Excavating method for jump-digging of double-side wall guide pit combined arch part of tunnel

Abstract

The invention relates to a novel large-span tunnel excavating construction method, namely, an excavating method for jump-digging of a double-side wall guide pit combined arch part. After the construction of a double-side wall guide pit and side wall secondary lining is completed, a large-span tunnel arch soil body is excavated by blocks. During the excavation of the arch part of the tunnel, a middle guide pit of the arch part is excavated first, then two side guide pits of the arch part of the tunnel are excavated from the excavation surface of the middle guide pit to the two sides by departing from an opening, a primary supporting structure and the secondary lining of the arch part at the position are constructed, and then the excavation of a arch part structure of the tunnel with large span is completed gradually from inside to outside. The method considers the space effect of tunnel excavation and support, reduces stress concentration at the opening during the excavation of the arch part, and has remarkable effects in ensuring the stability of excavating surrounding rocks at the section of the tunnel with large span and controlling the settlement of a larger area caused by the tunnel excavation.

Description

technical field [0001] The invention relates to a tunnel construction method, in particular to a double-side-wall pilot hole combined with an arch skip excavation method for a large-span tunnel. Background technique [0002] Excavation is the first process of tunnel construction. During tunnel excavation, the stability of surrounding rock is not only related to the geological conditions around the tunnel and pre-support measures such as grouting and pipe shed, but also affected by the tunnel section. Especially for large-span and large-section tunnels, there are many excavation steps, which lead to frequent stress changes, resulting in a large-scale plastic zone around the tunnel, which is more likely to cause ultimate soil damage. [0003] An important measure of the quality of tunnel engineering construction is ground surface settlement and the stability of surrounding rock. A large number of engineering practice experience shows that the size and shape of the tunnel secti...

AI Technical Summary

Problems solved by technology

Excavation methods currently used mainly include full-section method, step method and partial excavation method. The long time makes it difficult for these two excavation methods to control the stability of the surrounding rock and the settlement of the ground surface

Therefore, at present, excavation of large-section tunnels in weak strata mostly adopts partial excavation methods, mainly including ring excavation reserved core soil method, double side wall pilot pit method, middle partition method, etc. Although these construction methods are stable Great progress has been made in surrounding rock and settlement reduction, but the excavation of the tunnel soil is carried out step by step from the entrance to the back during construction, which makes the stress concentration phenomenon at the entrance obvious and the force is complicated, and the tunnel soil is not considered. The spatial effect of body excavation is not conducive to the stability of surrounding rock

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