Abstract: To effectively control the ground deformation induced by shield tunneling in sandycobble strata, a case study is conducted on the Beijing metro line 17 crossing above the existing SouthtoNorth water transfer tunnel project, and the insitu monitoring and numerical simulation methods are employed to examine the ground deformation control effect of tunneling parameters, special new segment design, soil grouting prereinforcement, supplemental grouting reinforcement, and clay shock products filling. The research results show the following: (1) The newlybuilt tunnel induces surface soil subsidence, as a result, supplemental grouting should be conducted after the first tunnel passes to avoid dramatic increasing in ground settlement induced by later tunnel construction. (2) The horizontal deformation of deep soil decreases gradually from top to bottom with increasing soil depth, and the surface soil deformation is the largest. (3) Vertical lifting occurs to the lower existing water transfer tunnel at the intersection of the two tunnels, and basically no horizontal deformation occurs. (4) In sandycobble strata, reasonable shield tunneling parameters and grouting reinforcement can effectively reduce the impact of new shield tunneling on the existing tunnel structure.

Key words: sandycobble strata, newlybuilt shield tunnel, existing water transfer tunnel, upper crossing construction, ground deformation, insitu monitoring, numerical simulation