地铁重叠隧道上覆地层变形的数值模拟

以在建的深圳地铁I期工程重叠隧道为例,采用FLAC3D非线性大变形程序对重叠隧道暗挖四步台阶法施工引起的地层三维变形规律进行了数值模拟研究。结合现场试验断面的实测数据对比分析,得到隧道开挖过程中开挖引起的地层变形和失水引起的地层变形量值,并区分一般地层和含水、含砂地层的环境控制标准,明确了深圳一般软土地层地表沉降最大值为60mm,含水、含砂地层地表沉降最大值为120mm。同时指出,对沉降控制要求较高的地段,可采用造价较高的地表垂直旋喷等辅助施工措施减小地层变形,这已在实际工程中取得了成功。研究结果对深圳地铁后期建设和同类地层地铁施工环境控制有借鉴和参考价值,对浅埋暗挖法在富水软土地层中的推广应用提供部分理论依据。

NUMERICAL SIMULATION OF STRATUM DEFORMATION ABOVE OVERLAPPING METRO TUNNEL

Taking the overlapping tunnel of Shenzhen Metro Phase I project for example,the FLAC~3D (fast Lagrangian analysis of continua)codes was adopted to model the stratum 3D deformation regularity caused by four-step shallow tunnel construction method(STCM). By comparing with the in-situ monitor data of the test section,the value of stratum deformation caused by tunnel excavation or seepage of groundwater was obtained, and the environment control standard of general stratum is differentiated from that of aqueous sand stratum. According to the standard,the maximum value of ground settlement of general soft stratum of Shenzhen Metro is 60 mm and that of aqueous sand stratum is 120 mm. For some position with high standard of ground settlement control requirement,second reinforcement measures are taken to decrease stratum deformation,such as ground vertical jet grouting reinforcement which costs more than the general reinforcement measures. The technique has been applied successfully in Shenzhen Metro Phase I project. The research result will provide reference for controlling the construction environment of the construction of Shenzhen Metro and the project with the similar stratum. It will also offer theoretical reference for the application of shallow tunnel construction method(STCM) to aqueous soft sand stratum.