桩间缝隙注浆加固对基坑围护桩变形的影响

Pile Displacement Effect of Compaction Grouting on the Gap between Retaining Piles and Improvement Soil

软土地区深基坑往往需要对被动区土体进行水泥土搅拌加固,以减小基坑变形。而坑底加固土与围护桩之间存在的缝隙需要通过压密注浆加固。以上海地区某基坑为背景,采用有限差分法建立了三维数值计算模型。将数值计算结果与实测进行了对比,验证数值计算模型的合理性。计算结果表明,桩间缝隙注浆加固对基坑围护桩位移的影响可占到被动区加固总影响量的24%。围护桩位移随着注浆加固体的弹性模量、粘聚力、内摩擦角的增加而减小,且减小幅度逐渐降低。粘聚力在10kPa以下时,对围护桩位移影响不大,而当粘聚力继续增加,围护桩位移随着粘聚力增加而快速减小。内摩擦角变化对围护桩位移影响显著大于弹性模量及粘聚力。

Soil mixing on the passive zone is often used in deep excavations on soft soil ground to minimize the displacement induced by the excavation. The gaps between the columns of ground improvement and the retaining piles need to be treated by compaction grouting. Based on a deep excavation case in Shanghai a three - dimensional finite difference model was established to study the gap soil improvement. The accuracy of the numerical model was verified by comparing the calculated results with the field data. The analysis results showed that the decrease of the pile displacement induced by the gap soil improvement is 24% of the total decrease induced by the passive zone improvement. The pile displacement decreased with the increase of elasticity modulus and friction angle of the improved gap soil then the displacement tend to be constant with their increase. The pile displacement had no obvious change when the cohesion of the improved gap soil increased under 10kPa. While the cohesion goes on increasing the displacement decreases. Compared to the elasticity modulus and cohesion the friction angle had a greater influence on the pile displacement.