A small-section diversion tunnel primary support large deformation replacement structure and a construction method thereof

Abstract

This invention provides a replacement structure for the initial support of a small-section water diversion tunnel with large deformation and its construction method. The structure includes a horseshoe-shaped steel arch frame with grouting anchor pipes extending into the surrounding rock. A double-row of advanced grouting guide pipes extending into the surrounding rock are installed on the arched top of the horseshoe-shaped steel arch frame. The web of the arched top has perforations arranged along its arc. The pre-reinforcement system effectively controls the expansion of large deformation, ensuring the safety of the arch replacement construction. The horseshoe-shaped closed structure replaces the original portal-type design, fundamentally solving the lateral extrusion problem from a mechanical perspective. The differential expansion locking mechanism achieved by shear sleeves and sliding wedge arrays solves the problem of asymmetric gap locking under oblique insertion conditions of the guide pipes, enabling the guide pipes and steel arch frame to couple to form a high-strength shear nail structure, significantly improving the overall stiffness, deformation resistance, and construction efficiency of the small-section tunnel support system.

Images