Excavation technique for shallow-buried large-span small-spacing loess tunnel

Abstract

The invention provides a construction method for a shallow-buried large-span small-spacing loess tunnel in order to resolve the problems that an existing large-section small-spacing loess tunnel is high in construction difficulty and high in danger coefficient, and sedimentation is difficult to control. According to the method, two holes of the tunnel are constructed at the same time, and each hole is divided into two guide holes for construction. An annular surface formed by sealing the distance between a face of a later passing hole and an inverted arch of a former passing hole is one time diameter of each hole. Each hole is divided into the left guide hole and the right guide hole, wherein the guide hole at the side far away from a soiled-clamped pillar is firstly excavated, the interval between faces of the two guide holes keeps 5-8m, the guide hole at each side is excavated through three steps of an upper step, a middle step and a lower step, and interval between the steps keeps 3-5m. Compared with a similar excavation technique for the tunnel, the construction method effectively guarantees safe construction of the tunnel, reasonably controls the sediment of the tunnel, reduces the influence on the ground surface from construction, and improves the construction efficiency to some extent.

Description

technical field [0001] The invention relates to an excavation method for a tunnel structure, in particular to an excavation method for a loess tunnel with a large span and a small clear distance. Background technique [0002] With the development of economy and transportation, more and more large-span and small-distance tunnels are being built. At the same time, loess is a special soil body. Construction is even rarer. Therefore, due to the particularity and novelty of this type of tunnel, there are many problems that need to be solved urgently in the process of design and construction. [0003] For large-span and small-space tunnels, due to factors such as the large span of the tunnel, complex structural forces, and the mutual influence of many processes during the double-line excavation during construction, it is easy to cause instability of the surrounding rock or cracking and damage of the tunnel lining structure. , usually for long-span tunnels, according to different...

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Problems solved by technology

[0003] For large-span and small-space tunnels, due to factors such as the large span of the tunnel, complex structural forces, and the mutual influence of many processes during the double-line excavation during construction, it is easy to cause instability of the surrounding rock or cracking and damage of the tunnel lining structure. , usually for long-span tunnels, according to different engineering geological conditions, methods such as double-side-wall pilot-pit method, arc-shaped pilot-hole advance method, and step method can be used. It will cause different degrees of tunnel bias, and at the same time, it is difficult to protect or strengthen the interlayer rock in the tunnel. There is no detailed description for small-space tunnels in the code. Usually, single-hole tunnels are used for the design of small-space tunnels. During the construction process There is a certain risk, and it is easy to cause the tunnel to collapse, especially for the soft surrounding rock area, the surrounding rock disturbance caused by double-hole excavation is more serious, and the traditional construction method and design have certain risks

[0004] For tunnels passing through the loess layer, there is no mature construction method. During the construction of loess tunnels, the arch in the tunnel generally settles as a whole and the settlement is relatively large, and through cracks are prone to appear on the ground surface. Cracks appear, these problems are difficult to solve during the construction process

The protection of interbedded soil columns in loess is also a key joint in construction, and the corresponding construction technology research is rare. For ultra-small clear distance loess tunnels, the distance between the two lines of the tunnel is small, and the construction impact is great. How to adopt an effective method The construction method and how to strengthen the weak position are not clear, and it is difficult to ensure that the construction can be carried out quickly, safely and effectively during the tunnel construction process.

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