地震作用下边坡稳定性分析的拟静力法研究

Research on quasi-static method of slope stability analysis during earthquake

在极限平衡框架领域内,考虑直线、圆弧和任意曲线这3种滑动面型式,基于拟静力法对地震作用下的边坡稳定性进行分析。首先,对3种滑动面型式下边坡安全系数和临界水平地震作用系数的计算公式进行推导,其中,不考虑条间力的瑞典圆弧滑动面法和考虑条间力的M-P任意曲线滑动面法分别被采用。然后,当坡高、坡比、土层内摩擦角和黏聚力及水平地震作用系数均在一定范围内取值时,研究这5个参数变化对边坡稳定性的影响。在坡高和坡比一定时,分析不同土层内摩擦角和黏聚力下比例系数ξ(即竖直与水平地震作用系数之比)的取值对临界水平地震作用系数的影响,并采用正交实验比较坡高、坡角和土层参数对不同强度地震下边坡稳定性的影响。研究结果表明:在不同坡高、坡比和地震强度下,边坡的最小安全系数与土层黏聚力和内摩擦角近似呈线性比例关系;在极限平衡方法中,采用曲线滑动面分析较强地震作用下黏聚力较大而内摩擦角、坡高和坡比均较小的边坡稳定性时,得出其滑动面的破坏范围显著增大且得不到合理的最小安全系数;当黏聚力和内摩擦角均较小时,比例系数ξ越大,则计算所得的临界水平地震作用系数越大,而当黏聚力或内摩擦角较大时,比例系数ξ越大,则计算所得的临界水平地震作用系数越小;坡高和坡角是影响地震作用下边坡稳定性的2个主要因素,因此,地震区域中的边坡应该尽量降低坡高或放缓坡角。

In the field of limit equilibrium framework, based on quasi-static method, the stability of slope was analyzed during earthquake considering three kinds of slip surface（line, circular and arbitrary curve）. Firstly, when adopting three kinds of slip surface, the calculation formula for factor of safety（FOS） and the critical horizontal seismic coefficient were respectively derived. Swedish method without considering infer-forces in type of circular slip surface and M-P method considering infer-forces in type of arbitrary curve slip surface were respectively adopted. When five parameters, i.e.,slope height, slope ratio, internal friction angle and cohesion of soil, and the horizontal seismic coefficient, were all selected in a reasonable range, the effect on slope stability was studied with change of these parameters. When slope height and slope ratio is constant, the effect of proportion coefficient ξ（i.e., ratio of vertical and horizontal seismic coefficient） on the critical horizontal seismic coefficient was analyzed with different friction angles and cohesions of soil.And orthogonal experimental method was adopted to contrast influence relation of some factors such as slope height,slope angle and soil parameters on slope stability in different earthquake intensities. The results show that there is approximately relation of linear proportion between the minimum FOS of slope and cohesion, internal friction angle of soil in different slope heights, slope ratios and earthquake intensities. In the limit equilibrium method, when the curve slip surfaces are adopted to analyze stability of slope in strong earthquake, which has a large cohesion and small internal friction angle, slope height and slope radio, instability range of slip surface in the slope increases significantly and the minimum FOS can not be gotten reasonably. When cohesion and internal friction angle are both small, the calculated critical horizontal earthquake coefficient is greater with greater proportion coefficient ξ, while the calculated critical horizontal earthquake coefficient is smaller with greater proportion coefficient ξ if cohesion or internal friction angle is large. Slope height and slope angle are two main factors of affecting stability of slope during earthquake, so height of slopes located in earthquake zone should be reduced and angle of these slopes should be also slowed down.