基坑降水对下卧地铁盾构隧道的影响

结合某公寓基坑工程,针对地铁盾构隧道下穿该基坑的复杂环境条件,首先采用简化大井法计算帷幕失效(工况一)下基坑降水坑外地层的水力坡降曲线,采用二维有限元渗流法计算帷幕有效(工况二)下基坑降水坑外地层的水力坡降曲线;接着采用分层总和法计算基坑降水引起地铁盾构隧道的附加沉降,分析基坑降水对下卧地铁的影响.结果表明:(1)考虑截水帷幕失效与有效两工况下,基坑降水引起下卧地铁盾构隧道右线中轴线处水位降深分别为4.2 m、1.5 m;(2)考虑截水帷幕失效与有效两工况下,基坑降水引起下卧地铁盾构隧道右线、中轴线底部最大沉降分别为-2.83 mm、-1.3 mm,均满足轨道交通安全运营的要求.

Influence of Dewatering of Foundation Pit on Beneath Subway Shield Tunnel

Combined with a complex environment condition of foundation pit engineering with an apartment,considering the condition including shield tunnel of metro beneath foundation pit,a simplified big well method is firstly used to calculate the hydraulic gradient curve of outer stratum of foundation pit under the dewatering condition of curtain failure(condition one),and two-dimensional finite element method is used to calculate the hydraulic gradient curve of outer stratum of foundation pit under the dewatering condition of effective curtain(condition two). Then the additional settlement of subway shield tunnel caused by dewatering of foundation pit is calculated by the layered summation method,and the influence of dewatering of foundation pit on underground subway is analyzed. The results show that:(1) Considering two dewatering conditions including the failure and effective of water proof curtain,the drawdown of the central axis on the right line of subway shield tunnel are 4.2 m and 1.5 m,respectively;(2) Considering two dewatering conditions including the failure and effective of water proof curtain,the maximum settlement of the central axis on the right line of subway shield tunnel are-2.83 mm and-1.3 mm,respectively,which meets the safety operation requirements of rail traffic.