渗流条件下具有张裂缝边坡的稳定性分析

Stability analysis of slope with tensile crack under condition of seepage

针对渗流条件下具有张裂缝边坡的稳定性,将流网合理简化,采用以土体(总应力法)或土骨架(有效应力法)为研究对象的2种方法,基于直线、圆弧和任意曲线3种滑动面型式,推导出折线型和台阶型边坡的安全系数计算公式。通过算例分析比较这些方法的异同,并研究张裂缝位置与张裂缝水位对边坡稳定性的影响。研究结果表明:从计算所得的安全系数来看,直线滑动面最大,任意曲线滑动面与圆弧滑动面相接近,但比之较小,说明任意曲线滑动面所得结果更偏于安全;当采用同种类型滑动面时,以土体和土骨架为研究对象的2种计算方法所得的安全系数和临界滑动面均接近,但以土骨架为研究对象的计算方法所得结果偏小一些,因而,以该种计算方法分析所得边坡状态更偏于安全;曲线滑动面(包括圆弧和任意曲线)计算认为张裂缝位置离坡顶距离越近,边坡稳定性越小,而直线滑动面计算认为张裂缝对边坡稳定性影响最大的位置存在特定值;当张裂缝水位升高时,各方法计算所得的安全系数均减小,说明张裂缝水位越高,边坡状态越不稳定。

To study stability of slope with tensile crack during seepage, flow nets were simplified reasonably, and two methods, i.e taking soil body （total stress method） and soil skeleton （effective stress method） as research object, were used. Based on three kinds of sliding surface, including linear, circular and arbitrary curve, formulas for calculating factor of safety （FOS） were derived into slopes with shape of broken lines and steps. Through analyzing some examples, the similarities and differences of these methods were compared, and the effects of crack location and water level of crack on slope＇s stability were studied. The results show that the FOS calculated by using linear sliding surface is the biggest, and that calculated by using arbitrary curve sliding is close, but smaller than that calculated by using circular sliding surface, which shows that calculated results of arbitrary curve sliding surface is safer. When adopting the same type of sliding surface, the calculated FOS is quite close, and the critical sliding surfaces are almost the same through using two methods of taking soil body and soil skeleton as research object. The results calculated by method of taking soil skeleton as research object are small. Therefore using method of taking soil skeleton to analyze slope＇s state could make the results tend to be safer. The results calculated by curve sliding surface show that the closer to the top of slope the location of tension crack is, the more dangerous the slope is. The results calculated by linear sliding surface show that there is a specific crack＇s location that has greatest impact on stability of slope. When water table of tensile crack increases, the FOS calculated by each method all decreases, which indicates that the higher the water table of tensile crack is, the unsafer the state of slope is.