CN-121992804-A - Double-layer steel sheet pile cofferdam underwater tunnel open cut construction method with drainage decompression cavity

CN121992804ACN 121992804 ACN121992804 ACN 121992804ACN-121992804-A

Abstract

The invention relates to the technical field of underwater tunnel and deep foundation pit engineering construction, in particular to an underwater tunnel open-cut construction method of a double-layer steel sheet pile cofferdam with a drainage decompression cavity, which comprises the specific steps of constructing an outer-layer steel sheet pile along the outer contour of a tunnel foundation pit in an underwater construction area to form an outer-layer cofferdam for retaining soil; the method comprises the steps of arranging an inner steel sheet pile on the inner side of an outer cofferdam to form an inner cofferdam for water stopping, forming a drainage decompression cavity between the inner cofferdam and the outer cofferdam, arranging a drainage device in the drainage decompression cavity, actively dewatering the drainage decompression cavity through the drainage device, excavating a foundation pit in the inner cofferdam, completing open excavation construction of a tunnel main structure in a dry working environment, and transferring and releasing water pressure from the water stopping cofferdam through the arrangement of the double-layer steel sheet pile cofferdam and the drainage decompression cavity, so that the water pressure born by the inner water stopping cofferdam can be reduced, and the water stopping safety of the cofferdam is improved.

Inventors

PAN ZIYANG
REN JIE
ZHANG JUN
HUANG JINGEN
Li Xunjin
LIU YULI
MA WEN

Assignees

安徽建工建设投资集团有限公司

Dates

Publication Date: 20260508
Application Date: 20260209

Claims (8)

1. The double-layer steel sheet pile cofferdam underwater tunnel open cut construction method with the drainage decompression cavity is characterized by comprising the following specific steps: Firstly, an outer steel sheet pile (1) is applied to an underwater construction area along the outer contour of a tunnel foundation pit to form an outer cofferdam for retaining soil; arranging an inner side steel sheet pile (2) on the inner side of the outer cofferdam to form an inner cofferdam for water stopping, and forming a drainage decompression cavity between the inner cofferdam and the outer cofferdam; Arranging a drainage device in the drainage pressure reducing cavity, and actively dewatering the drainage pressure reducing cavity through the drainage device to reduce the water level in the drainage pressure reducing cavity below the elevation of the bottom of the foundation pit, so that the water pressure acting on the outer side of the inner cofferdam is reduced; and fourthly, excavating a foundation pit in the inner cofferdam, and completing open-cut construction of the tunnel main body structure in a dry working environment.
2. The underwater tunnel open excavation construction method of the double-layer steel sheet pile cofferdam with the drainage pressure reducing cavity as set forth in claim 1, wherein at least one layer of inner support (3) for connecting the inner cofferdam and the outer cofferdam is horizontally installed in the drainage pressure reducing cavity, and the inner support (3) is used for transmitting soil pressure from the outer cofferdam to the inner cofferdam or foundation pit inner support system.
3. The method for constructing the underwater tunnel of the double-layer steel sheet pile cofferdam with the drainage decompression cavity according to claim 2 is characterized in that a broken stone filter layer is paved at the bottom of the drainage decompression cavity, and a plurality of decompression drainage wells (4) with filter pipes are arranged in the broken stone filter layer; The pressure-reducing drainage well (4) is communicated with a drainage pump serving as a drainage device.
4. The underwater tunnel open-cut construction method of the double-layer steel sheet pile cofferdam with the drainage decompression cavity as claimed in claim 3, wherein the outer steel sheet pile (1) adopts Larson steel sheet piles, and the inner steel sheet pile (2) adopts high-performance steel sheet piles with water-stopping locking openings on connecting surfaces.
5. The underwater tunnel open-cut construction method of the double-layer steel sheet pile cofferdam with the drainage decompression cavity of claim 4, wherein the distance between the inner layer cofferdam and the outer layer cofferdam is 2-4m.
6. The underwater tunnel open-cut construction method of the double-layer steel sheet pile cofferdam with the drainage pressure reducing cavity as set forth in claim 2, wherein the inner support (3) adopts a section steel pair support and is arranged at a position close to the upper part of the drainage pressure reducing cavity.
7. The method for open excavation construction of the double-layer steel sheet pile cofferdam underwater tunnel with the drainage decompression cavity as claimed in claim 2, wherein in the fourth step, a layered, segmented and symmetrical excavation mode is adopted in the excavation process of the foundation pit, and the inner support (3) is arranged step by step along with the increase of the excavation depth of the foundation pit.
8. The underwater tunnel open-cut construction method of the double-layer steel sheet pile cofferdam with the drainage decompression cavity as claimed in claim 2, wherein after the open-cut construction of the tunnel main body structure is completed, backfilling is sequentially carried out on a foundation pit and the drainage decompression cavity, dewatering is gradually stopped, and after the inner support (3) is removed, the inner steel sheet pile (2) and the outer steel sheet pile (1) are sequentially pulled out.

Description

Double-layer steel sheet pile cofferdam underwater tunnel open cut construction method with drainage decompression cavity Technical Field The invention relates to the technical field of underwater tunnel and deep foundation pit engineering construction, in particular to an open cut construction method of a double-layer steel sheet pile cofferdam underwater tunnel with a drainage decompression cavity. Background When a tunnel is constructed by adopting an open cut method in underwater environments such as rivers, sea areas and the like, a cofferdam is firstly constructed to form a dry working foundation pit, and a single-row steel sheet pile cofferdam or an underground diaphragm wall cofferdam is commonly adopted in the prior art. The single-row steel sheet pile cofferdam is high in construction risk and cost, and the underground diaphragm wall cofferdam is good in water stopping performance, high in construction cost, long in construction period and obviously limited by water construction conditions. Therefore, the existing underwater tunnel open-cut construction method is difficult to achieve both water stopping safety and economy, and a new construction method is needed to solve the problem, and in view of the problem, the double-layer steel sheet pile cofferdam underwater tunnel open-cut construction method with a drainage decompression cavity is provided. Disclosure of Invention The invention aims to solve the defects in the background art and provides an open-cut construction method for an underwater tunnel of a double-layer steel sheet pile cofferdam with a drainage decompression cavity. In order to solve the technical problems, the invention adopts the following technical scheme: an open-cut construction method for an underwater tunnel of a double-layer steel sheet pile cofferdam with a drainage decompression cavity comprises the following specific steps: firstly, an outer steel sheet pile is applied to an underwater construction area along the outer contour of a tunnel foundation pit to form an outer cofferdam for retaining soil; arranging an inner steel sheet pile on the inner side of the outer cofferdam to form an inner cofferdam for water stopping, and forming a drainage decompression cavity between the inner cofferdam and the outer cofferdam; Arranging a drainage device in the drainage pressure reducing cavity, and actively dewatering the drainage pressure reducing cavity through the drainage device to reduce the water level in the drainage pressure reducing cavity below the elevation of the bottom of the foundation pit, so that the water pressure acting on the outer side of the inner cofferdam is reduced; and fourthly, excavating a foundation pit in the inner cofferdam, and completing open-cut construction of the tunnel main body structure in a dry working environment. Preferably, at least one layer of inner support used for connecting the inner cofferdam and the outer cofferdam is horizontally arranged in the drainage decompression cavity, and the inner support is used for transmitting soil pressure from the outer cofferdam to the inner cofferdam or foundation pit inner support system. Preferably, a broken stone filter layer is laid at the bottom of the drainage pressure reducing cavity, and a plurality of pressure reducing drainage wells with filter pipes are arranged in the broken stone filter layer; The pressure-reducing drainage well is communicated with a drainage pump serving as a drainage device. Preferably, the outer steel sheet pile is a Larson steel sheet pile, and the inner steel sheet pile is a high-performance steel sheet pile with a water stop locking opening on a connecting surface. Preferably, the distance between the inner cofferdam and the outer cofferdam is set to be 2-4m. Preferably, the inner support adopts a section steel pair support and is arranged at the upper part of the drainage decompression cavity. Preferably, in the foundation pit excavation process in the fourth step, a layered, segmented and symmetrical excavation mode is adopted, and the inner support is arranged step by step along with the increase of the excavation depth of the foundation pit. Preferably, after the open excavation construction of the tunnel main body structure is completed, backfilling is sequentially carried out on the foundation pit and the drainage decompression cavity, dewatering is stopped gradually, and after the inner support is removed, the inner steel sheet pile and the outer steel sheet pile are pulled out sequentially. Compared with the prior art, the invention has the beneficial effects that: 1. According to the double-layer steel sheet pile cofferdam underwater tunnel open-cut construction method with the drainage decompression cavity, through the arrangement of the double-layer steel sheet pile cofferdam and the drainage decompression cavity, water pressure can be transferred and released from the water stop cofferdam, water pressure born by the inner-layer water stop cofferdam