CRD construction method and structure suitable for blasting excavation of stratum with soft upper part and hard lower part

Abstract

The invention discloses a CRD construction method and structure suitable for blasting excavation of an upper-soft lower-hard stratum. The CRD construction method comprises the steps of erecting a grating steel frame, temporary vertical supports and temporary transverse supports and spraying early strength concrete. The temporary cross braces of the left and right pilot tunnels are erected behind the upper step tunnel face, and the lag distance is not larger than one time of the tunnel hole diameter; lagging temporary cross braces are replaced by sprayed early strength concrete; the lower step and the upper step are excavated through a micro-step method, and the sprayed early strength concrete between the tunnel face of the lower step and the lagging cross brace is broken during blasting excavation of the lower step; earthwork dug out of the upper step needs to be transported to the lower step through the gap between the tunnel face of the lower step and the lagging cross brace and then carried away from the lower step, and the situation that holes are formed in the cross brace for soil unloading is avoided. The method effectively solves the problem that the cross brace is damaged in CRD blasting excavation of the upper-soft lower-hard stratum and the problem that the upper step is unearthed, ensures engineering safety, accelerates the construction speed and shortens the construction period.

Description

technical field [0001] The invention relates to the construction field of subway interval tunnels and railway tunnels, in particular to a CRD construction method and structure suitable for blasting excavation in upper soft and lower hard strata. Background technique [0002] At present, the CRD method is generally used in uniform Quaternary strata, and mechanical excavation is adopted, which has little effect on temporary cross braces. In conventional CRD method excavation, the upper pilot hole is excavated first, and the temporary steel frame, temporary vertical braces and temporary horizontal braces are erected immediately after the excavation. To achieve a better force. The lower steps are excavated mechanically, and temporary steel frames and temporary vertical braces are erected immediately after excavation. Generally, it is necessary to set the excavation opening at a certain distance on the temporary cross brace, so as to facilitate the excavation of the upper steps...

AI Technical Summary

Problems solved by technology

When the lower part is excavated by blasting, it will cause damage to the temporary cross braces that have been erected, endangering the safety of the structure, and also causing a waste of engineering materials

In addition, the practice of opening excavation holes on temporary cross braces to meet the needs of climbing steps is not only relatively inefficient, but also, small vehicles walking on the cross braces increase the load on the cross braces and increase the risk

[0004] To sum up, the current CRD method cannot well meet the needs of blasting and excavation in the upper soft and lower hard strata, and we need to propose a new solution to solve the problem.

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