Landslide stability for Shuitianba in the Three Gorges area

According to the data of preliminary survey, the authors established a landslide geological model,on the basis of analyses on the sensitivity of landslide, tried to simulate and calculate the landslide stability of Shuitianba with the method of transfer coefficient when it is under different strength parameters, and study the landslide mechanism. The results show that it is sensitive to the effects of shear strength parameters of sliding zone and groundwater level on landslide stability safety coefficient, which provides reliable basis for calculation of landslide stability.

A process-oriented approach for identifying potential landslides considering time-dependent behaviors beyond geomorphological features

Geomorphological features are commonly used to identify potential landslides.Nevertheless,overemphasis on these features could lead to misjudgment.This research proposes a process-oriented approach for potential landslide identification that considers time-dependent behaviors.The method integrates comprehensive remote sensing and geological analysis to qualitatively assess slope stability,and employs numerical analysis to quantitatively calculate aging stability.Specifically,a time-dependent stability calculation method for anticlinal slopes is developed and implemented in discrete element software,incorporating time-dependent mechanical and strength reduction calculations.By considering the time-dependent evolution of slopes,this method highlights the importance of both geomorphological features and time-dependent behaviors in landslide identification.This method has been applied to the Jiarishan slope(JRS)on the Qinghai-Tibet Plateau as a case study.The results show that the JRS,despite having landslide geomorphology,is a stable slope,highlighting the risk of misjudgment when relying solely on geomorphological features.This work provides insights into the geomorphological characterization and evolution history of the JRS and offers valuable guidance for studying slopes with similar landslide geomorphology.Furthermore,the process-oriented method incorporating timedependent evolution provides a means to evaluate potential landslides,reducing misjudgment due to excessive reliance on geomorphological features.

Stability assessment of landslide-prone road cut rock slopes in Himalayan terrain:A finite element method based approach

Large-scale slope destabilization could be aggravated due to swift urbanization and ever-rising demands of geoengineering projects such as dams,tunnels,bridges and widening roads.National Highway-58 connects Delhi to Badrinath in India,which passes through complex geomorphological and geological terrain and often encounters cut slopes susceptible to slope failures.In the present investigation,a detailed geotechnical appraisal is conducted along the road cut slopes from Rishikesh to Devprayag in the Himalayas.Twenty vulnerable road cut slopes were demarcated for detailed slope stability analysis using Phase2D finite element modeling simulator.Nonlinear generalized Hoek-Brown(GHB)criterion was adopted for stability analyses.Out of 20 slopes,five slopes(S6,S7,S18,S19 and S20)are unstable with factor of safety(FoS)less than or equal to 1,and thus needs immediate attention.The FoS values of four slopes(S2,S9,S13 and S17)lie between 1 and 1.3,i.e.marginally stable,and slopes S1,S3,S4,S5,S8,S10,Sll,S12,S14,S15 and S16 are stable.Mohr-Coulomb(MC)criterion was also adopted to compare the slope stability analysis with GHB criterion.The FoS calculated from GHB criterion is close to that using MC criterion for lower values of FoS whereas for higher values,the difference is marked.For the jointed rock in the Himalayan region,the nonlinear GHB criterion gives better results as compared to MC criterion and matches with the prevailing field conditions.Accordingly,some suggestions are proposed to strengthen the stability of cut slopes.

Three-dimensional stability of landslides based on local safety factor

Unlike the limit equilibrium method(LEM), with which only the global safety factor of the landslide can be calculated, a local safety factor(LSF) method is proposed to evaluate the stability of different sections of a landslide in this paper. Based on three-dimensional(3D) numerical simulation results, the local safety factor is defined as the ratio of the shear strength of the soil at an element on the slip zone to the shear stress parallel to the sliding direction at that element. The global safety factor of the landslide is defined as the weighted average of all local safety factors based on the area of the slip surface. Some example analyses show that the results computed by the LSF method agree well with those calculated by the General Limit Equilibrium(GLE) method in two-dimensional(2D) models and the distribution of the LSF in the 3D slip zone is consistent with that indicated by the observed deformation pattern of an actual landslide in China.

Optimal mining sequence for coal faces under a bedding slope:insight from landslide prevention

Repetitive mining beneath bedding slopes is identified as a critical factor in geomorphic disturbances, especially landslides and surface subsidence. Prior research has largely concentrated on surface deformation in plains due to multi-seam coal mining and the instability of natural bedding slopes, yet the cumulative impact of different mining sequences on bedding slopes has been less explored. This study combines drone surveys and geological data to construct a comprehensive three-dimensional model of bedding slopes. Utilizing FLAC3D and PFC2D models, derived from laboratory experiments, it simulates stress, deformation, and failure dynamics of slopes under various mining sequences. Incorporating fractal dimension analysis, the research evaluates the stability of slopes in relation to different mining sequences. The findings reveal that mining in an upslope direction minimizes disruption to overlying strata. Initiating extraction from lower segments increases tensile-shear stress in coal pillar overburdens, resulting in greater creep deformation towards the downslope than when starting from upper segments, potentially leading to localized landslides and widespread creep deformation in mined-out areas. The downslope upward mining sequence exhibits the least fractal dimensions, indicating minimal disturbance to both strata and surface. While all five mining scenarios maintain good slope stability under normal conditions, recalibrated stability assessments based on fractal dimensions suggest that downslope upward mining offers the highest stability under rainfall, contrasting with the lower stability and potential instability risks of upslope downward mining. These insights are pivotal for mining operations and geological hazard mitigation in multi-seam coal exploitation on bedding slopes.

Stability analysis and monitoring study of Jijia River landslide based on WebGIS

On the basis of in situ investigation and deformation monitoring of the Jijia River landslide （JJRL）, the rigid body limit equilibrium method and finite element method （FEM） were used to analyze the stability of the JJRL; the grey system theory method was applied to forecast the deformation trend of the JJRL; and the information system about the landslide deformation and monitoring, and forecasting systems based on the platform of the Web Geographical Information System （WebGIS） were developed, which can be used to analyze in situ monitoring data and predict the deformation of the landslide. The study results can be summarized as follows： （1） the JJRL is stable as a whole; the water content in the landslide has a great effect on its stability; （2） the developed Web Geographical Information System has realized many functions, including inputting, computing, inquiry, analyzing, and the function of forecasting; it has also realized the functions of distance data management, analysis, and forecasting based on the WebGIS; （3） the information resource can be shared by the WebGIS developed all over the world.

Engineering Geological and Geotechnical Studies of Taprang Landslide, West-central Nepal: An Approach for Slope Stability Analysis

Detailed investigation of Taprang landslide was carried out in order tounderstand the surface, subsurface lithological information and physicalproperties of soil by using multi-disciplinary methods such as engineeringgeological, geophysical and geotechnical studies for the determinationof factor of safety for slope stability analysis. Geological study wascarried out by detail mapping of surface geology, soil condition, propertiesof bedrock and its discontinuities. The geophysical survey (ElectricalResistivity Tomography-ERT) were carried out to know the electricalresistivity of soil for identifying the groundwater table and slip surface ofthe landslide. Geotechnical analysis such as grain size analysis, liquid limitand direct shear test were carried out in order to evaluate soil classification,moisture content, cohesion and the angle of internal friction of soil forknowing the strength the soil. These soil parameters indicate the soil is verylow strength. The combination of these results were used for calculatingthe factor of safety (FoS) by Limit Equilibrium Method (LEM) proposedby Bishop and Janbu methods. The result of factor of safety in the Tapranglandslide demonstrates that the slope become stable in drained (dry)condition, remain ultimate stage in undrained (wet) condition and finallyfailure occurs if applied the seismic load in both drained and undrainedconditions.

Landslide Hazard and Risk Assessment on the Northern Slope of Mt. Changbai, China

Landslide hazard and risk assessment on the northern slope of Mt. Changbai, a well-known tourist attraction near the North Korean-Chinese border, are assessed. This study is divided into two parts, namely, landslide hazard zonation and risk assessment. The 1992 Anbalagan and Singh method of landslide hazard zonation （LHZ） was modified and used in this area. In this way, an Associative Analysis Method was used in representative areas to get a measure for controlling factors （slope gradient, relative relief, vegetation, geology, discontinuity development, weak layer thickness and ground water）. For the membership degree of factor to slope failure, the middle range of limited values was used to calculate LHZ. Based on an estimation of the potential damage from slope failure, a reasonable risk assessment map was obtained using the relationship of potential damage and probable hazard to aid future planning and prediction and to avert loss of life.

Reactivation of a huge ancient landslide by surface water infiltration

An ancient landslide, situated in Deqin County, Yunnan Province, China, was used to investigate the reactivation by water infiltration. This study considers the infiltration process and landslide stability using finite-element method(FEM)-based models. The results show that the reactivation of old landslide deposit was triggered by the long-term leakage of diversion ditch before October 2012, and the reactivation was triggered again by the intense rainfall on 7-9 October 2012. The old cracks, which formed in the earlier reactivation of landslide, played a key role for the rainfall infiltration. They offered a preferential path for much more rainfall to infiltrate fast into deep soil, and caused wetting front to move down faster in landslide. The old slip zone with lower permeability was another important factor to cause the infiltrated water to accumulate and form a high pore water pressure above slip zone. Then the high pore water pressure decreased the shear strength of slip zone and triggered the reactivation of the old landslide deposit again.

Analysis of Danba Landslide

This paper using finite element method analyzed present slope and contrasted it with the original slope shape, plastic deformation figures and stress changes. At the same time, some deformation figures and stress figures were got, and the potential sliding surface and the stability coefficient were calculated. The conclusions are： This slope is provided with sliding conditions and began to slide when its foot was cut without any support in time. At the foot of the slope, some support measures must be taken to keep the slope steady and the slope surface need to be stabilzed to protect the lower people. These suggestions and conclusions are also useful to the slope constructions and succeeding inspecting works.

Landslide Reliability Analysis Based on Transfer Coefficient Method: A Case Study from Three Gorges Reservoir

To evaluate the reliability of a landslide in a reservoir, the universal transfer coefficient method, which is popularized by the Chinese standard, is adopted as performance function in this study for： （1） common deterministic method stability evaluation; （2） reliability evaluation based on a Monte Carlo method; （3） comparison of landslide reliability under different water levels and under different correlation coefficients between soil shear strength parameters （c, Φ）, respectively with mean, standard deviation, reliability coefficient and failure probability. This article uses the Bazimen （八字门） landslide, which is located at the outlet of Xiangxi （香溪） River in the Three Gorges Reservoir, as an example to evaluate its stability and reliability under different water levels with two-dimensional deterministic and probabilistic methods. With the assumption that constant mean and normal distributed shear strength parameters （c, Φ）, correlation coefficient c, Φ=-1 based reliability analysis, compared with c, Φ=0 and 1, indicates obviously more increase of reliability index and lower standard deviation as water levels rise. To the case of a certain water level, c, Φ=-1 does not have constantly positive or negative effects on landslide reliability compared with c, Φ=0 or 1, but is associated with water level. Whereas the safety factor Fs by deterministic method, which is almost the same value as corresponding mean of safety factor from probabilistic analysis, will increase slightly as water level increases.

Evaluation of potential surface instability using finite element method in Kharsali Village,Yamuna Valley,Northwest Himalaya

Kharsali village, located in the Northwest Himalaya near the confluence of the Yamuna River and Unta Gad, is situated on a thick(>150 m) paleolandslide deposit. The village is continuously being eroded at its base by the two rivers. Cracks are noted in most houses while the ancient Shani Temple lying to the south of the village has tilted ~5° towards the northeast. Three slope sections(S-1, S-2, S-3) were modelled and analysed to determine the displacement and shear strain patterns of the slopes. Based on surface failure conditions, potential slope instability of the Kharsali village was evaluated from 2D Finite Element Method(FEM) using Shear Strain Reduction(SSR) analysis in the Phase2 software. Results indicate a critical Stress Reduction Factor(SRF) of 1.5 for the southern edge of the village(S-1) housing the Shani Temple. The development of failure surfaces at its lower portion signifies the propagating, progressive nature of the slope. The S-2 slope section is most vulnerable to slope failure, with a critical SRF of 1.08. This has been inferred by the formation of failure surfaces with displacements of 0.05-0.08 m. The S-3 section in the northern part of the Kharsali shows highest critical SRF of 2.76. The un-metalled road section in the north of the village near S-3 hasdeveloped a failure surface with displacement of 0.003-0.004 m, and a zone of subsidence. The S-3 section is relatively stable, whereas the S-2 section is the most vulnerable portion of the village.

The Ellipsoidal Surface Method Solving by Integration for Slope Stability Analysis

Landslide is common phenomena in construction field. Nowadays the cylindrical surface method has been used widely to analyze slope stability. However, this method contains two main disadvantages： firstly, the slip surface is assumed to be in circular shape while in fact it is ellipsoid commonly; and secondly, resolve by difference method causing immensely complicated process due to statically indeterminate equations. In this paper, the authors have presented a method that allows transferring of ellipsoid slip surface to cylindrical shape and carries out a single variable equation （by applying integration method）. Also thanks to this method, the current cylindrical surface method has been proved that its application is proper for man-made slopes but usually inappropriate for natural ones. Those results help analysis of slope stability reaching closer to reality.

Study on high and steep slope stability of surface mine based on RFPA-SRM

The instability and failure mechanism of high and steep slopes in surface mines, and the basis for some reasonable landslide prevention measures were provided using the RFPA-SRM. Based on the actual progress of the Pingzhuang Western Surface Mine and based on strength reduction method, the dynamic instability processes of the top high and steep slope was simulated. Also, the landslide mode was determined, the characteristics of the displacement distribution, the deformation, failure, and the stress distribution in the slope were demonstrated, and the stability was calculated. Conclusions can be drawn as follows： the landslide or failure of high and steep slopes on a surface mine is a gradual process, in which the slope undergoes the generation, expansion, and connection of the fractures and the displacement increases until landslide occurs; a small portion of the upper rocks fail due to the tension and the lower rocks fail due to the shear; the potential sliding surface is combined and the essential cause of the landslide is the shear stress concentration.

地聚物固化黄土力学性能及边坡稳定性研究

研究以中国西北地区近年来黄土路基滑坡为背景.通过击实试验和直剪试验,测得不同地聚物掺量下固化土的试验数据,并通过扫描电镜(SEM)和X射线衍射(XRD)对钢渣-粉煤灰地聚物固化土进行微观结构分析,同时结合pF-Meter仪器测定不同地聚物掺量下固化土的基质吸力与体积含水率.后基于强度折减法,将试验数据代入COMSOL Multiphysics中,通过饱和-非饱和理论的Richards方程,建立固化黄土路基边坡有限元模型.分析降雨前后路基层中地聚物掺入量和坡比对路基边坡的整体稳定性的影响.结果表明:当固化土中地聚物掺入量为25%时,内摩擦角为31.2°,内摩擦角增幅相比于重塑黄土提高了62.5%.随着地聚物掺入量的增加,黏聚力呈现出先升后降的趋势,当地聚物掺入量为20%时达到最高峰,为81.09 kPa,相比于重塑黄土提高了75.86%.路基边坡的稳定性随着地聚物掺入量的增加先上升后下降,随着坡比减小而上升.在特定条件下,边坡稳定性会随着降雨时间的延长而降低,随着降雨强度的增大而减小.

双层滑带滑坡土环剪试验与稳定性分析

以云南省文山至麻栗坡高速公路K39段复合型双层滑带滑坡为例,采用室内环剪试验探明该滑坡深层、浅层滑带各自的残余强度,分析不同含水率、法向应力和剪切速率对滑带土残余强度的影响;采用FLAC3D软件进行数值模拟,基于滑坡应力-应变历史对滑坡稳定性进行评价。结果表明:滑带土在低含水率情况下力学强度较高,饱和状态抗剪强度参数表现出明显的衰减趋势;在地下水位保持高位时,深层滑带更易发生渐进式蠕动滑移。模拟结果显示:滑坡的深层滑带应力集中现象较为显著,浅层滑坡危险性较小,滑坡在暴雨工况下整体稳定性明显降低,存在一定风险,可通过设置排水洞等降水措施进行治理。

滑坡在役防治工程缺陷分类和健康评价方法

为快速评估常见在役滑坡防治工程的运行状态并采取科学有效的维护手段,笔者在三峡库区、汶川震区和川东地区实地调查了160余处抗滑挡墙、抗滑桩和格构锚固工程,获取了上述三类滑坡防治工程表征损伤的第一手资料,总结分析了其变形破坏模式及特征,定义了滑坡防治工程缺陷的概念,定性地提出了缺陷程度分级标准。在统计分析滑坡防治工程损伤特征基础上,选取了墙身滑移距离、墙身沉陷位移、墙身倾斜程度、墙身裂缝密度、桩体倾斜程度、桩体剪切程度、桩体裂缝密度、格梁最大裂缝宽度、单根格构梁裂缝率和受损格构变形区比例等10个控制指标作为其缺陷分类指标,结合多元线性回归法,对单体工程结构进行综合量化评分评定,进而建立了半定量的滑坡防治工程健康评价方法。

基于双折减系数法与极限平衡法的顺层滑坡稳定性分析

以四川省布拖县龙潭乡冯家坪滑坡为例,利用FLAC3D软件设计了基于双折减系数法的滑坡稳定性分析程序,应用“GIS-Rhino-FLAC3D”耦合技术建立三维地质体模型。考虑黏聚力和内摩擦角在滑坡失稳过程中衰减速度和弱化程度的不同,以及非饱和土中基质吸力对土体抗剪强度的影响,提出一种以黏聚力和摩擦力的衰减权重定义综合安全系数的双折减系数法,并采用极限平衡法作对比计算,研究分析了顺层滑坡的稳定性。结果表明:设计的抗剪强度参数双折减程序可以得出安全系数云图,直观地反映滑坡安全系数的空间分布特征;与传统强度折减法相比,所提出的双折减系数法计算的滑动面分布范围和综合安全系数更精确,较极限平衡法误差更小,可以准确地反映滑坡的稳定状态。研究结果可为双折减系数法应用于滑坡灾害的防治提供参考。

级配与拦挡位置对滑坡碎屑流运动影响研究

为了研究不同级配的高位滑坡碎屑流经多级偏转后冲击不同拦挡结构的运动特性以及致灾效应,结合自然地形构建固定坡度和偏转角度均为45°的离散元模型,并利用DEM软件进行数值模拟分析不同拦挡工况和不同级配对碎屑流颗粒运动过程中能量耗散、最终堆积形态,以及碎屑流冲击挡板的作用高度的影响,进而建立相关冲击力学模型。研究结果显示:(1)上下均设置挡板的工况能有效减缓碎屑流颗粒的平均动能和势能,且能有效降低颗粒流翻越挡板的数量,并降低颗粒流的最大运动距离从而减小致灾范围;随着颗粒组级配的增大,势能时程曲线分散点出现的时间越晚,颗粒流最终堆积面积中细颗粒组最大,粗颗粒组最小。(2)当滑槽底部反作用力位置取2/3静止堆积体长度时,计算所得碎屑流最大冲击作用高度与模拟试验结果相接近,力学模型计算的冲击作用高度在0.017~0.138 m。在实际工程中,可按研究相似比对此范围进行加强抗冲击防护。(3)由于侧板的切向力和“颗粒分选效应”,大颗粒会主要冲击挡板的中上部,小颗粒主要冲击挡板的下部,并受偏转角影响集中在一侧,因此工程设计可根据实际情况避免在沟道偏转方向的反向建设工程。研究结果可为高位滑坡碎屑流灾害的治理防护提供参考。

渣土填埋场滑坡风险等级评估——以杭州某渣土场为例

“渣土围城”是我国城镇化发展以来最大的障碍之一,渣土场滑坡给周边环境带来了极大的安全隐患。针对渣土场滑坡风险评估的复杂性,建立了一种渣土场滑坡风险等级评估方法,该方法以定性和半定量的方式将渣土自身特性和滑坡特点考虑在滑坡风险评估的各个物理过程中,构建边坡安全系数与失稳概率等级的对应关系,将边坡失稳概率等级与危害性等级分为极高、高、中、低4级,并建立4×4的风险等级矩阵;提出贯穿渣土场建设全过程的滑坡风险管控对策,涉及渣土场选址、建设和治理、监测和预警、应急响应4个部分;以杭州某渣土场为例详细说明该方法在实际场地中的应用,通过对研究区域进行边坡稳定性分析、运移距离估计和危害性结果统计,评估了该渣土场在堆填结束后的滑坡风险等级。