Advance Excavation Method of Pilot Pit with Multiple Steps Under Frozen Advance Support

Abstract

The invention discloses a multi-step middle drift heading advance excavation method under freezing forepoling. The multi-step middle drift heading advance excavation method comprises the steps that afreezing pipe is arranged horizontally along a tunnel on the outer side of an excavation contour line in advance, and surrounding soil bodies are refrigerated through a circulating salt solution in the freezing pipe to form frozen soil pipe curtain group forepoling; the tunnel is divided into at least three steps from top to bottom for excavation, the layer where each step is located is divided into a middle drift heading, a left drift heading and a right drift heading for excavation, the middle drift heading is excavated first, and then the left drift heading and the right drift heading are excavated; and a tunnel lining and a waterproof layer are constructed from bottom to top, and freezing construction of the freezing pipe is stopped. Under the support effect of the frozen soil pipe curtain group forepoling, the strength of frozen soil is fully utilized to speed up the excavation in the tunnel, the advantages of safety and reliability are achieved, the construction period can be greatly shortened and the construction cost can be greatly saved.

Description

technical field [0001] The invention belongs to the technical field of tunnel construction, and in particular relates to a method for first excavating a pilot pit with multiple steps under the freezing advance support. Background technique [0002] The artificial ground freezing method has become one of the main means of underground engineering construction because it is basically not limited by the support range and support depth, and has an absolute water sealing effect. Underground excavation construction under frozen advanced support generally adopts traditional mine construction methods, such as step method and CRD method. [0003] The core principle of the freezing method excavation method in the prior art is to construct the initial support as soon as possible, and the initial support is quickly closed to form a ring, without considering the particularity of the frozen soil during the excavation process—the frozen soil near the excavation area Due to the influence of...

AI Technical Summary

Problems solved by technology

[0003] The core principle of the freezing method excavation method in the prior art is to construct the initial support as soon as possible, and the initial support is quickly closed to form a ring, without considering the particularity of the frozen soil during the excavation process—the frozen soil near the excavation area Due to the influence of air convection, the temperature gradually rises and the strength is lost, while the frozen soil far away from the excavation area is not affected by air convection and still has high strength

Therefore, the existing construction method fails to effectively utilize the strength of frozen soil and the excavation speed is slow, and the time of freezing construction is directly proportional to the cost, so the total cost is relatively high

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