Field tests on large deformation control method for surrounding rock of deep tunnel in fault zone with high geostress

In view of the actual situation of large buried depth, high crustal stress and large deformation of Xinlian tunnel, field tests on support force and deformation control methods are carried out with single-layer support, double-layer support, rigid strong support, advanced pilot tunnel + expansion scheme. The results show that: (1) The original design scheme No.1 is not strong enough to resist the deformation pressure of surrounding rock. The stress ratio of flat guide support exceeds the design stress value by 100%, the invading limit of support is serious, and the arch replacement rate is 100%. (2) The double-layer support scheme No.2 of combining resistance with resistance is adopted. The synchronous operation of lower bench and inverted arch simplifies the operation sequence, but it is not conducive to stress release. The inverted arch is uplift crack and the rate of changing arch of side wall is 84%. When the lower bench and the inverted arch are sectioned and operated, the stress in the inverted arch is slowly released, and the large deformation is controlled. (3) Scheme No. 3 of rigid strong support by 'H175 steel+large arch boot sleeve+lock foot anchor sleeve’ is adopted, the overall rigidity of the arch is improved, the maximum convergence deformation rate is reduced by 42.4%, and the excavation per month can reach more than 90 m. (4) Scheme No. 4 of 'leading tunnel + enlarging excavation’ is adopted to realize the stress release by stages, and the large deformation is effectively controlled. However, the application of fiber-reinforced concrete and the demolition of leading tunnel support increase the cost and process. Scheme No.3 is recommended of for its economical rationality, simple construction procedure, and flexible support adjustment. Scheme No.4 can be as a preparation scheme for larger deformation of surrounding rock. At the same time, the reserved deformation of vault can be approximately 1/2 of the reserved deformation of side wall.