Method for tunnel excavation and karst cave treatment when small karst cave is located at bottom of inverted arch of excavated tunnel

Abstract

The invention discloses a method for tunnel excavation and karst cave treatment when a small karst cave is located at the bottom of an inverted arch of an excavated tunnel. The method includes the specific steps that filling is performed on the karst cave at the bottom of the inverted arch of the tunnel; a forepoling is arranged on the arch portion of the tunnel, an arc-shaped guiding pit is excavated in the annular direction, and core soil is reserved; a left side middle step, a right side middle step, a left side lower step and a right side lower step are excavated, and the circulating footage of excavation does not exceed 1.5 m and is set in cooperation with the interval of initial supporting steel frames; core soil is reserved at the positions of an upper step, a middle step and a lower step; and the tunnel bottom is excavated circularly, the footage of excavation is 2-3 m, after excavation, a primary lining of the inverted arch is constructed, after two excavating and supporting circulation of the tunnel is completed, the inverted arch is constructed in time, and the fractional length of the inverted arch is 4-6 m. The tunnel construction method is suitable for the situation that the small karst cave exists at the bottom of the inverted arch, the influences of non-uniform stress on sedimentation convergence of the tunnel can be reduced, tunnel deformation can be controlled effectively, the safety, the economical efficiency and the construction speed of construction of the tunnel are balanced, and the tunnel construction quality is guaranteed.

Description

technical field [0001] The invention relates to the technical field of tunnel construction, in particular to a tunnel excavation and karst cave treatment method when a small karst cave is located at the bottom of an excavated tunnel invert. Background technique [0002] The formation of caves is the result of long-term dissolution of groundwater in limestone areas. The insoluble calcium carbonate in limestone can be converted into slightly soluble calcium bicarbonate by the action of water and carbon dioxide. This geological phenomenon will affect the stability and mechanical distribution of surrounding rock, and affect the quality of surrounding engineering construction. [0003] In engineering construction, some construction techniques have a great influence on the stress distribution of surrounding rocks. Unavoidable karst caves are encountered, unsafe and unstable factors of engineering structures increase, construction techniques become complicated, and the uncertaintie...

AI Technical Summary

Problems solved by technology

This geological phenomenon will affect the stability and mechanical distribution of surrounding rocks, and affect the quality of surrounding engineering construction.

[0003] In engineering construction, some construction techniques have a great influence on the stress distribution of surrounding rocks. Unavoidable karst caves are encountered, unsafe and unstable factors of engineering structures increase, construction techniques become complicated, and the uncertainties and risks of the entire project also increase. increasing

[0004] During the construction process, it is not uncommon for karst caves to appear near the tunnel. Small karst caves appear at the bottom of the inverted arch, which will also affect the safety and quality of tunnel construction

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