Construction method for entering shallow-buried multi-arch tunnel under water-rich geological conditions

Abstract

A construction method for a shallow-buried multi-arch tunnel under water-rich geological conditions includes the following steps: cleaning a grouting ground surface; marking a grouting reinforcement scope; performing survey setting-out; drawing a cross-section diagram to scale; calculating out coordinates and angles of anchor points that need to be set; marking drilling positions; nailing small wooden piles at the drilling positions for identifying; determining a setting depth of the anchor rods according to ground elevation; drilling holes, cleaning bottom of hole, grouting, performing construction preparation, performing long pipe shed construction at the entrance after an earth-rock of a tunnel entrance and an open cut tunnel is excavated to flush with a springing line of the tunnel. A down-the-hole drill is used for drilling in construction. Long pipe shed grouting is designed based on solidifying a soil mass in limited scope around a consolidation pipe shed.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This patent application claims the benefit and priority of Chinese Patent Application No. 202010465066.3, entitled “Construction Method for Multi-arch Tunnel Entrance under Shallow-buried and Water-rich Geological Conditions” filed on May 28, 2020, the disclosure of which is incorporated by reference herein in its entirety as part of the present application.BACKGROUND OF THE INVENTIONField of the Invention[0002]The present disclosure relates to the technical field of tunnel engineering, in particular, to a construction method for a multi-arch tunnel entrance under shallow-buried and water-rich geological conditions.Description of the Related Art[0003]Shallow-buried tunnel is a tunnel engineering under specific conditions. The buried depth is less than twice the diameter of the tunnel. Its construction is not only restricted by geological factors of overburden, but also affected by ground environment. The shallow-buried tunnel does not sim...

AI Technical Summary

Benefits of technology

This patent is about a method to prepare a ground surface for grouting and to create drainage systems to prevent sedimentation. The method aims to maintain the natural appearance of a mountain and to control ground surface settlement and stability in a tunnel affected by adverse factors. The technical effects of this patent include a cleaning step to remove debris and a construction preparation step to create drainage systems to prevent sedimentation. These steps help to improve the overall quality and stability of the tunnel construction.

Problems solved by technology

Its construction is not only restricted by geological factors of overburden, but also affected by ground environment.

The structural trace is mainly manifested by the development of joints and fissures, so the geological conditions are poor.

The surrounding rocks of fully weathered mixed granites at the entrance and the exit of the tunnel are at Grade V. The fully weathered mixed granites at the entrance of the tunnel is thick and loose in structure, and easily collapses, so that the stability of a rock-soil mass of an face upward slope at the entrance of the tunnel is extremely poor, which is extremely easy to cause shallow engineering landslide or large collapse during construction and excavation, and the quaternary eluvial slope layer at the upper part of the exit of the tunnel is thick and is loose in structure.

A strongly weathered rock mass is broken under the influence of joints, fissures and weathering, and the broken rock mass is easy to be soften in case of water, which results in rapid reduction of strength of the rock mass.

It is easy to cause large collapse of shallow engineering during construction and excavation.

However, it is very difficult to control ground surface settlement and the stability of the surrounding rock in the tunnel effectively by only using pipe-shed support when the geological conditions at the tunnel entrance are complex, the weathering of the surrounding rock is sever, and a tunnel entrance is affected by adverse factors, such as shallow burial and rich water.

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