A bottom sealing method for bottomless steel cofferdam

Abstract

The invention discloses a bottom sealing method for a bottomless steel cofferdam, which belongs to the field of bottom sealing methods in bottomless cofferdam construction, and is used for the bottom sealing construction of a bottomless steel cofferdam with a cofferdam area greater than 2900 square meters and a water level in the cofferdam lower than that outside the cofferdam by more than 22.5 meters. The bottom sealing construction steps are as follows: 1) the bottomless steel cofferdam is sunk into place, and the bottom base of the cofferdam is lower than the design elevation after cleaning; 2) before the underwater bottom sealing concrete is formally poured, a layer of leveling layer concrete is poured in advance, and the leveling layer concrete only needs to meet the requirements of leveling the bottom of the foundation pit and consolidating the bottom sediment at the same time, and the thickness of the leveling layer concrete is lower than the thickness of the subsequent bottom sealing concrete; 3) after the leveling layer concrete is finally set, the floating slurry sediment in the base is cleaned again by an air suction mud machine; 4) after the cleaning is completed, the underwater bottom sealing concrete is poured according to the normal process to complete the bottom sealing construction. The invention can improve the quality of the bottom sealing concrete and prevent leakage.

Description

Technical Field

[0001] The invention belongs to the field of bottom sealing methods in bottomless cofferdam construction, and in particular relates to bottom sealing construction under conditions of large warehouse surfaces and poor geology. Background Art

[0002] In the prior art, in order to construct the underwater bridge pier cap, a bottom steel cofferdam is usually used to form a waterless construction environment. The bottom seal concrete is either directly cast underwater once or divided into a secondary bottom seal of a primary underwater bottom seal and a secondary dry seal. In this secondary bottom seal method, a steel mesh is usually laid on the bottom mold of a bottom steel casing, and then the primary bottom seal concrete is poured underwater, and then the water is pumped out to form a waterless construction environment, and then the secondary bottom seal concrete is poured.

[0003] The construction of bottomless cofferdam is more difficult than that of steel cofferdam with bottom. The steel cofferdam has a large area, a low blade elevation of -23m (water surface elevation is +2~6m), and is basically buried in the riverbed. The cofferdam has a large head difference and is deep in the mud. The base is a silty silt layer, which is soft and fluid. The existing technology is all underwater bottom sealing, and the quality of concrete is difficult to control. At the same time, it is impossible to directly use the bottom sealing method of the existing steel cofferdam with bottom, because the steel cofferdam is a bottomless structure, and it is impossible to set the bottom steel mesh on the steel bottom plate and cast it into shape, which cannot provide the prerequisite for secondary bottom sealing.

[0004] The traditional bottom sealing technology of bottomless cofferdam is to directly pour the bottom sealing concrete, or lay steel plate (reinforcement) mesh or gravel in the foundation pit to prevent the concrete from being entrained with mud and sand.

[0005] The quality of the bottom sealing concrete of the traditional bottomless cofferdam bottom sealing technology cannot be guaranteed. The underwater steel plate (reinforcement) mesh is laid over a large area, and the construction is difficult and greatly affected by the geological conditions of the base. The impact on the base during the concrete pouring process can easily form sand inclusions, causing leakage of the bottom sealing concrete.

[0006] Especially for the bottom sealing construction of bottomless steel cofferdams with large storage surfaces, high water level differences and poor geology, it is more difficult. Summary of the invention

[0007] The purpose of the present invention is to propose a bottom sealing method for a bottomless steel cofferdam, which is used for the bottom sealing construction of a bottomless steel cofferdam with a cofferdam area greater than 2900 square meters and in which the water level inside the cofferdam is more than 22.5 meters lower than the water level outside the cofferdam after the cofferdam bottom sealing is completed and the water is pumped out, thereby improving the quality of the bottom sealing concrete and preventing leakage.

[0008] The object of the present invention is achieved through the following technical solutions:

[0009] A bottom sealing method for a bottomless steel cofferdam is used for bottom sealing construction of a bottomless steel cofferdam with a cofferdam area greater than 2900 m2, and the cofferdam bottom sealing is completed and the water level inside the cofferdam is more than 22.5 m lower than the water level outside the cofferdam after the water is pumped out. The bottom sealing construction steps are as follows:

[0010] 1) The bottomless steel cofferdam is sunk into place, and the bottom of the cofferdam is lower than the design elevation after cleaning;

[0011] 2) Before the underwater bottom seal concrete is poured, a layer of leveling layer concrete is poured in advance. The leveling layer concrete only needs to meet the requirements of leveling the bottom of the foundation pit and consolidating the bottom sediment. The thickness of the leveling layer concrete is lower than the thickness of the subsequent bottom seal concrete;

[0012] 3) After the leveling layer concrete is finally set, use an air suction mud machine to clean the floating slurry and sand in the base again;

[0013] 4) After cleaning, pour underwater bottom concrete according to normal process to complete the bottom construction.

[0014] As an option, the inner base of the cofferdam is cleaned to a level between 0.5m and 1m lower than the design elevation.

[0015] As an option, before officially pouring the underwater bottom sealing concrete, pour 0.5 to 1m of underwater concrete in advance to level the bottom of the foundation pit and consolidate the base sediment.

[0016] As an option, when the underwater bottom seal concrete is officially poured, the thickness of the underwater bottom seal concrete is 6m.

[0017] The aforementioned main scheme of the present invention and its further options can be freely combined to form multiple schemes, all of which are schemes that can be adopted and claimed for protection by the present invention; and in the present invention, (non-conflicting options) options and other options can also be freely combined. After understanding the scheme of the present invention, those skilled in the art can understand that there are many combinations based on the prior art and common knowledge, all of which are technical schemes to be protected by the present invention, and they are not exhaustively listed here.

[0018] The beneficial effects of the present invention are as follows: by pouring the leveling layer concrete underwater first, since the leveling layer concrete only needs to meet the requirements of leveling the bottom of the foundation pit and consolidating the bottom sediment, the construction is simple and the efficiency is much higher than the existing technology of pouring underwater bottom seal concrete. At the same time, the thickness is also lower than the conventional pouring of underwater bottom seal concrete. Through the leveling layer concrete, possible quality problems are controlled in the leveling concrete, and when normal underwater bottom seal concrete pouring is carried out, the efficiency and quality are greatly improved, so that the quality of the bottom seal concrete is reliably guaranteed, the quality defects of the bottom seal concrete of the bottomless steel cofferdam are eliminated, and leakage, bottom seal failure, etc. are prevented from affecting the construction period and increasing cost investment. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic structural diagram of an embodiment of the present invention;

[0020] Among them, 1 is the steel cofferdam, 2 is the casing, 3 is the leveling layer concrete, and 4 is the bottom sealing concrete. DETAILED DESCRIPTION

[0021] The following non-limiting examples serve to illustrate the invention.

[0022] refer to Figure 1 As shown in the figure, a bottom sealing method of a bottomless steel cofferdam is used for the bottom sealing construction of a bottomless steel cofferdam with a cofferdam area greater than 2900 m2, and the cofferdam bottom sealing is completed and the water level inside the cofferdam is more than 22.5 m lower than the water level outside the cofferdam after the water is pumped out. The bottom sealing construction steps are as follows:

[0023] 1) The bottomless steel cofferdam is sunk into place, and the bottom of the cofferdam is cleaned to be 0.5m to 1m lower than the design elevation;

[0024] 2) Before the underwater bottom seal concrete 4 is formally poured, a layer of 0.5 to 1m thick leveling layer concrete 3 is poured in advance. The leveling layer concrete 3 only needs to meet the requirements of leveling the bottom of the foundation pit and consolidating the bottom sediment. The thickness of the leveling layer concrete 3 is lower than the thickness of the subsequent bottom seal concrete 4;

[0025] 3) After the leveling layer concrete 3 is finally set, the floating slurry and sand in the base are cleaned again by using an air suction mud machine;

[0026] 4) After the cleaning is completed, pour 6m of underwater bottom seal concrete according to the normal process to complete the bottom seal construction.

[0027] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A bottom sealing method for a bottomless steel cofferdam, characterized in that It is used for the bottom sealing construction of bottomless steel cofferdams with a cofferdam area greater than 2900㎡, and the cofferdam bottom sealing is completed, and the water level inside the cofferdam is more than 22.5m lower than the water level outside the cofferdam after the water is pumped out. The bottom sealing construction steps are as follows: 1) The bottomless steel cofferdam is sunk into place, and the bottom of the cofferdam is lower than the design elevation after cleaning; 2) Before the underwater bottom seal concrete is poured, a layer of leveling layer concrete is poured in advance. The leveling layer concrete only needs to meet the requirements of leveling the bottom of the foundation pit and consolidating the bottom sediment. The thickness of the leveling layer concrete is lower than the thickness of the subsequent bottom seal concrete; 3) After the leveling layer concrete is finally set, use an air suction mud machine to clean the floating slurry and sand in the base again; 4) After cleaning, pour underwater bottom seal concrete according to normal process to complete the bottom seal construction; Before the formal pouring of underwater bottom concrete, 0.5 to 1m underwater concrete is poured in advance to level the bottom of the foundation pit and consolidate the bottom sediment; when the underwater bottom concrete is formally poured, the thickness of the underwater bottom concrete is 6m.

2. The bottom sealing method of bottomless steel cofferdam according to claim 1, characterized in that: After cleaning, the inner base of the cofferdam is between 0.5m and 1m lower than the design elevation.

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