Construction method for converting three-step seven-step method to middle rock column method of ultra-large section tunnel

Abstract

The invention discloses a construction method for converting a three-step seven-step method to a middle rock column method of an ultra-large section tunnel. The construction method comprises the following steps that firstly, the three-step seven-step method is used for excavation to a to-be-converted excavation area, the to-be-converted excavation area is then subjected to regional division usingthe middle rock column method, the to-be-converted excavation area is sequentially divided into left and right side guide pits and middle rock columns, the guide pits on the left side and the right side still be continuously advanced by a three-step method in the advancing and converting process of the construction method, the right guide pit is advanced by changing the leading-out guide pit intothe leading-in guide pit, the middle three-step core soil is gradually folded to form a middle rock column support body, after the construction method is converted, the guide pits on the left side andthe right side still be continuously advanced by the three-step method, and the middle three-step core soil is folded to form the middle rock column support body in the same section. In the double-hole middle rock column method, guide holes on two sides are excavated firstly and are subjected to initial support and temporary support, the middle rock column is reserved to support the upper load, and the settlement amount is reduced. Finally, the middle rock column is removed, and an arch part of the operation and an inverted arch initial support are applied to form a closed support.

Description

technical field [0001] The invention relates to a construction method for converting the three-step seven-step method to the middle rock pillar method for a super-large-section tunnel, and belongs to the technical field of tunnel construction. Background technique [0002] During the excavation process of urban subway station tunnels, due to the large excavation span and large excavation cross-sectional area of ​​the station tunnels, the most commonly used excavation method is the three-step seven-step method. The three-step seven-step method is an excavation method in which the core soil is reserved in the middle to support the excavation surface. Due to the support of the core soil and the timely application of the initial support of the arch, the construction is safer and the length of the steps can be extended. However, there are many excavation divisions, which cause more disturbances to the surrounding rock, and the closing time of the cross-section support is long, ma...

AI Technical Summary

Problems solved by technology

The three-step seven-step method is an excavation method in which the core soil is reserved in the middle to support the excavation surface. Due to the support of the core soil and the timely application of the initial support of the arch, the construction is safer and the length of the steps can be extended. However, there are many excavation divisions, which cause more disturbances to the surrounding rock, and the closing time of the cross-section support is long, so the deformation of the surrounding rock is difficult to control

Usually, when faced with such working conditions, it is often converted to the double-side wall pilot pit method, but the pilot pit method is small, the interaction between mechanical construction is large, and the speed is slow

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