JP4348830B2 - Construction method for underwater foundation structures - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a construction method for an underwater foundation structure, and more particularly to a construction method for an underwater foundation structure in which a skirt portion is penetrated into a water bottom ground by a suction load or a ballast load.
[0002]
[Prior art]
When constructing a foundation structure in water, if the foundation structure is a pile foundation, construction is generally performed using hammering or vibration as the pushing force. However, when the foundation structure is large and the construction site is deep, there is a limit to pushing in by striking and vibration, and it is very difficult to adopt a pile foundation under such conditions. Become.
[0003]
Therefore, when constructing a large-scale foundation structure at a large depth in the water, it is necessary to apply an additional ballast load to the weight of the foundation structure integrally formed at the lower end of the skirt, or to apply a suction. For example, a method of forcibly penetrating into the submarine ground is adopted.
[0004]
However, such underwater foundation construction methods have the following technical problems.
[0005]
[Problems to be solved by the invention]
That is, when constructing an underwater foundation structure at a deep water depth or where the sedimentary layer on the support layer with a sufficient strength is thick, if the bottom end of the skirt reaches the support layer, the construction period and cost will be reduced. Since it increases significantly, the intermediate layer may be stopped without penetrating the support layer.
[0006]
However, if an underwater structure is constructed in such a state, after installation, the ground below the foundation will continue to collapse even after completion, and the structure may sink or tilt above the allowable value, It will interfere with service.
[0007]
The present invention has been made in view of such conventional problems, and the purpose of the present invention is that even if an additional load or the like is applied after the construction, a problem occurs that hinders service. The purpose is to provide an underwater foundation construction method that does not need to be done.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides an underwater structure in which a skirt portion is integrally formed at the lower end of a foundation body installed in water, and the skirt portion is subjected to suction load or ballast load to penetrate into the bottom floor ground. In the construction method of the foundation structure, after allowing the skirt portion to penetrate into a predetermined depth position in the water bottom ground, a water collecting portion is extended and installed in the lower ground from the lower end of the skirt portion, and the water collecting The water collected in the part was discharged to the outside through the drainage passage provided in the skirt part.
According to the construction method of the underwater foundation structure configured as described above, after the skirt portion has penetrated to a predetermined depth position in the bottom of the water, the water collecting portion is extended from the lower end of the skirt portion into the lower ground. Since the water collected and collected in the water collection part is discharged to the outside through the drainage passage provided in the skirt part, the subsidence of the bottom of the bottom of the skirt part before the superstructure is built To be promoted.
Therefore, even if the foundation structure is constructed in a state where the lower end of the skirt does not reach the support layer and an additional load is applied after the foundation structure is constructed, subsidence or inclination that may hinder service will occur. Can be prevented.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. 1 and 2 show an embodiment of a construction method for an underwater foundation structure according to the present invention.
[0010]
The underwater foundation structure shown in the figure includes a foundation main body 10 and a skirt portion 12. The base body 10 has a plate-shaped upper plate 10a, cylindrical inner and outer walls 10b, 10c provided integrally with the lower end of the upper plate 10a, and the inner and outer walls 10b, 10c closed. And a plate-like lower plate 10d provided so as to be provided.
[0011]
The shape of the base housing 10 may be various, for example, such as a shape in which circles having different diameters are doubled, or a shape in which a plurality of circles having substantially the same diameter are arranged so that parts of the outer periphery are mutually coupled. There is a shape.
[0012]
The basic body 10 configured in this way has a horizontal cross section formed in a circle or a square, and is divided into upper and lower plates 10a and 10d and inner and outer walls 10b and 10c. 10e is provided, and the compartment 10e is filled with seawater or the like that becomes a ballast load when the underwater foundation is set.
[0013]
The skirt portion 12 is inserted into the bottom ground A. In this embodiment, the skirt portion 12 is connected to the inner and outer walls 10b, 10b, It is composed of inner and outer cylindrical bodies 12a and 12b that are integrally extended downward and have the same thickness as 10c and are located on the same straight line.
[0014]
The base body 10 and the skirt portion 12 are formed with through holes 16 into which a water collecting portion 14 to be described later is inserted. The through hole 16 of the present embodiment has a lower end that opens to the lower end of the outer cylindrical bodies 12a and 12b in the skirt portion 12, and the inner and outer walls of the inner and outer cylindrical bodies 12a and 12b and the base body 10 connected thereto. 10b and 10c are penetrated in the up-and-down direction, and the upper end is opened to the upper end surface of the inner and outer walls 10b and 10c.
[0015]
Although only four through holes 16 are shown in FIG. 1, a plurality of through holes 16 are arranged at predetermined intervals in the circumferential direction. When constructing an underwater foundation structure, the foundation body 10 is manufactured by a dock or the like together with the skirt portion 12.
[0016]
The manufactured basic body 10 is transported to a setting point by a towing ship or the like. The base body 10 transported to the installation point applies a ballast load by injecting seawater or the like into the compartment 10e or placing a counterweight, and if necessary, a suction is applied by decompression. It is made to sink in the bottom bottom ground A.
[0017]
In this case, the skirt portion 12 has a predetermined depth of the skirt portion 12 in the water bottom ground A. In the case of this embodiment, the strong support layer B is at a large depth position, and the deposited layer on the support layer B is thick. Therefore, the lower end of the skirt portion 12 is stopped at the intermediate layer above the support layer B.
[0018]
When the foundation body 10 is sunk in such a state, a curable grout material 18 such as mortar is filled between the lower plate 10d of the foundation body 10 and the upper surface of the water bottom ground A, and the lower plate of the foundation body 10 is filled. Eliminate the gap between 10d and the bottom ground A.
[0019]
In parallel with the filling operation of the grout material 18, the water collecting portion 14 is inserted into each through-hole 16 from the upper end opening side, and the front end side of the water collecting portion 14 is placed in the lower ground of the skirt portion 12. (See FIG. 2).
[0020]
The water collecting section 14 used in this case is a water drainer that can collect water from the side surface along the depth direction, such as a well or a drain. Insert and install each.
[0021]
The protruding length of the water collecting portion 14 from the lower end of the skirt portion 12 is not particularly limited, but in the case of the present embodiment, the tip of each water collecting portion 14 reaches the vicinity of the upper surface of the strong support layer B. I have to. In addition, the depth position of the firm support layer B is confirmed by conducting a ground survey before constructing the foundation structure.
[0022]
When the installation of the water collecting unit 14 is completed and the filled grout material 18 is cured, the pump 20 is installed in the foundation body 10 so as to communicate with the upper end of the water collecting unit 14.
[0023]
In the case of the present embodiment, the pump 20 is installed in the compartment 10e in the foundation body 10, and a plurality of suction pipes 22 are connected in communication at the intermediate positions of the through holes 16, and the drain pipe 24 is connected to the foundation body. 10 is extended outside.
[0024]
In this case, the water absorption pipe 22 and the water collecting portion 14 are communicated with each other through the through hole 16, and the through hole 16 functions as a part of the drainage passage.
[0025]
When the pumping pump 20 configured as described above is driven, the water collected in the water collecting unit 14 is sucked into the pumping pump 20 and discharged to the outside. If such drainage is continued, the water in the ground near the water collecting portion 14 is sequentially discharged to the outside through the water collecting portion 14 extending in the lower ground of the skirt portion 12.
[0026]
When water in the ground is drained in such a region, the pore water pressure is reduced by the drainage, and consolidation settlement of the intermediate layer supporting the skirt portion 12 is promoted.
[0027]
The consolidation settlement below the skirt portion 12 is performed before the upper structure is constructed above the base body 10. Therefore, it is desirable to perform consolidation settlement due to drainage from the water collecting portion 14 in consideration of the load of the superstructure to be constructed later.
[0028]
Now, according to the construction method of the underwater foundation structure configured as described above, the consolidation of the lower part of the skirt portion 12 is performed in advance, so that the base body is in a state where the lower end of the skirt portion 12 does not reach the support layer B. Even if an additional load or the like is applied by installing the upper structure 10 after that, it is possible to prevent the occurrence of subsidence or inclination that would hinder service.
[0029]
【The invention's effect】
As described above in detail in the embodiment, according to the construction method of the underwater foundation structure according to the present invention, even if an additional load or the like is applied after the construction, a problem occurs that hinders the service. There is nothing.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of an initial stage of construction showing an embodiment of a construction method for an underwater foundation structure according to the present invention.
2 is an explanatory diagram of a process performed subsequent to FIG. 1. FIG.
[Brief description of symbols]
DESCRIPTION OF SYMBOLS 10 Base body 10a Upper plate 10b Inner side wall 10c Outer side wall 10d Lower plate 12 Skirt part 12a Inner cylinder 12b Outer cylinder 14 Water collecting part 16 Through hole 18 Grout material 20 Lift pump

Claims (1)

In the construction method of an underwater foundation structure in which a skirt portion is integrally formed at the lower end of the foundation main body installed in the water, and the skirt portion is subjected to suction load and ballast load to penetrate into the underwater ground.
After penetrating the skirt portion into a predetermined depth position in the water bottom ground, from the lower end of the skirt portion, a water collecting portion is extended and installed in the lower ground, and the water collected in the water collecting portion is A construction method for an underwater foundation characterized in that it is discharged to the outside through a drainage passage provided in the skirt portion.

Images