钢套管灌注群桩施工顺序对多隧道的影响

通过理论研究和数值分析方法，分析了钢套管桩不同的施工顺序对邻近既有隧道的影响，并结合现场实测数据对分析结果进行了验证。首先，采用理论方法分析钢套管旋转下压过程中土塞柱的受力情况，建立微分方程计算土塞柱底端的应力、土塞柱受到的剪切扭矩和自身抗剪扭矩，进而分析得到了土塞柱发生剪切破坏和土塞效应的临界深度。在此基础上按是否产生闭塞效应，分两种情况研究了钢套管旋压过程中产生的土体膨胀率。然后，利用既得的土体膨胀率，通过理论分析和数值模拟方法分析了群桩不同的施工顺序对既有多条盾构隧道的影响，得出了相对较优的群桩施工顺序方案。工程现场实测数据与数值模拟结果的对比分析表明，上述计算结果与实际情况能较好吻合。该研究对类似工程具有理论指导意义和实践参考价值。

Influence of construction sequence of cast-in-place group piles with steel sleeve on tunnels

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.