膨胀土边坡失稳机理分析及基于完全软化强度的边坡极限平衡计算方法

Study on the failure mechanism of expansive soil slope and limit equilibrium analysis method based on fully softening strength

通过有荷膨胀率试验、干湿循环试验和强度试验,研究裂隙发育对土体强度及坡体渗流条件的影响;基于温度场、湿度场等效理论模拟吸湿膨胀;分别采用干湿循环强度和完全软化强度计算膨胀土边坡安全系数;综合考虑边坡土层分区、土体强度参数取值、浸润线等因素,提出基于完全软化强度的膨胀土边坡滑动稳定性极限平衡分析方法,模拟膨胀土边坡浅层渐进式破坏过程,并用算例验证所提方法的适用性。研究结果表明:随裂隙发育程度增大以及浸润线位置升高,膨胀土边坡稳定性降低;膨胀土裂隙性是影响边坡稳定性的关键因素,裂隙引起的土体强度衰减及渗流条件改变是导致边坡失稳的直接原因;由于在强度衰减中已体现膨胀作用对边坡稳定性的影响,因此,在膨胀土边坡稳定性分析中,无需单独考虑膨胀作用影响;采用干湿循环强度和完全软化强度计算膨胀土边坡安全系数,两者计算结果具有较好的一致性,表明本文所提方法可用于分析膨胀土边坡的稳定性。

The influence of crack development on soil strength and seepage conditions of slope was studied by the load expansion ratio test,the wet and dry cyclic test and the strength test.Based on the equivalent theory of temperature and humidity field,the expansion of slope induced by the increase of moisture was simulated.The stability of the expansive soil slope was calculated using the wet and dry cyclic strength and the fully softened strength respectively.Considering the slope soil zone partition,the values of strength parameters and the determination of saturation line,a limit equilibrium analysis method for shallow sliding stability of expansive soil slope based on fully softening strength was proposed.The progressive failure process of expansive soil slope was simulated,and the applicability of the proposed method was verified by examples.The results show that with the increase of fissure development and the lift of the location of the infiltration line level,the stability of the expansive soil slope decreases;fissures are the key factors that induce the stability of expansive soil slopes.The reduction of soil strength caused by cracks and the change of seepage conditions are the direct causes of slope instability.The influence of expansion on slope stability is reflected in strength reduction,and so it is not necessary to take into consideration of the influence of expansion additionally in the stability analysis of expansive soil slope.The safety factor of the expansive soil slope calculated by using the wet and dry cyclic strength is in good agreement with that caclulated by using the fully softened strength.The method proposed in this paper can be used to analyze the stability of expansive soil slope.