粉土与粉质黏土互层中静压桩桩土界面孔隙水压力

Pore Water Pressure at Pile-Soil Interface of Jacked Pile in Silty Soil and Silty Clay

为研究层状黏性土在静压桩沉桩过程中桩土界面孔隙水压力的分布规律,依托山东东营某桩基工程开展了现场足尺静压桩试验,分析了桩土界面孔隙水压力的变化规律,探讨了桩土界面超孔隙水压力的分布特征,明确了桩土界面孔隙水压力和超孔隙水压力的消散特性,并结合水力压裂理论和孔穴扩张理论,揭示了沉桩过程中桩土界面沿桩长方向超孔隙水压力的分布形式。试验结果表明:孔隙水压力、超孔隙水压力与土层性质密切相关,二者均在粉土层中增长较慢,在粉质黏土层中增长较快;在同一深度处,两者均存在明显的消散现象,在粉土中的消散程度明显大于粉质黏土中;采用水力压裂理论结合孔穴扩张理论计算的超孔隙水压力沿桩长方向的变化规律与试验值相吻合;桩身贯入深度越大,超孔隙水压力理论计算值与现场实测值越接近。

In order to study the distribution of pore water pressure at the pile-soil interface in the process of static pressure pile sinking in a layered clay, based on a pile foundation project in Dongying, Shandong Province, a full scale static pressure pile test was carried out. The variation law of pore water pressure at the pile-soil interface was analyzed, the distribution characteristics of excess pore water pressure at the pile-soil interface were discussed, and the dissipation characteristics of pore water pressure and excess pore water pressure at the pile-soil interface were clarified. Combined with the theory of hydraulic fracturing and the theory of hole expansion, the distribution pattern of excess pore water pressure at the pile-soil interface along the direction of pile length during the process of pile sinking was revealed. The experimental results show that pore water pressure and excess pore water pressure are closely related to soil layer properties. Both of them increase slowly in the silt soil layer and faster in the silty clay layer. At the same depth, both of them are obviously dissipated, and the degree of dissipation in silty soil is obviously greater than that in silty clay. The variation law of excess pore water pressure along the direction of pile length calculated by hydraulic fracturing theory combined with hole expansion theory is consistent with the test value. The greater the penetration depth of pile, the closer the theoretical calculation value of excess pore water pressure is to the field measured value.