JPH11140879A - Penetration method and device for caisson foundation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a penetration resistance when a caisson is forced to penetrate underwater ground. SOLUTION: A caisson 12 has a side wall 12a, a top board 12b, a bottom board 12c, and a skirt part 12d. A device has a side wall 12a and has an air feed passage 14, a water feed passage 16, and a draining passage 18 which are provided inside the skirt part 12d. A nozzle 22 at the lower end of the air feed passage 14 opens to a position upwardly spaced from the end face of the skirt part 12d. The water feed passage 16 is extended vertically along the vertical direction of the side wall 12a and the skirt part 12d and opens at its lower end to face the nozzle 22 of the air feed passage 14. The draining passage 18 is extended vertically along the vertical direction of the side wall 12a and the skirt part 12d and opens at its lower end to the end face of the skirt part 12d so as to face the nozzle 22 of the air feed passage 14. To sink the caisson 12 into position, compressed air is supplied from an injection hole 20 and ejected from the nozzle 22 so that the separated soil is floated upward by the floating force of the compressed air.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for penetrating a caisson foundation, and more particularly to a technique for reducing the penetration resistance of a caisson when penetrating into a submarine ground.

[0002]

2. Description of the Related Art When constructing a foundation underwater, in the case of a pile foundation, mechanical force such as impact or vibration can be used as a pushing force. For example, large piles of coasts, ports and marine structures can be used. In such a deep water foundation, it is difficult to lay the foundation structure due to such mechanical force.

Therefore, in such a deep water foundation, a method of laying a caisson by its own weight and ballast load is generally adopted. In such a method of constructing a foundation, the skirt portion provided at the lower end of the caisson is made to penetrate into the underwater ground by applying the weight of the caisson and a ballast load while the skirt portion provided at the lower end of the caisson is landed on the underwater ground. .

However, even in such a method of constructing a foundation, the penetration resistance of the skirt portion is large only by its own weight and ballast load due to various conditions such as the condition of the underwater ground, and the skirt portion penetrates to the required penetration length. It can be difficult to do so.

Conventionally, in such a case, the pressure in the skirt portion is reduced and the skirt portion is penetrated into the underwater ground by utilizing the pressure difference (suction) between the inside and outside of the skirt portion. .

[0006] However, such a method of penetrating the caisson foundation has the following technical problems.

[0007]

That is, in the method of lowering the pressure in the skirt portion and using the suction of the skirt portion to penetrate the caisson foundation into the underwater ground, the pressure difference acting on the inside and outside of the skirt portion is reduced. If is increased, the penetration force also increases. However, when the ground to be submerged is sandy soil, a so-called boiling phenomenon occurs in which the earth and sand flow around the skirt due to a pressure difference.

When such a boiling phenomenon occurs,
The inside of the skirt portion is filled with earth and sand, which makes it impossible to penetrate, so that the necessary depth of penetration cannot be secured, and the caisson's attitude control (tilt, rotation, etc.) becomes impossible by adjusting the amount of penetration.

SUMMARY OF THE INVENTION The present invention has been made in view of such conventional problems, and has as its object to penetrate a caisson foundation which can facilitate penetration and prevent inconveniences such as a boiling phenomenon. It is to provide a method and a penetration device.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to a method of making a skirt provided on a lower end of a caisson in a submerged ground, and applying a load to the caisson. In the method of penetrating a caisson foundation into which a part penetrates into the underwater ground, a high-pressure gas is injected through an air supply passage provided in the caisson toward the underwater ground with which the skirt portion is in contact. The water sucked by the gas injection and the earth and sand separated by the injection are mixed, floated along the skirt portion, and discharged to the outside of the caisson. According to the method of penetrating the caisson foundation configured as described above, the high-pressure gas is injected toward the underwater ground where the skirt portion is in contact, and the water sucked by the injection of the high-pressure gas and the sediment separated by the injection are formed. Is mixed and floated along the skirt portion, so that the penetration resistance of the skirt portion is reduced, and the skirt portion can easily penetrate into the underwater ground. In the penetration method of the present invention, the caisson's sinking load may be its own weight, a ballast load, or a suction load alone or in combination. The high-pressure gas can be injected from a tip of the skirt portion toward the underwater ground. According to this configuration, mainly
The penetration resistance to the tip of the skirt can be reduced, and when high-pressure gas is injected from the tip of the skirt toward the underwater ground, the high-pressure gas jet blocks the flow of earth and sand toward the skirt, and Can also be prevented from flowing into the skirt. The high-pressure gas can be injected from a side on a tip end side of the skirt portion toward a water bottom ground on an outer surface side of the skirt portion. According to this configuration, the frictional resistance on the outer peripheral surface side when the skirt portion penetrates can be reduced. The high-pressure gas may be injected from a side of a tip end side of the skirt portion toward an underwater ground on an inner surface side of the skirt portion. According to this configuration, the frictional resistance on the inner peripheral surface side when the skirt portion penetrates can be reduced. Further, the present invention provides a penetrating device of a caisson foundation, in which a skirt portion provided at a lower end of a caisson is landed in a submarine ground and a load is applied to the caisson to penetrate the skirt portion into the submarine ground. A plurality of air supply and water supply passages provided at predetermined intervals along a circumferential direction in the caisson; and a drainage passage provided inside or on a side surface of the caisson. Injecting a high-pressure gas from the air supply passage toward the underwater ground that is located, supplying water sucked by the injection of the high-pressure gas to the injection port of the air supply passage through the water supply passage,
Mix the supplied water and the sediment separated by the jet,
Floating along the drain passage, and discharging to the outside of the caisson. According to the caisson foundation penetrating device configured in this way, the water sucked by the injection of the high-pressure gas and the sediment separated by the injection are mixed and floated along the skirt portion, so that the penetration resistance of the skirt portion is reduced. The skirt portion can be easily penetrated into the underwater ground. In this case, by controlling the injection amount of the high-pressure gas injected from the plurality of air supply paths, the penetration amount can be adjusted, and the caisson attitude control (tilt, rotation, and the like) can be performed. Moreover, since the air supply and water supply passages are provided in the caisson, the penetration resistance of the caisson does not increase. In addition, inside or on the side of the caisson,
Since a drainage passage is provided for guiding the mixture of water and earth and water along the skirt, the separated earth and sand can be discharged smoothly. The caisson foundation penetrating device is configured to penetrate the caisson in the up-down direction, extend along the up-down direction of the caisson, the air supply passage opening to the tip side of the skirt portion, and open one end in water. The water supply passage, the other end of which is open so as to face the injection port of the air supply passage, extends along the up and down direction of the caisson, one end is opened in water, the other end of the air supply passage. And the drainage passage that opens to face the injection port. According to this configuration, the penetration resistance when the skirt portion penetrates can be reduced. The caisson foundation penetrating device vertically penetrates the caisson, the air supply passage that opens to the tip side of the skirt portion, and extends along the vertical direction of the caisson, one end of which extends underwater. The water supply passage, which is open and the other end is opened so as to face the injection port of the air supply passage, is cut out and extended along the vertical direction of the outer surface or the inner surface of the caisson, and one end is opened in water,
The drainage passage may be configured so that the other end is opened so as to face the injection port of the air supply passage. According to this configuration, the frictional resistance on the outer peripheral surface or the inner peripheral surface side when the skirt portion penetrates can be reduced.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. 1 to 3 show an embodiment of a method and an apparatus for penetrating a caisson foundation according to the present invention.

In the method and apparatus for penetrating a caisson foundation shown in FIG. 1, a caisson 12 to be submerged and installed in a submerged ground 10 is a side wall 12 a which is a cylindrical caisson body.
A top plate 12b formed on the upper end side of the side wall 12a after being laid, and a bottom plate 12 provided on the inner surface side of the side wall 12a.
c, and a skirt portion 12d integrally provided on the lower end side of the side wall 12a.

The caisson 12 has a side wall 1 on its upper side.
2a, a top plate 12b, and a bottom plate 12c, and an upper compartment 12e separated by a bottom plate 12c and a skirt portion 12d.
A lower compartment 12f is formed, and the lower end of the lower compartment 12f is open.

The penetrating device of the caisson 12 has an air supply passage 14, a water supply passage 16, and a drain passage 18 provided in the side wall 12a and the skirt portion 12d of the caisson 12.

The air supply passage 14, the water supply passage 16 and the drainage passage 18 each constitute a penetrating device. For example, a pipe is buried in the caisson body 12. A plurality of these sets are provided at predetermined intervals along the circumferential direction of the cylindrical side wall 12a and the skirt portion 12d.

As shown in FIG. 3, the air supply passage 14, the water supply passage 16, and the drainage passage 18 are provided in pairs.
A water supply passage 16 and a drainage passage 18 are arranged on both sides of the center of the caisson 4, and are arranged in a line on the central axis in the thickness direction of the caisson 12.

The air supply passage 14 is located above the center of the caisson 12 in the thickness direction, and is provided so as to vertically penetrate the side wall 12a and the skirt portion 12d in the vertical direction. High-pressure gas open to
The inlet 20 is a compressed air inlet.
Are connected to a compressed air supply device (not shown).

The lower end side of the air supply passage 14 is an injection port 22 for the compressed air supplied from the injection port 20, and this injection port 22 is, as shown in FIG. It is open at a position separated upward.

The water supply passage 16 is located on one side in the circumferential direction of the air supply passage 14 and extends vertically along the vertical direction of the side wall 12a and the skirt portion 12d of the caisson 12, and the upper end of the water supply passage 16 is It is open to the water on the outside, and its lower end is curved and open to face the injection port 22 of the air supply passage 14.

The drain passage 18 is provided on the other side in the circumferential direction of the air supply passage 14 and extends vertically along the vertical direction of the side wall 12a and the skirt portion 12d of the caisson 12, and the upper end of the drain passage 18 is It is open to the water on the outside, and the lower end is open to the tip end surface of the skirt portion 12d so as to face the injection port 22 of the air supply passage.

The caisson 12 configured as described above is manufactured in advance, towed to the submersion site, and submerged and installed in the underwater ground 10. When the caisson 12 is laid down, first, the tip of the skirt portion 12 d is landed on the underwater ground 10.

Then, compressed air (high-pressure gas) is supplied from the injection port 20 of the air supply passage 14, and is injected from the injection port 22. The compressed air injected from the injection port 22 is jetted toward the underwater ground 10 with which the tip of the skirt portion 12d is in contact, and releases the soil of the ground 10.

In this case, when compressed air is injected from the injection port 22, the water in the water supply passage 16 is sucked by the flow of the injection and the negative pressure generated by the injection, and mixed with the separated earth and sand.

The earth and sand mixed with water floats upward by the lift of compressed air due to the air lift action.
The floating direction at this time is guided along a drain passage 18 provided along the skirt portion 12d, and the earth and sand that has floated along the skirt portion 12d is discharged from the upper end of the drain passage 18 to the outside of the caisson 12. Is done.

When the earth and sand on the underwater ground 10 is discharged in this manner, the penetration resistance is reduced. In some cases, the skirt portion 12d can be gradually penetrated into the underwater ground 10 by the weight of the caisson 12 alone. .

In this penetration process, the upper compartment 12e is filled with ballast and the ballast load is reduced.
d, or the pressure in the lower compartment 12f may be reduced to apply a suction load to the skirt portion 12d.

When the supply of compressed air (high-pressure gas) to the inlet 20 of the air supply passage 14 is continued to allow the skirt portion 12d to penetrate the underwater ground 10 for a predetermined length, the caisson 12 is settled down. After finishing, the top plate 12b
A structure such as the pier 24 is constructed on the top.

According to the caisson foundation penetrating method configured as described above, compressed air is injected toward the underwater ground 10 in contact with the skirt portion 12a, and the compressed air is sucked by the injection of the high-pressure gas. Since the water and the earth and sand separated by the jetting are mixed and floated along the skirt portion 12d, the penetration resistance of the skirt portion 12d is reduced, and the skirt portion 12d can easily penetrate into the underwater ground 10.

Further, according to the caisson foundation penetrating device configured as described above, the penetration resistance of the skirt portion 12d can be reduced, and the injection amount of the compressed air injected from the plurality of air supply paths 14 can be reduced. By controlling
The amount of penetration of the skirt portion 12d can be adjusted, and the posture control (tilt, rotation, etc.) of the caisson 12 can be performed.

The posture of the caisson 12 can be adjusted either while the skirt portion 12d is penetrating the underwater ground 10 or finely adjusted after the penetration.

Since the air supply passage 14 and the water supply and drain passages 16 and 18 are provided in the caisson 12,
The caisson 12 does not increase the penetration resistance.

Further, in the case of this embodiment, the caisson 1
2 is filled with a mixture of water and earth and sand.
The drainage passage 18 for floating and guiding along the can be provided, so that the separated earth and sand can be discharged smoothly.

FIGS. 4 to 6 show a second embodiment of a method and an apparatus for penetrating a caisson foundation according to the present invention. The same reference numerals are given to the same or corresponding parts as in the above embodiment. A description thereof will be omitted, and only the characteristic points will be described below.

In the embodiment shown in the figure, the caisson foundation penetrating device has an air supply passage 14a, a water supply passage 16a, and a drainage passage 18a as in the above embodiment.

The drain passage 18a is provided on the side wall 1 of the caisson 12.
2a, the skirt portion 12d extends vertically along the vertical direction. The upper end side is open to the water outside the caisson 12, and the lower end side is open above the cutting edge portion of the skirt portion 12a.

In the case of the present embodiment, the drain passage 18a is
The outer surface of the caisson 12 is formed by concavely cutout grooves, and is provided so as to go around the caisson 12 at predetermined intervals along the circumferential direction.

The air supply passages 14a are arranged at every other position on the central axis between a pair of drain passages 18a adjacent in the circumferential direction.
A high-pressure gas, for example, a compressed air inlet 2 is provided so as to penetrate the side wall 12a and the skirt portion 12d vertically in the vertical direction, and has an upper end opened at the upper end surface of the side wall 12a.
0a, and the injection port 20a is connected to a compressed air supply device (not shown) as in the first embodiment.

The lower end side of the air supply passage 14a is branched into two branches, and the ends of the branched portions are formed as injection ports 22a for compressed air supplied from the injection ports 20a, respectively. As shown in FIGS. 5 and 6, the pair of drainage passages 18a is open at the side of the pair of drainage passages 18a at a position spaced upward from the distal end surface of the skirt portion 12d.

The water supply passages 16a are arranged at every other position on the central axis between the drainage passages 18a adjacent in the circumferential direction, and extend vertically along the vertical direction of the side wall 12a and the skirt portion 12d of the caisson 12. The upper end side is open to the water outside the caisson 12, and the lower end side is bifurcated, and each branch is opened so as to detour from the lower side to the injection port 22a of the air supply passage 14a. doing.

The air supply and water supply passages 14a and 16a are formed, for example, by embedding a pipe in the caisson 12 body.

The means for forming the drainage passage 18a is not limited to the structure of this embodiment. For example, similarly to the air and water supply passages 14a and 16a, a pipe may be buried inside the caisson 12. It is also possible to form the drainage passage 18a by closing the open portion of the concave notch with a plate or the like.

The air supply and water supply passages 14a and 16a shown in the above embodiment are arranged alternately in the middle of the drainage passages 18a arranged in the circumferential direction.
One air supply and water supply passage 14a, 16a may be arranged adjacent to one drain passage 18a.

The caisson 12 thus constructed is manufactured in advance and the skirt 1
The tip of 2 d is landed on the underwater ground 10.

Then, compressed air is supplied from the injection port 20a of the air supply passage 14a, and is injected from the injection port 22a. The compressed air injected from the injection port 22a is jetted toward the underwater ground 10 where the outer surface of the skirt portion 12d is in contact, and releases the soil of the ground 10.

When compressed air is injected from the injection port 22a, water is sucked and supplied from the water supply passage 16a, mixed with the separated earth and sand, and the earth and sand mixed with the water, as in the above embodiment.
By the action of the air lift, it floats while being guided along the drain passage 18a, and is discharged from the upper end of the drain passage 18a to the outside of the caisson 12.

By discharging the earth and sand from the underwater ground 10 in this manner, the tip resistance of the skirt portion 12d of the caisson 12 and the peripheral friction on the outer surface side can be reduced. Can penetrate.

FIG. 7 shows a third embodiment of a method and a device for penetrating a caisson foundation according to the present invention. A description thereof will be omitted, and only the characteristic points will be described below.

In the embodiment shown in FIG.
Is directed toward the inside of the caisson 12, and the drainage passage 18a is formed on the inside of the caisson 12. The inside and outside of the caisson 12 of the second embodiment shown in FIGS. The configuration is reversed.

In the case of such a configuration, since the compressed air rises along the inner surface of the skirt portion 12d, the resistance at the tip of the caisson 12 and the peripheral surface friction on the inner peripheral surface can be reduced.

The penetrating devices shown in the first, second, and third embodiments can be provided independently of each other in the caisson 12, but they can be combined, and these devices can be combined. In this case, the penetration resistance of the skirt portion 12d and the frictional resistance of the inner and outer peripheral surfaces can be simultaneously reduced, so that the caisson 12 can be more easily penetrated.

[0051]

As described above in detail in the embodiments,
According to the method and the device for penetrating the caisson foundation according to the present invention, the penetration resistance of the skirt portion can be reduced, so that the caisson can be easily penetrated into the underwater ground.

[Brief description of the drawings]

FIG. 1 is a partially broken perspective view of the entire structure showing a first embodiment of a method and a device for penetrating a caisson foundation according to the present invention.

FIG. 2 is an explanatory sectional view of a main part of FIG.

FIG. 3 is an explanatory plan view of a main part of FIG. 1;

FIG. 4 is a partially cutaway perspective view of the entire structure showing a second embodiment of the method and apparatus for penetrating a caisson foundation according to the present invention.

FIG. 5 is an explanatory sectional view of a main part of FIG. 4;

FIG. 6 is an explanatory plan view of a main part of FIG. 4;

FIG. 7 is an explanatory sectional view of a principal part showing a third embodiment of the method and apparatus for penetrating a caisson foundation according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Underwater ground 12 Caisson 12a Caisson main body 12b Top plate 12c Bottom plate 12d Skirt part 14,14a Air supply passage 16,16a Water supply passage 18,18a Drainage passage 20,20a Inlet 22,22a Injection port

Claims (7)

[Claims] 1. A method of penetrating a caisson foundation in which a skirt provided at a lower end of a caisson is settled in a submarine ground and a load is applied to the caisson to penetrate the skirt into the submarine ground. Through a gas passage provided in the caisson, a high-pressure gas is injected toward the underwater ground where the skirt portion is in contact, and the water sucked by the injection of the high-pressure gas and the sediment separated by the injection are discharged. A method of penetrating a caisson foundation, comprising mixing, floating along the skirt portion, and discharging the caisson outside. 2. The method for penetrating a caisson foundation according to claim 1, wherein the high-pressure gas is injected from the tip of the skirt portion toward the underwater ground. 3. The penetrating caisson foundation according to claim 1, wherein the high-pressure gas is injected from a lateral side of a tip end side of the skirt portion toward a water bottom ground on an outer surface side of the skirt portion. Method. 4. The caisson foundation according to claim 1, wherein said high-pressure gas is injected from a side of a tip end side of said skirt portion toward a water bottom ground on an inner surface side of said skirt portion. Method. 5. A penetrating device of a caisson foundation, wherein a skirt portion provided at a lower end of a caisson is landed in a submarine ground and a load is applied to the caisson to penetrate the skirt portion into the submarine ground. A plurality of air supply and water supply passages provided at predetermined intervals along a circumferential direction in the caisson, and a drain passage provided inside or on the side of the caisson, and the skirt portion is in contact with the caisson. A high-pressure gas is injected from the air supply passage toward the bottom of the water, and water sucked by the injection of the high-pressure gas is supplied to the injection port of the air supply passage through the water supply passage. And the sediment separated by injection, and floated along the drain passage,
A caisson foundation penetrating device, wherein the caisson is discharged to the outside. 6. The caisson foundation penetrating device according to claim 5, wherein the air supply passage penetrates the caisson in the up-down direction and opens on the tip side of the skirt portion, and along the up-down direction of the caisson. The water supply passage, which is extended, one end of which opens into water, and the other end of which opens to face the injection port of the air supply passage, extends along the up and down direction of the caisson, and one end of which opens into water. And a drain passage opening at the other end so as to face an injection port of the air supply passage. 7. The caisson foundation penetrating device according to claim 5, wherein the air supply passage penetrates the caisson in the up-down direction and opens to the tip side of the skirt portion, and the up-down direction of the caisson. The water supply passage is extended along, one end is open to the water, the other end is open so as to face the injection port of the air supply passage, notch extending along the vertical direction of the outer surface or the inner surface of the caisson And a drain passage that opens at one end into the water and opens at the other end so as to face the injection port of the air supply passage.