stage, and wire fracture stage, which well reflects the tensile behavior of double-twisted hexagonal wire mesh. The tensile behavior of gabion wire mesh is influenced by the structure pattern of wire mesh and the mechanical characteristic of steel wire. Full article

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13 pages, 2426 KiB

Open AccessArticle

Experiment on the Performance of Recycled Powder of Construction Waste on Adobe Materials

by Mei Zeng, Huanan Huang and Xianggang Zhang

Buildings 2023, 13(5), 1358; https://doi.org/10.3390/buildings13051358 - 22 May 2023

Cited by 1 | Viewed by 1859

Abstract

With the widespread use of adobe materials in buildings, their durability can deteriorate under harsh weather conditions such as long-term low temperatures and rainfall, which can easily lead to safety accidents. This article takes adobe material mixed with construction waste recycled powder as [...] Read more.

With the widespread use of adobe materials in buildings, their durability can deteriorate under harsh weather conditions such as long-term low temperatures and rainfall, which can easily lead to safety accidents. This article takes adobe material mixed with construction waste recycled powder as the research object and adds the prepared construction waste recycled concrete powder and recycled brick powder to the adobe material in different proportions to study the mechanical and durability properties of the adobe material. The results indicate that under normal temperature curing conditions, the compressive strength of the adobe sample significantly increases with the increase in the recycled powder content, and then decreases. Under high-temperature conditions, with the increase in the recycled powder content, the compressive strength of the adobe sample first significantly increases and then decreases. When the powder content is within the range of 6% to 10%, good moisture absorption and desorption performance can be achieved. When the content of recycled powder is between 2% and 10%, the effect on the dry–wet cycling performance of the adobe is weakest. When the content of grade I/II recycled brick powder is between 2% and 6%, and the content of grade I recycled concrete powder is between 2% and 6%, the negative impact on the freeze–thaw cycle performance is relatively weak. The research results provide theoretical data support for the mixed-use of recycled powder and adobe materials. Full article

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15 pages, 4653 KiB

Open AccessArticle

Experimental Research on the Creep Behavior of the Interface of Compacted Loess and High-Density Polyethylene Geogrid

by Yi-Li Yuan, Chang-Ming Hu, Jian Xu, Yuan Mei, Fang-Fang Wang and Ge Wang

Buildings 2023, 13(5), 1353; https://doi.org/10.3390/buildings13051353 - 22 May 2023

Cited by 1 | Viewed by 1282

Abstract

The stability of geogrid-reinforced soil structure is closely related to the interface characteristics between geogrid and soil. However, the creep behavior of the soil–geogrid interface is still unrevealed. In this study, using a modified stress-controlled pullout device, influence of the normal pressure, dry [...] Read more.

The stability of geogrid-reinforced soil structure is closely related to the interface characteristics between geogrid and soil. However, the creep behavior of the soil–geogrid interface is still unrevealed. In this study, using a modified stress-controlled pullout device, influence of the normal pressure, dry density, and water content on creep behavior of interface of compacted loess and high-density polyethylene (HDPE) geogrid is investigated. A three-parameter empirical model and a Merchant element model were established through fitting analysis. Analysis results show that the normal pressure, dry density, and water content have significant effects on the creep shear displacement of the reinforced soil interface. Under the same pullout level, creep displacement of the interface increases with the increase of water content and decreases with the increase of dry density and normal pressure. Both the three-parameter empirical model and Merchant element model can describe the creep characteristics of the reinforced soil interface. The Merchant model is more accurate in the early stage, while the three-parameter empirical model is more suitable for predicting the long-term creep deformation of the interface of compacted loess and geogrid. Full article

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16 pages, 5429 KiB

Open AccessArticle

Laboratory Test Study on Pile Jacking Penetration Mechanism Considering Different Diameter and Length Based on Photoelectric Integration Technology

by Lifeng Wang, Shuo Zhang, Shiqiang Li, Jun Wang, Xunlong Niu, Donglei Wang and Yonghong Wang

Buildings 2023, 13(5), 1247; https://doi.org/10.3390/buildings13051247 - 9 May 2023

Cited by 1 | Viewed by 1605

Abstract

Model tests are carried out on the jacked single piles of different diameters and pile lengths under the model pile of different diameters and pile lengths in clayey soil, which aims to investigate the penetration mechanical mechanism. How to accurately test the pile [...] Read more.

Model tests are carried out on the jacked single piles of different diameters and pile lengths under the model pile of different diameters and pile lengths in clayey soil, which aims to investigate the penetration mechanical mechanism. How to accurately test the pile end resistance and pile side resistance during jacked pile sinking is particularly important. In this paper, a full-section spoke-type pressure sensor, a double diaphragm temperature self-compensating fiber Bragg grating (FBG) earth pressure sensor and a sensitized miniature FBG strain sensor are jointly applied to a single pile penetration model test to test a single pile driving force, pile end resistance and pile body stress during penetration. The test results show that the load transfer performance of test piles will be affected by different diameters, and the axial force transfer capability of a large diameter in the depth direction is better than that of a small diameter since the compacting effect is more obvious. The unit skin friction of the pile increases gradually as the depth increases, which is larger due to the lateral extrusion force increasing as the diameter increases. At the same depth, the unit skin friction of two different diameter piles demonstrates “friction fatigue”, which also decreases obviously as the depth increases. Under the conditions of this test, the maximum frictional resistance of the pile TP1 pile side is about 27.7% higher than that of the test pile TP2. In the static pile sinking process of three test piles in cohesive soil, 50% is end bearing; therefore, there is 50% friction, and the diameter influences the end bearing and the length influences the friction. Full article

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19 pages, 4893 KiB

Open AccessArticle

Uncertainty Analysis of Creep Behavior of Compacted Loess and a Non-Deterministic Predication Method for Post-Construction Settlement of a High-Fill Embankment

by Yi-Li Yuan, Chang-Ming Hu, Yuan Mei, Fang-Fang Wang and Ge Wang

Buildings 2023, 13(5), 1118; https://doi.org/10.3390/buildings13051118 - 22 Apr 2023

Viewed by 1624

Abstract

Property of geotechnical materials has inherent uncertainty due to the complex formation process and inevitable test error. However, existing long-term deformation prediction methods for geotechnical structure such as a filling embankment are deterministic, which ignores the uncertainty of soil property. In this study, [...] Read more.

Property of geotechnical materials has inherent uncertainty due to the complex formation process and inevitable test error. However, existing long-term deformation prediction methods for geotechnical structure such as a filling embankment are deterministic, which ignores the uncertainty of soil property. In this study, the uncertainty of creep behavior of compacted loess was investigated through repetitive creep tests and statistical analysis. Five different loading levels and two loading modes were considered in the tests. The creep test was repeated 45 times for each condition. Through a statistical analysis for the test results, a modified Merchant creep model was established to improve the accuracy of long-term deformation prediction. An empirical transformation equation between staged loading and separated loading mode of the creep test results was also introduced to improve applicability of the method. On this basis, a non-deterministic predication method for post-construction settlement of loess fill embankment was proposed. Furthermore, the proposed method was applied to the prediction of the post-construction of a 61.5 m loess filling embankment. The measured on-site post-construction settlement value falls within the 95% confidence interval of the predicted range which proves the efficiency and practicability of the proposed non-deterministic predication method. Compared to deterministic methods, the proposed method can describe the predicted deformation in a probabilistic way in the form of contour plot. The proposed method provides a basic approach for the probabilistic design and reliability assessment of filling engineering. Full article

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14 pages, 3925 KiB

Open AccessArticle

Experimental Study on Influence of Initial Relative Dry Density on K₀ of Coarse-Grained Soil

by Ming-Jie Jiang, Huo-Liang Xie, Chao-Rong Fang, Ke-Xin Zhang and Jun-Gao Zhu

Buildings 2023, 13(4), 1059; https://doi.org/10.3390/buildings13041059 - 17 Apr 2023

Viewed by 1588

Abstract

The coefficient of earth pressure at rest, K₀, is a significant mechanical parameter, and the investigation of the K₀ of coarse-grained soil has important theoretical significance and applicational value in geotechnical engineering. However, there are few studies on the influence [...] Read more.

The coefficient of earth pressure at rest, K₀, is a significant mechanical parameter, and the investigation of the K₀ of coarse-grained soil has important theoretical significance and applicational value in geotechnical engineering. However, there are few studies on the influence of the initial dry density (ρ_d) on the K₀ of coarse-grained soil due to the limitations of the related test instruments or methods. A series of K₀ tests for two types of coarse-grained soils (rockfill soil and sandy-gravel soil) were conducted based on a newly developed large-scale apparatus to reveal the relationship between the K₀ and ρ_d of coarse-grained soil. The test results showed that the K₀ of coarse-grained soil decreases with an increase in vertical stress, and this trend tends to be gentle with respect to the increase in vertical stress. The results also implied that there was a negative linear relationship between the K₀ of coarse-grained soil and ρ_d. Furthermore, a comparative analysis between rockfill soil and sandy-gravel soil indicated that the relative equation proposed by the authors was appropriate for any type of coarse-grained soil with any ρ_d. Moreover, an empirical equation that can accurately describe the effective relationship of σ_v and ρ_d with the K₀ for coarse-grained soil was proposed, and the accuracy of the empirical equations were verified by the K₀ test results concerning sand-gravel soil. Finally, based on the published research findings, the empirical equations’ applicability to any coarse-grained soil was verified. Full article

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15 pages, 3707 KiB

Open AccessArticle

Analysis of the Seismic Response of Unequal-Span Metro Station in Saturated Site

by Jian Su, Wei Xiao, Minze Xu, Chunyi Cui, Jingtong Zhao and Ling Ling

Buildings 2023, 13(4), 953; https://doi.org/10.3390/buildings13040953 - 3 Apr 2023

Viewed by 1393

Abstract

To analyze the seismic response characteristics of unequal-span subway station structures in saturated sites, a three-dimensional numerical model of an unequal-span subway station structure is established, based on the finite element analysis software MIDAS-GTS. The elastic modulus, cohesion, Poisson’s ratio, and friction angle [...] Read more.

To analyze the seismic response characteristics of unequal-span subway station structures in saturated sites, a three-dimensional numerical model of an unequal-span subway station structure is established, based on the finite element analysis software MIDAS-GTS. The elastic modulus, cohesion, Poisson’s ratio, and friction angle are selected as the sensitivity parameters. Moreover, combined with the saturated two-phase medium dynamic analysis method, the orthogonal test method is also utilized, to obtain the corresponding seismic response range. The results show that, the lower end of the shear wall and the vicinity of the cantilever span are prone to bending failure, and that the central columns are prone to shear failure. Under the action of a horizontal ground motion, or under the combination of horizontal and vertical ground motions, the influence of the elastic modulus is the largest, the influence of the Poisson’s ratio and the friction angle is the second largest, and the influence of cohesion is the smallest. This procedure of seismic response characteristics for unequal-span subway station structures can provide a reference for the seismic design of these structures. Full article

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15 pages, 9458 KiB

Open AccessArticle

Effect of Expanded Body Diameter on the Soil Surrounding a Pile Based on the Half-Face Pile Model Test of Undisturbed Soil

by Lina Xu, Chenhui Qi, Lei Niu and Xu Ding

Buildings 2023, 13(4), 951; https://doi.org/10.3390/buildings13040951 - 3 Apr 2023

Cited by 1 | Viewed by 1505

Abstract

The effect of expanded body diameter on the displacement field of soil surrounding a pile under different vertical loads was investigated using the half-face pile model test of undisturbed soil. Digital image correlation technology was used to record the displacement characteristics of soil [...] Read more.

The effect of expanded body diameter on the displacement field of soil surrounding a pile under different vertical loads was investigated using the half-face pile model test of undisturbed soil. Digital image correlation technology was used to record the displacement characteristics of soil around the pile in real time. The displacement and failure characteristics of the soil around the pile were analyzed. The results show that with an increased load, the soil below the expanded body is compressed, and the soil at both ends will slip, leading to the continuous development of cracks. In a horizontal direction, the soil surrounding the pile first moves close to the pile and then tends to stabilize or move away from the pile. The horizontal and vertical displacement of the soil decreases as the distance from the pile increases. The main area of influence on the soil is below the expanded body, in which the increased diameter of the expanded body results in a gradual increase in the area of influence. Furthermore, all of the load-settlement curves show a slow decline and the bearing capacity increases with the increased diameter of the expanded body. Therefore, the research in this paper can provide an experimental method for the study of soil displacement around drill-expanded concrete piles. Full article

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12 pages, 1066 KiB

Open AccessArticle

Identifying Collapsible Soils from Seismic Cone (SCPT): A Qualitative Approach

by Breno Padovezi Rocha, Isabela Augusto Silveira, Roger Augusto Rodrigues, Paulo Cesar Lodi and Heraldo Luiz Giacheti

Buildings 2023, 13(3), 830; https://doi.org/10.3390/buildings13030830 - 22 Mar 2023

Cited by 2 | Viewed by 1962

Abstract

Collapsible soils are unsaturated low-density soils that undergo abrupt settlement when flooded without any increase in the in-situ stress level. The first stage of the site characterization is identifying collapsible soils, since these are problematic soils. Seismic cone testing (SCPT) has been increasingly [...] Read more.

Collapsible soils are unsaturated low-density soils that undergo abrupt settlement when flooded without any increase in the in-situ stress level. The first stage of the site characterization is identifying collapsible soils, since these are problematic soils. Seismic cone testing (SCPT) has been increasingly used for site characterization, because it allows combining stratigraphic logging with the maximum shear modulus (G₀) determination. In this paper, laboratory and in-situ tests carried out at 21 sites with collapsible and non-collapsible soils are interpreted to differentiate between such soils, based on the seismic cone test (SCPT). Collapsible soils have G₀/q_c values greater than 23 and q_c₁ values less than 70, while non-collapsible soils have G₀/q_c values less than 23 and q_c₁ values greater than 70. The investigated collapsible soils have microstructure (bonding/cementation), but the classical approach cannot be sufficient to identify collapsible soils alone. An approach was used to identify collapsible soils based on maximum shear modulus (G₀), normalized cone resistance (q_c₁), and cone resistance (q_c). The chart G₀/q_c versus q_c₁ and boundaries is an alternative for distinguishing between collapsible and non-collapsible soils in the early stage of site investigation. This qualitative approach should be used in the preliminary investigation phase to select potentially collapsible soils and helps guide the sampling of potentially collapsible soils for laboratory testing. Further SCPT data from different soil types, particularly the collapsible ones, are valuable to adjust or confirm the boundary equations suggested. Full article

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19 pages, 5242 KiB

Open AccessArticle

Influence of Small Radius Curved Shield Tunneling Excavation on Displacement of Surrounding Soil

by Bo Yang, Chengyao Zhang, Na Su and Zhaoran Xiao

Buildings 2023, 13(3), 803; https://doi.org/10.3390/buildings13030803 - 18 Mar 2023

Cited by 6 | Viewed by 1838

Abstract

In contrast to straight tunnels, the mechanisms of displacement of surrounding soil induced by shield excavation of small radius curved tunnels are more complex. Based on field monitoring data of surface settlement and horizontal displacement of a small radius curved shield tunnel in [...] Read more.

In contrast to straight tunnels, the mechanisms of displacement of surrounding soil induced by shield excavation of small radius curved tunnels are more complex. Based on field monitoring data of surface settlement and horizontal displacement of a small radius curved shield tunnel in a section of Zhengzhou Metro Line 3, a numerical model using three-dimensional a finite element method is established to evaluate factors of the displacement of surrounding soil. The results verify the validity of numerical simulation by comparison with field monitoring data and the influence of unbalanced additional thrust at tail jacks, curvature radius of a tunnel and tail grouting pressure on surface settlement and horizontal displacement of surrounding soil. Maximum surface settlement and horizontal displacement of surrounding soil at the outer side and inner side of curved tunnel axes are positively related to thrust ratio, while negatively related to curvature radius and grouting pressure. The ultimate objective of this study is to ascertain factors of displacement of surrounding soil induced by small radius shield excavation and provide a theoretical basis and technical support for the design and construction of similar tunnel. Full article

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19 pages, 10266 KiB

Open AccessArticle

Numerical Analysis of Modified PVA Fiber Rubber Concrete in Frame Beams

by Lijuan Li, Fang Xing, Zhijun Xu, Wang Chen, Wuxin Chen and Yongquan Li

Buildings 2023, 13(3), 791; https://doi.org/10.3390/buildings13030791 - 17 Mar 2023

Cited by 1 | Viewed by 1526

Abstract

The feasibility of PVA fiber rubber concrete modified by modifier in the structure was investigated using the portal frame as the research object. The basic mechanical properties of modified PVA rubber concrete materials were tested mechanically first, and then ABAQUS was used to [...] Read more.

The feasibility of PVA fiber rubber concrete modified by modifier in the structure was investigated using the portal frame as the research object. The basic mechanical properties of modified PVA rubber concrete materials were tested mechanically first, and then ABAQUS was used to establish the ordinary concrete portal frame model, and after confirming the model’s rationality, the rubber concrete, PVA rubber concrete, and modified PVA rubber concrete models were established on this basis, and the displacement and strain comparison analysis with ordinary concrete was carried out. The simulation results show that using PVA rubber concrete material in the concrete frame structure can improve the large deformation of rubber concrete, and using PVA rubber concrete treated with a modifier can improve structural strength and deformation even more. Full article

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17 pages, 4377 KiB

Open AccessArticle

Numerical Simulation of Anchorage Performance of GFRP Bolt and Concrete

by Gan Sun, Xiaoyu Bai, Songkui Sang, Ling Zeng, Jichao Yin, Desheng Jing, Mingyi Zhang and Nan Yan

Buildings 2023, 13(2), 493; https://doi.org/10.3390/buildings13020493 - 11 Feb 2023

Cited by 5 | Viewed by 1938

Abstract

We conducted anchoring performance, stress distribution, and full-scale indoor pulling tests on glass-fiber-reinforced polymer (GFRP) bolts. The tests were conducted using finite element software while considering the multi-interface contact and BK criterion by using the cohesive element to simulate the contact relations between [...] Read more.

We conducted anchoring performance, stress distribution, and full-scale indoor pulling tests on glass-fiber-reinforced polymer (GFRP) bolts. The tests were conducted using finite element software while considering the multi-interface contact and BK criterion by using the cohesive element to simulate the contact relations between the anchor rod body and concrete and building an axial symmetry calculation model of the GRFP bolt and concrete. The results indicated that the finite element model based on cohesive element accurately represents the load–displacement relationship of the GFRP bolt and the distribution law of axial stress along the anchoring length. In addition, the simulation outcomes of the load–displacement relationship were in good agreement with the measured test values. Under the same load, the axial-force-transferred depth of the bolt body was identical regardless of the anchorage length. As anchoring length increases, the pull load on the bolt and the decay rate of axial stress along the anchoring length rises gradually. There is a critical value for the anchorage length of the bolt. Full article

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14 pages, 2612 KiB

Open AccessArticle

Investigation into Viscoelastic Properties of Fiber-Reinforced Asphalt Composite Concrete Based on the Burgers Model

by Chunshui Huang, Danying Gao, Tong Meng and Changde Yang

Buildings 2023, 13(2), 449; https://doi.org/10.3390/buildings13020449 - 6 Feb 2023

Cited by 5 | Viewed by 1618

Abstract

Asphalt composite concrete pavement is one of the common pavement forms in China. However, due to the influence of design, materials, construction quality, and other aspects, asphalt composite concrete pavement develops various degrees of cracks after being put into use, which affects the [...] Read more.

Asphalt composite concrete pavement is one of the common pavement forms in China. However, due to the influence of design, materials, construction quality, and other aspects, asphalt composite concrete pavement develops various degrees of cracks after being put into use, which affects the service performance and life of asphalt pavement. The Burgers model is used to examine the effects of fiber-volume-fraction and length–diameter-ratio on the viscoelastic mechanical behavior model parameters and viscoelastic properties of asphalt composite concrete through the bend test for creep of polyester fiber asphalt composite concrete beam. The findings indicate that the fiber’s ability to control asphalt composite concrete bending creep deformation increases initially and subsequently diminishes as fiber-volume-fraction and length–diameter-ratio increase. Fiber-volume-fraction and length–diameter-ratio effects can be fully reflected by fiber amount characteristics. A viscoelastic mechanical behavior model of fiber-reinforced asphalt composite concrete is developed on this foundation while taking into account the influence of fiber amount characteristic factors. Theoretical study and practical research indicate that the ideal fiber volume ratio of polyester fiber asphalt composite concrete is 0.35 percent, the ideal length-to-diameter ratio is 324, and the ideal fiber amount characteristic parameter is 1.13. The test results can provide a certain reference value for the improvement of the long-term durability of fiber asphalt composite concrete pavement of road engineering. Full article

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20 pages, 11209 KiB

Open AccessArticle

Compressive Test Investigation and Numerical Simulation of Polyvinyl-Alcohol (PVA)-Fiber-Reinforced Rubber Concrete

by Yong Feng, Zijuan Niu, Chen Zhao and Lijuan Li

Buildings 2023, 13(2), 431; https://doi.org/10.3390/buildings13020431 - 3 Feb 2023

Cited by 6 | Viewed by 2116

Abstract

To investigate the mechanical properties of polyvinyl-alcohol (PVA)-fiber-reinforced rubber concrete, 13 groups of PVA rubber/concrete specimens with PVA volume fractions of 0%, 0.5 vol%, 1.0 vol%, and 1.5 vol% and rubber particles with volume replacement sand ratios of 0%, 10%, 20%, and 30% [...] Read more.

To investigate the mechanical properties of polyvinyl-alcohol (PVA)-fiber-reinforced rubber concrete, 13 groups of PVA rubber/concrete specimens with PVA volume fractions of 0%, 0.5 vol%, 1.0 vol%, and 1.5 vol% and rubber particles with volume replacement sand ratios of 0%, 10%, 20%, and 30% were prepared, and the uniaxial compression full curve test was performed. The findings indicate that the bridging effect of PVA, as well as the synergistic effect of PVA and rubber particles, can improve the compressive properties of concrete, and the failure of the specimens demonstrates obvious ductile characteristics. Furthermore, PVA has a better impact on rubber concrete’s bearing capacity, crack propagation of the failure surface, and compressive strength in the latter stages. PVA-fiber-reinforced rubber concrete is thought to be a six-phase composite made up of the aggregate phase, mortar matrix, PVA fiber, rubber particles, aggregate–mortar interface, and rubber–mortar interface on the mesoscale. To simulate the entire process of concrete with varying PVA rubber/content from integrity to damage and cracking, a meso-numerical model of PVA rubber/concrete was constructed. The simulation results and test results are in good agreement, demonstrating the validity of the mesomodel and offering a theoretical foundation for the structural analysis and design of this type of concrete. Full article

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18 pages, 15922 KiB

Open AccessArticle

Parameter Sensitivity Analysis of the Seismic Response of a Piled Wharf Structure

by Jingtong Zhao, Chunyi Cui, Peng Zhang, Kunpeng Wang and Min Zhao

Buildings 2023, 13(2), 349; https://doi.org/10.3390/buildings13020349 - 26 Jan 2023

Cited by 7 | Viewed by 2140

Abstract

To investigate the seismic response characteristics of piled wharf structures, a numerical model of the soil-structure interaction system is established. Extensive fiducial error and grey correlation analyses are also conducted to obtain the grey correlation degree sequence of the internal force of piled [...] Read more.

To investigate the seismic response characteristics of piled wharf structures, a numerical model of the soil-structure interaction system is established. Extensive fiducial error and grey correlation analyses are also conducted to obtain the grey correlation degree sequence of the internal force of piled wharf structure and deformation, as well as the acceleration of surrounding soils. The results show that the peak acceleration at the typical point of the soil is more sensitive to the variations in friction angle and ground motion intensity, while the lateral extreme displacement is the most sensitive to the variations in the elastic modulus of the soil. The grey correlation sequences of the peak acceleration and lateral extreme displacement at the feature points of the soil around the pile greatly vary, indicating that the key factors of the different sequences control the target parameters corresponding to them. The sensitivity of the internal force of the pile foundation of the pier structure to the ground motion intensity and friction angle is more sensitive than the elastic modulus and cohesion. This presented parameter sensitivity analysis procedure for the seismic response of piled wharf structures can provide a reference for the seismic design of piled wharf structures, as well as for disaster prevention prediction. Full article

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20 pages, 7706 KiB

Open AccessArticle

Mechanical Properties and Numerical Analysis of Underground Continuous Wall in Underground Grain Silo Foundation Pit

by Chen Zhao, Yong Feng, Weijian Wang and Zijuan Niu

Buildings 2023, 13(2), 293; https://doi.org/10.3390/buildings13020293 - 19 Jan 2023

Cited by 4 | Viewed by 2127

Abstract

Foundation pit monitoring can only provide feedback regarding the deformation of the formation and envelope structure after construction, and it is difficult to predict the deformation law of a continuous underground wall in the later stage of underground grain silo support. Taking the [...] Read more.

Foundation pit monitoring can only provide feedback regarding the deformation of the formation and envelope structure after construction, and it is difficult to predict the deformation law of a continuous underground wall in the later stage of underground grain silo support. Taking the deep foundation pit of a continuous underground wall of an underground grain silo as an example, this paper uses Abaqus software to simulate the force of the project, explores the calculation results of the planar elastic foundation beam considering the arch effect and the numerical simulation technology of the foundation pit’s support, and analyzes and compares the rationality of the model. The analysis of the deformation form of the continuous underground wall by both calculation methods is a parabolic combination. The maximum horizontal displacement of the continuous underground wall, according to the Abaqus software, is 6.23 mm, and the other calculation result is 4.7 mm; the maximum settlement on the surface is 11.34 mm, according to the Abaqus software, and the other maximum settlement is 8 mm. The simulation results show that the simulated value is basically consistent with the measured value, and the simulated value is slightly larger than the measured value because the interference conditions are idealized during simulation. The accuracy and rationality of the numerical simulation are verified, and the parameters, such as the thickness and burial depth of the continuous underground wall, can be changed to provide a reference for the support method of a deep foundation pit similar to a continuous underground wall. Full article

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20 pages, 8465 KiB

Open AccessArticle

Influence of Different Industrial Waste Residues on Engineering Properties of High Liquid Limit Soil and Its Microscopic Mechanism

by Liansheng Tang, Yang Chen, Jialun Peng and Zihua Cheng

Buildings 2023, 13(1), 235; https://doi.org/10.3390/buildings13010235 - 14 Jan 2023

Cited by 1 | Viewed by 2080

Abstract

High liquid limit soil has unfavorable engineering geological characteristics, such as strong disintegration, dry shrinkage and easy cracking, and easy uplift when encountering water, which will cause various problems to the engineering. At present, the relationship between the physical and mechanical properties of [...] Read more.

High liquid limit soil has unfavorable engineering geological characteristics, such as strong disintegration, dry shrinkage and easy cracking, and easy uplift when encountering water, which will cause various problems to the engineering. At present, the relationship between the physical and mechanical properties of high liquid limit soil and the characteristics of water-soil interaction is still not clear enough. In this study, the high liquid limit soil of Zhanjiang Avenue was selected to explore the influence of different ratios of three kinds of industrial waste residues (blast furnace slag, carbide slag, and tailing sand) on the high liquid limit soil. Aiming at the common adverse engineering geological phenomena of high liquid limit soil, such as easy disintegration, dry shrinkage crack, and easy uplift in water, the effects of different industrial waste residues on the water-soil interaction characteristics of high liquid limit soil are explored through disintegration and crack tests. In addition, the effects of different kinds and ratios on the free expansion rate, pH, unconfined compressive strength, and shear strength parameters of high liquid limit soil were studied. The improvement mechanism of different industrial waste residues on the engineering properties of high liquid limit soil is discussed in terms of mineral composition and microstructure. Based on the experimental results of this study and considering the cost and engineering practice, it is suggested that the modified carbide slag optimal ratio of high liquid limit soil of Zhanjiang Avenue is 8%. The results can provide certain guidance for the improvement and application of different industrial waste residues on high liquid limit soil to achieve the effect of sustainable development. Full article

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2022

Jump to: 2024, 2023

14 pages, 3026 KiB

Open AccessArticle

Research on Displacement Field of Soil around Pile with Different Density Based on Particle Image Testing Technology

by Xiujie Zhang, Hongzhong Li, Kaiyan Xu, Zhanwu Ma, Yonghong Wang and Rongtao Yan

Buildings 2022, 12(12), 2136; https://doi.org/10.3390/buildings12122136 - 5 Dec 2022

Viewed by 1397

Abstract

Particle image testing technology has the advantages of non-intervention and high precision. In this paper, the particle image testing technology is combined with the indoor model test to explore the displacement development trend of the soil around the horizontal loaded pile under the [...] Read more.

Particle image testing technology has the advantages of non-intervention and high precision. In this paper, the particle image testing technology is combined with the indoor model test to explore the displacement development trend of the soil around the horizontal loaded pile under the difference of soil properties between layers. The principle of PIV technology is described, and the single-layer soil test group and the layered soil test group are set up, respectively. To this end, the indoor model test is carried out by changing the soil density. The study reveals that particle image testing technology can reduce the influence of data acquisition equipment on model tests in the maximum range, and restore the development trend of surface soil displacement in the horizontal load pile test to the greatest extent. Under the same load, the displacement influence area formed in front of and behind the pile of the two groups of tests takes the shape of a spindle centred on the pile body. The influence range of surface soil decreases with the increase of density. Moreover, the results of Tecplot analysis show that the soil stiffness is ranked from small to large as follows: single layer coarse sand, upper layer large particle size and lower layer small particle size test group, upper layer small particle size and lower layer large particle size test group, single layer fine sand. The test results can provide reference for the deepening of practical engineering. Full article

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15 pages, 3166 KiB

Open AccessArticle

Numerical Test and Strength Prediction of Concrete Failure Process Based on RVM Algorithm

by Chunyang Xia, Xuedong Guo and Wenting Dai

Buildings 2022, 12(12), 2105; https://doi.org/10.3390/buildings12122105 - 1 Dec 2022

Cited by 1 | Viewed by 1711

Abstract

Recycled aggregate concrete (RAC) based on the machine learning (ML) method predicts the nonlinear uncertainty relationship between various mixing ratios and strength. Uniaxial compressive strength is one of the important indices to evaluate its performance. Machine learning is one of the essential methods [...] Read more.

Recycled aggregate concrete (RAC) based on the machine learning (ML) method predicts the nonlinear uncertainty relationship between various mixing ratios and strength. Uniaxial compressive strength is one of the important indices to evaluate its performance. Machine learning is one of the essential methods for solving this nonlinear uncertainty relationship. To realize the selection of concrete raw materials and the learning and application of other influencing factors and provide guidance for engineering construction and application, this paper establishes a database of concrete uniaxial compressive strength based on Abaqus simulation software. The simulation results are highly consistent with the actual values. Based on the simulation database, with different water-cement ratios, different curing days, and recycled aggregate replacement rates as the input data set, the uniaxial compressive strength of concrete is the output data set. The data set is divided into a training set and a test set. A prediction model of the uniaxial compressive strength of concrete based on a relevance vector machine (RVM) algorithm is established. The results show that the maximum error between the simulated and experimental uniaxial compressive strength values is only 0.2 MPa. The correlation coefficient R between the predicted and simulated values of the concrete uniaxial compressive strength prediction model based on the RVM algorithm is 0.975. The model can effectively predict the compressive strength of RAC to meet the engineering requirements. Full article

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14 pages, 25498 KiB

Open AccessArticle

Research on the Soil-Plugging Effect on Small-Diameter Jacked Piles through In Situ Testing and DEM Simulation

by Xueyan Wang, Yuan Mei, Yili Yuan, Rong Wang and Dongbo Zhou

Buildings 2022, 12(11), 2022; https://doi.org/10.3390/buildings12112022 - 18 Nov 2022

Cited by 4 | Viewed by 1956

Abstract

Small-diameter jacked piles are widely used in civil engineering. The formation and development of the soil-plugging effect and surface frictional behavior of jacked piles have a high impact on the construction process and pile quality. Clarifying the developmental pattern of the soil-plugging effect [...] Read more.

Small-diameter jacked piles are widely used in civil engineering. The formation and development of the soil-plugging effect and surface frictional behavior of jacked piles have a high impact on the construction process and pile quality. Clarifying the developmental pattern of the soil-plugging effect and the change law of frictional force forms the premise of scientific construction and construction quality. Firstly, we carried out two groups of in situ tests on the small-diameter jacked piles, recording the relationship between penetration depth and resistance force. Then, the discrete element method (DEM) was used to analyze the mechanical behavior of the small-diameter jacked piles during the construction process. The particle flow code (PFC) 2D was used to carry out the DEM simulation. The research results show that pile resistance exhibited an irregular development trend as the construction process proceeded. There is a sudden change in pile resistance when the pile tip reaches the interface of certain soil layers. Both tests revealed the same phenomenon, yet both occurred at different depths. The DEM analysis showed that plug sliding was the main reason for the above phenomenon. The difference in strength and stiffness of adjacent soil layers causes the soil plug to slide, leading to a sudden change in pile resistance. When the upper layer is soft and the layer below is hard, this phenomenon is especially obvious. This also leads to a difference in the location of the sudden change in pile resistance between the two groups of tests. The research results of this paper can be helpful for revealing the relationship between the soil-plugging effect of small-diameter jacked piles and the development of pile resistance and also provides a reference for relevant engineering construction and design. Full article

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14 pages, 3447 KiB

Open AccessFeature PaperArticle

Numerical Analysis of Passive Piles under Surcharge Load in Extensively Deep Soft Soil

by Meixiang Gu, Xiaocong Cai, Qiang Fu, Haibo Li, Xi Wang and Binbing Mao

Buildings 2022, 12(11), 1988; https://doi.org/10.3390/buildings12111988 - 16 Nov 2022

Cited by 43 | Viewed by 2440

Abstract

The three-dimensional finite difference method was used in this study to analyze the deformation and stresses of a passive pile under surcharge load in extensively deep soft soil. A three-dimensional numerical model was proposed and verified by a field test. The horizontal displacements [...] Read more.

The three-dimensional finite difference method was used in this study to analyze the deformation and stresses of a passive pile under surcharge load in extensively deep soft soil. A three-dimensional numerical model was proposed and verified by a field test. The horizontal displacements of the pile agreed well with the field results. This study investigated the pile-foundation soil interaction, the load transfer mechanism, the excess pore water pressure (EPWP), and the horizontal resistance of the foundation soil. The results show that the soil in the corner of the loading area developed a large uplift deformation, while the center of the loading area developed a large settlement. The lateral displacement of the pile decreased sharply with the increase of the depth and increased with the surcharge load. The lateral displacement of the soil was negligible when the depth exceeded 30 m. The EPWP increased in a nonlinear way with the increase of the surcharge load and accumulated with the placement of the new lift. The distribution of the lateral earth pressure in the shallow soil layer was complex, and the negative value was observed under a high surcharge load due to the suction effect. The proportion coefficient of the horizontal resistance coefficient showed much smaller value in the situation of large lateral deformation and high surcharge load. The design code overestimated the horizontal resistance of the shallow foundation soil, which should be given attention for the design and analysis of the laterally loaded structures in extensively soft soil. Full article

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24 pages, 12486 KiB

Open AccessArticle

Experimental Study on Vibration Velocity of Piled Raft Supported Embankment and Foundation for Ballastless High Speed Railway

by Qiang Fu, Meixiang Gu, Jie Yuan and Yifeng Lin

Buildings 2022, 12(11), 1982; https://doi.org/10.3390/buildings12111982 - 15 Nov 2022

Cited by 46 | Viewed by 2515

Abstract

In recent years, the high development of high-speed railway lines cross through areas with poor geological conditions, such as soft soil, offshore and low-lying marsh areas, resulting geotechnical problems, such as large settlements and reduction of bearing capacity. As a new soil reinforcement [...] Read more.

In recent years, the high development of high-speed railway lines cross through areas with poor geological conditions, such as soft soil, offshore and low-lying marsh areas, resulting geotechnical problems, such as large settlements and reduction of bearing capacity. As a new soil reinforcement method in high speed railway lines, the piled raft structure has been used to improve soil conditions and control excess settlement. In order to study the dynamic behavior of piled raft supported ballastless track system in soft soil, an experimental study on vibration velocities of piled raft supported embankment and foundations is presented in soft soil with different underground water levels. Vibration velocities at specified positions of the piled raft supported embankment and foundations are obtained and discussed. The vibration velocity curves on various testing locations of piled raft foundations are clearly visible and have sharp impulse and relaxation pattern, corresponding to loading from train wheels, bogies, and passages. Vibration velocity distribution in the horizontal direction at three train speeds clearly follows an exponential curves. Most of the power spectrums of vibration velocity at various locations are mainly concentrated at harmonic frequencies. The change in water level has slight impaction on the peak spectrum of vibration velocity at harmonic frequencies. The vibration power induced by train loads are transmitted, absorbed, and weakened to a certain extent through embankment and piled raft structure. The dynamic response character of embankments are affected by their self-vibration characteristics and the dynamic bearing capacity of the piled raft structure. Full article

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21 pages, 11741 KiB

Open AccessArticle

Experimental Study of Frame-Supported Shear Wall Structure of High-Rise Buildings with Transfer Slab in Metro Depot

by Yishu Xia, Wuxiong Li, Weiya Liu, Yanhui Liu, Xin Xu and Chenyun Zhang

Buildings 2022, 12(11), 1940; https://doi.org/10.3390/buildings12111940 - 10 Nov 2022

Cited by 3 | Viewed by 4713

Abstract

Taking the frame-supported shear wall structure of a 102.1 m high metro depot as the test object, the structure has obvious vertical irregularity, and a quasi-static test was carried out on the structural model with the scale of 1/5. The damage development and [...] Read more.

Taking the frame-supported shear wall structure of a 102.1 m high metro depot as the test object, the structure has obvious vertical irregularity, and a quasi-static test was carried out on the structural model with the scale of 1/5. The damage development and strain of the structure were observed by applying displacement loads under different seismic actions, and the experimental phenomena and measured data were analyzed. The results show that the safety performance of the structure meets the seismic requirements of the MCE (Maximum considered earthquake) condition. Under the action of load, a reasonable damage mechanism is formed in which the components above the transfer story crack first and those below the transfer story crack later, which is in line with the design concept of “the performance objective of the bottom frame structure is higher than that of the upper shear wall structure”. The transfer plate is mainly subjected to shear deformation, the possible shear failure of the transfer plate should be avoided by reasonable design. Due to the large height difference between the first floor and the second floor, the structure may be adversely affected, so it is necessary to make the yielding floor appear in the bottom strengthening part above the transfer story. Under the SLE (Service level earthquake) and DBE (Design based earthquake) conditions, the bottom frame of the structure is mainly subjected to elastic deformation. Under the MCE (Maximum considered earthquake) condition, the bottom frame of the structure causes a lot of damage, increases energy consumption and decreases stiffness, which further proves that “the performance goal of the bottom frame structure is higher than that of the upper shear wall structure”. Full article

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18 pages, 7147 KiB

Open AccessArticle

Numerical Simulation of Bearing Characteristics of Bored Piles in Mudstone Based on Zoning Assignment of Soil around Piles

by Yamei Zhang, Fengjiao Wang, Xiaoyu Bai, Nan Yan, Songkui Sang, Liang Kong, Mingyi Zhang and Yufeng Wei

Buildings 2022, 12(11), 1877; https://doi.org/10.3390/buildings12111877 - 4 Nov 2022

Cited by 1 | Viewed by 2216

Abstract

This study conducts a field indoor simulation test, SEM observation, and penetration test to determine the bearing capacity of the dynamic driving pile in the mudstone foundation. It comprehensively analyzes the variation laws of structure and strength of mudstone around piles after piling. [...] Read more.

This study conducts a field indoor simulation test, SEM observation, and penetration test to determine the bearing capacity of the dynamic driving pile in the mudstone foundation. It comprehensively analyzes the variation laws of structure and strength of mudstone around piles after piling. Indeed, the strength of mudstone structure is significantly reduced from outside to inside. Therefore, the numerical simulation of piles in mudstone should consider the actual characteristics of soil damage around piles. The strength of mudstone after pile driving damage is measured, and the scatter diagram depicting the relationship between mudstone strength and pile side distance is produced. Then, the best-fitting curve of the relationship between the strength ratio and the distance ratio of the simulated pile driving test is established by the nonlinear fitting of multiple curves. A numerical simulation method is proposed to consider the damaged area and parameters surrounding the pile. The range of soil damage caused by pile driving in the mudstone foundation is determined to be two times that of the pile diameter. The disturbance area is divided into four parts on average, and the width of each part is 0.5d. The simulation results are compared to the conventional approach of uniform parameter assignment to prove the rationality of the method. Full article

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17 pages, 11935 KiB

Open AccessArticle

Study on Comprehensive Technology of Preventing Mud Cake of Large Diameter Slurry Shield in Composite Stratum

by Yuan Mei, Dongbo Zhou, Hang Gong, Xin Ke, Wangyang Xu and Wenyan Shi

Buildings 2022, 12(10), 1555; https://doi.org/10.3390/buildings12101555 - 28 Sep 2022

Cited by 5 | Viewed by 2002

Abstract

When large-diameter slurry shields are tunneling in a composite stratum with a high clay content, the cutter head may form a mud cake. After the mud cake is formed, it will cover the cutter and reduce the opening rate of the cutter head, [...] Read more.

When large-diameter slurry shields are tunneling in a composite stratum with a high clay content, the cutter head may form a mud cake. After the mud cake is formed, it will cover the cutter and reduce the opening rate of the cutter head, thus reducing the penetration of the cutter and the driving speed. Based on a road upgrading project, this paper studies the prevention and treatment of a mud cake and forms a set of comprehensive treatment methods. For a large mud cake, through theoretical analysis, two calculation methods of the cutter head sealing coefficient are obtained, and the cutter head sealing coefficient relationship model is established. Comparing the calculated cutter head’s actual opening coefficient with the required cutter head opening coefficient can provide a judgment basis for the time of manual warehousing. For medium and small mud cakes, the numerical simulation is carried out based on the cutter head and the scouring system, the distribution characteristics of the flow field near the cutter head are analyzed, and the angle of the central scouring hole is optimized. For a small mud cake, hydrogen peroxide is selected as an additive through microscopic mechanism analysis. The effect of the hydrogen peroxide solution concentration on dissolving a mud cake is obtained through laboratory tests, and its effectiveness is verified through field tests. The research results can provide a reference for the mud cake prevention of slurry shields in similar strata. Full article

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21 pages, 12243 KiB

Open AccessArticle

Study on the Mechanical Response Mechanism and Damage Behavior of a Tunnel Lining Structure under Reverse Fault Dislocation

by Huifeng Su, Zhongxiao Zhao, Kun Meng and Shuo Zhao

Buildings 2022, 12(10), 1521; https://doi.org/10.3390/buildings12101521 - 23 Sep 2022

Cited by 1 | Viewed by 1479

Abstract

In this paper, the mechanical response mechanism and damage behavior of a railway tunnel lining structure under reverse fault dislocation were studied. The damage behavior of railway tunnel linings under reverse fault dislocation was validated by undertaking laboratory tests and three-dimensional numerical simulations, [...] Read more.

In this paper, the mechanical response mechanism and damage behavior of a railway tunnel lining structure under reverse fault dislocation were studied. The damage behavior of railway tunnel linings under reverse fault dislocation was validated by undertaking laboratory tests and three-dimensional numerical simulations, where Coulomb’s friction was used in the tangential direction of the interface. The failure damage, which increasingly accumulates with displacements, mainly concentrates in fault fracture neighborhoods 0.5 D to 1.5 D (D is the tunnel diameter) within the footwall. The maximum surrounding rock pressure and the maximum longitudinal strain develop in the tunnel near the hanging wall area. The damage begins as longitudinal cracking of the inverted arch. With the increase in dislocations, those cracks develop upward to the arch foot and the waist. Consequently, those oblique cracks separate lining segments, leading to abutment dislocation. The research results provide technical guidance and theoretical support for on-site construction and follow-up research, and they have important application value. Full article

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17 pages, 6181 KiB

Open AccessArticle

Laws and Numerical Analysis of Surface Deformation Caused by Excavation of Large Diameter Slurry Shield in Upper-Soft and Lower-Hard Composite Stratum

by Yuan Mei, Dongbo Zhou, Wenyan Shi, Yuhang Zhang and Yu Zhang

Buildings 2022, 12(9), 1470; https://doi.org/10.3390/buildings12091470 - 16 Sep 2022

Cited by 10 | Viewed by 2086

Abstract

Due to the large cross-section design of large-diameter shield tunnels, most of the rocks and soils it crosses are composite strata with upper soft and lower hard. In order to reduce the construction cost of shield working shafts, large-diameter shield launching is usually [...] Read more.

Due to the large cross-section design of large-diameter shield tunnels, most of the rocks and soils it crosses are composite strata with upper soft and lower hard. In order to reduce the construction cost of shield working shafts, large-diameter shield launching is usually buried at a shallow depth. Based on the typical large-diameter slurry shield tunnel, the following research results were obtained according to field monitoring and PLAXIS 3D finite element simulation. (1) The electronic level is used to monitor the surface settlement, and the field monitoring data were obtained; the surface settlement duration curve at the axis of the shield tunnel during the construction period can be divided into four stages: pre-deformation, shield passing, shield tail exit and shield moving away, of which the surface settlement accounts for the largest proportion during the shield passing. (2) In order to ensure the accuracy of the numerical simulation results, the linear shrinkage of the shield needs to be considered in the modeling. (3) The maximum surface settlement value at the center of the tunnel increases with the increase of the support pressure; when the support pressure exceeds 300 kPa, the surface uplift and the settlement caused by the formation loss will offset, and the surface settlement will decrease instead. The maximum surface settlement value is inversely proportional to the grouting pressure, but with the increase of the grouting pressure, the maximum uplift of the surface continues to increase. (4) With the numerical simulation of excavation step construction, the surface uplift increases with the increase of grouting pressure and shield radius, and decreases with the increase of shield buried depth. Full article

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21 pages, 8054 KiB

Open AccessArticle

Monitoring Axial Force Development in a Super-Long Pile during Construction Using BOFDA and Data Interpretation Approaches: A Case Study

by Dongning Li, Deshan Ma, Dong Su, Shaohua Rao, Wenbin Wang and Chengyu Hong

Buildings 2022, 12(9), 1462; https://doi.org/10.3390/buildings12091462 - 15 Sep 2022

Cited by 2 | Viewed by 1936

Abstract

Long-term monitoring data for super-long piles are scarce and valuable. This paper reports axial strain measurements of a cast-in-place large-diameter pile embedded 76.7 m into a “weathered trench” of granite in Nanshan District, Shenzhen, China, using BOFDA monitoring technology. An approach based on [...] Read more.

Long-term monitoring data for super-long piles are scarce and valuable. This paper reports axial strain measurements of a cast-in-place large-diameter pile embedded 76.7 m into a “weathered trench” of granite in Nanshan District, Shenzhen, China, using BOFDA monitoring technology. An approach based on the load-transfer method to interpret data is proposed, in which the axial load at the pile head and the shear behavior at the pile–soil interface can be analyzed. Results show that these data can well reflect the increase in axial strain as the number of floors built increases, although there is deviation related to fiber cable bending due to the installation and compaction of concrete, and the complex loading condition at the pile head. Sensitivity analysis of parameters disclosed that the friction angle between the soil and the pile was approximately 10° for the cast-in-place pile monitored in this study, which is approximately one third of the interface friction angle, considering the slurry cake effect. The average axial force exerted on the pile head induced by building one floor ranged from 116.00 kN to 297.43 kN; this increased with the number of floors built and the total loads of the superstructure. This implies that the raft carried a large portion of the structural load during the early construction stage; piles gradually carried a major portion of the increased load due to continuous construction. The overall mobilized percentage of skin friction was approximately 40.8% when 40 floors were built, and the pile had the potential to carry more axial load. Full article

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16 pages, 4435 KiB

Open AccessArticle

Fuzzy Comprehensive Evaluation of APTS Dispatcher Working Level Based on Cloud Model

by Deyong Guan, Yue Xu, Yuxuan Xue and Kun Meng

Buildings 2022, 12(9), 1331; https://doi.org/10.3390/buildings12091331 - 30 Aug 2022

Cited by 2 | Viewed by 1514

Abstract

Many cities in China have built an advanced public transportation system (APTS) in recent years. These systems cannot carry out automated dispatches but rely on the dispatcher to ensure normal operations. Based on the theory of fuzzy comprehensive evaluation, this study created a [...] Read more.

Many cities in China have built an advanced public transportation system (APTS) in recent years. These systems cannot carry out automated dispatches but rely on the dispatcher to ensure normal operations. Based on the theory of fuzzy comprehensive evaluation, this study created a hierarchical evaluation model to evaluate the work level of the dispatcher. Firstly, a hierarchical evaluation system was established based on the data of line complexity and dispatch workload provided by the APTS. Secondly, we assigned the weight of the evaluating indicator by combing an expert scoring method and the entropy weight method. We then transformed the quantitative data into qualitative evaluation data with a cloud model. Through a comparison with the standard cloud, the work level of an APTS dispatcher can be defined. The evaluation results for 12 cities in China showed that there was no obvious connection between the working level and bus company size, but the work level was always higher in large cities. We finally obtained the standard range of the evaluation indicator through cluster analysis. This method can be used as a reference to evaluate the work level of dispatchers in other cities, and can reflect the correlation between the work level and dispatching system construction, population and city size. Full article

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