The Construction Method of Transitioning from the Three Steps and Seven Steps Method to the Middle Rock Pillar Method in Super-large Section Tunnel

Abstract

The invention discloses a construction method for converting a super-large-section tunnel from a three-step seven-step method to a middle rock column method. First, the three-step seven-step method is used to excavate to the excavation area to be converted, and then the middle rock is used in the excavation area to be converted. The pillar method is used to divide the area, which is divided into left and right pilot pits and middle rock pillars in turn. During the process of advancing and switching construction methods, the left and right pilot pits still continue to advance with the three-step method, and the right pilot pit is continued from the rear. The row guide pit is changed to the first guide pit and advances forward. The core soil of the three steps in the middle is gradually gathered to form the middle rock pillar support body. The core soil gathers to form the rock column support in the same section. The rock pillar method in the double hole first excavates the pilot tunnels on both sides and provides initial support and temporary support. The middle rock pillar is reserved to support the upper load and reduce the settlement. Finally, the rock pillar in the middle is removed, and the initial support of the arch and the inverted arch is 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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