富水软弱地层中桩周水土压力现场实测分析

为了解富水软弱地层沉桩过程中桩周水土压力变化规律,进而指导现场施工,开展沉桩过程中土压力和孔隙水压力现场监测分析。结果表明:沉桩过程中桩周孔隙水压力和土压力显著增长;孔压占比超过60%,最高达88%,易引起桩周有效应力损失,降低桩身稳定性;沉桩对桩周土压力影响范围较广,本项目实测中水平向影响范围为20倍桩宽;深度方向桩端距测点30倍桩宽开始影响孔隙水压力,距离10倍桩宽内影响显著增加;水土压力7 d后即可下降48%。在现场施工中,应通过控制沉桩速率、改变沉桩顺序等方法减小桩周挤土和孔压影响。

Field measurement and analysis of pore water pressure and earth pressure around piles in weak water-rich stratum

In order to understand the variation law of pore water pressure and soil pressure around the pile during pile sinking in the water-rich and weak stratum,and then to guide the on-site construction,we carry out the on-site monitoring and analysis of soil pressure and pore water pressure during pile sinking.The results show that the pore water pressure and soil pressure of the piles increase significantly during pile sinking;the pore pressure ratio exceeds 60%,and the highest reaches 88%,which easily causes the effective stress loss at the pile circumference and reduces the stability of the pile body;the influence of the soil pressure around the pile is wide.The effect range of the project is 20 times the pile width in the horizontal direction.The influence range of pore water pressure is 30 times the pile width in the depth direction.The influence increases sharply while the range is within 10 times the pile width.The pore water pressure and soil pressure could dissipate 48% after 7 days.During the on-site construction,the effects of pile-soil compaction and pore pressure could be reduced by controlling the rate of pile sinking and changing the order of pile driving.