Search

Landslides represent one of the most frequent and destructive natural hazards in recent years. In highly seismic countries, the occurrence of large earthquakes is a significant triggering factor in the generation of these landslides. Therefore, it is of interest to various disciplines within civil engineering to study these phenomena through empirical analysis, analytical methods, and numerical modelling, aiming to provide a more accurate representation of these complex phenomena. For this purpose, a computational modelling approach is developed to describe the dynamics of a landslide or rockslide induced by seismic loading, using the Material Point Method (MPM). Presently, the utilization of MPM holds considerable significance because it is a numerical method engineered to simulate large deformations. This stands in contrast to conventional methods like the Finite Element Method (FEM), which struggles to precisely deal with this type of problems due to the generation of errors related to mesh distortion. In this study, it is performed a modelling process involving a real and documented scenario--a massive landslide occurrence in the vicinity of Daguangbao, China, triggered by the 2008 Wenchuan Earthquake. The obtained results successfully capture the landslide dynamics in terms of velocities, deformations, and travel distances in accordance with existing reports and other research endeavours. The maximum attained velocities of the landslide are approximately 100 km/h, affirming the catastrophic nature of this event. [ABSTRACT FROM AUTHOR]

During the construction of a highway in northwest China, large deformation of mudstone caused severe deformation of and damage to side walls, initial support, and secondary lining to various extents. To reveal the causes of mudstone's large deformation in the tunnels of this highway, a comprehensive study was conducted by using engineering geological survey, on-site monitoring and measurement, indoor rock mechanics test, numerical simulation, and macroscopic analysis. For the problem of large deformation of this highway's tunnel section from YK209 + 500 m to YK210 + 030 m, the 3D finite difference method FLAC3D was used to simulate the large deformation of the wall rock and compare the deformation of the tunnel and the mechanical characteristics of the lining structure under different conditions by means of inverse analysis of the rheological characteristics of the mudstone and simulation of the softening of the mudstone in water. The research results provide a reference and basis for the construction design of similar mudstone tunnel projects. For the management of tunnel deformation, it is recommended to enhance the tunnel's drainage measures, thereby mitigating the intensification of mudstone softening when exposed to water. [ABSTRACT FROM AUTHOR]

The reactivation of coüuviai Landslides in reservoir banks poses a serious threat to the safety of hydropower projects and nearby towns. This study aims to research the morphological evolution of this type of landslides under the action of reservoir water and the impact of morphological evolution on landslide stability. The study focused on the Yulinerzu landslide, a large reactivated colluvial landslide in the Xiluodu Reservoir, China. Field surveys were conducted to analyze the geological structure of the landslide. In situ monitoring and surveys were used to obtain the deformation characteristics and morphological evolution of the landslide. A combined seepage-slope stability analysis was conducted to reveal the deformation mechanism. The results show that the reactivation of the Yulinerzu landslide is dominated by reservoir water fluctuations rather than rainfall. The underlying geological condition of the colluvial landslide is its hydrogeological structure, which causes the landslide to deform in a step-like manner during reservoir operation. With the accumulation of displacement and morphology evolution, the landslide displayed self-stabilizing characteristics. Therefore, in the stability analysis and risk assessment of large deformation landslides, it is essential to take into account not only the hydraulic effects of reservoir fluctuation but also the evolution of landslide morphology. [ABSTRACT FROM AUTHOR]

During the excavation of a water-conveyance tunnel in Tertiary soft rocks in China, significant deformation of the surrounding rocks and damage to the support were observed. Substantial horizontal deformation, reaching magnitudes of meters, was observed in the right side wall after a certain period of tunnel excavation. Extensive investigations, including field surveys, monitoring data analysis, laboratory tests, and numerical simulations, were conducted to understand the underlying mechanisms of this large deformation. The section of the tunnel with large deformation consisted of Tertiary sandy mudstone, mudstone interbedded with marl, and glutenite. Laboratory tests and mineral composition analysis revealed that the sandy mudstone and mudstone interbedded with marl exhibited low strength, which was closely related to the water content of the rock specimens. The compressive strength gradually decreased with increasing water content, and when the water content of mudstone interbedded with marl reached 26.96%, the uniaxial compressive strength decreased to only 0.24 MPa. Additionally, sandy mudstone and mudstone interbedded with marl contained a significant amount of hydrophilic minerals, with montmorillonite constituting 30% and 34% of the two rock samples, respectively. The tunnel passed beneath a perennially flowing gully, and a highly permeable glutenite layer was present in the middle of the tunnel. This resulted in groundwater seepage from the inverted arch during excavation, leading to the softening effect on the mudstone interbedded with marl in the lower part of the tunnel. Through numerical simulation and back-analysis techniques, the varying degrees of softening induced by groundwater were quantitatively analyzed in the surrounding rocks on the left and right sides. The study revealed that the large deformation of the tunnel was triggered by two factors: the plastic flow caused by tunnel excavation under the low strength of the surrounding rocks and the softening effect of groundwater. The damage to the support system was primarily attributed to the squeezing and swelling deformation of the surrounding rocks and the non-uniform deformation between different rock layers. [ABSTRACT FROM AUTHOR]

During tunnel excavations through shale formations in central and southwest China, engineering problems, such as large deformations and distorted arches, were encountered due to radial stress unloading and groundwater pressure. Few studies have been carried out on the issues exhibited by soft shale tunnels that have considered the comprehensive influence of unloading and water effects. To characterize the unloading behaviors, a series of conventional triaxial compression (CTC) tests and unloading confining pressure (UCP) tests were performed under drained conditions and compared. Based on theoretical and experimental analyses, deformation parameters from the UCP process were derived and compared with those from the CTC test. The stress–strain response, evolution of deformation and strength parameters, and postpeak mechanical behavior and failure modes were analyzed in order to reveal the unloading and water effects. To quantify the difference between the CTC and UCP behaviors in geotechnical practice, a tunnel excavation was simulated using the CTC and UCP models. The distributions of damage and displacement were analyzed in a numerical case study. The results showed the comprehensive dependency of shale behaviors on unloading and water effects. The numerical case revealed significant tunnel deformation and fewer plastic zones in the excavation when using the UCP model rather than the CTC model. To accurately simulate the deformation and damage distribution, this study provided a methodology for construction design using the UCP test and the model for unloading and water-affected geotechnical engineering. [ABSTRACT FROM AUTHOR]

The accelerated creep plays an important role in the disasters of soft-rock tunnels under high stress. However, most of previous studies only involved attenuation creep and uniform creep. Large deformation disasters of soft rock occurred during the tunneling process in the Qianzhou–Sanyangchuan Tunnel, Gusu Province, China. In the paper, we developed the nonlinear generalized Nishihara rheological model with non-stationary parameter creep (NGNRM) to simulate the accelerated creep behaviors of soft rocks under high stress, and implemented it in ABAQUS, to reveal the mechanism of large deformation of soft rock. We proposed the multi-objective back analysis method of surrounding rock mechanical parameters based on the eXtreme Gradient Boosting and the non-dominated sorting genetic algorithm-II. In addition, the orthogonal test design method was used to determine the main parameters affecting the displacement of the tunnel. Using the proposed method, we can evaluate the large deformation mechanism of deep soft rock tunnels, and scientifically determine when to reinforce to prevent a large deformation disaster of the tunnel. [ABSTRACT FROM AUTHOR]

Loess tunnels often undergo large-scale deformation with complex spatial and temporal distribution. Mastering the characteristics of spatial and temporal deformation is conducive to precise policy implementation and the control of large deformation of the tunnel. In this study, relying on the Yulinzi Tunnel in Gansu Province, China, based on 3D laser scanning technology, the tunnel was monitored for a short period of 24 h and a long period of 36 days. The refined characteristics of the temporal and spatial deformation of the representative points of the interrupted surface, the tunnel face, and the excavation mileage during the excavation process of the three-bench and seven-step method of the tunnel were analyzed. The results show that the tunnel's arch has large deformation, and there is twisting deformation. The distribution of the overall deformation of the tunnel is related to the excavation sequence, showing a stepped deformation law. With the construction of the following excavation process, the deformation rate of the tunnel always indicates the characteristics of significant in the early stage and small in the later stage, and the overall deformation changes with time in accordance with the distribution law of the exponential function. The research results provide a reference for predicting the deformation development trend of loess tunnels and providing reasonable deformation control methods. [ABSTRACT FROM AUTHOR]

Ground deformation in the coal mining area of Northwestern China is usually featured by large and inconsistent subsidence. Large subsidence brings great challenge to Differential Interferometric Synthetic Aperture Radar (DInSAR) and Permanent Scatterer Interferometry (PSI) technology due to the pixel-level offset in the range direction after co-registration, which could directly result in complete coherence loss even for the artificial Corner Reflectors (CRs). Offset tracking provides an alternative to capture the large deformation although the results could be biased due to the large deformation gradient and use of fixed correlation window size. In this paper, the point-like target (PT) offset tracking method is introduced to deformation monitoring in coal mining area with a levelly decreasing correlation window size. For each PT-centered SLC patch in the reference SAR image, the estimate from the larger correlation window will serve as a guide for the smaller one to locate the matching SLC patch in the slave SAR image, thus providing a guarantee that the residual offsets to be estimated remain to be a small fraction of the decreasing patch size. The offset estimates were evaluated by ground surveying results at 34 CRs obtained using single reference real-time kinematic (RTK) GPS technique, with a RMS error of 1/13-1/14 SLC pixel in both the range and azimuth directions. [ABSTRACT FROM AUTHOR]

Deep roadways within fractured rock mass present substantial challenges for mining and construction due to the risk of large deformations. This study focuses on investigating the formation and evolution of cracking zones in the surrounding rock, specifically analyzing the 790-m level segment within the Jinchuan Mine No. 2 Mining area. Our comprehensive approach integrates field investigations, laboratory tests, in-situ monitoring, and numerical simulations. The findings highlight the vulnerability of surface surrounding rock in the σ 3 direction, leading to spalling and failure after excavation, while shallow surrounding rock acts as a natural barrier against deeper crack propagation. Over time, the elliptical cracking zone, aligned with the σ 1 direction, expands, which progressively degrades the internal rock mass, ultimately resulting in support failure due to instability and increasing deformation pressures. To mitigate these challenges, strategies were proposed to minimize the initial cracking zone and halt its growth. The insights and guidance provided herein are invaluable for enhancing project safety and efficiency in designing and constructing roadways in similar geological settings. • Shallow rock, a barrier against deep cracks, shields excavation; surface rock in σ 3 is prone to spalling and failure. • Elliptical cracking zone along σ 1 grow, leading to rock degradation, support failure, and heightened deformation over time. • Controlling large deformation hinges on minimizing the initial cracking zone and halting its ongoing evolution. [ABSTRACT FROM AUTHOR]

Large squeezing deformation has always been a critical concern in the construction of deep-buried tunnels in soft-weak rock masses. This paper describes a case study on the large deformation mechanism and supporting method of the Maoxian tunnel in Sichuan Province, China, which is located in the core area influenced by the 2008 Wenchuan earthquake and suffered severe large deformation in broken phyllite under high geo-stress. Through a survey on the geological features, the deformation mechanism of surrounding rock and the failure characteristics of supporting structures of the Maoxian tunnel in F1 fault zone were studied. It was found that the occurrence of large deformation was due to the combined action of the high geo-stress and poor self-stability of carbonaceous phyllite. In order to control the squeezing deformation, single and double primary support methods were adopted in succession. A comparative field test was conducted to study their supporting mechanism and mechanical behavior in terms of surrounding rock pressure, internal stress of the steel arch, and axial force and bending moment of the secondary lining. The results revealed that the single primary support method cannot ensure the long-term safety of the tunnel, since many cracks in concrete occurred after about 180 days. The double primary support method, however, was able to control the large deformation and rheological effects of broken phyllite under high geo-stress effectively. [ABSTRACT FROM AUTHOR]

In this paper, two different research methods are applied to predict large deformation behavior in tunnels and take Tianjiashan tunnel as the case study which is located in Xindianping town, Zhejiang city, Hunan province. The paper introduces the basic principle of the analytic hierarchy process and the fuzzy mathematics method, and classifies the influence factors of the large deformation in tunnels into eight kinds (C1–C8). Basing on the AHP–FUZZY method, this paper applies the results into the large deformation prediction analysis of Tianjiashan tunnel. In order to verify the accuracy of the evaluation results of AHP–FUZZY method, a numerical simulation model of DK394 + 625–DK394 + 650 section of Tianjiashan tunnel is established. The results show that the tunnel deformation is very large, and the tunnel excavation is sure to cause large deformation. The numerical simulation result is in accordance with the AHP–FUZZY method. Finally, we track record of occurrence of large deformation during the actual construction in tunnel, and the actual results are coincide with AHP–FUZZY method and numerical simulation results, which reflects the effectiveness of AHP–FUZZY method and numerical simulation method in predicting the large deformation behavior in tunnels. [ABSTRACT FROM AUTHOR]

The Yanmenguan Tunnel runs through Hengshan Mountain in Shanxi Province, China. The mountain is mainly composed of metamorphic rock cut by a well-developed strike-slip fault system. As a result of the local geological setting, significant deformation and mud bursting occurred during excavation of the tunnel. In this paper, a representative 170-m-long section of the tunnel (from Sta. 118 K + 30.0 to Sta. 118 K + 200.0), which is located in the restraining bend area of the strike-slip fault system, is chosen as a case study to investigate the influence of such a fault on tunnel stability. The characteristics of strike-slip faults and asymmetrical pressure are then investigated, in conjunction with monitoring stress and displacement in the tunnel. The results of the analysis suggest that the strike-slip fault complicates the geological condition and decreases the quality of the rock masses. Different rock mass classifications for the surrounding rocks are the dominant factor causing asymmetrical pressure in the tunnel, which in turn significantly influences deformation in the tunnel. Shear and crushing failure are the mechanisms of failure in the surrounding rocks in the surveyed section, where significant deformation and mud bursting occurred. It indicates that stress and the classifications of surrounding rock masses should be carefully investigated and analyzed during the design and construction of underground engineering works in such a setting. [ABSTRACT FROM AUTHOR]

This paper presents an integrated approach for theoretical analysis and numerical modeling to investigate the ground response mechanism of entries and control methods induced by hard roof in longwall top coal caving panel (LTCC). The test site is located in the city of Jinzhong, Shanxi Province, China. A roof mechanical model for the main roof's different breaking positions was created to study the ground response mechanism of gob-side entries. The theoretical analysis indicated that the closer the main roof fracture line is to the gob, the smaller the lateral cantilever length of the main roof above the gob, and the surrounding rock of the roadway are more stable. Therefore, an innovative approach is proposed t to reduce the lateral cantilever length of the main roof above the gob area and automatically retain entry. This approach involves applying the "directional roof split blasting technique for pressure relief and automatic retained entry" (DRSBPRRE) in the thick coal seam of the LTCC panel. Meanwhile, numerical modeling results verified the results of the theoretical analysis. The results of the numerical simulation and practical application suggest that the DRSBPRRE approach can eliminate the cantilever length of the main roof, significantly reduce the peak vertical stress in the solid coal rib by approximately 13.76 % and reduce the surrounding rock damage and deformation. Therefore, the DRSBPRRE approach is a safe and efficient mining method for pressure relief and entry retention. This research could provide an important reference for thick coal seam LTCC panel non-pillar coal mining technology. [ABSTRACT FROM AUTHOR]

• We proposed a new support plan and conducted field tests. • Broken surrounding rock, low degradation strength, unreasonable support parameters, and uncoupling of support and surrounding rock were the main causes of roadway deformation. • The active–passive coupling support scheme had an amplifying effect. • The deformation of the roadway surrounding rock was effectively controlled and the scheme could ensure the stability of the roadway. The safe mining of Xin'an Coal Mine was challenging because of several problems, including the soft roadway seams, fracture development, fracturing and deformation of the incompact surrounding rock, and the unreasonable support parameters. Through the investigation of these problems and the analysis of the influence of active and passive support on the stability of the roadway combined with the theory, we proposed a new support plan and conducted field tests. The obtained results were as follows: broken surrounding rock, low degradation strength, unreasonable support parameters, and uncoupling of support and surrounding rock were the main causes of roadway deformation. To a certain extent, the passive support could prevent the damage of the surrounding rock, prevent the attenuation of the stress of the rock around the anchor point, and enhance the effect of active support. The active support could pre-support the gravity of the broken surrounding rock, improve the stress environment of the surrounding rock, and increase the self-balancing ability of the surrounding rock structure. It also could control the damage zone of surrounding rock and the expansion of the stress arch to the depth, restrict the range of rock strata that the passive support system needed to control, and play a protective role. The active–passive coupling support scheme had an amplifying effect. In this regard, the active–passive coupling support scheme of "bolt, W steel belt" + "anchor cable, anchor cable beam" + "I-steel shed" was practiced, and the relevant support parameters were determined. The scheme was implemented in the 2301 mining roadway, and the displacement convergence deformation of the two walls and the roof and floor of the roadway was monitored. It was found that the deformation of the roadway surrounding rock was effectively controlled and the scheme could ensure the stability of the roadway. The research results could provide a basis for the stability analysis of large deformation of broken soft coal of mining roadway and also a basis for the optimization of support parameters. [ABSTRACT FROM AUTHOR]

Abstract: Rock slope deformation stability for Antaibao open pit coal mine under mining was analyzed using finite difference technique (FLAC3D). Optimal excavated scheme with relatively steeper slope angle of 47° instead of 30° was successfully implemented at the west wall on the geological section 73200 of the mine area, where the three-dimensional (3D) effect of nonlinear large deformation of the slope was taken into account. Physico-mechanical properties of the rock materials were obtained by laboratory tests conducted on samples cored from exploration drilling and rock blocks taken directly from the mine. A nonlinear Mohr–Coulomb material model with a tension cutoff was used in all present simulations. Nonlinear effect on excavated sequence was also discussed. It is demonstrated by dynamical response analysis that the action of earthquake magnitude VII (Richter) upon the relatively steeper excavated slope could not be more than that slope could bear. [Copyright &y& Elsevier]

Interferometric synthetic aperture radar (InSAR) technology can obtain one-dimensional surface displacements in the radar line of sight (LOS). In the field of mining subsidence, large 3D movements often occur at the same time, and hence InSAR derived one-dimensional LOS displacements can hardly reflect the actual surface motion in mining areas. To realize the monitoring of three-dimensional large surface displacements in mining areas, a method for monitoring three-dimensional large surface displacements in mining areas that combines SAR pixel offset tracking (OT) and an improved mining subsidence model is proposed in this article. First, a new functional relationship between surface subsidence and horizontal movement combined with the characteristics of the overburden rock stress and the deformation characteristics of the fractured rock mass in coal mining areas is established. Then, a three-dimensional surface deformation model is established based on the proposed relationship between surface subsidence and horizontal movement and the radar projection equation, and finally, the optimal parameters of the deformation model are inverted iteratively using LOS deformation results obtained by OT method to retrieve the three-dimensional large displacements of the surface. The significant advantage of the method proposed in this article is that it can accurately acquire the 3D large surface displacements using only two SAR amplitude images with the same imaging geometry. To verify the accuracy and reliability of the proposed algorithm, two scenes of high-resolution spotlight TerraSAR-X images are used in this paper to conduct a three-dimensional surface displacement monitoring experiment on a working panel in the Daliuta mining area in Shaanxi Province, China, based on the proposed method. Experimental monitoring results show that the maximum surface subsidence is approximately 4.5 m, and the maximum horizontal movements in the strike and dip directions are approximately 1.4 m and 1.2 m, respectively. Using GPS measurements to verify the monitoring results, the root mean square error (RMSE) of vertical subsidence is 6.8 cm, and the RMSE of horizontal movement is 7.1 cm. Compared with those in the original mining subsidence model, the accuracies of vertical subsidence and horizontal movement in the proposed model are increased by 28.2% and 37.5%, respectively, which proves the reliability and accuracy of the proposed method. [ABSTRACT FROM AUTHOR]

This study considered the mining roadway with coal pillar protection in the fully mechanized caving face of the Dananhu No.1 Coal Mine, China. Theoretical analysis, numerical simulation, and field tests were conducted, and the stress environment, deformation, and failure characteristics of the mining roadway in the fully mechanized caving face were analyzed. The results revealed that the intrinsic cause for the large asymmetrical floor deformation in the mining roadway is the asymmetrical phenomenon of the surrounding rock's stress environment, caused by mining. This also results in the non-uniform distribution of the mining roadway floor's plastic zone. The degree of asymmetrical floor heave is internally related to the thickness of the caving coal. When the thickness of the caving coal was in the range of 5.9 m, the deformation of the asymmetrical floor heave, caused by the plastic failure in the floor, became more obvious as certain parameters increased. As the rotation angle of the principal stress direction increased, the maximum plastic failure depth position of the floor gradually moved toward the middle of the roadway. This caused a different distribution for the maximum deformation position. The control of the floor heave deformation was poor, and it was not feasible to use high-strength support under the existing engineering conditions. Hence, the control should mainly be applied to the floor heave deformation. When the thickness of the caving coal was more than 5.9 m, the main roof strata was prone to instability and being cut along the edge of the coal pillar; the rock stress environment surrounding the roadway tended to revert back to the initial geostress state. The proposed floor heave control strategy achieved good results, and as the deformation of the floor heave decreased, the workload of the floor heave was also greatly reduced. [ABSTRACT FROM AUTHOR]