Abrupt-change expanding excavation construction method for bifurcation section of tunnel

Abstract

The invention discloses an abrupt-change expanding excavation construction method for a bifurcation section of a tunnel. The abrupt-change expanding excavation construction method comprises the following steps of: step (1) carrying out construction on a standard section by adopting a benching stepping method, and carrying out expanding excavation along the standard section by adopting a gradually-changing method to form a single-side top heading cross section; step (2) carrying out construction on the bifurcation section along the single-side top heading cross section for a specified construction distance, carrying out preliminary bracing for a single-side top heading which is formed, and erecting double temporary sidewalls; step (3) arranging a gantry inside the single-side top heading ofwhich a crossbeam is positioned at the top of the single-side top heading and is perpendicular to a large cross section; step (4) carrying out top brushing construction along the outline of the largecross section by taking the gantry as a cross section so as to form a transverse gallery, and carrying out preliminary bracing for the transverse gallery; and step (5) by taking the front and rear side surfaces of the transverse gallery as cross sections, carrying out construction by adopting a double-sidewall pilot tunnel method. According to the construction method disclosed by the invention, by utilizing the single-side top heading, the broadside of the other side of the tunnel is expanded and excavated by carrying out top brushing construction on the temporary sidewalls to form the transverse gallery, so the construction method realizes abrupt change and one-time formation of the cross sections in abrupt-change expanding excavation construction of the bifurcation section of the tunnel.

Description

technical field [0001] The invention relates to the field of excavation technology of a tunnel bifurcation section. More specifically, the present invention relates to a construction method for sudden expansion and excavation of a tunnel bifurcation section. Background technique [0002] With the rapid development of highway construction in my country, there are more and more plane crossing and bifurcated tunnels in tunnel engineering. The bifurcated tunnels have brought great difficulties to the construction due to their complex stress structure and frequent process conversion. There are not many engineering examples built and put into use at home and abroad. [0003] During the construction process of the tunnel transitioning from the branch tunnel to the main tunnel, due to the large drop of the tunnel section, the method of first longitudinal gradual expansion and then reverse expansion is conventionally used to construct the tunnel bifurcation section. This process met...

AI Technical Summary

Problems solved by technology

This process method needs to go through multiple gradual expansion excavations, and the original support needs to be removed when the reverse expansion is performed, and the conversion mileage required for section expansion is long and the construction period is long; For tunnel construction projects with low overall stability (surrounding rock grades III, IV, and V), this conventional construction method still has the problem of high construction safety risks during the excavation process from the standard section of the tunnel to the bifurcation section of the tunnel

[0004] Therefore, a new type of sudden expansion excavation technology for the bifurcation section of the tunnel connecting line is needed, and the conventional method of sudden expansion excavation of the tunnel section is optimized to solve the problem of partially broken surrounding rock, poor stability, and large section changes during the construction of the bifurcation section tunnel. There are high safety risks and low construction efficiency

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