地震动土压力水平层分析法

Mononobe-Okabe公式是挡土结构设计中关于侧向动土压力计算的常用方法。但Mononobe-Okabe公式的诸多假设使得其公式适用范围受限,而且无法给出地震动土压力合力作用点位置及地震动土压力强度沿墙背分布情况。为弥补以上不足,基于Mononobe-Okabe平面破裂面假设,采用水平层分析法推导地震条件下主动和被动土压力合力及其作用点位置、土压力强度分布公式,并采用图解法得到临界破裂角的显式解答。公式考虑水平和垂直地震加速度、墙背倾角、挡墙墙背与填料黏结力和外摩擦角、均布超载等诸多因素,可以适用于黏性土和无黏性土的主动和被动土压力计算。分析结果表明,地震条件下土压力强度沿墙高为非线性分布,在相应简化假设条件下公式与Mononobe-Okabe公式完全一致。

HORIZONTAL SLICES ANALYSIS METHOD FOR SEISMIC EARTH PRESSURE CALCULATION

Mononobe-Okabe formula is widely used in lateral seismic earth pressure calculation in the design of retaining walls. However，application scope of Mononobe-Okabe formula is strictly limited because of too many assumptions. The distribution of seismic earth pressure strength along the back of retaining wall and the position of application point of resultant force of seismic earth pressure can¢t be obtained. In order to compensate above shortcomings，based on planar rupture surface assumption of Mononobe-Okabe theory，horizontal slices analysis method is suggested to deduce analytical formulas of resultant force of seismic earth pressure，application position of resultant force and distribution of seismic earth pressure；and the explicit solution of critical rupture angle is obtained by graphic method. The influencing factors including horizontal and vertical seismic accelerations，batter angle of wall back，cohesion and external friction angle between filler and back of retaining wall，equispaced overloading are considered. The formulas can be used for seismic active and passive earth pressure calculations of cohesive soil or non-cohesive soil. The analysis results show that the distribution of seismic earth pressure strength along the back of retaining wall is nonlinear. The formula is the same as Mononobe-Okabe formula under corresponding simplified assumptions.