Five-step construction method for three steps of IV-stage surrounding rock ultra-large cross section

Abstract

A five-step construction method with three steps for super-large sections of Class IV surrounding rock, S1, advanced support; S2, excavation of steps and initial support; S3, pouring of the second lining inverted arch; S4, pouring of the second lining and other parts a8; In S2, no core soil is left on the excavated steps; the deformation of the tunnel face is monitored, and when the deformation of the tunnel face exceeds the standard, the tunnel face is reinforced in advance. The construction process is arranged reasonably, and after the cyclical construction of each section of the tunnel, the construction period can be effectively reduced and the cost can be saved. At the same time, the support is timely, and the support can be closed early, which is safe and reliable; It is convenient for fast operation of large machinery and conversion of construction methods, and is suitable for the construction of large-span and large-section tunnels with poor surrounding rock conditions.

Description

technical field [0001] The invention relates to the field of tunnel construction, in particular to a three-step and five-step construction method for a super-large section of Class IV surrounding rock, especially suitable for a span of about 20m and an area of ​​200m 2 Construction of left and right tunnel sections. Background technique [0002] In recent years, with the rapid growth of my country's economy, people's requirements for transportation are getting higher and higher. For this reason, the country has carried out a lot of transportation infrastructure construction. At the same time, more and more railway tunnels and highway tunnels are being built, and the construction of tunnels is developing in the direction of large cross-sections, which brings many challenges to the construction design of tunnels and has attracted the attention of experts at home and abroad. [0003] In actual construction, the excavation section of large-section tunnels is large, and affected...

AI Technical Summary

Problems solved by technology

Among them, the CD method, CRD method and double-side-wall pilot-pit method limit the use of large-scale construction machinery. It is difficult to adjust the construction method of the tunnel with soft and hard surrounding rocks, which reduces the work efficiency. A lot of temporary support is required, and the cost is high; the three-step seven-step method is to leave the core soil and divide the seven excavation faces into three steps, the upper, middle and lower steps, to stagger and advance in parallel along the longitudinal direction of the tunnel. It is generally used for excavation sections of 100- 180m 2 , and has a certain self-stabilizing ability for large-section tunnels with grades IV and V surrounding rocks. When the geological conditions change, this construction method can flexibly and timely switch the construction process and adjust the construction method, which is suitable for tunnels with various cross-section forms. At the same time, the initial support construction is convenient, avoiding the adverse effects of uneven force caused by the demolition of temporary support by CD method and CRD method, but the core soil needs to be reserved during construction, and there are many construction procedures, resulting in insufficient clearance of each step The narrow space makes manual and mechanical operation inconvenient, construction organization is difficult, and the construction period is long, and there is no application for a span greater than 20m and an area greater than 200m 2 tunnel section construction

Images