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17 pages, 10309 KiB

Open AccessArticle

Energy-Dissipation Support Technology for Large Deformation Tunnels Based on the Post-Peak Behavior of Steel Plate Buckling: A Case Study

by Wanqi Wang and Wenge Qiu

Appl. Sci. 2023, 13(21), 11972; https://doi.org/10.3390/app132111972 - 2 Nov 2023

Viewed by 1245

Abstract

Large deformations can easily occur when tunneling through weak surrounding rock with high underground stresses. Under high-stress environments, the surrounding rock stores a large amount of strain energy, and the strain energy stored in the soft and weak surrounding rock enclosure is dissipated [...] Read more.

Large deformations can easily occur when tunneling through weak surrounding rock with high underground stresses. Under high-stress environments, the surrounding rock stores a large amount of strain energy, and the strain energy stored in the soft and weak surrounding rock enclosure is dissipated through the large traveling plastic deformation. Therefore, the effective use of the surrounding rock’s bearing capacity and energy dissipation is a feasible solution to the large deformation problem. Based on the energy principle, this study designs a high compressibility, large stroke energy-dissipation element, which transforms the traditional support into energy-dissipation support and solves the problem of large deformation by reasonably utilizing the “displacement” of the surrounding rock. The experimental results showed that the steel plate assembled structure had an initial peak value of about 15 MPa, a constant resistance of about 2 MPa with a large stroke, and a compression rate of more than 75%, with good post-compression flexural peak characteristics. Elastic–plastic buckling analyses of defective steel plate composite structures were carried out using finite element analysis software, and the deformation and force characteristics of a variety of steel plate composite structures after buckling under actual field conditions were investigated. Based on the 3D laser scanning system, the thickness of the upper and lower steel plates of the steel plate composite structure was set to 1 cm, the height of the vertical plate was set to 28 cm, and the thickness was set to 8 mm. The original rigid supporting method was converted into one of compression support by circumferentially embedding the steel plate composite structure into the initial support structure. The resulting support configuration offered a high safety factor because the pressure of the surrounding rock was released by the deformation of the steel plate composite structure. Full article

(This article belongs to the Special Issue Tunneling and Underground Engineering: From Theories to Practices)

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13 pages, 5057 KiB

Open AccessArticle

Behavioral Investigations of Three Parallel Large Reinforced Concrete Circular Pipes with the Construction of Pipe Jacking

by Minglei Ma, Lei Han, Yuanhao Wu, Quanying Li and Yongxing Zhang

Appl. Sci. 2023, 13(15), 8901; https://doi.org/10.3390/app13158901 - 2 Aug 2023

Cited by 1 | Viewed by 1304

Abstract

The pipe jacking method is gradually attracting increasing levels of attention and is becoming an important method for constructing underground engineering. However, jacking large-size concrete pipes in urban core areas subjected to complicated geological conditions is still a big problem preventing the employment [...] Read more.

The pipe jacking method is gradually attracting increasing levels of attention and is becoming an important method for constructing underground engineering. However, jacking large-size concrete pipes in urban core areas subjected to complicated geological conditions is still a big problem preventing the employment of the pipe jacking method, and further studies related to pipe jacking are required. This paper presents a case study on the construction of three parallel large-size reinforced concrete circular pipes in the upper-soft and lower-hard composite formations, in which the construction work was implemented using the slurry balance pipe jacking method with the sequence of jacking the 1# and 3# pipes prior to the 2# pipe being implemented in field construction. This case study was implemented by employing numerical simulations with the aforementioned pipe jacking sequence, which focused on the stress and deformation variations of the reinforced concrete circular pipes, as well as the vertical settlement of the ground surface during the jacking processes, and considering the influences from the excavation pressure and grouting pressure of the drag-reducing thixotropic slurry. The simulation results revealed that a higher excavation pressure from the pipe jacking machine can easily induce an excessive pushing and squeezing effect of the excavated soil with the uplift phenomenon, while the increasing grouting pressure can be used to reduce the overall vertical settlement of the ground surface, whereas an excessive grouting pressure may have no effectiveness on protecting the reinforced concrete circular pipes. This work provides the numerical foundations for investigating the behavior of jacked parallel large-size reinforced concrete circular pipes. Full article

(This article belongs to the Special Issue Tunneling and Underground Engineering: From Theories to Practices)

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14 pages, 3930 KiB

Open AccessArticle

Evaluation of Longitudinal Equivalent Bending Stiffness of Shield Tunnel with Residual Jacking Force

by Xuehui Jiang, Wenjun Luo, Bitang Zhu, Jianwei Yan and Tianyu Liu

Appl. Sci. 2023, 13(13), 7421; https://doi.org/10.3390/app13137421 - 22 Jun 2023

Cited by 1 | Viewed by 1259

Abstract

Existing tunnels are often subject to longitudinal bending when undercrossing tunnelling. It is of significance to more accurately evaluate the longitudinal equivalent bending stiffness (LEBS) of the existing tunnel within the influential zone. A new analytical method is proposed for the LEBS of [...] Read more.

Existing tunnels are often subject to longitudinal bending when undercrossing tunnelling. It is of significance to more accurately evaluate the longitudinal equivalent bending stiffness (LEBS) of the existing tunnel within the influential zone. A new analytical method is proposed for the LEBS of tunnel segmental lining joints with consideration of incorporating combined action of residual jacking force and bending moment. The solution can degenerate into a special case with no residual jacking force, which agrees well with other classical solutions and validates the model and solutions. Sensitivity analyses are carried out for the bending moment, tunnel geometry, tensile stiffness of bolts and concrete grade on the LEBS, and effective ratio of the LEBS considering residual jacking force. The LEBS and the effective ratio of LEBS increase nonlinearly as an S-curve with the residual jacking force and decrease with an increasing bending moment. The results show that the LEBS of the shield tunnel is variable stiffness, which exhibits a significant nonlinearity. The maximum increment of the LEBS reaches 80.3% as the ring width increases from 1 m to 2 m, and the LEBS of the shield tunnel increases by approximately 1.3 × 10⁷ kN·m² for every 4-bolt added. The influential order on the LEBS of shield tunnels is the tunnel diameter > lining thickness > bolts diameter > ring width > the number of bolts > elastic modulus of bolts. When the effective ratio of LEBS is more than 0.85, it does not change with the ring width, lining thickness, tensile stiffness of bolts, and concrete grade. The response characteristics of the tunnel parameters on the LEBS, considering the residual jacking force, could provide a theoretical basis for the design and deformation control of shield tunnels when undercrossing tunnelling. Full article

(This article belongs to the Special Issue Tunneling and Underground Engineering: From Theories to Practices)

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23 pages, 6508 KiB

Open AccessArticle

Study on Stratified Settlement and Weak Reflectivity Fiber Grating Monitoring of Shield Tunnel Crossing Composite Strata

by Fucai Zhao, Xingli Lu, Hongbing Shi, Bin Liu, Shaoran Liu, Kaohong Dai and Ying Fan

Appl. Sci. 2023, 13(3), 1769; https://doi.org/10.3390/app13031769 - 30 Jan 2023

Cited by 3 | Viewed by 1730

Abstract

This paper proposes a set of field test technology system for layered settlement of composite strata based on weak reflectivity fiber Bragg grating sensing technology based on the shield project of “Keyuan Station ~ Shenzhen University Station” section of Shenzhen Metro Line 13, [...] Read more.

This paper proposes a set of field test technology system for layered settlement of composite strata based on weak reflectivity fiber Bragg grating sensing technology based on the shield project of “Keyuan Station ~ Shenzhen University Station” section of Shenzhen Metro Line 13, and through the comparison and verification of three-dimensional numerical simulation and field monitoring, the law and distribution characteristics of disturbance settlement of ground surface and overlying strata during shield tunneling are systematically analyzed, and the vertical and horizontal zoning (layer) system for the spatial and temporal evolution of layered settlement of composite strata during shield tunneling is constructed. On this basis, the targeted settlement control technical measures and recommendations are proposed. The findings show that the weak reflectivity fiber grating sensing technology can better perceive the evolution law and distribution characteristics of vertical and horizontal settlement of composite strata caused by shield tunneling, which is in good agreement with the numerical simulation results, and has the advantages of automation and high precision, it can be used as a supplement and alternative method for traditional measurement methods. The stratum deformation is small and layered settlement is not obvious in shield approaching stage (−5D~0), after shield crossing and shield tail falling (0~3D), the stratum is the longitudinal main deformation zone of shield tunneling disturbance, and the influence range of the whole tunneling disturbance is about (−1D~3D). Meanwhile, according to the influence degree of shield tunneling disturbance, the overlying strata of the tunnel can be divided into main disturbance layer and secondary disturbance layer, and the main disturbance layer is located in the range of 0.5D above the tunnel. In addition, based on the different stages of shield tunneling and the vertical and horizontal zoning (layers) of existing structures such as buildings (structures), the settlement control measures and suggestions are proposed. The research results demonstrate the feasibility of weak reflectivity fiber grating for distributed and continuous strata monitoring. It has important guiding value for improving the understanding of settlement law produced from shield construction in composite strata and analyzing and predicting potential risks resulting from shield construction. It also provides reference value for future subway design and construction. Full article

(This article belongs to the Special Issue Tunneling and Underground Engineering: From Theories to Practices)

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27 pages, 5405 KiB

Open AccessArticle

Structural Evaluation of Cable Bolts under Static Loading

by Faham Tahmasebinia, Adam Yang, Patrick Feghali and Krzysztof Skrzypkowski

Appl. Sci. 2023, 13(3), 1326; https://doi.org/10.3390/app13031326 - 19 Jan 2023

Cited by 16 | Viewed by 2339

Abstract

Rock bursts are a natural phenomenon that are caused by high stresses and faults within the deep geological profile. The framework within deep mining excavations, comprising various rock and face supports such as cable bolts, is required to withstand rock bursts. These mechanisms [...] Read more.

Rock bursts are a natural phenomenon that are caused by high stresses and faults within the deep geological profile. The framework within deep mining excavations, comprising various rock and face supports such as cable bolts, is required to withstand rock bursts. These mechanisms are subject to static and dynamic loading conditions which possess unique challenges. This study focused on the shearing impact of static loads on cable bolts, a key structural support mechanism designed to absorb energy and investigate the impacts of bolt diameter and strength. A double shear test was modelled using the Finite Element Analysis (FEA) software ABAQUS/Explicit. A double shear test was modelled using Finite Element Modelling (FEM) by creating individual parts, assigning material and contact properties and applying a load directly on the central block. Because ABAQUS/Explicit was used, a primarily dynamic analysis tool, quasi-static loading, was applied to negate the natural time scale. A total of six bolt diameters and six bolt strengths were tested. A positive correlation was exhibited between the bolt diameter, yield strength and the maximum force and displacement. Full article

(This article belongs to the Special Issue Tunneling and Underground Engineering: From Theories to Practices)

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20 pages, 6541 KiB

Open AccessArticle

Research on the Interaction between the Pile and Shield Machine in the Process of Cutting a Reinforced Concrete Pile Foundation

by Xiaoyu Wang and Dajun Yuan

Appl. Sci. 2023, 13(1), 245; https://doi.org/10.3390/app13010245 - 25 Dec 2022

Cited by 5 | Viewed by 1737

Abstract

As the urban underground space environment gets more complex, the cases of shield machines encountering and cutting through piles are becoming more common. The interaction between the cutter head and pile foundation directly affects the tunneling performance of the shield machine and the [...] Read more.

As the urban underground space environment gets more complex, the cases of shield machines encountering and cutting through piles are becoming more common. The interaction between the cutter head and pile foundation directly affects the tunneling performance of the shield machine and the safety of the existing structure. To study the interaction between the pile and the shield machine, a calculation model of the interaction force is established. A field test of cutting two piles was conducted and the rationality of the model is verified by comparing the calculation results with field test data. The model is applied in the project of a shield machine cutting bridge piles in Harbin Metro Line 3, China. The shield operation parameters are predicted and compared with field test results. Besides, the impacts of cutting surface width and eccentric distance on interaction force are discussed. The study shows that there is a significant interaction between the cutter head and the piles when the shield machine cuts reinforced concrete piles, which causes obvious changes in the shield operation parameters and shield performance. The number of tools that are inside the cutting area has a significant effect on the additional torque. The additional torque fluctuates with the rotation of cutter head and increases with the increase of the number of tools. The number of these tools is determined by factors such as the layout of tools in the cutter head, cutting surface width and eccentric distance, which influence the position of each tool relative to the cutting area. As the cutting distance increase, the additional torque of the cutter head shows a trend of first increasing and then decreasing and reaches the maximum value when the cutting distance reaches the radius of the pile. Besides, the additional force and additional moment of the cutter head increase with the increase of the cutting surface width. The impacts of eccentric distance on additional force and additional moment are complicated. The results in this paper can provide reference for similar engineering. Full article

(This article belongs to the Special Issue Tunneling and Underground Engineering: From Theories to Practices)

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18 pages, 11462 KiB

Open AccessArticle

Active Bearing Technology of Foot Steel Pipe Applied in Controlling the Large Deformation of Tunnels: A Case Study

by Zhizhong Zhao, Yimin Wu, Lin Wang, Kaixun Hu and Changqing Tian

Appl. Sci. 2022, 12(22), 11716; https://doi.org/10.3390/app122211716 - 18 Nov 2022

Viewed by 1484

Abstract

Foot steel pipe was the main arch foot supporting structure to control large deformation of loess tunnels, but the supporting effect was not ideal. Taking Yulinzi Tunnel in Qingyang, Gansu Province, as the engineering background, the design concept and implementation scheme of a [...] Read more.

Foot steel pipe was the main arch foot supporting structure to control large deformation of loess tunnels, but the supporting effect was not ideal. Taking Yulinzi Tunnel in Qingyang, Gansu Province, as the engineering background, the design concept and implementation scheme of a foot steel pipe active bearing was put forward. The purpose was to solve the problem that it was difficult to control the surrounding rock settlement with the foot steel pipe. Numerical simulation and field experiments were used to verify the effect of the active bearing technology of the foot steel pipe. The main conclusions were as follows: (1) The effect of increasing the diameter of the foot steel pipe is better than that of increasing the number of foot steel pipes. (2) The active bearing mode of exerting its bearing capacity in advance by prepressing the foot steel pipe can effectively reduce the settlement of the vault. The settlement rate of the vault can be reduced by about 70% in 1–2 days and more than 50% in 1–3 days. (3) At the initial stage of surrounding rock deformation, this technology can provide a large bearing capacity, thereby reducing the overall deformation of the surrounding rock, slowing down the release of the surrounding rock pressure, and playing a positive role in the settlement control of the vault. Full article

(This article belongs to the Special Issue Tunneling and Underground Engineering: From Theories to Practices)

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20 pages, 6068 KiB

Open AccessArticle

Effects of Blasting Vibrations on an Arch in the Jiaohuayu Tunnel Described by Energy Response Spectrum Analysis

by Shijun Hou, Feng Xie, Shuaikang Tian and Shufeng Liang

Appl. Sci. 2022, 12(22), 11395; https://doi.org/10.3390/app122211395 - 10 Nov 2022

Cited by 2 | Viewed by 1327

Abstract

The vibrations caused by tunnel blasting strongly affects the construction safety and progress of the tunnel itself. The arch vibration attenuation law, structural energy response, and safety criterion were systematically investigated using blasting vibration monitoring in the Jiaohuayu Tunnel. The peak particle velocity [...] Read more.

The vibrations caused by tunnel blasting strongly affects the construction safety and progress of the tunnel itself. The arch vibration attenuation law, structural energy response, and safety criterion were systematically investigated using blasting vibration monitoring in the Jiaohuayu Tunnel. The peak particle velocity (PPV) at the vault was always larger than that at the arch waist and was greater than that at the sidewall, regardless of the direction. The arch waist was where the initial lining had the highest risk of damage. Existing safety criteria can be supplemented and improved using the maximum instantaneous input energy to measure the first passage damage, the hysteretic energy consumption to measure the cumulative damage, and the input-hysteretic energy criterion to judge the structural failure. The energy threshold of the first passage damage of the initial lining structure was 200 J, and the plastic cumulative damage was 3000 J of the test section. This study is important when evaluating the safety of a tunnel’s initial lining structure. Full article

(This article belongs to the Special Issue Tunneling and Underground Engineering: From Theories to Practices)

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19 pages, 10449 KiB

Open AccessArticle

Theoretical Analysis of Rock Blasting Damage in Construction of Tunnels Closely Under-Passing Sewage Box Culverts

by Jiancong Xu, Huihao Xue and Guorong Rui

Appl. Sci. 2022, 12(19), 9875; https://doi.org/10.3390/app12199875 - 30 Sep 2022

Viewed by 1597

Abstract

With the large-scale construction of urban traffic tunnels in China, it has become common to underpass existing buildings and structures such as sewage box culverts and pipelines using the drilling-blasting method. How to analyze accurately the blasting damage of surrounding rock and reasonably [...] Read more.

With the large-scale construction of urban traffic tunnels in China, it has become common to underpass existing buildings and structures such as sewage box culverts and pipelines using the drilling-blasting method. How to analyze accurately the blasting damage of surrounding rock and reasonably determine the safe distance between tunnel and box culvert or pipelines is an urgent issue to be solved. In this paper, the Cowper-Symonds plastic kinetic hardening model was improved using both rock initial damage degree and damage modification coefficient considering rock residual strength. The proposed model was implemented into LS-DYNA. The proposed damage model was used to evaluate the blasting construction of rock tunnels closely under-passing sewage box culverts. The results of numerical simulation using the proposed damage model shows that the blasting damage range of rock with a damage degree of more than 0.5 very significantly reduces from 1.0 m to 0.3 m as the spacing between the box culvert and the tunnel increases from 1.0 m to 4.0 m, and the evolution process of rock blasting damage can be well-presented. Moreover, the safe distance between tunnel and box culvert in blasting construction can be reasonably determined to be no less than 4.0 m. The findings in this paper could be significant for guiding the blasting construction of rock tunnels closely under-passing sewage box culverts. Full article

(This article belongs to the Special Issue Tunneling and Underground Engineering: From Theories to Practices)

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21 pages, 6608 KiB

Open AccessArticle

Numerical Investigation of Slurry Fracturing during Shield Tunneling under a Reservoir

by Bingyu Han, Dajun Yuan, Teng Wang and Zhongxin Wang

Appl. Sci. 2022, 12(15), 7929; https://doi.org/10.3390/app12157929 - 8 Aug 2022

Cited by 3 | Viewed by 1876

Abstract

The Jinan Jiluo Road Crossing the Yellow River Tunnel North Extension Project will intersect the Queshan reservoir, which currently supplies 60% of the domestic water in Jinan City. During the excavation process of the large-diameter slurry type shield used in this project, it [...] Read more.

The Jinan Jiluo Road Crossing the Yellow River Tunnel North Extension Project will intersect the Queshan reservoir, which currently supplies 60% of the domestic water in Jinan City. During the excavation process of the large-diameter slurry type shield used in this project, it may lead to slurry fracturing of the stratum in front of the excavation face and slurry blow-out from the surface if the slurry support pressure is too high. The leakage of shield slurry will pollute the reservoir water, and the safety of domestic water in Jinan will be threatened. Shield slurry blow-out may also lead to water inrush accidents. It is difficult to prevent slurry blow-out during shallow shield tunnel construction due to an insufficient understanding of the shield slurry fracturing mechanism. The initiation and extension of shield slurry fracturing are very complex and difficult to observe in the stratum. Currently, there is no effective method to study the slurry fracturing mechanism of shield tunneling. This paper presents a numerical simulation method of shield tunneling slurry fracturing based on the extended finite element method (XFEM). The risk of slurry blow-out in shield tunnel crossing reservoir engineering is analyzed. The advantages of the XFEM for simulating crack propagation are fully exploited. Considering the coexistence of tensile and shear failures in soft soils, embedding the combined tensile and shear failure criterion is realized in the XFEM by the secondary development of the ABAQUS extended finite element. Compared with the slurry fracturing test of blind-hole clay samples, the rationality of the simulation method for slurry fracturing in cohesive soil is verified. Through the establishment of the slurry fracturing extension model, the slurry fracturing process of shield tunneling in cohesive soil layer is simulated. The variation law of slurry pressure in the process of fracture extension is studied, and the influence of shield slurry support pressure, overburden thickness, formation shear strength, and slurry viscosity on fracture extension pressure and extension path is analyzed. Based on this numerical simulation method, the risk of slurry blow-out is analyzed in the shield tunneling intersecting the Queshan Reservoir of the Jinan Jiluo Road Crossing the Yellow River Tunnel North Extension Project. Full article

(This article belongs to the Special Issue Tunneling and Underground Engineering: From Theories to Practices)

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22 pages, 8880 KiB

Open AccessArticle

Model Test Study on a Shield Tunnel Adjacent to Pile in the Sub-Clay of a Coastal Area

by Xuan Guo, Zhitong Li, Xiaoli Zhang and Mengjun Pu

Appl. Sci. 2022, 12(15), 7718; https://doi.org/10.3390/app12157718 - 31 Jul 2022

Cited by 2 | Viewed by 1594

Abstract

In this study, a model test system of shield driving adjacent to pile is realized to study the response of surrounding rock and pile induced by an advanced shield tunnel in silty clay layer in a coastal area. The function of automatic pushing [...] Read more.

In this study, a model test system of shield driving adjacent to pile is realized to study the response of surrounding rock and pile induced by an advanced shield tunnel in silty clay layer in a coastal area. The function of automatic pushing and the synchronous grouting of the shield were partially simulated. Similar materials of lining, soft rock and pile, were developed. A total of 33 sets of orthogonal model tests were designed to study the progressive failure caused by excavation in silty clay and the change in stratum displacement and soil pressure; the displacement and internal force response of the pile were also analyzed. The following conclusions can be given: (1) the best grouting filling coefficient range of the shield test for the case study is 1.4 to 1.6; (2) the fitting of the experimental data to obtain the settlement through the width parameter suggests that the K value of the surrounding rock is decreased by 0.075 at least, and the K value increases with the increase in pile-tunnel distance and decreases with the increase in pile depth; and (3) the weak surrounding rock in the tunnel system can be divided into five zones according to the displacement and pressure change in soft surrounding rock and the pile response in the case study. The key condition control factor was also determined. Full article

(This article belongs to the Special Issue Tunneling and Underground Engineering: From Theories to Practices)

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11 pages, 3203 KiB

Open AccessArticle

Reliability and Efficiency of Metamodel for Numerical Back Analysis of Tunnel Excavation

by Yo-Hyun Choi and Sean Seungwon Lee

Appl. Sci. 2022, 12(14), 6851; https://doi.org/10.3390/app12146851 - 6 Jul 2022

Cited by 4 | Viewed by 1287

Abstract

During tunnel construction, the ground properties, initially evaluated, are continuously assessed and verified through back analysis. This procedure generally requires many numerical analyses, so a metamodel based on artificial neural networks has been used to reduce the number of analyses. More datasets can [...] Read more.

During tunnel construction, the ground properties, initially evaluated, are continuously assessed and verified through back analysis. This procedure generally requires many numerical analyses, so a metamodel based on artificial neural networks has been used to reduce the number of analyses. More datasets can be used to create more reliable metamodels. However, there are no established rules regarding the optimum number of datasets for a reliable metamodel. Metamodels predicting the vertical displacement of the tunnel crown using five ground parameters (unit weight (γ), uniaxial compressive strength (UCS), material constant m_i, geological strength index (GSI), and coefficient of lateral pressure (K)), with 3, 4, 6, 8, and 10 values per property, were created to confirm the reliability of the metamodel based on the number of datasets in this study. Metamodels using 6 and 8 values for each property showed 5% and 1% mean absolute percent errors, respectively. These numbers of each of the properties would be appropriate for developing the metamodel. Among the five parameters, only the results of the global sensitivity analyses of GSI and K are higher than 0.9. According to these results, it is verified that assessments based only on these parameters are sufficient in the back analysis. Full article

(This article belongs to the Special Issue Tunneling and Underground Engineering: From Theories to Practices)

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18 pages, 6159 KiB

Open AccessArticle

Centrifugal Model Test Study on the Mechanical Characteristics of Shield Tunnels Influenced by Different Types of Openings for Cross Passages

by Ping Lu, Dajun Yuan, Weiping Luo, Dalong Jin and Minggao Liu

Appl. Sci. 2022, 12(13), 6421; https://doi.org/10.3390/app12136421 - 24 Jun 2022

Cited by 2 | Viewed by 1631

Abstract

To investigate the mechanical characteristics of shield tunnels when openings are made for the construction of cross passages, a series of centrifugal model tests were conducted. The segmental features of the shield tunnel were simulated in the tests, and the influence of different [...] Read more.

To investigate the mechanical characteristics of shield tunnels when openings are made for the construction of cross passages, a series of centrifugal model tests were conducted. The segmental features of the shield tunnel were simulated in the tests, and the influence of different types of openings, namely, rectangular opening, small circular opening, and big circular opening was compared. External earth pressures, structural deformations, dislocations, and structural stresses were monitored during the tests, while the influence of different buried depths was also investigated. The results show that (1) soil arching effect occurred in the overlying soil due to the deformation of the tunnel, and the earth pressure reduction coefficients can guide the tunnel structural design; (2) vertical deformations of the main tunnel and the dislocations between adjacent rings increased with the opening sizes significantly; (3) significant stress concentration occurred close to the openings, and the compressive stress at the inner surface may even exceed the limit strength of the concrete. In summary, the adverse responses of the tunnel increased with the increase of the buried depth and the opening size. Targeted measures should be taken, such as temporary support, longitudinal connections, and high-strength materials near the openings. Full article

(This article belongs to the Special Issue Tunneling and Underground Engineering: From Theories to Practices)

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22 pages, 1032 KiB

Open AccessArticle

Early Warning of the Construction Safety Risk of a Subway Station Based on the LSSVM Optimized by QPSO

by Leian Zhang, Junwu Wang, Han Wu, Mengwei Wu, Jingyi Guo and Shengmin Wang

Appl. Sci. 2022, 12(11), 5712; https://doi.org/10.3390/app12115712 - 3 Jun 2022

Cited by 5 | Viewed by 2108

Abstract

Subway station projects are characterized by complex construction technology, complex site conditions, and being easily influenced by the surrounding environment; thus, construction safety accidents occur frequently. In order to improve the computing performance of the early risk warning system in subway station construction, [...] Read more.

Subway station projects are characterized by complex construction technology, complex site conditions, and being easily influenced by the surrounding environment; thus, construction safety accidents occur frequently. In order to improve the computing performance of the early risk warning system in subway station construction, a novel model based on least-squares support vector machines (LSSVM) optimized by quantum-behaved particle swarm optimization (QPSO) was proposed. First, early warning factors from five aspects (man, machine, management, material, and the environment) were selected based on accident causation theory and literature research. The data acquisition method of each risk factor was provided in detail. Then, the LSSVM with strong small sample analysis and nonlinear analysis abilities was chosen to give the early warning. To further ameliorate the early warning accuracy of the LSSVM, QPSO with a strong global retrieval ability was used to find the optimal calculation parameters of the LSSVM. Seventeen subway stations of Chengdu Metro Line 11 in China were picked as the empirical objects. The results demonstrated that the best regularization parameter was 1.742, and the best width parameter was 14.167. The number of misjudged samples of the proposed model was 1, and the early warning error rate was only 4.41%, which met the needs of engineering practice. Compared with the classic and latest methods, the proposed model was found to have a faster prediction speed and higher prediction accuracy. Full article

(This article belongs to the Special Issue Tunneling and Underground Engineering: From Theories to Practices)

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20 pages, 3958 KiB

Open AccessArticle

Prediction of EPB Shield Tunneling Advance Rate in Mixed Ground Condition Using Optimized BPNN Model

by Xuesong Fu, Quanmei Gong, Yaojie Wu, Yu Zhao and Hui Li

Appl. Sci. 2022, 12(11), 5485; https://doi.org/10.3390/app12115485 - 28 May 2022

Cited by 5 | Viewed by 2149

Abstract

Tunneling in mixed ground often results in severe torque fluctuations and a low advance rate. Therefore, choosing a reasonable set of parameters for accurate advance rate prediction is paramount to reduce cutter wear and improve tunneling efficiency. However, since the geological parameters in [...] Read more.

Tunneling in mixed ground often results in severe torque fluctuations and a low advance rate. Therefore, choosing a reasonable set of parameters for accurate advance rate prediction is paramount to reduce cutter wear and improve tunneling efficiency. However, since the geological parameters in mixed ground conditions are diverse and uncertain, the prediction of the advance rate (AR) of EPB shield tunneling is significantly more difficult than that in homogeneous ground (i.e., full-face hard-rock ground). In addition, the operating parameters of the EPB shield tunneling can be subjective and suboptimal, and each of them has some intricate influence on AR. In this paper, an optimized back-propagation neural network by genetic algorithm (BPNN-GA) was proposed for reasonable operating parameter selection and accurate AR prediction, and four typical machine learning methods were used for comparison. Five processing strategies with different input parameters were also proposed and compared to determine the optimum selection of geological parameters in mixed ground conditions. The proposed models with strategies were adopted in the case study of the Nanjing Metro Line S6 project, and a total of 1188 rings of datasets were used for this study. The results showed that the proposed modified BPNN with the genetic algorithm could be effectively implemented for the AR prediction. It concluded that Strategy B—i.e., using the composite ratio and the geological parameters of each layer as input—was the best strategy in mixed ground conditions for advance rate prediction. Hence, a high correlation between measured and predicted AR was observed in this study with a correlation coefficient (R²) of 0.920. Full article

(This article belongs to the Special Issue Tunneling and Underground Engineering: From Theories to Practices)

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16 pages, 3693 KiB

Open AccessArticle

Mechanical Behavior of Large-Diameter Adjacent Shield Tunnelling Bridge Piles: A Case Study of Chunfeng Tunnel

by Jingang Wu, Jinpeng Zhao, Zhongsheng Tan, Xiangyu Liu, Xia Wang and Minggao Liu

Appl. Sci. 2022, 12(11), 5418; https://doi.org/10.3390/app12115418 - 27 May 2022

Cited by 5 | Viewed by 2090

Abstract

When a large-diameter shield crosses through bridge piles, stress and deformation of the bridge piles caused by tunnel excavation occurs. This is a an exciting topic of engineering research into the construction of subways. We considered an 15.8 m large-diameter shield machine made [...] Read more.

When a large-diameter shield crosses through bridge piles, stress and deformation of the bridge piles caused by tunnel excavation occurs. This is a an exciting topic of engineering research into the construction of subways. We considered an 15.8 m large-diameter shield machine made in China to excavate the Chunfeng tunnel as the background of our research. First, based on the previous engineering experience, reinforcement measures of the shield crossing the bridge piles were investigated. PLAXIS 3D finite element software was used to simulate the process of shield tunnelling through the piles of Hongling Interchange No. 1 Bridge. We analyzed the mechanical characteristics of the piles in the process of shield tunnelling through the bridge piles and evaluated the reliability of the reinforcement measures. Finally, combined with field monitoring data, the accuracy of the model and the rationality of the treatment measures were verified. This research considered a successful case of 15.8 m large-diameter adjacent shield tunnelling bridge piles. Analysis of the stratum and the mechanical behavior of bridge piles in the process of crossing provides a theoretical reference for engineering measures on similar projects in the future. Full article

(This article belongs to the Special Issue Tunneling and Underground Engineering: From Theories to Practices)

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17 pages, 8966 KiB

Open AccessArticle

Prediction of Ground Surface Settlements Induced by EPB Shield Tunneling in Water-Rich Soft Strata

by Yi Yang, Xinggao Li, Dalong Jin, Xingqi Jiang and Hanyuan Li

Appl. Sci. 2022, 12(9), 4665; https://doi.org/10.3390/app12094665 - 6 May 2022

Cited by 4 | Viewed by 2006

Abstract

The main goal of this study is to enhance the prediction of ground surface settlements induced by Earth pressure balance (EPB) shield tunneling. In the setting of Changzhou, China, a comprehensive database of long-term ground-displacement findings from Metro Lines No. 1 and No. [...] Read more.

The main goal of this study is to enhance the prediction of ground surface settlements induced by Earth pressure balance (EPB) shield tunneling. In the setting of Changzhou, China, a comprehensive database of long-term ground-displacement findings from Metro Lines No. 1 and No. 2 was analyzed with the goal of assessing the parameters characterizing the settlement, i.e., volume loss, trough width parameter. For the metro lines in the water-rich soft strata of Changzhou, the ground loss V_l is usually in the range of 0.1–0.75%, and the trough width parameter K is usually in the range from 0.3 to 0.7. A superposition analytical method is proposed to estimate the short-term ground settlements induced by shield tunneling, with attention given to ground loss as well as shield working loads. The suggested analytical approach was found to be in good agreement with the field measurements in the case of EPB shield tunneling. This study can provide a reliable assessment of the long-term as well as short-term ground surface settlements for tunnel design. Full article

(This article belongs to the Special Issue Tunneling and Underground Engineering: From Theories to Practices)

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17 pages, 5279 KiB

Open AccessArticle

Ground Settlement Due to Tunneling in Cohesionless Soil

by Mohammad Faraz Athar, Md Rehan Sadique, Abdullah H. Alsabhan and Shamshad Alam

Appl. Sci. 2022, 12(7), 3672; https://doi.org/10.3390/app12073672 - 6 Apr 2022

Cited by 3 | Viewed by 3330

Abstract

By the year 2035 it is estimated that Delhi and Mumbai will become two of the most populous cities around the globe. The massive population growth rate has led to the rise of land scarcity, urbanization, and industrialization and developments for rapid transit [...] Read more.

By the year 2035 it is estimated that Delhi and Mumbai will become two of the most populous cities around the globe. The massive population growth rate has led to the rise of land scarcity, urbanization, and industrialization and developments for rapid transit systems have made accordingly. Modern rapid transit systems comprise Metro rails and subways etc., and increase underground-construction activities. Nowadays, the tunnel-construction process heavily relies on massive machineries such as tunnelling-boring machines (TBM) and operations that produce great hindrance in the soil mass resulting in ground settlement at the surface. This study aimed to address these issues through small-scale laboratory experiments and further amplification to real-valued problems utilizing numerical methods. A cubic box of edge length 1 m made up of mild steel was generated to simulate a tunnelling operation and aluminum-made lining were used to simulate concrete tunnel linings. A finite element-based numerical investigation was done for a 2D elastoplastic numerical tunnel model with dimensions of 42 m × 42 m. Analysis was carried out on Optum G2 software. The analyzed variations in lining shapes of lining included circular, horseshoe, arch, elliptical, and square. Results showed that elliptical-shaped linings experienced the least ground settlement and these are recommended for places where surface settlement may cause major damage. It is also recommended that square-shaped linings should not be used in such situations due their higher settlement values. Full article

(This article belongs to the Special Issue Tunneling and Underground Engineering: From Theories to Practices)

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16 pages, 3725 KiB

Open AccessArticle

Short-Term and Long-Term Displacement of Surface and Shield Tunnel in Soft Soil: Field Observations and Numerical Modeling

by Hui Jin, Dajun Yuan, Shunxin Zhou and Di Zhao

Appl. Sci. 2022, 12(7), 3564; https://doi.org/10.3390/app12073564 - 31 Mar 2022

Cited by 15 | Viewed by 2413

Abstract

Constructing subways in soft soil strata by shields may cause large displacement of ground and tunnels during and after construction. To evaluate the corresponding short-term and long-term displacement, this paper presented a three-dimensional numerical model based on the project of Suzhou rail transit [...] Read more.

Constructing subways in soft soil strata by shields may cause large displacement of ground and tunnels during and after construction. To evaluate the corresponding short-term and long-term displacement, this paper presented a three-dimensional numerical model based on the project of Suzhou rail transit line S1. This model adopted the modified Cam-clay model to simulate the behavior of soft soil and can consider the grouting parameters and the water leakage of the assembled segment lining. In addition, an on-site monitoring project was implemented, and the field observations were compared with the simulation results. Finally, the sensitivity of key parameters was carried out by the established numerical model. The results indicated that the grouting volume, the thicknesses of soft soil under the tunnel, and the tunnel leakage conditions have a significant impact on the ground and tunnel settlement. Notably, serious tunnel leakage will cause large long-term consolidation settlement, and the increasing thicknesses of soft soil under the tunnel does not increase the long-term settlement of the stratum and the tunnel when the tunnel meets the secondary waterproof requirements, but does increase the corresponding short-term settlement. Full article

(This article belongs to the Special Issue Tunneling and Underground Engineering: From Theories to Practices)

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20 pages, 4731 KiB

Open AccessArticle

Analytical Solution and Shaking Table Test on Tunnels through Soft-Hard Stratum with a Transition Tunnel and Flexible Joints

by Gaoming Yan and Boming Zhao

Appl. Sci. 2022, 12(6), 3151; https://doi.org/10.3390/app12063151 - 19 Mar 2022

Cited by 8 | Viewed by 2093

Abstract

Tunnels, where they pass through soft-hard strata, are severely damaged during earthquakes. These issues have not yet been well understood. In this study, the seismic performances of a tunnel passing through soft-hard stratum with a transition tunnel and flexible joints under earthquake motion [...] Read more.

Tunnels, where they pass through soft-hard strata, are severely damaged during earthquakes. These issues have not yet been well understood. In this study, the seismic performances of a tunnel passing through soft-hard stratum with a transition tunnel and flexible joints under earthquake motion were investigated by proposed analytical solutions and scaled shaking table tests. First, a mechanical model of a tunnel passing through soft-hard stratum with flexible joints is proposed, and it is derived by the Green’s function method. Then, a parametric analysis is conducted to investigate the effects of important variables on tunnels through soft-hard stratum. Finally, shaking table tests are conducted to verify the proposed solution and further investigate the seismic behaviors of the tunnel. The results show that: (1) the analytical solutions are workable and effective; (2) the influence of the soft-hard stratum junction on the tunnel responses is remarkable—the largest bending moment is located at the side of soft rock near the sharp contact area and the maximum shear force appears at the contact; (3) the joints and the transition tunnel could mitigate the potential adverse effects of the sharp contact area—the region affected by the joint is approximately 4.5 times the tunnel diameter on both sides of the stratum interface; and (4) the influence of sharp change of ground layers is more remarkable with a larger excitation amplitude. Full article

(This article belongs to the Special Issue Tunneling and Underground Engineering: From Theories to Practices)

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12 pages, 4984 KiB

Open AccessArticle

Highway Tunnel Defect Detection Based on Mobile GPR Scanning

by Junli Zhai, Qiang Wang, Haozheng Wang, Xiongyao Xie, Mingyi Zhou, Dongyang Yuan and Weikang Zhang

Appl. Sci. 2022, 12(6), 3148; https://doi.org/10.3390/app12063148 - 19 Mar 2022

Cited by 5 | Viewed by 2414

Abstract

In order to overcome the difficulty in rapid detection for expressway tunnels, the coherence calculation of dual-frequency radar signal in the time domain is proposed to suppress the interference. A dual-frequency (400 MHz and 900 MHz) GPR and a manipulator are developed. In [...] Read more.

In order to overcome the difficulty in rapid detection for expressway tunnels, the coherence calculation of dual-frequency radar signal in the time domain is proposed to suppress the interference. A dual-frequency (400 MHz and 900 MHz) GPR and a manipulator are developed. In the horizontal direction, it has a −90°~90° range, a vertical rotation range from 0 to 90°, a length range from 5~9.5 m, and an antenna rotation between −40°~40°. The mobile scanning has been realized in the expressway tunnel, taking the vehicle as the mobile carrier. The research shows that: This equipment realizes the rapid detection of the tunnel without affecting the expressway’s opening. The imaging algorithm recognizes the structural thickness, reinforcement distribution characteristics, and structural diseases. According to the detection carried out in Zhejiang, China, the spacing between reinforcement in the second lining is 4 cm, and the thickness of the structure is about 0.55 m. However, the reinforcement has deformed badly, and the defects are also discerned in the structure. Compared with the traditional handheld radar detection, the equipment dramatically reduces the labor demand, time, and cost and can meet engineering needs. With the proposed method, the detection time is reduced to 12 min/km from 0.5 d/km, and the cost is reduced by more than two times. Furthermore, during the detection, the traffic can be maintained normally. Full article

(This article belongs to the Special Issue Tunneling and Underground Engineering: From Theories to Practices)

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21 pages, 5942 KiB

Open AccessArticle

Study on Longitudinal Stress Relaxation Effect and Reinforcement Technology of Segment Lining during Shield Docking

by Zhe Geng, Dajun Yuan, Dan Wang, Yajie Zhao and Tingwei Xie

Appl. Sci. 2022, 12(6), 2831; https://doi.org/10.3390/app12062831 - 9 Mar 2022

Cited by 4 | Viewed by 1961

Abstract

Shield docking technology is widely used in underwater shield tunnels. As the technology is not perfect, the instability of the tunnel face and the stress relaxation of segment lining caused by shield dismantling need to be solved. Using a cross-sea tunnel project, the [...] Read more.

Shield docking technology is widely used in underwater shield tunnels. As the technology is not perfect, the instability of the tunnel face and the stress relaxation of segment lining caused by shield dismantling need to be solved. Using a cross-sea tunnel project, the segment lining reinforcement technology with steel channel in the process of shield docking is studied. The longitudinal stress relaxation effect of segment lining after thrust unloading is analyzed, and the theoretical solution of segment circumferential joint opening, with or without steel channel reinforcement, is derived. The accuracy of the theoretical model and the shell connector numerical model is verified by comparison. Then, the influence of key parameters, such as reinforcement range, steel channel quantity and steel channel model, on reinforcement effect is discussed. The results show that: (1) with the increase in the range of reinforcement, the maximum longitudinal displacement and the opening of the circumferential joints decrease first and then increase; (2) with the increase in the quantity and model of the steel channel, the maximum longitudinal displacement and the opening of the circumferential joints gradually decrease, and the reduction rate also decreases. The farther away from the shield tail, the weaker the reinforcement effect on segment lining. Full article

(This article belongs to the Special Issue Tunneling and Underground Engineering: From Theories to Practices)

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18 pages, 5528 KiB

Open AccessArticle

Design of Fast Acquisition System and Analysis of Geometric Feature for Highway Tunnel Lining Cracks Based on Machine Vision

by Haozheng Wang, Qiang Wang, Junli Zhai, Dongyang Yuan, Weikang Zhang, Xiongyao Xie, Biao Zhou, Jielong Cai and Yuanshuai Lei

Appl. Sci. 2022, 12(5), 2516; https://doi.org/10.3390/app12052516 - 28 Feb 2022

Cited by 4 | Viewed by 2217

Abstract

Under the dual effects of the rapid growth of tunnel mileage and operating years, the application and research of tunnel crack identification based on machine vision are increasing with the vigorous development of machine vision. However, due to the complex environment in tunnels, [...] Read more.

Under the dual effects of the rapid growth of tunnel mileage and operating years, the application and research of tunnel crack identification based on machine vision are increasing with the vigorous development of machine vision. However, due to the complex environment in tunnels, it is difficult to quickly obtain tunnel lining cracks via computer visions in the tunnel. Therefore, this paper presents the design of a fast acquisition system with the geometric feature analysis for tunnel lining cracks, which has been integrated into a tunnel fast inspection vehicle with a machine vision module. Through the research on the image acquisition system of the tunnel lining, the parameter selection of the crack shooting hardware system is determined, and the fast calculation method of shooting parameters is proposed. The geometric characteristic analysis of the tunnel lining crack image is employed to calculate crack width and determine the optimal gray value of crack extraction. Field tests have been conducted in the highway tunnels in Zhejiang and Yunnan provinces in China and the result indicates that the proposed approach yields much better performance in the detection efficiency, whose time of detection is only 1%, and the number of personnel required is only 40% of the traditional pure manual method. Compared with similar systems, it also has significant advantages in crack resolution and detection speed. This research provides a means of rapid acquisition of tunnel cracks and laying a foundation for the evaluation of the service performance of the tunnel. Full article

(This article belongs to the Special Issue Tunneling and Underground Engineering: From Theories to Practices)

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18 pages, 9290 KiB

Open AccessArticle

Development and Application of a New Reduction Coefficient of Water Pressure on Sub-Sea Tunnel Lining

by Jinpeng Zhao, Zhongsheng Tan and Ning Ma

Appl. Sci. 2022, 12(5), 2496; https://doi.org/10.3390/app12052496 - 27 Feb 2022

Cited by 4 | Viewed by 2279

Abstract

Limited drainage tunnels face pore water pressure, water inflow, and permeability challenges. At present, there is little systematic analysis and research on the lining water pressure of sub-sea tunnels, and there is a lack of verification of relevant engineering examples and field monitoring [...] Read more.

Limited drainage tunnels face pore water pressure, water inflow, and permeability challenges. At present, there is little systematic analysis and research on the lining water pressure of sub-sea tunnels, and there is a lack of verification of relevant engineering examples and field monitoring data. Based on the numerical simulation method, this paper discusses the lining water pressure and its reduction coefficient of the horseshoe section tunnel, which is verified by an engineering example. Based on many numerical simulations, the recommended value of the water pressure reduction coefficient considering the thickness of the grouting ring and grouting effect is put forward. The stress law and safety of tunnel lining under different water reduction coefficients are studied, and the safety of lining is evaluated combined with the measured data of lining stress. The results show that the numerical simulation has been well verified. Considering the water pressure according to the water pressure reduction coefficient method proposed in this paper can ensure the structural safety of tunnel lining. The method of lining water pressure reduction coefficient proposed in this paper can provide a reference for the subsequent lining design of the sub-sea tunnel. Full article

(This article belongs to the Special Issue Tunneling and Underground Engineering: From Theories to Practices)

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18 pages, 1421 KiB

Open AccessArticle

Construction Risk Assessment of Deep Foundation Pit Projects Based on the Projection Pursuit Method and Improved Set Pair Analysis

by Long Zhang and Hongbing Li

Appl. Sci. 2022, 12(4), 1922; https://doi.org/10.3390/app12041922 - 12 Feb 2022

Cited by 23 | Viewed by 3249

Abstract

Accurately evaluating the construction risk of deep foundation pit projects is crucial to formulate science-based risk response measures. Here, we propose a novel construction risk assessment method for deep foundation pit projects. A construction risk evaluation index system based on a work breakdown [...] Read more.

Accurately evaluating the construction risk of deep foundation pit projects is crucial to formulate science-based risk response measures. Here, we propose a novel construction risk assessment method for deep foundation pit projects. A construction risk evaluation index system based on a work breakdown structure-risk breakdown structure matrix was established to deal with the complex risks of deep foundation pit construction. The projection pursuit method optimized by particle swarm optimization was used to extract the structural features from the evaluation data to obtain objective index weights. The calculation method of the five-element connection number in the set pair analysis was improved to evaluate the static construction risk. The partial derivatives of the five-element connection number were utilized to assess the dynamic construction risk. The Qi ‘an Fu deep foundation pit project in China was selected as a case study. The results show that the construction risk was acceptable and decreased during the construction period, which was consistent with actual conditions, demonstrating the effectiveness of this novel method. The proposed model showed better performance than classical methods (analytic hierarchy process, entropy weight method, classical set pair analysis, fuzzy comprehensive evaluation, gray clustering method, backpropagation neural network, and support vector machine). Full article

(This article belongs to the Special Issue Tunneling and Underground Engineering: From Theories to Practices)

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15 pages, 3989 KiB

Open AccessArticle

An Improved Analytical Approach for Segmental Joint Rotational Behavior Considering the Elastic Gasket

by Ming Huang and Fan Yang

Appl. Sci. 2022, 12(3), 1512; https://doi.org/10.3390/app12031512 - 30 Jan 2022

Viewed by 1951

Abstract

To fully consider the effect of elastic gasket (EG) on the segmental joint rotational behavior, an improved analytical approach is proposed to simulate the joint rotations and obtain the rotational stiffnesses. By comparing the analytical results with the experimental results and numerical results, [...] Read more.

To fully consider the effect of elastic gasket (EG) on the segmental joint rotational behavior, an improved analytical approach is proposed to simulate the joint rotations and obtain the rotational stiffnesses. By comparing the analytical results with the experimental results and numerical results, the joint compression zone should be simulated by the concrete–EG–concrete (CGC) model instead of rigid–EG–rigid (RGR) model or concrete–concrete (CC) model. Since the analytical approach with the CGC model can simulate the combined work of EG and concrete well, it is a more effective approach to obtain the joint rotational stiffnesses. According to these analytical results, the EG has a great impact on softening the joint rotations, and this leads the rotational stiffnesses of the joint with EG to be evidently smaller than those of the joint without EG. In addition, with decreasing the axial force or increasing the EG thickness, this softening effect tends to be more obvious. Therefore, the EG is a significant factor which should be fully considered during the theoretical analysis for the joint rotation behavior, or it may lead to an unreliable design for the segmental lining. Full article

(This article belongs to the Special Issue Tunneling and Underground Engineering: From Theories to Practices)

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17 pages, 3394 KiB

Open AccessArticle

Kinematic Analysis and Virtual Prototype Simulation of the Thrust Mechanism for Shield Machine

by Xuyang Wang, Dajun Yuan, Xiaoyu Wang and Jin Wu

Appl. Sci. 2022, 12(3), 1431; https://doi.org/10.3390/app12031431 - 28 Jan 2022

Cited by 6 | Viewed by 2701

Abstract

The hydraulic thrust system of the shield machine is used for driving forward and pose adjustment. It is of great significance to figure out the thrust mechanism and motion characteristics of the shield machine to ensure the safety of tunnel excavation. This study [...] Read more.

The hydraulic thrust system of the shield machine is used for driving forward and pose adjustment. It is of great significance to figure out the thrust mechanism and motion characteristics of the shield machine to ensure the safety of tunnel excavation. This study aims to develop a model to explore the influence of thrust cylinder advancement on the motions of the shield machine. Firstly, the study carried out mechanism analysis of the thrust mechanism for the shield machine and established a method to describe the position and attitude of the shield machine during the tunneling process by the homogeneous transformation matrix. Then, a new inverse kinematic model was proposed to quantify the relationship between the telescoping movements of cylinders and shield machine motions, and the Jacobian matrix was derived to solve the instantaneous kinematics analysis. Furthermore, a virtual prototype model was developed to simulate the kinematic behavior of the shield machine and validate the accuracy of the kinematic model. The model provides the basic constraint relations for the practical position control system and lays a strong foundation for the dynamic model and automatic trajectory tracking control of shield machines for future studies. Based on the proposed model, the displacement, velocity, and acceleration of cylinders that drive the shield machine to the target motions can be solved exactly. It can provide a reference for the pose control of the shield machine during the practical shield tunneling. Full article

(This article belongs to the Special Issue Tunneling and Underground Engineering: From Theories to Practices)

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15 pages, 4841 KiB

Open AccessArticle

A New Calculation Method of Cutterhead Torque Considering Shield Rolling Angle

by Xiang Shen, Dajun Yuan, Dalong Jin and Chengyong Cao

Appl. Sci. 2022, 12(1), 396; https://doi.org/10.3390/app12010396 - 31 Dec 2021

Cited by 3 | Viewed by 2367

Abstract

The existing cutterhead torque calculation method usually simplifies the characteristics of the shield, which ignores the rolling angle. In this paper, the cross-river shield project of Wuhan Metro Line 8 is taken as the research focus. Firstly, the measured data of the cutterhead [...] Read more.

The existing cutterhead torque calculation method usually simplifies the characteristics of the shield, which ignores the rolling angle. In this paper, the cross-river shield project of Wuhan Metro Line 8 is taken as the research focus. Firstly, the measured data of the cutterhead torque (CT), the rolling angle and rotation direction were analyzed. Then on this basis, the penetrability, tunneling thrust, and rolling angle were taken as the influential factors to analyze CT sensitivity. Finally, based on the theoretical calculation model, a modified solution of CT was obtained considering the rolling angle. The results show that the rolling angle can be reduced to zero by changing the direction of the cutterhead rotation; the rolling angle has a greater impact on CT than the other two factors as shown through the analysis of the range difference and Statistical Product and Service Solutions (SPSS) method. As the absolute value of the rolling angle increases, CT also increases, and the relationship between them is linear. To a certain extent, the rolling angle of the shield can reflect the difficulty of tunneling and the running status. By monitoring the rolling angle of the shield, the prediction of CT can be more in line with the actual construction conditions. Full article

(This article belongs to the Special Issue Tunneling and Underground Engineering: From Theories to Practices)

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17 pages, 8981 KiB

Open AccessArticle

Experimental Study on Electrical Resistivity Characteristics of Saturated Sand Mixes with Bentonite Slurry

by Jiahua Mao, Dajun Yuan, Dalong Jin, Binghui Wang and Shangkun Wu

Appl. Sci. 2021, 11(24), 12126; https://doi.org/10.3390/app112412126 - 20 Dec 2021

Cited by 3 | Viewed by 2612

Abstract

Bentonite slurry is widely used in underground and geotechnical engineering because of its strong ability of wall protection. Slurry penetration, which is of great significance for the soil stability, is difficult to observe directly during the soil and slurry interaction. Slurry penetration would [...] Read more.

Bentonite slurry is widely used in underground and geotechnical engineering because of its strong ability of wall protection. Slurry penetration, which is of great significance for the soil stability, is difficult to observe directly during the soil and slurry interaction. Slurry penetration would change the electrical resistivity of soil, which provides an indirect method to monitor the degree of slurry penetration. This paper aimed to investigate the electrical resistivity characteristics of soil-bentonite mixtures. Several test groups with different material components were carried out. The effects of some factors including water environment, CMC (carboxymethyl cellulose) contents, soil particle gradation, and electrode distance on the electrical resistivity of slurry-soil mixtures were studied and the relationship between soil electrical resistivity and slurry concentration was established. The results in this paper can provide references for the application of the electrical method on slurry penetration. Full article

(This article belongs to the Special Issue Tunneling and Underground Engineering: From Theories to Practices)

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24 pages, 7051 KiB

Open AccessArticle

Dynamic Risk Assessment of Ultra-Shallow-Buried and Large-Span Double-Arch Tunnel Construction

by Jianxiu Wang, Ansheng Cao, Zhao Wu, Zhipeng Sun, Xiao Lin, Lei Sun, Wuji Liu, Xiaotian Liu, Huboqiang Li, Yuanwei Sun and Yanxia Long

Appl. Sci. 2021, 11(24), 11721; https://doi.org/10.3390/app112411721 - 10 Dec 2021

Cited by 6 | Viewed by 2849

Abstract

Ultra-shallow-buried and large-span double-arch tunnels face complex risks during construction. The risk sources are hidden, complicated, and diverse. The dynamic risk assessment problem cannot be solved satisfactorily by using the static method as an insufficient amount of research has been conducted. The land [...] Read more.

Ultra-shallow-buried and large-span double-arch tunnels face complex risks during construction. The risk sources are hidden, complicated, and diverse. The dynamic risk assessment problem cannot be solved satisfactorily by using the static method as an insufficient amount of research has been conducted. The land part of the Xiamen Haicang double-arch tunnel was selected as the background for the dynamic risk assessment of ultra-shallow-buried and large-span double-arch tunnel construction. The construction process was divided into five stages: pre-construction preparation; ground and surrounding rock reinforcement; pilot tunnel excavation; and the single-and the double-tunnel excavations of the main tunnel. Through consultation with tunnel experts, six first-level and thirty second-level risk evaluation indexes were proposed. The benchmark weight of the dynamic risk assessment index was determined by using the analytic hierarchy process. The weight of the risk evaluation index was revised according to the monitoring data and the construction stage. The fuzzy evaluation matrix of the construction risk membership degree was obtained by using the fuzzy comprehensive assessment method, and the calculation results were analyzed using the subsection assignment method. Control measures were suggested according to the risk assessment results. The risk assessment result of the double tunnel excavation stage of the main tunnel was level II, and the risk level was the highest among the five construction stages. The risk assessment result of the ground and surrounding rock reinforcement stage was level IV, and the risk level was the lowest. The dynamic construction safety risk assessment based on the fuzzy comprehensive assessment method is more timely, accurate, and reasonable than the traditional assessment method. The method can be adopted in similar engineering projects. Full article

(This article belongs to the Special Issue Tunneling and Underground Engineering: From Theories to Practices)

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19 pages, 11854 KiB

Open AccessArticle

Numerical Simulation of Rock Mass Structure Effect on Tunnel Smooth Blasting Quality: A Case Study

by Jianxiu Wang, Ansheng Cao, Jiaxing Liu, Huanran Wang, Xiaotian Liu, Huboqiang Li, Yuanwei Sun, Yanxia Long and Fan Wu

Appl. Sci. 2021, 11(22), 10761; https://doi.org/10.3390/app112210761 - 15 Nov 2021

Cited by 6 | Viewed by 2165

Abstract

Taking the Zigaojian tunnel, Hangzhou–Huangshan high-speed railway, China, as background, the rock mass structure effect on smooth blasting quality was studied. Four rock mass structures were determined on the basis of the information collected on the tunnel site. Smooth blasting finite element models [...] Read more.

Taking the Zigaojian tunnel, Hangzhou–Huangshan high-speed railway, China, as background, the rock mass structure effect on smooth blasting quality was studied. Four rock mass structures were determined on the basis of the information collected on the tunnel site. Smooth blasting finite element models were established using LS-DYNA. The accuracy of the numerical calculation model was verified by comparing the overbreak and underbreak between the numerical simulation and monitoring. Orthogonal numerical test was used to study the rock mass structure effect through single factor and main effect analysis methods. With the decrease in rock mass integrity, the smooth blasting overbreak of tunnels with massive integrity structure, massive structure, layered structure, and cataclastic structure increased. For massive integrity structure and cataclastic structure, the peripheral hole spacing should be emphatically considered. Meanwhile, in massive structure and layered structure, the included angle and spacing of structural planes had a great influence on the smooth blasting quality. The research results could provide a reference to improve the quality of similar tunnel smooth blasting. Full article

(This article belongs to the Special Issue Tunneling and Underground Engineering: From Theories to Practices)

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Review

Jump to: Research

25 pages, 2671 KiB

Open AccessReview

Review on Early Warning Methods for Rockbursts in Tunnel Engineering Based on Microseismic Monitoring

by Shichao Zhang, Chunan Tang, Yucheng Wang, Jiaming Li, Tianhui Ma and Kaikai Wang

Appl. Sci. 2021, 11(22), 10965; https://doi.org/10.3390/app112210965 - 19 Nov 2021

Cited by 9 | Viewed by 2763

Abstract

Due to the different geological conditions and construction methods associated with different projects, rockbursts in deep-buried tunnels often present different precursor characteristics, bringing major challenges to the early warning of rockbursts. To adapt to the complexity of engineering, it is necessary to review [...] Read more.

Due to the different geological conditions and construction methods associated with different projects, rockbursts in deep-buried tunnels often present different precursor characteristics, bringing major challenges to the early warning of rockbursts. To adapt to the complexity of engineering, it is necessary to review the latest advancements in rockburst early warning and to discuss general early warning methods. In this article, first, microseismic monitoring and localization methods applicable under tunneling construction are reviewed. Based on the latest engineering examples and research progress, the microseismic evolution characteristics of the rockburst formation process are summarized, and the formation process and mechanism of structure-type and delayed rockbursts are analyzed. The different methods for predicting the risk and level of rockbursts using microseismic indices are reviewed, and the implementation methods and application cases for predicting potential rockburst areas and rockburst probability based on a mechanical model are expounded. Finally, combined with the new practice in early warning methods, development directions for the early warning of rockbursts are put forward. Full article

(This article belongs to the Special Issue Tunneling and Underground Engineering: From Theories to Practices)

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