地震作用下土质边坡稳定性图表

Stability Charts for Soil Slopes under Seismic Excitation

针对评估边坡稳定性问题,边坡稳定性图表提供了一种简单但却行之有效的途径。选用对数螺旋面作为边坡破坏模式,利用拟静力法考虑地震效应的影响,并基于极限分析运动学定理推导了破坏机构内外功率计算公式,采用MATLAB最优化程序求解出边坡临界高度γH/c的上限解。通过确定边坡处于极限状态时的c/γH和tanφ关系曲线,绘制了一系列边坡稳定性图表。讨论了坡角、内摩擦角与地震荷载对边坡稳定性及其破坏模式的影响。结果表明:坡底破坏模式仅在坡角及内摩擦角均较小的情况下发生,且随着地震荷载的增大,坡底破坏模式更易发生;随着内摩擦角的增大,破坏模式逐渐由深层破坏转变为浅层破坏;边坡坡角较大时,边坡临界滑动面总是呈浅层破坏模式,并随着地震荷载的增大,边坡安全系数逐渐减小。对于内摩擦角接近于0°的土体,当坡角较小且边坡受到地震荷载影响时,需要对破坏深度作一定限制以得到合理解答。利用所建立的边坡稳定性图表无须迭代计算即可求得边坡安全系数以及对应的破坏模式。通过对比验证了所建立边坡稳定性图表的合理性。所得结果可为边坡工程稳定性评估提供一定参考。

To assess the stability of slopes,the slope stability chart provides a simple but effective way.Selecting the log-spiral surface as the failure mode of slope,using the pseudo-static method and considering the influence of earthquake effect,the calculation formulas of the internal and external powers of the failure mechanism are derived based on the kinematics theorem of limit analysis,and the upper limit of the critical heightγH/c of slope is solved by MATLAB optimization program.By determining the c/γH-tanφcurve when the slope is in the limit state,a series of slope stability charts are drawn.The influences of slope angle,internal friction angle and seismic load on the slope stability and failure mode are discussed.The result shows that(1)The failure of slope toe only occurs when the slope angle and the internal friction angle are both small,and the failure mode of slope toe is more likely to occur with the increase of seismic load.(2)With the increase of internal friction angle,the failure mode gradually changes from deep failure to shallow failure.(3)When the slope angle is large,the critical slip surface of the slope always presents a shallow failure mode,and the slope safety factor gradually decreases as the seismic load increases.For the soils with an internal friction angle close to 0°,it is necessary to limit the failure depth to get a reasonable answer when the slope angle is small and the slope is affected by seismic load.Using the established slope stability charts,the slope safety factor and the corresponding failure mode can be obtained without iterative calculation.The validity of the established slope stability charts are verified by comparison.The obtained result can provide a certain reference for the stability evaluation of slope engineering.