A study of residual strength and method for evaluating the stability of slopes

在滑坡稳定性评价中，明确滑面区域内材料的残余强度特征是十分重要的。残余强度是粘土颗粒最终定向的表面的最小抗剪强度。达到残余状态所需的最小剪切位移的大小取决于粘土颗粒的性质和法向有效应力。泥岩要求位移量为40 ~ 60 cm，砂质凝灰岩要求位移量为200 ~ 300cm。环剪试验是达到残余状态的有效方法，但受大位移剪切和排水条件的影响，需要较长时间。残余强度参数与滑坡土的物理矿物学特性密切相关。结果表明，粘土掺量、塑性指数和蒙脱石掺量是估算残余强度参数的有效指标，值得进一步研究。反分析的强度参数不能预测滑坡斜坡的稳定性。该方法结合了反分析、残余和峰值强度参数、残余系数、安全系数和Mohr-Coulomb方程，使大规模的稳定性评价成为可能。强度参数的计算方法有以下特点：(1)将室内强度参数纳入土力学有效性评价。(2)介绍了安全系数反分析中常用的标准切片法。(3)在引入残差因子后，将残差和峰值强度两个参数纳入表达式。(4)考虑滑块的类型和滑块表面的状况。通过估计剩余系数计算安全系数，可以有效地确定处于休眠状态的滑坡易发边坡的安全系数，特别是在滑坡块体分布较多的地区，其中一些地区实际发生了滑坡。少

In evaluating the stability of landslide, it is important to clarify the characteristics of residual strength of materials in the slip surface zone. The residual strength is the minimal shear strength along the surface where clay particles are finally oriented. The magnitude of the minimal shear displacement that is needed to attain to the residual state depends on the clay particle property and the normal effective stress. The magnitude of displacement as long as 40-60 cm for mudstone and 200-300cm for gravelly tuffaceous soil were required. A ring shear test is an effective method to attain the residual state, although long time is required due to the large-displacement shearing and the drained conditions.Residual strength parameter is closely connected with the physical and mineralogical characteristics in landslide soils. It is concluded that clay fraction, plastisity index and amount of smectite appear to be a useful guide to estimate the residual strength parameter, and that furt … More her examination of the matter is warranted.Back-analyzed strength parameters were not capable of predicting stability of landslide-prone slopes. The proposed method that incorporates a combination of back-analysis, residual and peak strength parameters, residual factor, safety factor and the Mohr-Coulomb's equation makes it possible to conduct a large scale stability evaluation.The method for calculations of strength parameters are featured by the followings: (1) Laboratory strength parameters are incorporated into the evaluation for soil mechanical validity. (2) The standard slice method, a method used in back-analysis for safety factors, is introduced. (3) Two parameters of residual and peak strengths are incorporated into the expression after residual factors are introduced. (4)The type of slides and the condition of slip surfaces are taken into considerations.Calculations of safety factors through the estimated residual factor are believed to be effective in determining safety factors of those landslide-prone slopes in dormant state, particularly of those found in areas where many landslide blocks are being spread out, some of which are actually undergoing slides. Less