Patent Application
20200173132
This application claims priority to Korean Patent Application No. 10-2018-0154244, filed on Dec. 4, 2018, and all the benefits accruing therefrom under 35 U.S.C. § 119, the contents of which in its entirety are herein incorporated by reference.
The present disclosure relates to a cofferdam construction method, which includes a process of installing a cofferdam in water to secure a dry working space and a process of removing the cofferdam after the work in the cofferdam is completed.
The present invention was the results of the study supported by the Ministry of Land, Infrastructure and Transport, Republic of Korea (Project No. 18SCIP-B119960-03) under the superintendence of Korea Agency for Infrastructure Technology Advancement.
A cofferdam is constructed in water such as rivers and seas to secure a dry working space therein. For example, when constructing a bridge foundation and a bridge structure, the cofferdam is installed, and the water in the cofferdam is drained to form a dry working space. After that, if the bridge foundation and the bridge structure are completely constructed in the dry working space, the cofferdam will be removed. In the prior art, a large steel pipe is used as the cofferdam. A large-diameter steel pipe having a vertical length longer than the water depth and open at both ends thereof is transported on the sea. By using a large floating crane, the large steel pipe is lifted and put into water, and then is submerged by the weight of the steel pipe. If the region between the large steel pipe and the seabed is watertight, the water in the large steel pipe is drained to form a dry working space. Necessary works for constructing a bridge structure or the like are carried out inside the cofferdam, and if the works are completed, the large steel pipe is lifted again using the floating crane and transported to the land.
However, if the large steel pipe is simply submerged with self-weight thereof, it may be difficult to make the region between the steel pipe and the seabed surface into a watertight state. In order to make watertight between the large steel pipe and the seabed surface, it may be necessary to insert a lower end of the steel pipe deep into the seabed. For example, a thick weak ground layer may exist at the surface layer of the seabed. In this situation, even if the lower end of the steel pipe is penetrated deeply into the weak ground layer, the vertical length of the steel pipe will increase significantly such that the upper end of the steel pipe is located above the surface of the water. If the vertical length of the steel pipe increases, the size and weight of the steel pipe increase as much, which makes it difficult to transport and handle the steel pipe. In order to put a large steel pipe with great size and weight into water, a floating crane with a very large capacity is required. The large-capacity floating crane must also be used to remove the cofferdam. Procuring and operating the large-capacity floating crane needs enormous expense and also highly depends on weather conditions. Thus, when constructing a cofferdam using a large steel pipe according to the prior art, there may be great difficulty and disruption in procuring and operating a large-capacity floating crane, which may delay the construction or demand a large construction cost.
In the specification and claims, the term “circular pipe member” should be understood to include pipes with not only a circular cross-sectional shape but also an elliptical or other polygonal shape. A cofferdam may be installed not only in the sea but also in rivers. Thus, in the specification and claims, the term “seabed” should be understood to mean not only underwater grounds in the sea but also bottoms in the rivers.
A main circular pipe member is submerged by its own weight. Subsequently, additional circular pipe members having a vertical height easily handled and transported are stacked on the main circular pipe member in the vertical direction as many as necessary, and upper and lower circular pipe members are water-tightly assembled to form a cofferdam 100. If the cofferdam is constructed in this way, even when the main circular pipe member is deeply penetrated into the seabed, the vertical length of the main circular pipe member may be prevented from being excessively increased. Thus, even though the cofferdam is installed at a deep depth or the cofferdam has a large cross-sectional size, it is possible to exclude the use of a large-capacity crane, so that the cofferdam may be efficiently and economically constructed.
If a weak ground of a significant depth is present at the surface layer of the seabed 300, even if a main circular pipe member 1 is placed on the seabed 300 by its own weight, the region between the main circular pipe member 1 and the seabed 300 is not completely watertight. This is because a lower end of main circular pipe member 1 may not be sufficiently penetrated into the seabed 300 just by simply submerging the main circular pipe member 1 by its own weight. If the lower end of the main circular pipe member 1 is not sufficiently penetrated into the seabed 300, the main circular pipe member 1 may not support the additional circular pipe member. In this case, the lower end of the main circular pipe member 1 is penetrated into the seabed by means of a suction pressure. Before or while stacking the additional circular pipe member onto the main circular pipe member, if necessary, the main circular pipe member is penetrated into the seabed to a depth capable of ensuring watertight property by a suction pressure. In this way, the region between the lower end of the main circular pipe member and the seabed may be securely watertight, and sufficient supporting force may be ensured.
As shown in
In
The work for penetrating the main circular pipe member into the seabed by the suction pressure to a depth capable of securing watertight property (the suction installation work) may be performed before the additional circular pipe member is stacked on the main circular pipe member, while the additional circular pipe member is being stacked, or after a required number of additional circular pipe members are entirely stacked and integrated with each other. Thus, the location where the cover 11 is assembled and installed is not necessarily limited to the main circular pipe member 1 as exemplarily shown in
The line marked with an alphabet W in the figure indicates a location of the water surface. The line marked with an alphabet S indicates a location of the upper surface of the seabed 300. In order to install the cofferdam, the main circular pipe member 1 to be located at the lowermost end is firstly transported to a site using a carrier such as a floating barge. As shown in
After the main circular pipe member 1 is placed at the designed location on the upper surface of the seabed 300, a plurality of vertical guide pin piles 9 are installed. The guide pin pile 9 is installed so that its lower end is penetrated into the seabed 300. As shown in
In a state where the main circular pipe member 1 is submerged by its own weight to be placed on the seabed 300 and the upper end of the main circular pipe member 1 is located above the water surface, the additional circular pipe member is further stacked on the main circular pipe member 1. The additional circular pipe member is transported to the site using a carrier. As shown in
The additional circular pipe member has the same diameter and cross-sectional shape as the main circular pipe member 1. Like the main circular pipe member 1, a pile coupling member 90 may be provided to an outer surface of the additional circular pipe member. In this case, the additional circular pipe member may move down to be stacked on the main circular pipe member 1 in a state where the guide pin pile 9 is inserted into the pile coupling member 90. Thus, the additional circular pipe member may be stably moved down accurately in a vertical state at a predetermined location. In the figures, a dashed line with two dots indicates a joined portion between the circular pipe members.
In a state where the main circular pipe member 1 is submerged by its own weight and its upper end is positioned above the water surface, the first-level additional circular pipe member 2a is placed thereon and stacked vertically. The joined portion between the main circular pipe member 1 and the first-level additional circular pipe member 2a is present above the water surface. Thus, the work for assembling the circular pipe members 1, 2a may be performed above the water surface as a whole, rather than under the water. In the case of further stacking and integrating the second-level additional circular pipe member 2b on the first-level additional circular pipe member 2a, the joined portion between the additional circular pipe members 2a, 2b is also present above the water surface. Thus, the work for assembling the additional circular pipe members may also be efficiently performed above the water surface as a whole.
Coupling flanges may be formed at upper and lower ends of the circular pipe member, respectively, and the coupling flanges may be bolted in a state where the coupling flanges face each other by stacking the circular pipe members. In this way, the regions between the main circular pipe member 1 and the additional circular pipe member thereabove and between the plurality of additional circular pipe members stacked thereon may be assembled and coupled in a watertight form so as to be capable of being disassembled later.
If the circular pipe member has a greater diameter, the cover 11 may sag down when the suction installation work is performed. As a countermeasure, an auxiliary pile may be further installed, if necessary. A perforation hole is formed at the center of the cover 11, and the auxiliary pile is inserted into the perforation hole so that a lower end of the auxiliary pile is penetrated into the seabed. The auxiliary pile is integrated with the cover 11. According to this configuration, the auxiliary pile supports the cover 11.
After the additional circular pipe member is completely stacked on the main circular pipe member 1, the main circular pipe member may be penetrated into the seabed to a depth capable of securing watertight property by the suction pressure. For this purpose, as shown in
The location where the upper and lower circular pipe members are assembled and connected may be at a constant height for the efficient joining of the upper and lower circular pipe members. To this end, it is preferable to sequentially stack a plurality of additional circular pipe members to meet the speed at which the main circular pipe member 1 is penetrated into the seabed 300. This process is performed in the following order:
By the suction, the lower end of the main circular pipe member 1 is penetrated into the seabed 300 to a depth necessary for securing the watertight property and the support force, and a required number of additional circular pipe members are stacked and assembled thereon in a watertight form. Also, if the upper end of the additional circular pipe member located at the uppermost side is positioned above the water surface, the cover 11 is separated and removed. As a result, as shown in
Since the lower end of main circular pipe member 1 is penetrated into the seabed to a required depth by the suction pressure, it is possible to ensure a certain watertight property and a support force between the main circular pipe member 1 and the seabed 300. Thus, the cofferdam 100 may be installed quickly and easily. A single additional circular pipe member or a plurality of additional circular pipe members with a vertical height easily handled and transported are stacked vertically on the main circular pipe member 1 and assembled to each other in a watertight form to construct the cofferdam 100 whose upper end is present at a sufficient height above the water surface. Even though the water level is deep and the depth at which the lower end of the circular pipe member is penetrated into the seabed is large, the vertical length of the main circular pipe member 1 may not be excessively increased. Thus, it is possible to easily handle the circular pipe members while eliminating the use of a large-capacity floating crane, thereby exhibiting advantageous effects such as reduced construction cost and shortened construction period. Since the cofferdam 100 may be easily constructed according to the depth of the site, the cofferdam 100 shows the advantage of having excellent applicability in various sites with different depths.
Next, the process of dismantling the cofferdam will be described with reference to
If the plurality of extendable jack devices 5 are installed, as shown in
If necessary, the lower end of the cofferdam 100 may be drawn to some extent or completely from the seabed 300 by increasing the pressure inside the cofferdam 100 before pulling the lifting wire 6. That is, the cover 11 is assembled again to the cofferdam 100 to seal the inner space of the cofferdam 100, and then an injection hose is connected to the cover 11 to inject water into the inner space of the cofferdam 100 through the injection hose so that the pressure in the inner space of the cofferdam 100 is increased. By doing so, the lower end of the cofferdam 100 is drawn from the seabed 300. If the upper end of the bridge structure 200 is located higher than the upper end of the cofferdam 100, an additional circular pipe member may be further installed at the upper end of the cofferdam 100 as described above, so that the upper end of the cofferdam 100 is located higher than the bridge structure 200, and then the cover 11 is assembled to the upper end thereof. Through this process, in a state where the lower end of the cofferdam 100 is pulled to some extent or entirely from the seabed 300, as shown in
If the joined portion between the additional circular pipe members at the upper and lower layers is located above the water surface as the lifting wire 6 is pulled to move the main circular pipe member 1 upward, the main circular pipe member 1 stops moving upward temporarily. In this state, as shown in
The work for removing the additional circular pipe member connected to the crane wire 50 by separating and disassembling from the additional circular pipe member therebelow is performed when the lower end of the additional circular pipe member connected to the crane wire 50 is present above the water surface. If all additional circular pipe members are removed, as shown in
As described above, the cofferdam 100 is dismantled by separating and removing the main circular pipe member and the additional circular pipe members of the cofferdam 100 in order. Thus, the dismantling and removing work may be efficiently performed just with a small-sized or medium-sized floating crane, thereby eliminating the use of a large-scale floating crane. In addition, the work for separating the main circular pipe member and the additional circular pipe member and the work for separating the additional circular pipe members are performed above the water surface. Thus, the cofferdam 100 may be disassembled and dismantled very easily and efficiently through the above separating work.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2018-0154244 | Dec 2018 | KR | national |
