Soft-rock large-span tunnel double-layer overlapped lining support removing method and structure

Abstract

The invention provides a soft-rock large-span tunnel double-layer overlapped lining support removing method and structure. The method comprises the following steps that a primary support base face is leveled, a middle partition wall reinforcing mesh is mechanically broken and removed, wet spraying concrete is sprayed, and part of profile steel supports are detached; a geotechnical cloth buffer layer and a waterproof layer are sequentially laid close to the primary support base face, and waterproof treatment is conducted on the temporarily-reserved embedded support joints of the profile steel support; a formwork project is erected on the inner side of the primary support, steel bars are bound, and an outer layer secondary lining is molded; after the outer-layer secondary lining reaches the design strength, the profile steel support and the outer-layer secondary lining formwork project are dismantled; the base faces of the embedded support joints are flattened through cement mortar, and a waterproof reinforcing layer is laid on the base face of the outer layer secondary lining; and the formwork project is erected on the inner side of the outer layer second lining, the steel bars are bound, the inner layer second lining is molded, and after the inner layer second lining reaches the strength required by design, the formwork project of the inner layer second lining is removed. According to the method, the support dismounting construction risk can be effectively avoided, the overall waterproof quality of the lining can be improved, and the engineering, economic and social benefits are remarkable.

Description

technical field [0001] The invention belongs to the technical field of municipal underground engineering design and construction, and particularly relates to a method and structure for dismantling a double-layer composite lining of a soft rock large-span tunnel. Background technique [0002] In order to ensure the safety of the project and the controllable risks during the excavation, when the construction of the long-span tunnel with the dark excavation encounters the adverse geological environment or the surrounding complex construction environment, the construction method of breaking the whole into parts, breaking the large into small, and excavating in blocks is often adopted. For example, the CRD method, the double-side wall guide pit method, etc., follow a certain distance from the tunnel face of the subsequent guide pit or after the entire line is penetrated, use the "jumping warehouse method" to remove temporary supports, lay waterproofing, bind steel bars and For th...

AI Technical Summary

Problems solved by technology

[0007] Option 1: a. The step distance of a single disassembly is short (generally less than 6m or less), the construction efficiency is low, the construction period is long, and the project economy is poor; b. There are more joints in waterproof construction, mostly ring joints, and the waterproof cost increase and the waterproof quality is difficult to guarantee; c. The intersection structure of the main tunnel and the branch tunnel is molded at the same time, and the step distance of the support hole is severely restricted by the size of the branch hole and is difficult to adjust; d. When the building length is too long, the construction operability is extremely poor or even impossible to construct

[0008] Option 2: a. Complicated brace replacement process, difficult construction organization, long construction period, and poor project economy; b. Newly added temporary braces are all abandoned engineering quantities, heavy tasks for early erection and later dismantling, and a surge in project investment; c. Waterproof construction joints The number of vertical joints is increasing, and most of them are mainly longitudinal joints, and the longitudinal joints basically cannot avoid the weak positions such as bending moment and shear force, which is not conducive to the permanent lining force and waterproof quality assurance; d. Damage to materials and finished concrete

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