Constructing method for basic pit at the upper part of shield tunnel

Abstract

The invention provides a constructing method for a basic pit at the upper part of a shield tunnel; the H-type steel inserted in a stake reinforces the soil body round the shield tunnel and encloses the basic pit; the stake provided in the pit is pumped and deformed; the separating stake divides the basic pit into plurality of small basic pits with width less than 8m; each basic pit is processing the digging by the barn jumping method; 2-4m soil is remained to the last layer of soil body for each basic pit; each small basic pit is divided into plurality of small blocks for digging the small blocks; after digging the small soil body, each small bottom plate is casted and each soil body is poured to compete the construction in 7 hours; the methods above can reduce the pumping and deformation while digging the basic pits to conform to the request of the shield tunnel and satisfy the requirement of the normal operation.

Description

technical field [0001] The invention relates to a foundation pit construction method in the civil engineering, transportation and construction industry, in particular to a construction method for a foundation pit located above a running shield tunnel. Background technique [0002] Temporary pits excavated for the construction of underground structures are called foundation pits. This kind of foundation pit includes retaining structure and support system, which can provide space for underground buildings on the one hand and protect the safety of existing surrounding buildings on the other hand. During foundation pit construction, it is necessary to excavate and transport away the earthwork in the foundation pit, so that underground structures can be constructed according to the designed position. Excavation of earthwork is a process of unloading and changing the natural foundation stress. After the foundation stress field is changed, it will inevitably cause the movement of ...

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Problems solved by technology

[0003]With the development of China's urban construction and the increasing pressure on urban public transport, there are more and more cases of intersection and connection of underground shield tunnel lines, which will require The excavation of the foundation pit is carried out on the top of the shield tunnel that has been built to build a new project, and the excavation of the foundation pit will cause the shield tunnel under the foundation pit to produce upward uplift deformation; however, in actual engineering, in order to ensure the shield The normal operation of the shield tunnel has very strict requirements on the deformation of the shield tunnel. It is required that the final absolute displacement of the shield tunnel structure should not exceed 20mm, the curvature radius of the deformation curve should not be less than 15000m, and the relative curvature should not be greater than 1 / 2500. Construction presents very large challenges

In addition, the auxiliary facilities around the shield tunnel are large-scale, the surrounding pipelines are intricate, the protection requirements are strict, and the quality and environmental protection requirements are high. The construction and connection between each other, ensuring the safe and normal operation of the shield tunnel brings huge challenges to the construction of the project

[0004] During the foundation pit construction, the traditional construction method can basically protect the surrounding buildings, but for the foundation pit construction above the shield tunnel, the shield tunneling The deformation of the tunnel is very large, which cannot meet the requirements of the shield tunnel structure; in addition, according to the traditional method of foundation pit construction, the lateral deformation of the foundation pit can reach 30mm

[0005] In view of the above shortcomings of the existing technology, there is an article in the technical literature "Railway Construction Technology" 2005 Issue 05 "The excavation of the foundation pit caused the lower shield tunnel Displacement Control Measures” preliminarily proposed construction measures for the excavation of the foundation pit above the shield tunnel to control the displacement of the shield tunnel, using mixing piles for reinforcement and isolation pile protection, and layered and block excavation. specific construction methods and clear construction parameters (such as the width of block excavation) to guide the construction

In this way, the method proposed in this document is difficult to have a clear guiding significance in the foundation pit construction above the shield tunnel with extremely strict deformation requirements, and is not very practical. Method of foundation pit construction

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