Experimental study on grouting uplift after induced settlement of existing tunnel under shield tunneling

In order to find out the effect of bag grouting method in treating the subsidence induced by shield tunneling under the existing tunnel, based on the model test of shield tunneling under the tunnel, the grouting process of bag grouting method was independently designed, and the experimental study on induced subsidence induced grouting uplift of shield tunneling under the tunnel was carried out. The flexural deformation, tunnel settlement, additional earth pressure change and grout diffusion mode of the upper tunnel during the induced settlement grouting test of the existing tunnel under shield tunneling are studied. The test results show that the transverse elliptic deformation occurs at the distance of 120cm-250cm from the north end of the tunnel. Similarly, the lifting height of the upper tunnel at this position is obvious, and the maximum lifting height is about 15mm in the middle of the tunnel. The increase of additional earth pressure is the largest in the middle of the tunnel. In the process of grouting, the bag grouting method has a good binding effect on the slurry, and the slurry is crowded and diffused in the bag during the grouting process, and the slurry pressure is mainly concentrated in the vicinity of the bag grouting mouth, which causes the soil around the soil arch effect. In the actual project, it is suggested to use multi-point grouting at the same time to lift the tunnel as a whole, so that the internal force and structural form of the tunnel structure after rectification can be restored to the state before the underpass. At the same time, the monitoring of tunnel lift should be strengthened in the process of grouting to prevent the tunnel lift from exceeding.