关键词: 钢套管灌注桩, 土塞效应, 土体膨胀率, 群桩施工顺序, 土塞剪切破坏

Abstract: This paper studies the influence of construction sequence of piles with steel sleeve on existing adjacent tunnels through theoretical research and numerical simulation. The results are tested and verified by the field testing data. Firstly, the stress conditions of soil plug column during the spinning down process of steel sleeve are analyzed through theoretical methods. Differential equations are established to calculate the bottom stress of the soil plug column as well as the suffered cutting torsion and the resistance shear torque of soil plug. As a result, the critical depth of shear failures and plugging effect of soil plug is obtained. Based on the study, the soil expansibility is studied in two cases according to whether the plugging effect happens. The influence on existing tunnels by construction sequence of group piles is then discussed through theoretical analysis and numerical simulation using the corresponding expansibility, resulting in a relatively optimal pile construction sequence scheme. The comparative analysis between field testing data and numerical simulation results indicates that the calculated results above are in good agreement with actual situation. This research provides theoretical guidance and practical reference for similar projects.

Key words: cast-in-place pile with steel sleeve, plugging effect, soil expansibility, construction sequence of group piles, shear failure of soil plug