静压桩挤土效应及施工措施试验研究

Testing Study on Squeezing Effects and Construction Control Measures of Jacked Piles

为减小静压桩施工对周围环境产生的影响,需要采取合理措施减小沉桩挤土效应。以软土地区某桩基工程建设项目为依托,选取预钻孔、预钻孔与应力释放孔结合的施工措施,进行了预制空心方桩的挤土效应试验。通过预埋孔隙水压力计与测斜管,监测了静压桩不同贯入深度下土中孔隙水压力和土体水平位移的变化规律。监测结果表明:超孔压的影响半径超过12d,且超孔隙水压力随上覆有效应力的增大而增大;静压桩挤土效应引起的水平位移在软硬土层交界面附近将发生突变;预钻孔及释放孔的影响半径超过12d;前一节桩压桩在桩周土体中产生裂缝有利于后续压桩过程中超孔压的消散。试验结果对认识静压桩沉桩挤土效应,进而制定减小沉桩挤土效应的合理措施提供有效帮助。

To reduce the influence of squeezing effects on surrounding environment, reasonable measures are expected to be taken to reduce the squeezing effects. Based on the pile construction projects in soft soil areas, pre-bored hole and pre-bored hole integrated with stress-release hole construction measures were used and three precast hollow square piles were selected to conduct the squeezing effect tests. With the help of embedded pore water pressure gauge and inclinometer tube, the rule of pore water pressure and radial displacement of soil under different driving stages were monitored. Results provided the influence radius of pore pressure. The study also shows that the excess pore water pressure increases with the increasing of overburden effective stresses. The largest radial displacement caused by the driving effects occurred in the vicinity of the interface between the hard and soft soil. The cracks in soil produced by the previous driving process facilitated the dissipation of excess pore pressure in subsequent driving stages. The experimental results provided the understanding of squeezing effects of jacked piles.