某输变电工程深基坑降水止水措施及开挖变形研究

Research on Water-stopping Measures and Excavation Deformation of Deep Foundation Pit in a Power Transmission Project

【目的】为了降低某输变电工程地下水和软弱土体带来的施工风险,保证深基坑安全施工,通过分析其工程和水文地质条件,设计了井管降水和高压旋喷桩止水方案。【方法】构建基坑剖面网格模型,采用有限差分法模拟该深基坑开挖导致的变形。【结果】计算结果表明,第一步放坡开挖后,最大水平位移为26.7 mm,最大坑底隆起为10 mm;第二步开挖后,基坑水平位移最大为24.6 mm,地连墙水平位移最大约为15 mm,最大地表沉降为6.5 mm,开挖变形均在安全范围内。【结论】模拟结果表明,在该工程的水文地质条件下,所设计的降水止水及开挖方案安全合理,对类似条件下的深基坑工程施工具有一定参考意义。

[Purposes]In order to reduce the construction risk caused by groundwater and soft soil in a power transmission project and ensure the safe construction of deep foundation pits,the well-pipe de-scending and high-pressure rotary piling water-stopping schemes are designed by analyzing its engineer-ing geological and hydrogeological conditions.[Methods]The pit profile grid model is constructed,and deformations caused by excavation of the deep foundation pit are simulated using finite-difference method.[Findings]Calculation results show that after the first step of sloping excavation,the maximum horizontal displacement is 26.7 mm,and the maximum pit bottom bulge is 10 mm;after the second step of excavation,the maximum horizontal displacement of the pit is 24.6 mm,the maximum horizontal dis-placement of the ground wall is about 15 mm,the maximum surface settlement is 6.5 mm,and the defor-mations of the excavation are within the safety range.[Conclusions]The simulation results show that un-der the engineering geological and hydrogeological conditions,the designed precipitation and water stop-ping as well as excavation schemes are safe and reasonable,and have certain reference significance for deep foundation pit projects under similar conditions.