CN110792449B

CN110792449B - Rapid underground excavation construction method for large-span shallow tunnel

Info

Publication number: CN110792449B
Application number: CN201911036069.9A
Authority: CN
Inventors: 凌贤长; 赵莹莹; 唐亮
Original assignee: 凌贤长
Current assignee: Qingdao PanYao New Material Engineering Research Institute Co.,Ltd.
Priority date: 2019-10-29
Filing date: 2019-10-29
Publication date: 2021-07-02
Anticipated expiration: 2039-10-29
Also published as: CN110792449A

Abstract

The invention provides a quick underground excavation construction method for a large-span shallow tunnel, wherein a large section of the large-span tunnel is decomposed into a plurality of small sections by using a middle partition wall and a cross brace, so that the tunnel is excavated in a segmented batch mode and a core earth pillar is reserved in the middle, and the difficulty of full-section excavation of the large-span tunnel is reduced. Excavating from the guide pits on two sides of the arch crown at the upper part, so that the supporting effect of the soil arch at the top of the tunnel can be effectively utilized, and the tunnel can also be used as a construction channel for subsequent excavation; the synchronous symmetrical excavation on the two sides can keep the stress balance in the excavation and avoid uneven stress; the reserved core soil column can be used as a stress supporting point in the whole construction process, so that the integral instability and damage of the tunnel are prevented; the temporary support of the middle partition wall and the cross braces can ensure the collapse of the top and the expansion and extrusion damage of the side walls and the bottom.

Description

Rapid underground excavation construction method for large-span shallow tunnel

Technical Field

The invention belongs to the technical field of tunnel engineering, and particularly relates to a quick underground excavation construction method for a large-span shallow tunnel.

Background

With the continuous development of social and economic construction and the increasing of underground space engineering, the tunnel underground excavation method is only used for excavating the cavern underground without damaging the ground, and is widely applied to the characteristics of small influence on the environment and no influence on traffic and ground buildings. The shallow-buried underground excavation method is a construction method for underground caverns with shallow underground excavation distances from the ground surface. In the current stage, the shallow-buried underground excavation method is basically mature in the construction technology of tunnels and underground engineering, but for the engineering with shallow buried depth, poor geological conditions and complex environment, a plurality of adverse factors exist in the shallow-buried underground excavation engineering of the large-span tunnel, and some engineering accidents also occur. The existing tunnel excavation technology has the problems of uneven stress, insufficient support and support strength, easy settlement at the vault, unstable integrity and the like.

Disclosure of Invention

Aiming at the defects of the prior art, the method for quickly and secretly excavating the large-span shallow-buried tunnel is provided based on the problems of large construction difficulty, multiple potential safety hazards, slow construction progress and the like of the traditional tunnel excavation construction method for the large-span tunnel, and is used for underground engineering with poor geological conditions and unstable rock masses.

In order to achieve the purpose of the invention, the invention is realized by the following technical scheme: a quick underground excavation construction method for a large-span shallow tunnel comprises the following steps:

step 1, synchronously and symmetrically excavating guide pits on two sides of the upper part of a tunnel along the longitudinal direction of the tunnel to form a left upper section and a right upper section in a horizontal state, and reserving an upper core earth pillar in the middle position;

step 2, supporting the left upper section and the right upper section dug at the upper part of the tunnel, permanently supporting two outer side walls of the arch crown part, and building two vertical upper middle partition walls and transverse cross brace temporary supports at two sides of the reserved upper core soil column;

step 3, synchronously and symmetrically excavating the lower part of the tunnel by adopting a step excavation method on the lower steps along the longitudinal direction of the tunnel to form a left lower section and a right lower section in a horizontal state, reserving a lower core earth pillar in the middle position, wherein the width of the lower core earth pillar is larger than that of the upper core earth pillar;

step 4, supporting left and right lower sections excavated at the lower part of the tunnel, permanently supporting two outer side walls of the tunnel, and building two vertical lower middle partition wall temporary supports at two sides of a reserved lower core soil column;

step 5, performing arc excavation on the reserved upper core soil column by adopting an annular excavation method, and performing permanent support on the vault;

step 6, excavating the remaining trapezoidal core soil of the reserved upper core soil column;

step 7, adopting a step excavation method to excavate the reserved lower core soil column;

step 8, after the arch part of the tunnel is supported to form a ring, primary lining pouring of an inverted arch at the bottom of the tunnel;

and 9, removing the vertical upper middle partition wall, the cross brace and the vertical lower middle partition wall in sequence, arranging a waterproof layer and a heat insulation layer after each removal, and performing full-section secondary lining construction.

The invention also has the following technical characteristics:

1. the two vertical upper middle partition walls are respectively positioned at the 2/5 and 4/5 positions of the cross-sectional span of the tunnel.

2. The two lower vertical middle partition walls are respectively positioned at the 1/3 and 2/3 positions of the cross-sectional span of the tunnel.

The invention has the advantages and beneficial effects that: the invention adopts a construction method of sectional batch excavation, synchronous symmetrical excavation at two sides, core soil column reservation and supporting while excavation. The large section of the large-span tunnel is decomposed into a plurality of small section forms by the aid of the middle partition wall and the cross braces, the tunnel is excavated in batches in a segmented mode, and difficulty in full-section excavation of the large-span tunnel is reduced. Excavating from the guide pits on two sides of the arch crown at the upper part, so that the supporting effect of the soil arch at the top of the tunnel can be effectively utilized, and the tunnel can also be used as a construction channel for subsequent excavation; the synchronous symmetrical excavation on the two sides can keep the stress balance in the excavation and avoid uneven stress; the reserved core soil column can be used as a stress supporting point in the whole construction process, and the integral instability and damage of the tunnel are prevented. Meanwhile, supporting support measures are taken after each excavation step, and the permanent support of the arch part side wall and the arch crown after excavation plays a role in stress support and prevents the arch crown from collapsing and settling; the temporary support of the middle partition wall can effectively protect the reserved core soil column from collapsing and damaging in the excavation process, and simultaneously plays a role of bearing stress with the core soil column to avoid the overall instability and damage of the tunnel; the arrangement of the cross braces can balance the stress on two sides of the core soil column clamped by the middle partition wall, and play an effective temporary supporting role on the arch crown and the side wall; the permanent support of the side wall and the primary lining pouring of the inverted arch can prevent the expansion extrusion deformation of the side wall and the bottom and can be used as a primary lining. The supporting structure and the construction method thereof provided by the invention are safe and practical, reasonable in step sequence, simple in construction, low in operation difficulty and efficient in process.

Drawings

FIG. 1 is a schematic construction view of a large-span shallow tunnel rapid subsurface excavation supporting structure provided by the invention;

FIG. 2 is a three-dimensional schematic diagram of the rapid subsurface excavation construction of a large-span shallow tunnel according to the present invention;

in the figure: 1. upper fracture surface; 2. permanently supporting the side wall of the vault; 3. a vertical upper middle bulkhead; 4. a cross brace; 5. lower section; 6. permanent support of the side wall; 7. a vertical lower middle bulkhead; 8. a trapezoidal core soil; 9. permanent vault support; 10. putting arc core soil; 11. a lower core column; 12. inverted arch, 13, upper core column.

Detailed Description

The invention will be further illustrated by the following examples in conjunction with the accompanying drawings:

example 1

As shown in fig. 1-2, a method for constructing a large-span shallow tunnel by fast subsurface excavation comprises the following steps:

step 1, synchronously and symmetrically excavating guide pits at two sides of the upper part of a tunnel along the longitudinal direction of the tunnel to form a left upper section and a right upper section in a horizontal state, and reserving an upper core earth pillar in the middle, wherein the width of the upper core earth pillar is 1/5 of the span of the section of the tunnel;

step 2, supporting the left and right upper sections excavated at the upper part of the tunnel, and permanently supporting two outer side walls of the arch crown part, wherein the left and right upper sections can be used as a primary lining in a form of sprayed concrete and/or anchor rod and sprayed concrete and steel frame combined support; two vertical upper middle partition walls and transverse cross brace temporary supports are built on two sides of a reserved upper core soil column, the two vertical upper middle partition walls are respectively positioned at 2/5 and 4/5 of the cross section span of the tunnel and are well attached to the reserved upper core soil column, and the vertical upper middle partition walls and the transverse cross brace temporary supports are made of I-shaped steel;

step 3, synchronously and symmetrically excavating the lower part of the tunnel by adopting a step excavation method on the lower steps along the longitudinal direction of the tunnel to form a left lower section and a right lower section in a horizontal state, reserving a lower core earth pillar in the middle, and ensuring that the width of the lower core earth pillar is 1/3 of the span of the section of the tunnel;

step 4, supporting the excavated lower section, and permanently supporting two outer side walls of the tunnel, wherein the form of sprayed concrete and/or anchor rod and sprayed concrete and steel frame combined support can be adopted and can be used as a primary lining; two vertical lower middle partition wall temporary supports are built on two sides of a lower core soil column and are well attached to the lower core soil column, the two lower vertical middle partition walls are respectively located at 1/3 and 2/3 of the cross section span of a tunnel, and the vertical lower middle partition walls are made of I-shaped steel;

step 5, performing arc excavation on the reserved upper core soil column by adopting an annular excavation method, and performing permanent support on the vault to be used as a primary lining;

step 6, excavating the residual trapezoidal core soil of the upper core soil column;

step 8, after the arch part of the tunnel is supported and looped, primary lining pouring is carried out on an inverted arch at the bottom of the tunnel, and the inverted arch is of a reinforced concrete structure;

and 9, removing the upper vertical middle partition wall, the cross brace and the lower vertical middle partition wall in sequence, arranging a waterproof layer and a heat insulation layer after each removal, and performing full-section secondary lining construction.

Claims

1. A quick underground excavation construction method for a large-span shallow tunnel is characterized by comprising the following steps:

step 2, supporting the left upper section and the right upper section dug at the upper part of the tunnel, permanently supporting two outer side walls of the arch crown part, and building two vertical upper part middle partitions and transverse cross brace temporary supports at two sides of the reserved upper core soil column, wherein the two vertical upper part middle partitions are respectively positioned at 2/5 and 4/5 of the cross section span of the tunnel;

step 4, supporting left and right lower sections excavated at the lower part of the tunnel, permanently supporting two outer side walls of the tunnel, and building two vertical lower middle partition wall temporary supports at two sides of a reserved lower core soil column, wherein the two vertical lower middle partition walls are respectively positioned at 1/3 and 2/3 of a cross section span of the tunnel;