边坡稳定slopstability

b
▪ Assumptions (假定):
▪ no ground water table (没有地下水)
z
▪ homogeneous cohesionless soil (均质
无粘性土)
▪ failure surface is parallel to the
surface of the slope (滑动面与坡面
▪ For the slope stability analysis using the LEM, two
analyses are considered for each slope: ▪ Effective Stress Analysis (c´ and ´) that represents
drained or long-term behaviour of the slope (有效应 力分析对应边坡长期的稳定) ▪ Total Stress Analysis (cu) that represents undrained or short-term behaviour of the slope (总应力分析对应 边坡短期的稳定)
平行)
▪ The slope is inclined at angle to the
slope (滑动面为平面与坡面平行 )
Sliding mass (滑体)
Sliding surface or weak zone (滑动面
或软弱层)
Detached landslide deposit
(ii) Rotational slides ▪ Sliding surface is an arc which is common
▪ In general, the sliding surface is assumed to be a circular arc for clays or a logarithmic spiral for sands and gravels.
▪ Factor of safety is defined as the ratio of shear strength over shear stress acting on the soil mass at the assumed slip plane in order to maintain a condition of limiting equilibrium. (安全糸数定义为在极限平衡条件下抗剪 强度与下滑力之比)
Madison (Montana)
1959
Vaiont (Italy)
1963
Aberfan (Wales)
1966
Huascaran (Peru)
1970
Nevado del Ruiz (Colombia) 1985
Casitas (Nicaragua)
1998
Venezuela
1999
Swiss/Italian Alps
7.2 Types of slope failures (滑坡的类型)
(i) Translational slides
▪ failure of a slope along a weak zone of soil (沿软弱层滑动) ▪ failure surface tends to be plane and roughly parallel to the
2. Slop in cohesionless soil 无粘土边坡
1）. General case 常规情况
▪ For an infinite slope, the depth of the
failure surface is small compared ope (滑动面深度比边坡长 度小)
1. Limit equilibrium method (极限平衡法)
▪ In the limit equilibrium method (LEM), the soil is considered to be on the verge of failure along an assumed or a known sliding surface. (在某一假设滑动面上,整个 块体处于极限平衡状态)
2000
Loess flow Rockslide Rockslide Rockslide Debris-slide Complex Debris flow Debris flow Complex Debris flow
200,000 killed ~40 killed >100 killed 2,600 killed 144 killed 25,000 killed 23,000 killed +2,000 killed +20,000 killed 38 killed
Alpine debris flow (2000)
Las Colinas landslide, El Salvador (2001)
Major slope-instability related catastrophes of the 20th century
Kansu (China)
1920
Gros Ventre (Wyoming) 1925
in cohesive soils (粘性土的滑动面为一曲面)
Sliding surface (滑动面)
7.3 Methods of slope stability analysis (边坡稳定分析方法)
▪ The stability of a slope can be analysed using one or more of the following methods: ▪ Limit equilibrium method - equilibrium of forces ( 极限平衡法) ▪ Limit analysis based on plasticity - equilibrium of stresses (极限应力分析法) ▪ Finite difference method (有限差分法) ▪ Finite element method (有限元法)