波动承压水作用下基坑底部弱透水层超静孔压试验研究

Experimental research on excess pore pressure in aquitard at bottom of foundation pit due to fluctuation of confined water

研制模拟承压水持续变化的试验装置,并利用该装置研究弱透水层在波动承压水作用下的孔压变化规律。研究结果表明:承压水波动引起的弱透水层超静孔压由振荡超孔压和平均超孔压2部分组成;振荡超孔压幅值沿着自下而上的渗流路径急剧衰减;平均超孔压在深度方向上呈非线性的分布;承压水波动周期、幅值对平均超孔压的影响较小,但对振荡超孔压幅值的比值衰减速度和传递范围影响较大;在承压水波动周期较长的情况下,孔隙水压力较容易在弱透水层中传递,在基坑突涌稳定性验算中应充分关注弱透水层底板渗流破坏的可能性;改变承压水初始水位对超孔压的传递影响不显著。

A test device for simulating continuous changing confined water was developed and used to study the response of excess pore pressure in aquitard due to the fluctuation of confined water.The results show that the excess pore pressure of the aquitard is composed of two parts:the oscillatory excess pore pressure and average excess pore pressure.The amplitude of oscillatory excess pore pressure decays rapidly along the seepage path,and the distribution of the average pore water pressure along the depth deviates from the linear relationship.The fluctuation period and amplitude of confined water have little influence on average excess pore pressure,while significantly affect the oscillating excess pore pressure attenuation speed and propagation range in soil.The pore water pressure is more easy to be propagated in the aquitard in longer period of confined water fluctuation,and the possibility of seepage damage to the foundation pit should be carefully considered in the design of the foundation pit stability.The influence of the initial water level on the propagation of the excess pressure is not significant.