Excavation method for middle and lower portion of underground cavern in high-crustal-stress area

Abstract

The invention discloses an excavation method for the middle and lower portion of an underground cavern in a high-crustal-stress area. After excavation of the top of the cavern, excavation is carried out in a layered way from top to bottom; deep-hole pre-crack explosion is carried out along the sidewall structure line of the cavern, a pre-crack is formed, the depth of the crack is 3 to 5 times of the thickness of a layered bench explosion layer, after that a cycle of crack is formed, and thin-layer bench explosion excavation is carried out on a rock within the crack depth range in 3 to 5 layersand shotcrete bolting is completed timely till excavation construction of the rock within the pre-crack depth range is completed; next deep-hole pre-crack explosion is carried out, and excavation iscarried out layer by layer till the design elevation of the bottom of the underground cavern is reached; and the depth and pitch of the pre-crack explosion hole are 12-20m and 0.8m respectively. Thus,construction of a relatively deep pre-crack can be implemented in advance, part of stress force can be released in advance, so that surrounding rocks can make stage and limited stress adjustment, andthe stress change rate of the surrounding rack is controlled by reserving the rock to be excavated of the cavern, and the local stress is less concentrated.

Description

Technical field [0001] The invention relates to a blasting excavation technology for preventing rock bursts in high ground stress areas in water conservancy and hydropower underground powerhouse projects, belonging to underground engineering construction technologies, and in particular to a method for excavating the middle and lower parts of underground caverns in high ground stress areas. Background technique [0002] Generally, in high ground stress areas where the initial ground stress of the hard and brittle rock mass is greater than 20 MPa, rock bursts are prone to occur during the excavation of the cavern. Rock burst is a common dynamic failure phenomenon during the construction of deep underground engineering. When the high elastic strain energy accumulated in the rock mass is greater than the energy consumed by the rock failure, the balance of the rock mass structure is destroyed, and the excess energy causes the rock burst , So that the rock fragments are stripped and co...

AI Technical Summary

Problems solved by technology

Its purpose is to provide an excavation in the middle and lower part of a large underground cavern that releases part of the ground stress in advance and uses the protection of the unexcavated rock mass to limit the deformation and damage of the surrounding rock structure, so that the surrounding rock can be adjusted in stages and limited stress in advance. method to solve problems such as rockbursts caused by excessive peak stress of surrounding rock

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