STUDY ON THE IMPACT OF CLOSELY SPACED TUNNELS CONSTRUCTION WITH LARGE CROSS-SECTION AND HYBRID METHOD

The metro stop line after the typical station on Xiamen metro line 1 is taken as the engineering background of this paper, based on engineering design drawings, the left tunnel and metro stop line construction by large section mining method(CRD excavation method) and the diameter of tunnel being about 11.53m, the right line tunnel construction by shield tunneling method and the diameter of tunnel being about 6.2m, the clear spacing of double-line tunnels is 3.85m. Through numerical simulation, the construction sequence of different sections, hybrid method, small spacing tunnels were studied, and the influence of tunnel spacing is also analyzed. As shown by calculation, engineers firstly construction the right line tunnel by shield tunneling method, then the large cross-section tunnel construction by mining method can efficiently decrease the surface subsidence, deformation of adjacent buildings and deformation of the tunnel structure. When the spacing between two tunnels greater than 1.5D(D:diameter of the large cross-section tunnel),the after built tunnel has less effect on the former tunnel, the additional deformation of the former tunnel smaller than 3mm. The computed result indicates the surface subsidence and deformation of adjacent buildings appears change suddenly in the stage of center pillar removal, attention should be paid to the rate of change at this time. The research findings would provide some references for the design and construction of similar tunnels.