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17 pages, 5540 KiB

Open AccessArticle

A Study on the Evacuation of an Extra-Long Highway Tunnel Fire—A Case Study of Chengkai Tunnel

by Kai Wang, Jingwei Hu, Ruiding Chen and Jianhua Wang

Sustainability 2023, 15(6), 4865; https://doi.org/10.3390/su15064865 - 9 Mar 2023

Cited by 5 | Viewed by 1995

Abstract

The smoke from tunnel fires spreads over long distances and is difficult to vent. Smoke accumulation leads to high temperatures, low visibility, and high concentrations of toxic gases, which greatly hinders the evacuation of people inside the tunnel. In this paper, a representative [...] Read more.

The smoke from tunnel fires spreads over long distances and is difficult to vent. Smoke accumulation leads to high temperatures, low visibility, and high concentrations of toxic gases, which greatly hinders the evacuation of people inside the tunnel. In this paper, a representative extra-long highway tunnel—Chengkai Tunnel—is selected as the engineering background, and a tunnel model is built using FDS and Pathfinder software to simulate the fire scenario and evacuation scenario under different longitudinal wind speeds. The concept of safe evacuation reliability is proposed to describe the relationship between the ASET (available safe egress time) and the RSET (required safe egress time). The simulation results show that with the increase in longitudinal wind speed, the ASET upstream of fire source increases first and then remains unchanged, while ASET downstream of fire source increases first and then decreases. The ASET upstream of the fire source is affected by visibility, while the ASET downstream of the fire source is affected by visibility when the wind speed is low, and is affected by temperature as the wind speed increases. The bottleneck effect is an important reason for the long evacuation time of people. The blockage time is a power function of the evacuation movement time, and increasing the width of the cross passage can improve the evacuation efficiency of the tunnel. The increase in the number of evacuees will reduce the reliability of the safe evacuation of personnel. Among all simulated scenarios, a longitudinal wind speed of 2.5 m/s has the highest safe evacuation reliability, with 0.79, 0.92, and 0.99 for scenarios R1, R2, and R3, respectively. Excessive wind speed reduces the safe evacuation reliability downstream of the fire source. Full article

(This article belongs to the Special Issue Hazard Control and Emergency Rescue in Underground Engineering)

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17 pages, 8272 KiB

Open AccessArticle

Experimental Evaluation of Conjugate Flaws on Rock Dynamic Fracturing

by Ziyun Li, Song Xie, Qianghui Song, Peiyong Wang, Dongyan Liu and Kaixi Xue

Sustainability 2023, 15(4), 3637; https://doi.org/10.3390/su15043637 - 16 Feb 2023

Viewed by 1438

Abstract

The fracture behaviors of rocks under dynamic loading are significantly affected by flaws. Understanding regarding this fundamental mechanism of flaw-induced dynamic fracturing could aid in reducing dynamic geohazards in deep rock engineering. In this study, a series of dynamic loading experiments are conducted [...] Read more.

The fracture behaviors of rocks under dynamic loading are significantly affected by flaws. Understanding regarding this fundamental mechanism of flaw-induced dynamic fracturing could aid in reducing dynamic geohazards in deep rock engineering. In this study, a series of dynamic loading experiments are conducted on conjugate flawed white sandstone specimens to study the effect of the geometric configuration of flaws on dynamic fracturing. The results show that the geometry configuration of flaws and the loading conditions both strongly affect cracking and failure behaviors. Two types of shear cracks and three types of tensile cracks are observed, four coalescence patterns are identified, and the global failure modes of rock are usually coupled with two or more coalescence patterns. The inhibiting and enhancing mechanism of flaws in regards to potential shear fracture are obtained. These two failure mechanisms depend on the angular relationship between the flaws and the potential shear strain field. The “guiding effect” of the flaws results in the deviation and deformation of shear cracks. Moreover, it is found that the loading condition dominates the fracture tendency of rock macroscopically, while the geometric setting of flaws significantly affects the fracture behavior and failure mode locally. Full article

(This article belongs to the Special Issue Hazard Control and Emergency Rescue in Underground Engineering)

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18 pages, 5539 KiB

Open AccessArticle

Analytical Damage Model for Predicting Coal Failure Stresses by Utilizing Acoustic Emission

by Muhammad Ali, Enyuan Wang, Zhonghui Li, Xiaoran Wang, Naseer Muhammad Khan, Zesheng Zang, Saad S. Alarifi and Yewuhalashet Fissha

Sustainability 2023, 15(2), 1236; https://doi.org/10.3390/su15021236 - 9 Jan 2023

Cited by 13 | Viewed by 1607

Abstract

Overburden collapse and water inrush in mines are primarily caused by rock fractures. Mining safety can be enhanced by monitoring and identifying early signs of coal failure in the mines. This article collected acoustic emission data synchronously throughout a series of uniaxial compression [...] Read more.

Overburden collapse and water inrush in mines are primarily caused by rock fractures. Mining safety can be enhanced by monitoring and identifying early signs of coal failure in the mines. This article collected acoustic emission data synchronously throughout a series of uniaxial compression (UC) experiments on natural and water-saturated coal. The influence mechanisms of water, mechanical properties, and acoustic emission signals on the stress–strain curve and the SEM results of water-saturated and dry samples are investigated. As a result, the mechanical properties of coal are not only weakened by water saturation, such as elastic modulus, strain, stress, and compressive strength but also reduced acoustic emissions. In comparison with saturated coal, natural coal has a uniaxial stress of 13.55 MPa and an elastic modulus of 1.245 GPa, while saturated coal has a stress of 8.21 MPa and an elastic modulus of 0.813 GPa. Intergranular fractures are more likely to occur in coal with a high water content, whereas transgranular fractures are less likely to occur in coal with a high water content. An innovative and unique statistical model of coal damage under uniaxial loading has been developed by analyzing the acoustic emission data. Since this technique takes into account the compaction stage, models based on this technique were found to be superior to those based on lognormal or Weibull distributions. A correlation coefficient of greater than 0.956 exists between the piecewise constitutive model and the experimental curve. Statistical damage constitutive models for coal are compatible with this model. Additionally, the model can precisely forecast the stress associated with both natural and saturated coal and can be useful in the prevention of rock-coal disasters in water conditions. Full article

(This article belongs to the Special Issue Hazard Control and Emergency Rescue in Underground Engineering)

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12 pages, 4331 KiB

Open AccessArticle

Distributed Fuzzy Clustering Analysis of Time-Lapse Electrical Resistivity Tomography for Water Inrush Monitoring in Coal Mines

by Zhang Herui, Wang Guolin, Teng Xiaozhen and Zheng Xiaohui

Sustainability 2022, 14(24), 17011; https://doi.org/10.3390/su142417011 - 19 Dec 2022

Cited by 1 | Viewed by 1667

Abstract

The majority of water inrush accidents in coal mines are caused by mining engineering activities. To avoid water inrush accidents, the Time-lapse Electrical Resistivity Tomography (TLERT) is applied to monitor water migration in fractured zone. A great challenge for the application of TLERT [...] Read more.

The majority of water inrush accidents in coal mines are caused by mining engineering activities. To avoid water inrush accidents, the Time-lapse Electrical Resistivity Tomography (TLERT) is applied to monitor water migration in fractured zone. A great challenge for the application of TLERT monitoring is the huge and numerous time series data sets generated by monitoring systems, which are difficult to process manually. This research proposed a distributed fuzzy clustering algorithm based on kernel function estimation to analyze TLERT images automatically. The resistivity date can be classified with different cluster centroids. The fuzzy c-means algorithm was chosen to display resistivity change. The algorithm was validated using a floor water inrush model. The results indicate that the water migration in the fractured zone can be monitored automatically and the edge of the resistivity changing area can be shown clearly. Full article

(This article belongs to the Special Issue Hazard Control and Emergency Rescue in Underground Engineering)

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13 pages, 2111 KiB

Open AccessArticle

Characteristics of Roof Collapse of Mining Tunnels in the Fault Fracture Zone and Distribution of the Boundary Force of the Accumulation Body

by Guohua Zhang, Mengsen Liu, Tao Qin, Lei Wang, Yanwei Duan and Zibo Li

Sustainability 2022, 14(24), 16811; https://doi.org/10.3390/su142416811 - 14 Dec 2022

Viewed by 1478

Abstract

Under the influence of coal mining, the gravel in mining tunnel sections of a fault fracture zone is prone to collapse, and the collapse accumulation body will block the tunnel, which has a very adverse influence on the safety production of coal mining [...] Read more.

Under the influence of coal mining, the gravel in mining tunnel sections of a fault fracture zone is prone to collapse, and the collapse accumulation body will block the tunnel, which has a very adverse influence on the safety production of coal mining and the evacuation of personnel after underground disasters. The macroscopic and mechanical characteristics of the collapse accumulation body have been studied extensively in previous works. The purpose of this paper is to provide theoretical support and reference for the rapid excavation of the tunnel blocked by the collapse accumulation body in the fault fracture zone. Taking the fault fracture zone in the tunnel as the research background, the physical characteristics and boundary mechanical characteristics of the collapse accumulation body in the fault fracture zone are studied by the method of combining on-site investigation and theoretical analysis. The results show that the force acting on the boundary on both sides of the accumulation body is passive resistance from the side wall, which is derived from the slip effect of the accumulation body slope. Similarly, the unstable boundary of the fault fracture zone caused by tunnel instability is elliptical, and the overlying load of the rescue channel to be excavated in the accumulation body is limited. On the basis of the collapse instability dimensions of the broken zone of the tunnel surrounding the rock, the calculation formulas of the height of the accumulation body and the horizontal force at the boundary were established, respectively, under two conditions of whether the collapse space was filled, and whether the curve relationship between the distribution of the horizontal force at the boundary of the accumulation body and the buried depth in the accumulation body was obtained. Full article

(This article belongs to the Special Issue Hazard Control and Emergency Rescue in Underground Engineering)

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17 pages, 8285 KiB

Open AccessArticle

Study on Occurrence Mechanism and Prevention Technology of Rock Burst in Narrow Coal Pillar Working Face under Large Mining Depth

by Shitan Gu, Huaixu Chen, Wenshuai Li, Bangyou Jiang and Xiang Chen

Sustainability 2022, 14(22), 15435; https://doi.org/10.3390/su142215435 - 20 Nov 2022

Cited by 2 | Viewed by 1604

Abstract

This paper presents a collaborative control scheme involving “unloading-solidifying” to prevent rock bursts during narrow pillar recovery at large mining depths. In this study, the stress distribution rule of coal rock mass during the excavation and mining process is studied, and the energy [...] Read more.

This paper presents a collaborative control scheme involving “unloading-solidifying” to prevent rock bursts during narrow pillar recovery at large mining depths. In this study, the stress distribution rule of coal rock mass during the excavation and mining process is studied, and the energy accumulation characteristics of the overlying hard and thick roof structure are investigated. In this way, the rock burst inducing mechanism of the narrow coal pillar working face under complex conditions is investigated. The results show that the peak lateral bearing pressure of the goaf and the maximum horizontal principal stress provide the static load condition for the occurrence of rock burst during roadway excavation. Affected by the superposition of “near-field high static load + far-field dynamic load”, it is extremely easy to reach the critical destabilization value during the mining period at the narrow coal pillar working face. According to the monitoring results, the developed coordinated control scheme, which focuses on the strong pressure relief and strong support in near-field high-bearing pressure coal mass and the pressure relief in far-field high-level hard roof with an advanced pre-cracking roof, can effectively avoid the occurrence of rock burst accidents on narrow coal pillar working face. Full article

(This article belongs to the Special Issue Hazard Control and Emergency Rescue in Underground Engineering)

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18 pages, 4031 KiB

Open AccessArticle

Coupling Study of Deformation Field Evolution and Acoustic Emission Response Characteristics in Rock Failure and Instability Process

by Zhengxing Yu, Quanjie Zhu, Erhui Zhang, Yihai Zhang, Lei Gu, Longkun Sui and Yongming Yin

Sustainability 2022, 14(22), 15037; https://doi.org/10.3390/su142215037 - 14 Nov 2022

Cited by 2 | Viewed by 1283

Abstract

During rock failure and instability, cracks usually appear as microcracks in local areas and then expand into significant macroscopic cracks. In this study, the whole process of rock deformation and instability under uniaxial loading is investigated with standard rock specimens, and acoustic emission [...] Read more.

During rock failure and instability, cracks usually appear as microcracks in local areas and then expand into significant macroscopic cracks. In this study, the whole process of rock deformation and instability under uniaxial loading is investigated with standard rock specimens, and acoustic emission (AE) and digital image correlation (DIC) technology are introduced to explore the process of rock failure and instability. AE technology is used to identify the location of crack propagation caused by microcracks and large cracks, and DIC is used to measure the crack propagation at different locations. Results show that the evolution of accumulated energy is closely related to the change in stress. When the specimen approaches failure, a “y” shaped localization zone is formed, and the evolution path is consistent with the through-through path of the crack, which better reflects the propagation law of the crack in the rock. The spatial distribution of the AE location event and energy density is consistent with the evolution path of the localization zone. The deformation value of the deformation field is closely related to the initiation and evolution of the deformation localization zone. On the basis of density-based spatial clustering of applications with a noise-clustering algorithm, AE positioning events are further processed and projected into the digital image of the deformation field, and the results of clustering projection are in good agreement with the deformation localization zone. Results show that AE and DIC coupling localization techniques can effectively identify the fracture process zone and fracture mechanism of rock, providing a new technical means for further studying the mechanical properties of rock materials. Full article

(This article belongs to the Special Issue Hazard Control and Emergency Rescue in Underground Engineering)

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17 pages, 13325 KiB

Open AccessArticle

Effect of Saturation Degree on Mechanical Behaviors of Shallow Unsaturated Expansive Soils

by Jinpeng Li, Hong Xu, Lichuan Chen, Boyi Li, Dan Liang, Shicong Ren, Shilei Zhang and Jun Wang

Sustainability 2022, 14(21), 14617; https://doi.org/10.3390/su142114617 - 7 Nov 2022

Cited by 2 | Viewed by 1756

Abstract

In the southwest of China, there are widely distributed expansive soils. However, to save costs and manage the speed of construction, these shallow expansive soils are often filled with subgrade materials. Therefore, it is necessary to clearly understand the mechanical behaviors of unmodified [...] Read more.

In the southwest of China, there are widely distributed expansive soils. However, to save costs and manage the speed of construction, these shallow expansive soils are often filled with subgrade materials. Therefore, it is necessary to clearly understand the mechanical behaviors of unmodified shallow expansive soils. Current research on the mechanical behaviors of shallow expansive soils is mainly focused on shear and compressive strengths but rarely on the tensile strength since general tests are costly, time consuming, and difficult to conduct. Therefore, uniaxial tensile, unconfined compression and direct shear tests were carried out to study the mechanical behavior of shallow unsaturated expansive soils under different saturation degrees, and the tests analyzed the change mechanism of its mechanical behavior. The following were found: (1) with an increase in saturation degree, the uniaxial tensile strength, unconfined compressive strength, shear strength, cohesive force, and internal friction angle first increased and then decreased; (2) when the saturation degree increased from 18.7% to the saturation degree corresponding to the peak, the uniaxial tensile strength, unconfined compressive strength, cohesive force, and internal friction angle increased by about 11 times, 3.24 times, 2.34 times, and 0.52 times, respectively; (3) when the saturation degree increased from the saturation degree corresponding to the peak to 80.3%, they decreases by about 42%, 51.4%, 36%, and 50%, respectively; (4) with the increase in dry density, the saturation degree corresponding to the peak of uniaxial tensile strength gradually increased, while the saturation degree corresponding to the peak of unconfined compressive and shear strength did not significantly change. Full article

(This article belongs to the Special Issue Hazard Control and Emergency Rescue in Underground Engineering)

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23 pages, 15816 KiB

Open AccessArticle

Relationship between Joint Roughness Coefficient and Statistical Roughness Parameters and Its Sensitivity to Sampling Interval

by Yong Luo, Yakun Wang, Heng Guo, Xiaobo Liu, Yihui Luo and Yanan Liu

Sustainability 2022, 14(20), 13597; https://doi.org/10.3390/su142013597 - 20 Oct 2022

Cited by 7 | Viewed by 2053

Abstract

Accurate determination of the surface roughness is of significant importance in estimating the mechanical and hydraulic behaviors of rock joints. The correlation between joint roughness coefficient (JRC) and various statistical roughness parameters calculated from digitized Barton’s roughness profiles was explored with [...] Read more.

Accurate determination of the surface roughness is of significant importance in estimating the mechanical and hydraulic behaviors of rock joints. The correlation between joint roughness coefficient (JRC) and various statistical roughness parameters calculated from digitized Barton’s roughness profiles was explored with Pearson’s correlation coefficient method. The results show the strongest correlation between the standard deviation of the roughness angle and JRC following an excellent linear relationship. In addition, the correlation in the JRC with textural parameters is better than its correlation with amplitude parameters. Twenty-nine rock joint surfaces from fine sandstone, coarse sandstone and granite joint samples with a wide range of surface morphology were digitized using a high-resolution 3D scanner instrument. Further, the statistical roughness parameter values were calculated for each joint profile at eight different sampling intervals for sensitivity analysis of these statistical roughness parameters with regard to the sampling interval. The result indicated that textural parameters generally have a certain degree of dependency on sampling interval, following a power-law relationship. Specifically, when the sampling interval increases, the structure function value increases whereas it decreases for other textural parameters. In contrast, the dependence of the amplitude parameters on the sampling interval is not significant. Full article

(This article belongs to the Special Issue Hazard Control and Emergency Rescue in Underground Engineering)

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16 pages, 2243 KiB

Open AccessArticle

Research on Sandstone Damage Characteristics and Acoustic Emission Precursor Features under Cyclic Loading and Unloading Paths

by Yong Wang, Chuan Deng, Zeng Ding, Feng He, Xiaojun Feng, Dongming Wang, Qinjing Hu and Xue Zhao

Sustainability 2022, 14(19), 12024; https://doi.org/10.3390/su141912024 - 23 Sep 2022

Cited by 4 | Viewed by 1713

Abstract

The deformation and failure features of rock formation in deep coal mines are basic mechanical problems in the complex geology environment and complicated excavation process. Under the effect of cyclic loading and unloading, the bearing capacity weakens and damage degree exacerbates significantly, which [...] Read more.

The deformation and failure features of rock formation in deep coal mines are basic mechanical problems in the complex geology environment and complicated excavation process. Under the effect of cyclic loading and unloading, the bearing capacity weakens and damage degree exacerbates significantly, which seriously threatens the safety and stability of the working face. To study the damage characteristics of sandstone, especially the precursor characteristics of acoustic emission (AE), this paper conduct the AE response experiments on sandstone under cyclic loading and unloading. The results show that with the increasing number of cycles, the loading modulus, unloading modulus, total strain energy, elastic energy, and dissipation energy of sandstone in the cycle stage all increase continuously. In the initial loading stage, the sandstone has fewer cycles and lower stress levels, fewer AE ringing counts and energy, and less rock damage. With the increasing cyclic times and loading stress, the damage degree of sandstone increases rapidly in a very short time. The damage variable represented by ringing count is more sensitive than by energy. Just before rock failure, the ringing count and the energy value increase significantly, and the damage curve rises sharply. In addition, AE waveform signals have obvious aggregation characteristics and four main bands. Just before sandstone failure, the main frequency band becomes wider, the low frequency bands f₁ and f₂ become connected, and the main signal frequency appears abnormally low and high. The waveform signals before sandstone instability and failure show a phenomenon where the low-frequency amplitude is generally at a high level, the high-frequency signal decreases, the amplitude becomes low, and the multipeak phenomenon weakens. The above characteristics of the AE time domain and waveform analysis can be used as the precursor characteristics of sandstone failure and instability. This study can reveal the process of the sandstone deterioration and AE response under the cyclic loading and unloading condition, and has certain guiding significance for roof and floor control in deep roadway, instability warming monitor of working faces, and guarantees for safety production. Full article

(This article belongs to the Special Issue Hazard Control and Emergency Rescue in Underground Engineering)

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19 pages, 5116 KiB

Open AccessArticle

Stability Analysis of Karst Tunnels Based on a Strain Hardening–Softening Model and Seepage Characteristics

by Hongyang Liu, Zhibin Lin, Chengwei Liu, Boyang Zhang, Chen Wang, Jiangang Liu and Huajie Liang

Sustainability 2022, 14(15), 9589; https://doi.org/10.3390/su14159589 - 4 Aug 2022

Cited by 3 | Viewed by 1730

Abstract

There are more and more tunnel projects in the karst-developed areas in Southwest China. Affected by karst caves and water, karst tunnels often experience geological disasters such as local collapses and water inrush. A simplified rock stress hardening-softening model was established based on [...] Read more.

There are more and more tunnel projects in the karst-developed areas in Southwest China. Affected by karst caves and water, karst tunnels often experience geological disasters such as local collapses and water inrush. A simplified rock stress hardening-softening model was established based on the triaxial compression test results of two kinds of carbonatite to accurately analyze the deformation and water inrush characteristics of the surrounding rocks after karst tunnel excavation. The total stress–strain curve of rocks was simplified into four linear stages: the linear elastic stage, strain hardening stage, strain-softening stage, and residual stage. The volumetric strain–axial strain curve was simplified into four corresponding linear stages: the elastic expansion stage, slow expansion stage, rapid expansion stage, and stable expansion stage. The stress hardening–softening model was used to deduce the relationship between the rocks’ mechanical parameters such as cohesion, internal friction angle, dilatancy angle, and plastic strain, as well as the relationship between seepage characteristic parameters such as permeability coefficient, porosity, and volumetric strain. A karst tunnel in Chongqing, China was taken as the engineering background. The stress hardening–softening constitutive model and seepage characteristic parameters were applied to the FLAC^3D numerical simulation by the programming language FISH to analyze the stability and water inrush characteristics of karst tunnels in overlying confining caves. The results showed that rock masses between the cave and tunnel were prone to overall sliding instability. Confined water in the karst cave intruded into the tunnel through the shear-slip rupture zone on both sides instead of the shortest path. Two water inrush points existed on the tunnel surface. The variation law of the permeability coefficients of the surrounding rocks could more truly reflect whether there was a seepage channel between the tunnel and karst cave, as well as the permeable area and water inrush speed of the seepage channel. The work provides a new idea for the stability control of karst tunnels. Full article

(This article belongs to the Special Issue Hazard Control and Emergency Rescue in Underground Engineering)

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16 pages, 7496 KiB

Open AccessArticle

Comparative Study on Compressive and Flexural Properties of Concrete-Filled Steel Tubular Arch Joints

by Huibin Sun, Wei Lu, Jiancai Wang, Quangang Ren, Xin Xu, Debin Han, Xu Li, Huixiang Yang, Lianbang Wei and Yan Liu

Sustainability 2022, 14(14), 8916; https://doi.org/10.3390/su14148916 - 21 Jul 2022

Cited by 1 | Viewed by 1552

Abstract

Studying the bearing mechanism of concrete-filled steel tubular (CFST) arch components and constructing the quantitative design method of the CFST arch is an important subject in underground support. In order to clarify the bending and compression properties of CFST arch joints, considering different [...] Read more.

Studying the bearing mechanism of concrete-filled steel tubular (CFST) arch components and constructing the quantitative design method of the CFST arch is an important subject in underground support. In order to clarify the bending and compression properties of CFST arch joints, considering different structural parameters of the joint, bending and compression tests of square CFST components without joints, with tubular joints and with flange joints were carried out. The mechanical properties and failure modes of the bending and compression combinations of each component were analyzed, and the influence of structural parameters of joints on their bearing capacity was clarified. The results show that (1) the failure mode of the component without a joint and the component with a tubular joint present uniform curve deformation, and the flange joint presents typical brittle failure and broken line failure; (2) compared to the specimens without a joint and with a flange joint, the tubular joint has higher yielding strength and ultimate strength due to the strengthening effect of the tubular joint, while the bending bearing capacity is 623.639 KN; (3) the tubular length and flange thickness are the key structural parameters of the two types of joints, which have a significant influence on the bending capacity of the specimens; (4) the tubular joint has a simple structure and high bearing capacity, so it should be used as the preferred joint connection form of the concrete-filled steel tubular support arch in deep mine roadways with complex conditions. Full article

(This article belongs to the Special Issue Hazard Control and Emergency Rescue in Underground Engineering)

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20 pages, 6618 KiB

Open AccessArticle

Combining Numerical Simulation and Deep Learning for Landslide Displacement Prediction: An Attempt to Expand the Deep Learning Dataset

by Wenhan Xu, Hong Xu, Jie Chen, Yanfei Kang, Yuanyuan Pu, Yabo Ye and Jue Tong

Sustainability 2022, 14(11), 6908; https://doi.org/10.3390/su14116908 - 6 Jun 2022

Cited by 10 | Viewed by 2635

Abstract

Effective landslide hazard prevention requires accurate landslide prediction models, and the data-driven approaches based on deep learning models are gradually becoming a hot research topic. When training deep learning models, it is always preferable to have a large dataset, while most available landslide [...] Read more.

Effective landslide hazard prevention requires accurate landslide prediction models, and the data-driven approaches based on deep learning models are gradually becoming a hot research topic. When training deep learning models, it is always preferable to have a large dataset, while most available landslide monitoring data are limited. For data missing or data sparseness problems, conventional interpolation methods based on mathematical knowledge lack mechanism interpretability. This paper proposes that numerical simulations can be used to expand the deep learning dataset we need. Taking the Jiuxianping landslide in the Three Gorges Reservoir Area (TGRA) as the geological background, a finite element numerical model was established, and the landslide displacement time series data were solved considering the boundary conditions of reservoir water level change and precipitation. Next, based on three metrics: Euclidean distance, cosine similarity, and dynamic time warping (DTW) distance, the time series similarity between the displacement data obtained from simulation and data obtained from actual monitoring were verified. Finally, the combined deep learning model was built to predict the displacement of the Jiuxianping landslide. The model was trained on both the simulated and monitored datasets and tested by the last 12 monitored data points. Prediction results with the testing set showed that the models trained using the expanded training set from numerical simulations exhibited lower prediction errors, and the errors had a more concentrated distribution. The results suggest that this landslide displacement prediction method combining numerical simulation and deep learning can solve the problem of inadequate datasets due to low monitoring frequency, as well as provide an interpretation of the physical mechanism for data vacancy filling. Full article

(This article belongs to the Special Issue Hazard Control and Emergency Rescue in Underground Engineering)

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11 pages, 2864 KiB

Open AccessArticle

Quantitative Analysis of Infrared Thermal Images in Rock Fractures Based on Multi-Fractal Theory

by Bin Miao, Xinyu Wang and Hongru Li

Sustainability 2022, 14(11), 6543; https://doi.org/10.3390/su14116543 - 27 May 2022

Cited by 7 | Viewed by 2043

Abstract

Rock disasters caused by rock fractures seriously threaten the safe and sustainable mining of deep coal resources. The infrared thermal imaging of rock fractures has a non-uniform distribution. This is important information for the monitoring and early warning of rock mass instability. In [...] Read more.

Rock disasters caused by rock fractures seriously threaten the safe and sustainable mining of deep coal resources. The infrared thermal imaging of rock fractures has a non-uniform distribution. This is important information for the monitoring and early warning of rock mass instability. In this paper, the multi-fractal theory was introduced to analyze the infrared thermal image obtained from the uniaxial loading of sandstone, which is expected to provide quantitative indicators for the infrared monitoring of rock failure. The results show that the multi-fractal parameters

Δ α

(non-uniformity of temperature) and

Δ f

(frequency diversity of minimum and maximum temperature) can be used to describe the distribution of the thermal field; they are sensitive to the rock macro fracture. Both

Δ α

and

Δ f

are constant during the initial loading stage. When the samples yield and there is a failure in the later stage of loading, the

Δ α

and

Δ f

change abruptly. The sudden change in

Δ α

and

Δ f

can be regarded as the precursor to rock failure. The research results preliminarily show the feasibility and potential of multi-fractal analysis in rock mass disaster monitoring and early warning. Full article

(This article belongs to the Special Issue Hazard Control and Emergency Rescue in Underground Engineering)

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17 pages, 5698 KiB

Open AccessReview

Crack Propagation and AE/EMR Response Characteristics of Pre-Holed Coal Specimens under Uniaxial Compression

by Xiaojun Feng, Qinjing Hu, Zeng Ding, Dongming Wang, Xue Zhao and Qilei Wei

Sustainability 2022, 14(22), 15196; https://doi.org/10.3390/su142215196 - 16 Nov 2022

Cited by 2 | Viewed by 1440

Abstract

Drainage boreholes in soft coal seams are prone to deformation and failure under the action of in situ stress and mining stress, which has a significant impact on gas drainage in coal mines. To simulate the development and propagation of cracks around the [...] Read more.

Drainage boreholes in soft coal seams are prone to deformation and failure under the action of in situ stress and mining stress, which has a significant impact on gas drainage in coal mines. To simulate the development and propagation of cracks around the shaft wall caused by in situ stress, the crack propagation of coals with different diameters and strengths during the failure process, and the acoustic emission (AE) and electromagnetic radiation (EMR) law and response characteristics are explored. The results show that: The failure process of coal with pores is divided into four stages: initial compaction stage (OA), elastic deformation stage (AB), yield deformation stage (BC), and macroscopic crack development stage (CD). The crack propagation develops significantly in the post-load peak stage, the coal body damage is aggravated, and the coal body is unstable and fractured. For the pre-holed coal specimens with the same diameter, as the coal becomes softer, the peak stress decreases significantly (from 15.73 to 10.05 MPa). The cumulative value of AE counts of hard coal samples increased from 2.3 × 10⁵ to 3.6 × 10⁵ with increasing diameters. The Digital Image Correlation system (DIC) strain cloud diagram found that there are ‘I’-type cracks around the axial direction of the prefabricated holes. Coal samples with smaller hole have shorter cracks, indicating that the diameter of the holes significantly changes the axial loading limit. The research results have a certain reference significance for understanding the crack propagation of coal under static loads and evaluating the deformation characteristic and spatiotemporal stability of gas drainage in soft coal seams. Full article

(This article belongs to the Special Issue Hazard Control and Emergency Rescue in Underground Engineering)

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