JPH06146305A - Underwater foundation and installation method thereof - Google Patents

Abstract

PURPOSE:To make it possible to correspond to a deep bearing layer accumulating thickly a weak stratum in the great depth of water and to provide the underwater foundation capable of being constructed economically and speedily without requiring any temporary structure such as a working scaffold, a guide frame, etc., even in a place having a swift current. CONSTITUTION:A pile is inserted into main columns 4 of a prefabricated pier stud 1 constituted of the main columns 4 consisting of a longer pipe at large diameter reaching the surface of the water from the base of the sea-bed 11 and a plurality of skirt columns 5 consisting of a shorter pipe at large diameter rigidly connected with a plurality of stages of connection members 22 arranged to the outside of the base of the main columns and the skirt columns 5 and is penetrated to the sea-bed ground 7. A gap between the columns and pile is filled with grout, and the insides of the main columns 4 are filled with concrete.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an underwater foundation such as an underwater pier and other civil engineering structures and a method of constructing the same, and is particularly suitable for a large-scale underwater foundation in deep water and soft ground and its rapid construction. Is.

[0002]

2. Description of the Related Art Conventionally, there are a large number of underwater foundations that have been put into practical use, but generally they can be roughly divided into three types: direct foundation, pile foundation, and caisson foundation. The direct foundation is a foundation that excavates the supporting ground in a relatively shallow and wide manner to build footing, and is a shallow rigid foundation that directly transfers an external load to the good supporting ground. In terms of construction, it is necessary to stop and drain spring water and stagnant water, and the cut-off construction method using a steel sheet pile water stop wall, the chemical injection method, the well point construction method, etc. are adopted. A pile foundation is an integrated elastic body made by connecting the heads of ready-made piles that have been constructed by the driving method or the medium excavation method, or cast-in-place piles that are created by the method of mechanical or human excavation with footing. It is the basis. There are two types of pile foundations that are built in deep water: when the footing is built on the water (water footing type pile foundation) and when it is built in the water bottom ground (underwater footing type pile foundation). As a construction method for a water footing type pile foundation, a construction method is used in which a pile support frame that also serves as a scaffold, a guide frame, a temporary structure such as a jetty is installed to construct multiple pillars, or a large pile driving ship is used. Has been done.

In the case of a conventional construction example of a water footing type pile foundation, for example, a bridge pier for Kansai International Airport, as shown in FIG. 11, a water bottom ground 33 is dug to install a footing 32,
The bottom of the floor is flattened with sand and the guide pile 34 is placed. The guide pile 34 is used as a guide to sunk the guide frame 35. The guide frame is used as a guide to place the main pile 36. Concrete is poured into the pile 36 to perform pile head treatment, leveling concrete is placed on the sand, and the undersea portion of the main pile 36 is cut underwater near the water bottom, and then prefabricated together with footing. The converted bridge pier 37 is installed on the crane ship using the guide pile 34 as a guide, and sea sand is put around the installed footing 32 to backfill it. The construction method of placing pre-packed concrete is adopted. For the caisson foundation, a tubular structure made of reinforced concrete or steel with an open bottom is constructed on the ground, towed on the sea, and it sinks into the ground while discharging the earth and sand inside the cylinder to reach the specified support ground. It is a deep rigid body foundation. Excavation and substraction methods can be broadly classified into open caisson method, pneumatic caisson method, and domed caisson method. Construction methods include installation of large-scale temporary structures such as mooring anchors, caisson support frames, and piers, reducing the cross section of the bridge foot structure due to sea and river management restrictions, and deepening the caisson crown. Due to the need to do so, the cut-off construction method using steel sheet pile water blocking walls is adopted.

[0004]

The following problems are generally cited in the conventional underwater foundations. The direct foundation is a construction method in which water is completely shut off by the cut-off construction method, etc., the support layer is excavated in a dry state, and footing is directly built on the finished rock, so large-scale temporary structures such as steel sheet pile water-stop walls. In addition, it requires advanced water stoppage and drainage technology, and it is difficult to deal with deep water and deep support layers with thick soft layers. Among the pile foundations, the water footing type pile foundation has a structural characteristic that the heads of the piles are connected by footing on the water surface, and since the rigidity above the ground floor is small, horizontal displacement during an earthquake is large. In addition, the strength due to twisting is weak, and a large shearing force may act on the footing due to uneven settlement of the pile. In addition, since the bearing capacity per pile is small, it is essential to increase the number of piles in order to cope with the large bearing capacity, and the footing area increases accordingly.
Close construction becomes difficult. Moreover, in terms of construction, large-scale temporary structures such as pile support frames, guide frames, and piers are required when constructing in deep water or in locations with fast currents, which is uneconomical.

On the other hand, the conventional underwater footing type pile foundation is
From the structural characteristic that the head of the pile is connected to the footing near the submarine ground, compared to the water footing type pile foundation, the rigidity is high, the horizontal displacement at the time of earthquake is small, and the strength due to twisting is also excellent, There are some problems in terms of construction. That is, (a) floor moat on the footing installation surface, leveling, and backfilling are required over a wide area, which makes it difficult to dig floors in water-bottom soil areas, places with deep water and fast tidal currents, and areas with strict environmental regulations. It is difficult to apply, (b) It is difficult to confirm whether the footing and the rigid connection of the pile head were securely made by the underwater prepacked concrete placing, and the prepacked concrete is not reliable in terms of quality. (c) It is uneconomical because a large guide frame is required to drive this pile, (d) it is difficult to install the guide pile and guide frame accurately, and (e) a place with a large water depth or fast current. In this case, it is difficult to insert the main pile into the guide frame at the bottom of the water, (f) Since there is only one guide frame as a guide when placing the main pile, it is difficult to secure the accuracy of placing the main pile, (g) In case of deep water Since the first built-in pile will be long, pile transportation, handling, pile driving, etc. A disadvantage, (h) special workers need a (diver), labor disasters such as Sensuibyo there is a problem such as likely to occur. The caisson foundation is a floating caisson towed and is used to excavate and sink to a predetermined depth under pressure or open while splicing the skeleton concrete, which is excellent as a completed structural system but difficult in terms of construction. Have a problem. That is, (a) it is difficult to correct the caisson if it is tilted during excavation subsidence, (b) it is difficult to subside when the support layer is tilted or there is a hard ground layer in the intermediate layer,
(c) Caisson support frame, mooring anchor,
It is uneconomical because it requires large-scale temporary structures such as work scaffolds, (d) large amount of excavated soil and long construction period, (e) poor stability during floating towing, (f) special workers (caisson) Husband) is required, and there is a problem that labor accidents such as caisson's disease are likely to occur.

The present invention is intended to solve the problems of the above-mentioned conventional underwater foundations. (A) It is possible to cope with a large depth of water and a deep support layer in which a soft layer is thickly deposited, and (b) rigidity. It has a large size and is excellent in earthquake resistance and unequal settlement prevention. (C) Economically without the need for large-scale temporary structures such as mooring wires, work scaffolds, support frames, and guide frames even in places with fast tidal currents. Can be constructed,
(d) The construction procedure is simple, easy and easy to construct, (e) Prefabing enables rapid construction, (f) no special workers are required, and labor accidents are unlikely to occur. It provides an underwater foundation having the above and an installation method thereof.

[0007]

In order to advantageously solve the above-mentioned problems, the underwater foundation of the present invention is constructed by a land yard or a dry dock, and has a length from the base of the water bottom 11 to a position above the water surface. 1. A prefabricated pedestal 1 composed of a main column 4 made of long large-diameter pipes and a plurality of skirt columns 5 made of short large-diameter pipes arranged outside the main column base and rigidly connected by a plurality of connecting members 22 When,
At the installation site, the main pile 2 or the skirt pile 3 inserted into the main column 4 or the skirt column 5 and penetrating to the support layer 8 in the subsea ground 7 is the main column 4 or the skirt column at the base of the prefab pedestal. 5 is grouting and the main column 4 is filled with the filled concrete 10. In order to advantageously solve the above-mentioned problems, in the method of installing an underwater foundation of the present invention, a plurality of skirt pile guides are provided at intervals on the side of the main column on the upward extension line of the skirt column 5 of the prefab pedestal 1. 23, a plurality of temporary pile guides 25 are provided at a plurality of positions on the side surface of the main column 4, and a work scaffold 26 is further provided at the top of the main column 4, and the prefab pedestal 1 is positioned and attached to the water bottom 11 of the installation site. After letting it bottom
A plurality of temporary piles 21 are driven through the temporary pile guides 25 and temporarily fixed, and then the main pile 2 is placed in the main column 4.
The skirt piles 3 through the skirt pile guides 23 in the skirt columns 5 and penetrate the piles up to the support layer 8 in the subseabed 7, and in the section of the prefab pedestal base, The grout material 6 is poured into the gap between the pile and the pile, and then the main column 4 is filled with the filled concrete 10 and the skirt pile guide 23 is removed.

[0008]

EXAMPLES Examples of the present invention will be described below. 1 to 3
Is an example of the underwater foundation of the present invention, and FIG.
2 is a plan view of the prefab pedestal, and FIG. 3 is a cross-sectional plan view of the prefab pedestal base. The submerged foundation of the present invention is composed of a main column 4 made of a long large-diameter pipe and a plurality of skirt columns 5 made of a short large-diameter pipe arranged outside the main column base and rigidly connected by a plurality of connecting members 22. The prefabricated pedestal 1 is erected on the water bottom surface 11, the main column 4 and the skirt column 5 are respectively inserted with the main pile 2 and the skirt pile 3, and the prefabricated pedestal base is integrally formed by the grout connection 6 at the base. It is a fixed structure.
As the main column 4, a large-diameter steel pipe having a diameter of 1 m or more is used, and one or a plurality of long objects having a length protruding from the lower end located at the water bottom to above the water surface are used. When a plurality of (4) main columns are used as in the above-described embodiment, a plurality of locations are fixed by the connecting member 22 so that they behave integrally, and in order to prevent local deformation at locations where external force acts. A stiffening ring 24 is provided. Skirt column 5
Is a short-sized large-diameter steel pipe with a length necessary to behave as a fixed structure, and a plurality of pipes are arranged outside the lower end of the main column 4,
Rigidly joined and fixed to the main column 4 by a plurality of connecting members 22 by welding or the like. Connecting member 22 of the main column 4
And the connecting member 22 between the skirt column 5 and the main column 4
As the steel plate, a thick plate made of a steel plate, an H-shaped steel, or another shaped steel is used.

As described above, the main column 4 and the skirt column 5 are mounted on a barge as a prefabricated stanchion 1 integrally manufactured in a land yard or a dry dock, or are hung by a crane ship, or levitated. Will be transported to the installation site. In addition, when a barge is used as a transportation means, both the main column 4 and the skirt column 5 are sealed with rubber partition walls that can be broken when the pile is inserted, when launching (launching) at the installation site or when floating towing. However, it is necessary to provide a pouring / draining valve so that it can float and sink. The main pile 2 and the skirt pile 3 for fixing the prefab pedestal 1 erected on the bottom of the water are inserted into the column by using steel pipe piles or caisson having a diameter about 100 mm smaller than the main column 4 and the skirt column 5, respectively. It penetrates to the water bottom ground support layer 8 by driving or press-fitting. The heads of the main pile 2 and the skirt pile 3 are fixed at the base of the prefab pedestal 1 by filling the gaps between the main column 4 and the skirt column 5 with a grout material 6 such as mortar by a known means. ing.
In addition, it is preferable that the grout connection be provided with shearing projections on the outer surface of the pile and the inner surface of the column to increase the bonding strength.

In this embodiment, the main columns 4, the main pile 2 and the skirt pile 3 are all made of concrete 9 and 1.
0 is filled, but at least the inside of the main column 4 needs to be filled with concrete 10 to the lower end. The reason for this is that the vertical load acting on the upper part of the prefab pedestal 1 is transmitted to the main pile head through the concrete 10 in the main column 4. In addition to this, the concrete fillings 9 and 10 of the main pile 2 and the skirt pile 3 aim at the effect of increasing the rigidity by the function of combining with concrete.

Next, a method of installing the underwater foundation of the present invention will be described. FIG. 4 is a side view of the underwater foundation immediately after the installation is completed by the installation method of the present invention, and FIG. 5 is a plan view thereof. When adopting the installation method of the present invention, the prefab pedestal 1 described above is provided with a plurality of tiers of skirt pile guides 23 and temporary pile guides 25 on the side surface of the main column on the extension line of the skirt column in advance. The main column 4 and the skirt column 5 at the lower end of the prefab pedestal base are provided.
Needs to be provided with a grout seal 31 and a work scaffold 26 at the top. The upper portion of the skirt pile guide 23 is expanded in a trumpet shape so that it can be easily guided to the guide when the skirt pile 3 is inserted. The mounting interval is equal to or less than one length of the skirt pile 3, and the guide centers are arranged so as to match the center of the skirt column 5. The skirt pile guide 23 is mounted by bolting to a rib fixed to the side surface of the main column, or as shown in the embodiment, the main column 4 is attached.
It may be provided integrally with the connecting member 22 and then cut and removed later.

The temporary pile guide 25 is moved by external force such as tidal current or waves after the prefab pedestal 1 is sunk at the installation site.
Temporary fixing temporary piles 21 for preventing overturning are provided in order to easily drive them, and it is necessary to provide a plurality of stages on the side surface of the main column 4 and at a plurality of places around the main column 4. In the embodiment, the connecting member 22 of the main column 4 is
Further, the connecting member 22 at the base of the prefab pedestal is provided in four stages and four places. Although the shape of the temporary pile guide 25 is not shown in the embodiment, it is preferable to increase the diameter of the upper portion into a trumpet shape like the skirt pile guide 23. Also, the grout seal 31 of the main pile 2 and the skirt pile 3
A known one as shown in FIG. 6 may be used. The work scaffolding 26 at the top is used for work such as pile insertion / placing, grouting, concrete filling, etc. In particular, in the case of a large-scale underwater foundation, a tower crane or the like may be installed. Further, in the embodiment, the example in which the top connecting member 22 of the main column 4 also serves as a work scaffold is shown.

The procedure for installing the underwater foundation will be described below. First, after transporting the above-mentioned prefab pedestal 1 manufactured in a land yard or dry dock to the installation site, it is sunk, positioned, and bottomed, and then immediately passed through the temporary pile guide 25 and a plurality of temporary piles 21 Is placed on the water bottom ground 7, and at least the temporary pile 21 and the temporary pile guide 25 at the upper end are fixed by welding with a liner plate or the like. Next, the main pile 2 is inserted into the main column 4, and the skirt pile 3 is inserted into the skirt column 5 via the skirt pile guide 23.
And each pile is penetrated to the support layer 8 of the subseabed 7. The pile penetration means has a pile diameter of 1 m to 2
If it is about m, it is hammered, and if it is larger than this, it is dug into the center and press-fitted. When the main pile 2 and the skirt pile 3 reach the predetermined supporting layer 8, the head is cut underwater at the same level as the upper end of the prefab pedestal base. Alternatively, the height of the pile head may be determined by the Yatco pile.

Next, the gap between the main column 4 and the main pile 2 at the base of the prefab pedestal, and the skirt column 5
Pre-fab pedestal 1
And each pile is completely fixed and integrated at the base.
Next, at least, the main column 4 is filled with concrete 10 to be filled with concrete. In addition, inside the main pile 2 and the skirt pile 3 other than the main column 4, concrete 9
Or the earth and sand. Finally, the skirt pile guide 23 of the prefab pedestal 1 is removed to complete the underwater foundation. The temporary pile 21 and the temporary pile guide 25 may be removed or left as they are.

FIGS. 7 to 10 show another embodiment of the underwater foundation structure of the present invention, in which two or four skirt columns 5 are arranged outside one main column 4 and two main columns 4 are provided.
Various variations are conceivable, such as one in which two skirt columns 5 are arranged outside the main column 4 of a book, one in which a large number of skirt columns 5 are arranged outside a large number of main columns 4, and the shape of the superstructure, It can be appropriately selected according to the load and environmental conditions.

[0016]

EFFECTS OF THE INVENTION Since the main column portion located in the underwater portion of the present invention has a smaller projected area than the base portion and the supporting pile portion, the acting area of tidal current or wave external force is small and the design external force is small. It is possible to reduce the total weight. Furthermore, since the center of gravity of the structure is low and it is not top heavy, the inertial force during an earthquake is small, it has excellent earthquake resistance, and uneven settlement does not occur easily. Further, among the loads of the superstructure acting on the top of the underwater foundation structure, the vertical load is mainly transmitted to the main pile 2 through the filled concrete 10 in the main column 4 which is advantageous as a compressive strength material. The support layer 8 can surely make resistance. On the other hand, the horizontal load and the overturning moment resulting therefrom are transmitted to the prefab pedestal base through the main column 4, and are connected to the main pile 2 at the prefab pedestal base by the grout connection and the main column 4 by the connecting members 22 in a plurality of stages. By grouting the skirt column 5, the skirt column 5 and the skirt pile, they work together and are transmitted to the entire pile to resist the horizontal ground reaction force and the pushing and pulling reaction force of the skirt pile 3 and the main pile 2. The structure is highly stable. In addition, the installation method of the underwater foundation of the present invention is such that, after transporting the prefab pedestal 1 to the installation site, the prefab pedestal 1 is sunk on the water bottom surface 11 and immediately installed on the side surface of the main column.
Through the stake pile guide 23 provided on the side surface of the main column, the skirt pile 3 is inserted into the skirt column 5, and the temporary pile 21 is tentatively fixed. The supporting scaffold 8 is penetrated to the inside, and similarly, the main pile 2 is inserted into the main column 4 to penetrate into the subseabed ground 7, and a series of these installation work is carried out at the top of the prefab pedestal 1. 26, it is not only unnecessary to install temporary structures such as guide piles and guide frames for installation work, but also prefab pedestal 1
Since it is carried out through a guide or column attached to itself, it can be constructed very accurately by water work even in places with deep water or fast currents, in a short construction period, and easily, and it is special for divers and caissons. It is possible to reduce or eliminate the work performed by various workers. Further, the present invention is a structure that does not require underwater footing, such as a pile foundation or a direct foundation, so floor digging on the water bottom, laying, backfilling,
In addition, a large amount of underwater prepacked concrete is not required, and seawater and river pollution can be minimized. Furthermore, unlike the caisson foundation, a large amount of excavated sediment is not discharged, so the burden of residual soil treatment is small.

[Brief description of drawings]

FIG. 1 is a side view of an embodiment of an underwater foundation of the present invention.

FIG. 2 is a view taken along the line AA of FIG.

FIG. 3 is a sectional view taken along line BB of FIG.

FIG. 4 is a side view of the underwater foundation of the present invention during installation.

FIG. 5 is a plan view of FIG.

FIG. 6 is a partially cutaway perspective view showing a grout seal of a prefab pedestal base.

FIG. 7 is a schematic plan view showing another embodiment of the underwater foundation of the present invention.

FIG. 8 is a schematic plan view showing another embodiment of the underwater foundation of the present invention.

FIG. 9 is a schematic plan view showing another embodiment of the underwater foundation of the present invention.

FIG. 10 is a schematic plan view showing another embodiment of the underwater foundation of the present invention.

FIG. 11 is a diagram showing an example of a conventional underwater footing type pile foundation.

[Explanation of symbols]

 1 Prefabricated pedestal 2 Main pile 3 Skirt pile 4 Main column 5 Skirt column 6 Grout material 7 Ground floor 8 Support layer 9 Filled concrete 10 Filled concrete 11 Water bottom 21 Temporary pile 22 Connecting member 23 Skirt pile guide 24 Stiffening ring 25 Temporary Pile Guide 26 Work Scaffold, Tower Crane Installation Base 31 Grout Seal

Claims (2)

[Claims] 1. A main column 4 composed of a long large-diameter pipe having a length reaching from the base of the water bottom 11 to a position above the water surface, which is constructed in a land yard or a dry dock, and arranged in a plurality of stages outside the main column base. The prefab pedestal 1 composed of a plurality of skirt columns 5 made of short large-diameter pipes rigidly connected by a connecting member 22 and the main column 4 or the skirt column 5 at the installation site and inserted into the subsea ground 7 The main pile 2 or the skirt pile 3 penetrating to the support layer 8 is connected to the main column 4 and the skirt column 5 by the grout material 6 at the base of the prefab pedestal, and the main column 4 is filled with the filled concrete 10. Underwater foundation characterized by being. 2. A plurality of tiers of skirt pile guides 23 are provided at intervals on the side surface of the main column on the extension line of the skirt column 5 of the prefab pedestal 1, and temporary pile guides 25 are provided at a plurality of positions on the side surface of the main column 4. Multiple stages,
Further, a work scaffold 26 is provided on the top, and the prefab pedestal 1 is positioned on the water bottom 11 of the installation site and set to the bottom, and then a plurality of temporary piles 21 are driven through the temporary pile guide 25 to temporarily mount it. After fixing, the main pile 2 is inserted into the main column 4, the skirt pile 3 is inserted into the skirt column 5 through the skirt pile guide 23, and each pile is penetrated to the support layer 8 in the subseabed 7. In the section of the base of the prefab pedestal, the grout material 6 is injected into the gap between each column and the pile, and then the main column 4 is filled with the filled concrete 10 and the skirt pile guide 23 is removed. Foundation installation method.