Pre-reinforcement and excavation construction method of tunnel entrance section based on zoned blasting

Abstract

The invention discloses a tunnel portal section pre-reinforcement and excavation construction method based on partition blasting. The construction method comprises the following steps of 1, precipitation pre-reinforcement; 2, earth surface pre-reinforcement, and specifically, reinforcing the surface of a backfill section in a construction tunnel portal section through adopting a cement soil stirring pile; and 3, tunnel excavation construction, and specifically, carrying out excavation construction from rear to front in a plurality of excavation sections, wherein the process comprises the following steps of surveying and setting out, performing drilling and blasting construction, excavating an upper portal body, excavating a middle portal body and excavating a lower portal body. The construction method is reasonable in design, simple and convenient in construction and good in use effect; the underground water level is reduced through precipitation pre-reinforcement, and then surroundingrock is effectively reinforced; after the backfill section is subjected to surface pre-reinforcement through using the cement soil stirring pile, a three-step synchronous excavation mode is used forcarrying out partition blasting excavation, so that it is ensured that the tunnel excavation process is safe and reliable and a tunnel structure is stable.

Description

technical field [0001] The invention belongs to the technical field of tunnel construction, and in particular relates to a pre-reinforcement and excavation construction method for a tunnel entrance section based on zoned blasting. Background technique [0002] In the construction process of railway and highway tunnel projects, due to the limitation and influence of geological conditions, it will cause great influence and difficulties to the construction during the construction process. In the process of tunnel construction, various combinations of rock formations are often encountered, such as weak and uneven surrounding rock, shallow buried bias landform, soil-rock mixed geology and so on. For the excavation and support of tunnels that pass through soil-rock mixed strata (also known as soil-rock interface geology or soil-rock boundary strata), at present, the main methods in China are advanced pipe shed grouting support, advanced horizontal jet grouting pile reinforcement, ...

AI Technical Summary

Problems solved by technology

During the actual tunnel construction, the main problems of tunnel excavation in the soil-rock boundary stratum are as follows: first, the hardness of the rock and soil is not uniform, and the blasting of the weathered rock layer in the lower part will easily cause the upper soil layer to collapse, which is harmful to the construction personnel; second, the groundwater The enrichment area further softens the soil-rock boundary strata, causing serious deformation of the surrounding rock; third, the swelling of the expansive soil with water causes the primary support to deform and crack, and in severe cases, the deformed structure of the primary support arch will be damaged and the support capacity will be lost

Moreover, the loose load of the overlying soil basically acts on the initial support. When the inverted arch does not follow up in time and the initial support is not closed in time to form a ring, a closed stressed structure cannot be formed, resulting in insufficient bearing capacity, resulting in Subsidence of the floor and vaults, creating cracks

In addition, the insufficient bearing capacity of the loess tunnel foundation will also cause the tunnel arch foot to sink and cause cracks

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