双动载源下土质边坡的失稳机理

在丘陵地域和山区，铁路和公路共坡的区段时有出现。根据双动载源下(坡顶受公路载荷，坡底承受铁路载荷)土质边坡的受力状况，采用理论分析和计算机模拟的方法，分别就车辆载荷对边坡的传载方式以及边坡在各种载荷作用下土体单元的最大不平衡力变化情况进行了初步分析，同时，也对动载作用下单元的位移、速度、加速度等进行了比较系统的分析。分析结果表明，公路载荷对边坡稳定性的影响远远大于铁路载荷。对于缓倾斜边坡而言，位于坡底的铁路动载对边坡的破坏力可以不予考虑：由于公路载荷直接作用于坡顶，此类边坡上部的稳定性比下部弱，潜在滑移面大都出现在中上部：在频繁的公路载荷作用下，土体单元在滑移过程中有“位移滞回”现象，并且达到极限平衡状态之前表现得比较明显，由于“位移滞回”的随机性和不确定性，增加了边坡滑移体滑移迹线的复杂性，对此需要做进一步的研究。

INSTABILITY MECHANISMS OF SOIL SLOPE UNDER DOUBLE DYNAMIC LOADING

It is common for highway and railway to share the same slope in foothill and mountainous areas. The soil slope there suffers double dynamic loadings,one is the vehicles running on the highway on the top of the slope,and the other is the train trucks acting on the bottom of the slope. According to the loading situation,the variations of maximum unbalance force in the soil elements is discussed,and some interactive problems between the dynamics loading and soil slope are analyzed by means of theoretic analysis and numerical simulation. The study result shows that (1) the effect of vehicle loading on the instability of slope is greater than that of train truck loading,(2) in the same loading situation and environment,in the stability analysis process,the effect of train truck loading on the slope can be ignored for the soil slope with small inclination,and (3) for this sort of soil slope,there would be the potential sliding wedges in the middle areas of the slope surface. Finally,phenomenon of displacement lagging is found in analysis,which appears within the moving soil elements,and seems more evidently in the initial phases before limit equilibrium. In term of the theory of constitutive relations and the property of lagging ring under the circle loading conditions of soil,it is very easy to explain the phenomenon. Because of displacement lagging,the sliding tracks of instable soil wedges become more complicated,and further study is needed to solve this problem.