基于动力学和材料软化特性的边坡渐进破坏特征研究

边坡的失稳是一个从量变到质变的动态渐进破坏过程，此问题也是边坡领域研究的重点与难点之一。在考虑岩土材料软化特性和动力学求解的基础上，建立了边坡渐进破坏仿真的理论框架；利用ABAQUS软件的动力显式求解模块实现了边坡的渐进破坏仿真；根据塑性应变揭露了剪切带的扩展过程，由软化本构确定了滑面材料的分区演化规律，根据等效塑性应变确定了边坡的滑面，通过滑面位置将边坡分为滑体、滑带、滑床，并分别研究了边坡各分区内部特征点运动学变量的发展过程，从而揭示了边坡的渐进破坏过程；基于材料参数沿滑面的时空分布，利用矢量和法得到了边坡不同演化阶段的安全系数。对比该方法与Bishop法确定的滑面位置与安全系数，发现两种方法峰值和残余强度对应的安全系数比较接近，该方法搜索所得滑面位于Bishop法自动搜索的滑面之间，验证了此方法的合理性及可靠性。最后分析了材料软化特征对边坡稳定性的影响，在保持其他参数不变的条件下，增大残余黏聚力，边坡的滑面位置加深，安全系数的初始值减小，安全系数的快速减小阶段有所推迟，并且快速减小阶段经历的时间有所延长，稳定后的安全系数有所增大。保持其他参数不变，增大残余黏聚力对应的等效塑性应变阈值，边坡的滑面位置加深，安全系数的初始值减小，安全系数的快速减小阶段有所推迟，但快速减小阶段经历的时间基本不变，达到稳定的时间有所推迟，同时稳定后的安全系数略微有所增大。

Progressive failure characteristics of slopes considering strain-softening behavior of geotechnical materials and dynamics

Slope instability is a dynamic progressive failure process from qualitative to quantitative, which is one of the key points and difficulties in slope investigations. A theoretical framework of the slope progressive failure is constructed by considering strain-softening behavior of geotechnical materials and the calculation of kinetic. The simulation of slope progressive failure is implemented into the dynamic explicit solution module of ABAQUS software. The extension process of shear band is revealed according to the developments of plastic strain. The partition evolution law of material parameters at the slip surface is determined by the softening constitutive model. The slope slip surface is obtained by the equivalent plastic strain. Slope can be divided into landslide body, sliding zone and slide bed by the location of the sliding plane. The development of kinematic variables of internal characteristic points in the partition zones is studied to reveal the progressive failure process of the slope. Based on temporal-spatial distribution of material parameters along the sliding plane, the safety factors of slopes are obtained at different evolutionary stages using the vector sum method. By comparing the vector sum method with the Bishop method, it is found that the safety factors corresponding to peak and residual strength parameters are relatively close using these two methods. The sliding plane determined by vector sum method is also located among sliding planes by Bishop method, which to a great extent demonstrates the procedure is rational and reliable. Finally, the influence of material softening characteristics on slope stability is analyzed. It is noticed that when the residual cohesion is increased but other parameters are constant, the sliding plane is deepened, the initial value of safety factor is reduced, the appearance time of rapid decreasing phase of the safety factor is delayed, the duration of rapid decreasing phase is extended, and the safety factor after slope stability is increased. When the threshold of the corresponding equivalent plastic strain of the residual cohesion is increased but other parameters are constant, the sliding plane is deepened, the initial value of safety factor is reduced; however the appearance time of rapid decreasing phase of the safety factor is substantially constant, the stable time is delayed, and the stability safety factor is slightly increased .