含地下水的回填砂土重力式岸墙地震残余角位移的拟静力计算

Calculation of seismic angular displacement of gravity quay walls with backfill sand and groundwater

引用液化度指标考虑含地下水的回填砂土地震过程中的超静孔隙水压力对墙体运动的影响,基于Mononobe-Okabe拟静力法修正考虑液化度的动主动土压力,根据静力水压力理论近似计算土颗粒里的动水压力。同时考虑了水平与竖向地震载荷,根据力矩极限平衡确定旋转门槛加速度系数,采用旋转块体方法计算岸墙主动旋转运动下的地震残余角位移。选用一理想的地震运动特征,应用该简单预测位移的方法对一算例进行了推算;并对回填砂土内摩擦角、墙体与土间摩擦角、水平与竖向地震加速度系数、回填土地下水位、墙前自由水位和码头墙宽高比多种参数下对旋转角位移的影响作了详细的定性分析,得出墙体残余角位移随着回填砂土液化度升高而逐渐增大,以及当液化度很高时土的内摩擦角和墙体的摩擦将不再起工程作用等有用结论。

The index of liquefaction extent is introduced to consider the effect of excess pore water pressure of backfill sand with groundwater acting on quay walls movement in the process of earthquake. The dynamic active earth pressure is calculated by modified Mononobe-Okabe pseudo-static method and the dynamic water pressure is approximately computed according to the static water pressure. The horizontal and vertical earthquake load are considered simultaneously and the threshold acceleration coefficient is determined by equilibrium of the rotating moment and restoring moment. On this basis, a simple calculation method of seismic angular displacement of gravity quay walls under the action of earthquake is developed by rotating block method. An application example under ideal ground acceleration is given. Furthermore, the effects of parameters such as soil friction angle, wall friction angle, horizontal seismic acceleration coefficient, vertical seismic acceleration coefficient, submergence of backfill, water level in front of the wall as well as the size of the cross section of quay are analyzed.