Selected aspects of the stability assessment of slopes with the assumption of cylindrical slip surfaces

A comprehensive analysis of maintaining stability by model homogeneous and stratified slopes, with possible surcharge loading, is carried out within the article. Calculations are performed by the Swedish method of Fellenius under the assumption of a cylindrical slip surface passing through the slope foot. Proposals for searching for the reach of the break-off wedge of a potential slip surface are put forward. An analysis of the effect of surcharge load location on general slope stability is also made, providing the capability to determine the safe distance of positioning of an excavator on the surcharge of a non-encased excavation.     

Development of a probabilistic approach for rock wedge failure

For rock slope engineering, uncertainty and variability are inherent in data collected on orientation and strength of discontinuities, yielding a range of results. Unfortunately, conventional deterministic analysis based on the factor of safety concept, requires a fixed representative value for each parameter without regard to the degree of uncertainty involved. Therefore, the deterministic analysis fails to properly represent uncertainty and variability, so common in engineering geology studies. To overcome this shortcoming, the probabilistic analysis method was proposed and used for more than a decade in rock slope stability analysis. However, most probabilistic analyses included a deterministic model as part of the analysis procedure causing subsequent problems, which went uncorrected. The objectives of this paper are to develop a solution for these difficulties in probabilistic analyses and to propose an appropriate simulation procedure for the probabilistic analysis of rock wedge failures. As part of the solution, probability of kinematic instability and probability of kinetic instability are evaluated separately to provide a proper, combined evaluation for failure probability. To evaluate the feasibility of this new probabilistic approach, the procedure is applied to a practical example, a major, highway rock cut in North Carolina, USA. Results of the probabilistic approach are compared to those of the deterministic analysis; findings are significantly different, indicating that the deterministic analysis does not depict rock slope variations, particularly where significant scatter in parameter data occurs.     

Accretion rates on some debris slopes in the Mt. Rae area,Canadian Rocky Mountains

Accretion of debris was monitored on six slopes in the Mt. Rae area of the Canadian Rocky Mountains for the period 1975–1982. Monitoring was accomplished by measuring annually the accumulated debris on fabric mats which were placed on the long profile of the slopes. Annual rates of accretion were extremely variable between points on the same slope, between slopes, and between years. The data do not show a systematic decrease in accretion downslope but indicate that an absence of accretion is more likely on the lower half of the slopes. In general, annual rates are comparable to previously published values from the Rockies and the maximum rates of 30 to 40 mm per year are comparable to those from Karkevagge in Scandinavia. Extremely high rates of accretion were all related to extreme events such as debris flows or full depth snow avalanches. The variation in accretion rates is not explained by single environmental factors such as lithology and slope exposure.     

Ground retreat and slope evolution on regraded surface-mine dumps,waunafon, gwent

Ground retreat was monitored on two vegetated and two unvegetated profiles over a five-year period. The average annual retreat of the two unvegetated profiles was 5.84 mm and 3.62 mm; that of the two vegetated profiles 2.34 mm and 2.07 mm. Slope evolution was controlled by the mid-slope-ward migration of two zones of accelerated erosion and the resulting replacement of a central rectilinear slope segment by the upper and lower slope elements.     

SLIP4EX – A Program for Routine Slope Stability Analysis to Include the Effects of Vegetation, Reinforcement and Hydrological Changes

SLIP4EX is a straightforward computer program developed in connection with the EU funded ECOSLOPES project for routine stability analysis and the assessment of the contribution of vegetation to slope stability. The slope section is drawn up and dimensions and parameters are fed in to the Microsoft Excel based program for stability calculations and comparisons of Factors of Safety using different methods of analysis (Bishop, Janbu, Fellenius, Simple, Greenwood). The background and assumptions involved in the derivation of each of the methods is briefly described. The simplicity of the program enables the user to understand the nature of the analysis, explore the parameter assumptions made and compare the different methods of analysis. Soil reinforcement by geosynthetic layers or anchors, and vegetation effects of enhanced cohesion, changed water pressures, mass of vegetation, wind forces and root reinforcement forces are readily included in the analysis. The program is freely available on request from the Author.     

Geomorphology of medium‐high mountains under changing human impact,from managed slopes to nature restoration: a study from the Sudetes,SW Poland

In the last few hundred years, medium‐high mountain geomorphic systems of the East Sudetes, central Europe, have evolved under varying human impacts and have shown distinctive behaviours, depending on the nature and intensity of human activities. The general trend within this period has been from initial disturbance brought about by the spread of agriculture, through managed rural landscapes in the 19th and early 20th century, to gradual restoration of natural conditions observed in the last few tens of years, concurrent with considerable population decline in the mountain valleys. Accelerated soil erosion was successfully mitigated by the introduction of agricultural terraces in the 19th century, and most sediment could have been stored within the slopes. The current phase of nature restoration is understood as a return to general slope stability, weak coupling between slopes and channels, and limited sediment transfer across and out of mountainous drainage basins, which typified most of the Holocene prior to human colonization. Copyright © 2006 John Wiley & Sons, Ltd.     

节理化块体边坡失稳机理数值分析

针对三峡库区移民新址的工程地质问题，用改进的岩土工程软件系统FINAL，研究了节理化块体岩坡的失稳机理，指出除了节理的C，值控制岩块的滑移、倾覆变形，倾倒等破坏形式外，岩块的模量E也对倾覆变形破坏起重要作用，从而不仅说明了保护坡脚，防止岩块浸水软化的必要性，也说明了应用传统离散元法分析这类问题的局限性。     

Extensive deformations of rock slopes in southern Coast Mountains, southwest British Columbia, Canada

Extensive deformations of mountain slopes occur in crystalline intrusive rocks in the southern Coast Mountains of British Columbia. Typical morphological evidence of slope movement includes extensive systems of tension cracks, grabens, and antislope scarps (collectively referred to here as linears). These landforms involve displacements along penetrative joints observed in surface exposures. Kinematic tests on rock-structural data indicate that the observed patterns of linears are generally consistent with the feasible gravitational movements along the dominant discontinuities. Most sites indicate sliding as the most likely initial mode of movement, followed by or accompanied by toppling and toppling-induced sliding movements, and do not support the view that linears are the traces of active faults.     

青藏高原背风坡地形对西南涡过程影响的数值试验

在一个有三重水平结构的台风数值模式基础上，发展了一个能考虑青藏高原及其背风坡不同尺度地形的数值模式，用于９８１年７月１２日２０：００￣７月１４日２０：００西南涡个例的数值研究。模式中设计了全地形、１／３地形和无地形三种方案。对比试验结果表明：全地形对西南涡的移动和发展、形状和范围均能较成功地模拟，降低地形或无地形时，模拟则不成功。全地形时急流轴为偏北方向，而在１／３地形或无地形时，急流走向为偏东方     

多层接地框架土-结构共同作用分析

多层接地框架是山地、丘陵地区多见的一种结构形式,但以往对其抗震性能研究不足很多。利用二次开发后的ANSYS对多层接地框架抗震性能进行了上下部共同作用分析,发现多层接地框架的抗震性能受到地基情况的明显影响。