考虑干燥裂缝时非饱和土垂直切坡临界自稳高度

利用双应力状态变量表示方法，建立了考虑干燥裂缝时吸力沿深度均匀分布和随深度线性减小两种情况下垂直切坡极限自稳高度表达式．研究表明，自稳高度不仅依赖于土的强度．而且与基质吸力有关．一方面基质吸力提高了土的抗剪强度，从而有助于提高垂直边坡的稳定性；另一方面地表干燥裂缝深度随吸力的增大而增大，从而吸力的增大又将削弱边坡的稳定性．与不考虑干燥裂缝情况相比，考虑干燥裂缝时垂直切坡的极限自稳高度将有所降低，这些结果对基坑无支护开挖具有理论指导意义和工程应用价值。

Assessment of critical stable height of vertical cut slopes of unsaturated soils considering drying shrinkage cracks on ground

Based on the two variables of stress state, formulas for estimating the critical stable height of vertical cut slopes of unsaturated soils are established respectively for two cases in which suction is constant or linearly decreases with depth. It is shown that the critical height is dependent on both matric suction and strength parameters. On one hand, suction can enhance the stability of vertical slope since shear strength will increase with the suction. On the other hand, suction will initiate surface cracks on ground, leading to the reduction of the stability of slopes. The feature of variation of the critical height with suction is associated with comprehensive effects of related parameters of soil. Compared with the condition that shrinkage cracks on ground are overlooked, the critical heights of slope considering drying shrinkage cracks get smaller. The study is instructive and useful in design of excavation of deep foundation pits without supports.