Construction method of two-sidestep and four-step excavation support of weak large-span tunnel of mountain ridge

Abstract

The invention discloses a construction method of a two-sidestep and four-step excavation support of a weak large-span tunnel of a mountain ridge. The construction method comprises the steps of: performing advanced support at a tunnel opening section by adopting a big pipe shed with the diameter phi of 108 mm before tunnel excavation; performing advance support at the tunnel body section by adopting a small guide pipe with the diameter of phi 42 mm or a big pipe shed with the diameter of phi 108 mm; and excavating the tunnel, wherein the tunnel excavation is divided into an upper sidestep annular excavation and a lower sidestep left-right excavation; and the tunnel excavation specifically comprises four steps as follows: step 1, performing annular excavation and primary support on pre-remained core soil (2) of the upper sidestep; step 2, performing excavation and primary support on the core soil (2); step 3, performing excavation and primary support on the left side of the lower sidestep; and step 4, performing excavation and primary support on the right side of the lower sidestep. The construction method of the two-sidestep and four-step excavation support of the weak large-span tunnel of the mountain ridge, disclosed by the invention, has the advantages of solving disadvantages of multiple procedures, difficult construction and organization, low work efficiency, long sealing time of an inverted arch, great deformation of surrounding stones and the like in the prior art.

Description

technical field [0001] The invention relates to an excavation and support construction method for a large-span weak mountain tunnel, in particular to an excavation and support construction method for tunnels with soft and hard surrounding rocks interbedded with water (surrounding rocks of grade V and VI). Background technique [0002] Weak, soft and hard interbedded surrounding rock has the characteristics of low foundation bearing capacity, high water content, poor cohesive force, difficult excavation and easy collapse. When this type of tunnel is being built in my country, the surrounding rocks of grades V and VI mainly adopt the CRD method and the double side wall pilot pit method. Due to the limitation of the mountain environment, this type of construction method cannot well control the settlement deformation, and the block is small, There are many processes, all of which are manual or small-scale mechanical operations. Large-scale machinery cannot be deployed, and the cr...

AI Technical Summary

Problems solved by technology

[0003] The technical problem to be solved by the present invention is to provide a construction method for two-step four-step excavation and support of a soft and large-span tunnel in a mountainous area, so as to overcome the problems of many procedures, difficult construction organization, low work efficiency and slow construction progress in the prior art. High cost, many disturbances to the surrounding rock, large deformation of the surrounding rock and long closure time of the inverted arch, etc.

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