The variational limit equilibrium method is adopted to calculate the active earth pressure with and without tension cracks appearing. According to static equilibrium equations of sliding soil, a functional extreme-value isoperimetric model of cohesive soil is deduced in the general case of an inclined wall, sloping backfill, and uniform surcharge on the backfill surface. The active earth pressure is caculated by a functional extreme-value problem of two unknown functions through introducing two undefined Lagrange multipliers. According to the corresponding Euler equations and the boundary conditions, functions of the sliding surface and the normal stress distribution along the sliding surface, which contain two undefined Lagrange multipliers, are deduced.

采用变分极限平衡法计算有无裂隙的有效土压力。根据滑土的静平衡方程，推导了在通常为倾斜墙，倾斜的回填和回填表面均匀附加费的情况下粘性土的功能极值等渗模型。通过引入两个未定义的拉格朗日乘数，通过两个未知函数的函数极值问题来计算主动土压力。根据相应的欧拉方程和边界条件，推导了包含两个未定义的拉格朗日乘数的滑动面函数和沿滑动面的法向应力分布。