地震作用下重力式挡土墙土压力特性数值模拟研究

Numerical Simulation of Soil Pressure Characteristics of Gravity Retaining Walls during Earthquake

重力式挡土墙在地震作用下的土压力特性一直是挡土墙设计的重要内容。本文通过数值模拟,在挡土墙墙背轴线上设置一系列监测点,得到地震过程中监测点的加速度、土压力强度时程曲线;然后根据时程曲线分析墙后土压力强度分布特征、根据土压力强度分布求出总土压力、根据总土压力求出其对墙趾的力矩;最后分别将土压力强度分布、总土压力、总土压力对墙趾的力矩与现有的研究方法及规范对比。结果表明:地震作用下墙背各点加速度峰值在同时刻发生,但土压力峰值不在同时刻发生;现有的一些研究方法未考虑土压力强度峰值时程变化,其结果比实际偏大;在低地震烈度条件下,规范计算的总土压力及倾覆力矩偏于保守,而在高烈度条件下则偏于危险。

The soil pressure characteristics of gravity retaining walls under seismic action are an important consideration in the retaining wall design.In the seismic design codes of many countries,including China,the seismic soil pressure of a retaining wall is calculated using the Mononobe-Okabe formula.Previous studies have identified many limitations with respect to some of the assumptions of the Mononobe-Okabe formula,which has led to results that are inconsistent with actual situations.As such,the reliability of this method must be further examined.In their detailed studies of the soil pressure characteristics of retaining walls,researchers have improved the pseudo static method,developed the pseudo dynamic method,and introduced model experimentation and numerical analysis,which have greatly improved the accuracy of the calculated results.However,most research has considered maximum earthquake intensity,but not the impact of the time-history variation of seismic waves on the soil pressure behind the wall.In this study,we used numerical simulation to establish a series of monitoring points on the back of the retaining wall and then obtained time-history curves of the acceleration and soil pressure strength.Based on these time-history curves,we then analyzed the distribution characteristics of soil pressure strength,calculated the total soil pressures,and obtained the overturning moment of the toe of the wall.Finally,we compared the soil pressure distribution,total soil pressures,and overturning moment of the toe of the wall with those calculated by existing methods and codes.The results show that the peak acceleration of each monitoring point occurs at the same moment,but the peak soil pressure does not.Some existing methods do not consider the time-history change of peak soil pressure strength,thereby yielding a bigger result than is practical.In low seismic intensity conditions,the total soil pressures and overturning moments calculated by codes tend to be conservative,whereas in high intensity conditions they tend to be dangerous.