Numerical Study on Shape Discrimination of Land Subsidence Groove during Double-line Shield Construction

Objective The shape of the land subsidence grooves during double-line shield construction varies with the clear distance and buried depth of the tunnel. Thus, it is necessary to conduct an in-depth study on the evolution mechanism of the subsidence groove with clear distance and buried depth. Method Based on the double-line shield project between Xiaonanjie Station and Renmin Park Station of Chengdu Line 17, numerical simulation is used to analyze the shape change process of the subsidence groove in the double-line shield construction under different clear distance-buried depth combination working conditions. Based on the double-line land subsidence formula, the values of each item in each working condition are fitted, and the shape criterion S of the subsidence groove is proposed. Result & Conclusion Peck formula and Liu Bo formula can express the simulated monitoring results of land subsidence well. When S∈0.319, 0.536), the subsidence groove is in a V-shape; when S∈0.536, 0.783), the subsidence groove is in a U-shape; when S∈0.783, 1.120), the subsidence groove is in a shallow W-shape; when S∈1.120, 3.873), the subsidence groove is in an asymmetric shallow W-shape; when S≥3.873, the subsidence groove is in a double V-shape or a double W-shape. When the buried depth of the tunnel is 1D (D is the tunnel diameter) and the clear distance between the two tunnels is 2D to 3D, the ground near the middle line of the two tunnels will bulge, and with the increase of the clear distance, the range of the bulge will increase accordingly. On the ground directly above the center of the two tunnels, due to the effect of the shield tail grouting pressure, part of the subsidence is offset, resulting in a unique double W-shape of the subsidence groove in this area.