Tunnel excavation method for extending existing single-hole tunnel into double-arch tunnel

Abstract

The invention belongs to the field of tunnel engineering, and particularly relates to a tunnel excavation method for extending the existing single-hole tunnel into a double-arch tunnel. The method comprises the following steps of: constructing mid-boards on a plurality of cross sections in the existing tunnel; after the mid-boards are constructed, filling a cavity on one side of the existing tunnel; excavating a side wall guide hole of a newly-constructed tunnel on the other side of the existing tunnel; excavating a middle soil body; after the second lining of the side tunnel is constructed, excavating a cavity on the other side; excavating a guide hole on the other side while excavating filling in the existing tunnel; after excavation, removing a lining and constructing the second lining; and excavating two caverns at a certain interval, wherein the interval is determined according to the diameter of a single hole of the double-arch tunnel. A newly-constructed cavern is excavated by excavating the side wall guide hole, constructing a temporary support, excavating the middle soil body, removing the temporary support and constructing the second lining of the tunnel in turn. Before the newly-constructed cavern is excavated, the other side of the existing tunnel opposite to the cavern to be excavated is filled, and a filled part is removed during excavation of the side cavern. Due to the consideration of the disturbance of excavation on enclosing rock, the excavation time and the space effect and under the assistance of a pre-supporting measure, the excavation method is suitable for extending tunnels under poor geological conditions such as soft soil layers, fracture zones and the like. The excavation method has the advantages of easiness and convenience in implementing and small quantity of procedures, the disturbance of enclosing rock can be reduced, and the construction period is reduced.

Description

technical field [0001] The invention belongs to the field of tunnel engineering, and in particular relates to a tunnel excavation method for expanding an existing single-hole tunnel into a double-arch tunnel. Background technique [0002] At present, a large number of single-hole tunnels built in the 1970s and 1980s are facing the problem of "capacity expansion" to meet traffic demand. The main way of tunnel "capacity expansion" is to reconstruct and expand the existing tunnel in situ. Generally, the original tunnel is used to expand. This method will lead to insufficient utilization of tunnel space (without changing the shape of the tunnel) or the emergence of long-span flat tunnels with a single tunnel. The expansion did not address issues such as two-way traffic interference. Expansion of double-arch tunnels based on single-tunnel tunnels can reduce traffic interference and expand capacity, but the principal stress of the surrounding rock changes during the construction ...

AI Technical Summary

Problems solved by technology

There are three methods for the construction of the partition wall of the expansion of the existing tunnel into a double-arch tunnel. One is to form a hole near the existing tunnel to construct the pilot tunnel, and then construct the partition wall. This method can be excavated at multiple sections. partition wall, but the alignment of the original tunnel needs to be adjusted, resulting in large changes in the alignment and elevation of the entrance and exit; the second method is to expand the existing tunnel and then construct a partition wall on one side. This method increases the excavation The span of the single-hole tunnel excavation is limited, which may easily lead to problems such as instability of the surrounding rock; the third method is to construct a partition wall in the existing tunnel, and then expand the left and right sections of the tunnel

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