Construction method for three-step six-step ultrashort step for large-section tunnel

Abstract

The invention discloses a construction method for three-step six-step ultrashort step for a large-section tunnel. The method comprises the following step: 1) sequentially dividing the cross section of a tunnel into a first part, a second part, a third part and a fourth part from high to low, then excavating the first part, and sequentially constructing in-advance forepoling and preliminary bracing of the hole structure of the first part; 2) after the first part is excavated to N m, excavating the second part, prolonging a steel frame, constructing preliminary bracing and temporary inverted-arch bracing of the hole structure of the second part, excavating the third part and constructing preliminary bracing of the hole structure of the third part; 3) excavating the fourth part, constructing preliminary bracing of the hole structure of the fourth part, building the inverted arch of the hole within a preset period of time, and constructing two linings for the arch wall in the hole; 4) repeating the step 1), 2) and 3) to complete excavation and hole forming of the tunnel. The construction method effectively guarantees the stability of both the tunnel structure and the tunnel face, and is simple in procedure, high in speed and low in cost.

Description

technical field [0001] The invention relates to a construction method for a large-section tunnel, in particular to a construction method for a large-section tunnel with three steps and six steps of ultra-short steps. Background technique [0002] At present, the CD method, CRD method and glasses method are commonly used for large-section tunnels passing through weak strata, all of which are layered and vertically divided into the upper and lower sections of the tunnel face, turning the large section into small sections that are closed step by step, which can ensure The stability of the face of the tunnel and the roof and side of the tunnel; however, the construction of the saturated soil-rock joint surface cannot guarantee the slump of the saturated soil along the saturated bedrock surface; Excavation, repeated construction disturbances will cause multiple redistribution of surrounding rock stress, especially for thixotropic soils that are sensitive to disturbances. Repeated...

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Problems solved by technology

[0002] At present, the CD method, CRD method and glasses method are commonly used for large-section tunnels passing through weak strata, all of which are layered and vertically divided into the upper and lower sections of the tunnel face, turning the large section into small sections that are closed step by step, which can ensure The stability of the face of the tunnel and the roof and side of the tunnel; however, the construction of the saturated soil-rock joint surface cannot guarantee the slump of the saturated soil along the saturated bedrock surface; Excavation, repeated construction disturbances will cause multiple redistribution of surrounding rock stress, especially for thixotropic soils that are sensitive to disturbances. Repeated construction disturbances will reduce the strength of the soil or even "flow" state, which is not conducive to the tunnel structure and tunnel face. stability, and this kind of construction method has complicated procedures, slow construction speed and high cost

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