地震作用下桩间挡土构件主动土压力极限分析方法

Limit analysis method for seismic active pressure on sheets between anti-slide piles

地震作用下抗滑桩或支护桩之间挡土构件的土压力计算是工程技术人员面对的难题之一。根据一系列试验现象归纳出的桩间土体滑塌面特点,建立了桩间挡土构件后侧土体局部失稳的三维滑动楔形体模型。通过计算三维失稳机构的内部能量耗损率和外荷载功率,根据极限分析上限定理建立了能够考虑地震作用的桩间挡土构件主动土压力解析计算方法。将桩间挡土构件土压力计算结果与等尺寸刚性挡墙土压力对比发现,基于三维楔形体模型得到的挡土构件主动土压力小于采用平面应变模型的挡墙主动土压力。通过分析多个水平和竖直地震加速度组合对应的桩间挡土构件主动土压力发现,水平地震加速度与竖直地震加速度对桩间挡土构件主动土压力均有明显影响,同时考虑双向地震作用得到的挡土构件主动土压力大于单独考虑水平或竖直地震作用时的挡土构件主动土压力。

Calculating the seismic active pressure on sheets between anti-slide piles or stabilizing piles remains a longstanding challenge for engineers and technicians. According to the characteristics of soil sliding surface between piles based on the generalization of a series of experiments, a three-dimensional sliding wedge model for the instability of local soil is established. By calculating the internal energy dissipation rate and the external load power of the three-dimensional instability mechanism, an analytical procedure for seismic active pressure calculation is proposed based on the limit analysis theorem. By comparing the seismic active pressure acting on sheets between piles with that on rigid retaining wall, it is found that the earth pressure on sheets by using the three-dimensional sliding wedge model is less than that on retaining wall by using the plane strain model. The analysis of multiple combinations of horizontal and vertical earthquake accelerations, indicates that both the horizontal seismic acceleration and the vertical earthquake acceleration have significant effect on the active earth pressure of sheets between anti-slide piles, and that the active earth pressure considering bi-directional seismic action is greater than that considering horizontal earthquake effect or vertical earthquake effect separately.