The stress release ratio of the surrounding rock in tunnel excavation is one of the most important indicators that affect the stress distribution and displacement of the surrounding rock. To determine the variation law of the stress release ratio of the surrounding rock during excavation in silty clay stratum, the stress release law is determined based on the convergence–confinement method (CCM) and field test data. The stress release law of the surrounding rock under support is determined based on the displacement back analysis method. The permitted displacement safety factor of silty clay under different subgrade conditions and the optimal supporting time of the initial supporting structure are determined by comparing the stress release ratio with surrounding rock displacement. The results indicated that the stress release ratio of surrounding rock in the silty clay stratum is approximately 78–90% when the coordinate displacement of the supporting structure and surrounding rock is stable under the current excavation and support conditions. For the surrounding rock of subgrade V in the silty clay stratum, the safety factor of the permitted displacement in the tunnel vault is approximately 2.91, and the initial support should be carried out within 1 m behind the face advancing. For the surrounding rock of subgrade VI1, the safety factor of the permitted displacement is 1.40, and the initial support must be carried out 1 m ahead of the tunnel face. For the surrounding rock of grade VI2, the initial support must be carried out 4 m ahead of the tunnel face.
Relying on the Shenyang Metro Line 4 Shifu Road station, the impact of the construction parameters of the transverse pilot tunnel on the surface subsidence and the pipe curtain deformation was first studied through numerical simulation, followed by the analysis of the impact of the excavation of the transverse pilot tunnel on the deformation characteristics of the pipe curtain through on-site monitoring. The results show the following: the excavation of the middle pilot tunnel is the key stage of the construction. The excavation sequence of H2 and H4 and H6 → H1 and H3 → H5 and H7 caused the least surface subsidence. Increasing the grouting width and improving the strength of the initial support can control the pipe curtain deformation very well, and it is reasonable to choose 1.5 m as the grouting width.
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