基于有限差分强度折减法的多级边坡破坏模式研究

总结了当前多级边坡的稳定性分析方法,引入FLAC3D程序和强度折减理论,并运用有限差分强度折减法研究了多级边坡随台阶宽度变化的破坏模式、变形及其稳定性。分析结果表明:多级边坡的滑移面的位置、形状和破坏模式随着台阶的宽度不同而不同,且其变形也随着台阶的宽度不同表现出不同的特性。最终通过对多级边坡进行稳定性分析,发现安全系数和滑移面广义剪应变大小也随台阶宽度的变化也表现出一定的规律性。

小型水库土坝护坡破坏原因及其防护措施

由于水库土坝护坡设计不当、施工质量差或管理不善等方面原因 ,在波浪、冰凌和其它外力作用下 ,水库往往遭受破坏 ,影响工程效益发挥 ,甚至威胁水库安全。通过对哈尔滨 7区 12县 (市 )小型水库土坝护坡的调查 ,对土坝护坡破坏的种类、原因进行详细探讨 。

植被破坏前后土壤微生物分布与肥力的关系

通过对子午岭林区林地、裸露休闲地、砍伐迹地及开垦农地不同处理，不同侵蚀部位土壤微生物区系分布以及肥力因素的研究，表明：林地开垦为裸露休闲地和农地，以及砍伐后的砍伐迹地，其土壤微生物区系在土壤剖面中的分布仍呈从上到下急剧下降的趋势，但其总量在裸露休闲地、砍伐迹地以及农地上明显低于林地。在几个试验处理坡面的不同侵蚀部位上，剖面中微生物分布有很大差异，说明土壤侵蚀对土壤微生物有显著影响。土壤细菌，放线菌和真菌与土壤有机质，全Ｎ等肥力因素有一定的相关性。

CFCs对臭氧层的破坏作用及其控制对策

ＣＦＣｓ对大气臭氧层的破坏作用已引起有关国际社会及许多国家的严重关注．１９９１年６月，我国成为新的《蒙特利尔议定书》的缔约国．因此，ＣＦＣｓ的控制对策及其替代技术的研究将对我国国民经济的发展和环境保护产生意义深远的影响．本文着重介绍了ＣＦＣｓ破坏臭氧层的机制，ＣＦＣｓ的全球控制对策及其替代技术研究等方面的情况．

缝管式锚杆支护破坏形式分析及改进措施

本文对缝管式锚杆支护破坏形式进行了分析,并提出改进措施.

黄石盘水库长石坝滑坡稳定分析

本文根据勘察资料对长石坝滑坡的地貌形态、滑体结构、滑床形态及滑动带等基本特征的描述,进行了滑坡成因与变形破坏机制的分析,通过对滑动带、滑坡体的物理力学试验成果的分析与研究,运用多种方法进行了滑坡的稳定性以及滑坡失稳涌浪和堰塞高度的分析与计算,为设计确定是否对滑坡进行保护和处理提供了地质依据。

黑岩头斜坡发生地质灾害的机理及稳定性分析

对黑岩头斜坡的地质环境特征,地质灾害发育的特征及地质灾害发生的机理进行分析,最终对斜坡的稳定性进行了评价。

生态旅游:古老的实践,新兴的研究领域

生态旅游虽然有着古老的实践历史 ,但却是一个新兴的领域。作为景观资源和环境保护与开发的一个持续发展途径 ,生态旅游是现代旅游业持续发展的重要方向 ,也是一个新的经济增长热点。目前旅游管理与规划决策者及公众对生态旅游的真正含义缺乏认识和理解具有普遍性 ,操作时常常与大众旅游相混淆。本文综述了生态旅游的内涵及近年来在国内外的发展与研究状况 ,归纳了生态旅游的基本类型及其特点 ,以及生态旅游与现代传统旅游的区别 。

Deformation features and failure mechanism of steep rock slope under the mining activities and rainfall

Underground mining activities and rainfall have potential important influence on the initiation and reactivation of the slope deformations,especially on the steep rock slope. In this paper,using the discrete element method(UDEC),numerical simulation was carried out to investigate deformation features and the failure mechanism of the steep rock slope under mining activities and rainfall. A steep rock slope numerical model was created based on a case study at the Wulong area in Chongqing city,China. Mechanical parameters of the rock mass have been determined by situ measurements and laboratory measurements. A preliminary site monitoring system has been realized,aiming at getting structure movements and stresses of unstablerock masses at the most significant discontinuities. According to the numerical model calibrated based on the monitoring data,four types of operation conditions are designed to reveal the effect of mining excavation and extreme rainfall on the deformation of the steep rock slope.

A modified Hoek-Brown failure criterion considering the damage to reservoir bank slope rocks under water saturation-dehydration circulation

After water is impounded in a reservoir, rock mass in the hydro-fluctuation belt of the reservoir bank slope is subject to water saturation- dehydration circulation （WSDC）. To quantify the rate of change of rock mechanical properties, samples from the Longtan dam area were measured with uniaxial compression tests after different numbers （1, 5, 10, 15, and 20） of simulated WSDC cycles. Based on the curves derived from these tests, a modified Hock- Brown failure criterion was proposed, in which a new parameter was introduced to model the cumulative damage to rocks after WSDC. A case of an engineering application was analyzed, and the results showed that the modified Hock-Brown failure criterion is useful. Under similar WSDC-influenced engineering and geological conditions, rock mass strength parameters required for analysis and evaluation of rock slope stability can be estimated according to this modified Hoek-Brown failure criterion.

Progressive failure processes of reinforced slopes based on general particle dynamic method

In order to resolve grid distortions in finite element method(FEM), the meshless numerical method which is called general particle dynamics(GPD) was presented to simulate the large deformation and failure of geomaterials. The Mohr-Coulomb strength criterion was implemented into the code to describe the elasto-brittle behaviours of geomaterials while the solid-structure(reinforcing pile) interaction was simulated as an elasto-brittle material. The Weibull statistical approach was applied to describing the heterogeneity of geomaterials. As an application of general particle dynamics to slopes, the interaction between the slopes and the reinforcing pile was modelled. The contact between the geomaterials and the reinforcing pile was modelled by using the coupling condition associated with a Lennard-Jones repulsive force. The safety factor, corresponding to the minimum shear strength reduction factor "R", was obtained, and the slip surface of the slope was determined. The numerical results are in good agreement with those obtained from limit equilibrium method and finite element method. It indicates that the proposed geomaterial-structure interaction algorithm works well in the GPD framework.

3D stability assessment of stepped slopes in inhomogeneous soils

Stability assessment of slopes has historically been performed assuming soils to be homogeneous in two-dimensional(2D) cases. In real cases, soils are usually inhomogeneous, and each slope collapse indicates a three-dimensional(3D) nature. Based on a 3D rotational failure mechanism, this work develops an approach to account for the impact of the vertical strength inhomogeneity on the 3D stability of stepped slopes. Seismic actions are taken into account by introducing the concept of a horizontal seismic coefficient. An upper-bound expression for stability factors is derived in the light of the kinematic approach, and the most critical solution is obtained from an optimization programming. In comparison with the previously published solutions, the validity of the proposed method is shown. A sensitivity analysis is carried out to discuss parametric effects on the stability of 3D stepped inhomogeneous slopes.

Probabilistic seismic stability of three-dimensional slopes by pseudo-dynamic approach

Probabilistic analysis is a rational approach for engineering design because it provides more insight than traditional deterministic analysis. Probabilistic evaluation on seismic stability of three dimensional (3D) slopes is studied in this paper. The slope safety factor is computed by combining the kinematic approach of limit analysis using a three-dimensional rotational failure mechanism with the pseudo-dynamic approach. The variability of input parameters, including six pseudo-dynamic parameters and two soil shear strength parameters, are taken into account by means of Monte-Carlo Simulations (MCS) method. The influences of pseudo-dynamic input variables on the computed failure probabilities are investigated and discussed. It is shown that the obtained failure probabilities increase with the pseudo-dynamic input variables and the pseudo-dynamic approach gives more conservative failure probability estimates compared with the pseudo-static approach.

Deep-seated large-scale toppling failure in metamorphic rocks：a case study of the Erguxi slope in southwest China

Deep-seated large-scale toppling failure presents unique challenges in the study of natural slope deformation process in mountainous regions.An active deep-seated toppling process was identified in the Erguxi slope located in southwest China,which affected a large area and damaged critical transportation infrastructure with the volume of the deforming rock mass exceeding 24×10~6 m^3.It poses significant risks to the downstream Shiziping Hydropower Station by damming the Zagunao River.Field investigation and monitoring results indicate that the deformation of the Erguxi slope is in the advanced stage of deep-seated toppling process,with the formation of a disturbed belt but no identifiable master failure surface.It was postulated that the alternating tensile and shear strength associated with the hard/soft laminated rock strata of metasandstone and phyllite layers preclude the development of either a tensile or shear failure surface,which resulted in the continuous deformation and displacement without a catastrophic mass movement.The slope movement is in close association with the unfavorable geological conditions of the study area in addition to the construction of transportation infrastructure and the increase of the reservoir level.On the basis of the mechanism and intensity of the ongoing toppling deformation,a qualitative grading system was proposed to describe the toppling process and toevaluate the slope stability.This paper summarized the field observation and monitoring data on the toppling deformation for better characterizing its effect on the stability of the Erguxi slope.The qualitative grading system intends to provide a basis for quantitative study of large-scale deep-seated toppling process in metamorphic rocks.

Mechanical Analysis for Progressive Failure of Debris Landslide

It is of significance to research failure mechanism of debris landslides that are widespread in the Three Gorges Reservoir Area. Based on the statistical analysis of the developmental law and failure mode of debris landslides in the Three Gorges Reservoir, the mode of progressive failure is found. The mechanical model for progressive failure of debris landslides with two slip bands is also established by applying slice method. According to the results of the downslide force between adjacent slices, if the downslide force of lower slice is larger than zero, the slice fails along the major sliding surface, otherwise it is stable. In result, the failure range is obtained. The stress function can be determined through dimensional analysis of failure slice. According to static boundary conditions of the slice, stress state of any point in the slice can be obtained. Then stress state of any point in the secondary slip band can also be established. The failure of the secondary slip band is judged on the basis of Mohr-Coulomb failure criterion. Therefore, a mechanical method is proposed to analyze the progressive failure of debris landslide with two slip bands.

AN EXAMPLE OF THREE-DIMENSIONALPROGRESSIVE SLOPE FAILURE

In fact, the failure of any slope takes place progressively, but the progressive failure mechanism has not been emphasized sufficently in the present stability analysis of slopes. This paper provides an example of the progressive slope failure which took place at Pingzhuang west surface coal mine and was numbered the 26th slide. The three-dimensional reliability model for progressive slope failure is used to study the failure process of the 26th slide. The outcomes indicate that the progressive failure is indeed the failure mechanism of the slide.

Failure mechanism and stability analysis of the Zhenggang landslide in Yunnan Province of China using 3D particle flow code simulation

Based on the principle of 3D particle flow code,a numerical landslide run-out model is presented to simulate the failure process of the Zhenggang landslide(in southwestern China) under the effect of water after a rainfall.The relationship between the micro-mechanical parameters and the macro-shear strength of the grain material is determined through numerical calibrations.Then the rainfall effect is considered in numerical simulations and rain-induced sliding processes are performed,which help us to discuss the mechanism of deformation and failure of this landslide together with field observations.It shows the Zhenggang landslide would most likely be activated in Zone I and would gain momentum in Zone II.In order to prevent the potential disaster,a tailing dam is advised to be designed about 175 m downstream from the current landslide boundary of Zone II.Verified by field observations,the presented landslide model can reflect the failure mechanism after rainfall.It can also provide a method to predict the potential disaster and draft disaster prevention measures.

Dynamic failure mode and energy-based identification method for a counter-bedding rock slope with weak intercalated layers

The dynamic failure mode and energybased identification method for a counter-bedding rock slope with weak intercalated layers are discussed in this paper using large scale shaking table test and the Hilbert-Huang Transform(HHT) marginal spectrum.The results show that variations in the peak values of marginal spectra can clearly indicate the process of dynamic damage development inside the model slope.The identification results of marginal spectra closely coincide with the monitoring results of slope face displacement in the test.When subjected to the earthquake excitation with 0.1 g and 0.2 g amplitudes,no seismic damage is observed in the model slope,while the peak values of marginal spectra increase linearly with increasing slope height.In the case of 0.3 g seismic excitation,dynamic damage occurs near the slope crest and some rock blocks fall off the slope crest.When the seismic excitation reaches 0.4 g,the dynamic damage inside the model slope extends to the part with relative height of 0.295-0.6,and minor horizontal cracks occur in the middle part of the model slope.When the seismic excitation reaches 0.6 g,the damage further extends to the slope toe,and the damage inside the model slope extends to the part with relative height below 0.295,and the upper part(near the relative height of 0.8) slides outwards.Longitudinal fissures appear in the slope face,which connect with horizontal cracks,the weak intercalated layers at middle slope height are extruded out and the slope crest breaks up.The marginal spectrum identification results demonstrate that the dynamic damage near the slope face is minor as compared with that inside the model slope.The dynamic failure mode of counter-bedding rock slope with weak intercalated layers is extrusion and sliding at the middle rock strata.The research results of this paper are meaningful for the further understanding of the dynamic failure mode of counter-bedding rock slope with weak intercalated layers.

The Séchilienne (France) Landslide:a Non-typical Progressive Failure Implying Major Risks

The National Road RN 91 has been threatened for about twenty-five years by a huge landslide, located 25 km south-east to the town of Grenoble (France). If several million cubic meters of rock fall down, the debris will dam the valley. Then the failure of the dam by overtopping and rapid erosion might result in a catastrophic flood and dramatic consequences for human life, environment and economy throughout the valley. The paper presents the hazard assessment based on geological and hydrological surveys, including small scale hydraulic tests, as well as the risk evaluation that has been performed. The risk management relies first upon a high level monitoring and an emergency plan; various mitigation strategies have been considered.

Comparisons between centrifuge and numerical modeling results for slope toppling failure

This paper presents series studies on the toppling mechanism by centrifuge tests and numerical simulations. Two different discrete element methods, i.e., the continuum-based discrete element method(CDEM) and the discontinuous deformation analysis(DDA), are adopted. The modeling results show that both the methods can accurately capture the failure modes of the centrifuge tests, including three distinct zones and two failure surfaces. Comparisons are made between the physical test and numerical simulation results. The critical inclination angle of the tilting table where the slope models are fixed on can be moderately predicted by the two methods, with different degrees of precision. The error between the test results and the simulated results is within 1% for the slope models without rock-bridges by both CDEM and DDA. However, it is amplified for the staggered-joint models that simulate the rock-bridges. With DDA, the average error is about 5%, and the maximum error is up to 17%. While with CDEM, the errors for the aligned-joint models are ranged from 1% to 6%, and it is from 10% to 29% for the staggered-joint models. The two numerical methods show the capability in simulating toppling failure of blocky rock mass with and without rock-bridges. The model with rock-bridges which provides a certain bending resistance is more stable than the one without any rock-bridge. In addition, the two failure surfaces were observed, which is different from the common understanding that only one failure surface appears.