粉土与淤质互层土中管桩压入过程孔隙水压力试验研究

Experimental study on pore pressure during pile driving in silty soil with mucky soil interbed

为了解管桩沉桩过程中孔隙水压力的变化情况,通过对杭州萧山某工地的沉桩挤土效应进行现场监测,得出以下结论:场地中央的超孔隙水压力明显大于应力释放孔两侧相应深度处的超孔隙水压力,且应力释放孔内侧的超孔隙水压力也要大于应力释放孔外侧同一深度的超孔隙水压力;超孔隙水压力的动态变化规律绝大多数呈先增长后减少的趋势,沉桩距离较远时,超孔隙水压力整体变化呈缓慢增长趋势,而沉桩距离较近的时候,超孔隙水压力变化多呈先增长后减少趋势;本工程3～7m左右为粉土与淤泥质土的交界面,由于粉土与淤泥质土的渗透性不同,导致超孔隙水压力在3～7m左右会发生突变;PTC-500(65)管桩沉桩时,周围超孔隙水压力的变化明显要大于PTC-400(60)管桩沉桩时周围超孔隙水压力的变化。当沉桩距离小于5m的时候,超孔隙水压力变化比较明显;当沉桩距离超过5m的时候,超孔隙水压力变化逐渐减缓,趋于均速。

In order to understand the changes of the pore water pressure during pile driving,field monitoring of compaction effect is carried out at a site in Xiaoshan Hangzhou and some rules can be concluded.The excess pore water pressure of field space is significantly greater than that of the both side of holes to relax stress,and the excess pore water pressure of the inside of holes to relax stress is also larger than that of the lateral side.The most dynamic change law of excess pore water pressure is mostly growth at the first and decline at the last.When the pile driving distance is large,the dynamic change law of excess pore water pressure is slow growth during the pile driving,and when the pile driving distance is small the dynamic change law of excess pore water pressure is growth at the first and decline at the last during the pile driving.Because the permeability of silty soil and mucky soil is different,the excess pore water pressure is mutation at the depth of 3 m to 7 m,where is the interface between silty soil and mucky soil.When the PTC-500(65) pile is driving,the excess pore water pressure is much larger than that of PTC-400(60) pile.When the pile driving distance is less than 5 m,the excess pore water pressure changes obviously and when the pile driving distance is larger than 5 m the excess pore water pressure changes slowly.