JPH045099B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a construction method for sinking a large caisson in combination with a small caisson in soft ground.

[Prior art]

When an open caisson is installed on soft ground, the caisson may undergo natural settlement, resulting in the caisson sinking too quickly or causing the caisson to tilt. Furthermore, when a large caisson is sunk in soft ground, there is a risk that heaving or boiling may occur if the soft ground inside the large caisson is excavated.

[Purpose and structure of the invention]

The purpose of this invention is to provide a caisson press-in construction method in soft ground that can advantageously solve the above-mentioned problems. Small caissons 2A and 2B are arranged, cover plates 4 are fixed to some of the small caissons, compressed air is supplied between the cover plates 4 and the soft ground 5, and large caisson 1 and each small caisson 2A, 2B is lowered to a certain position on soft ground, each small caisson is press-fitted using large caisson 1 as a reaction force support, and then the small caisson and large caisson are connected. It is in the submerged construction method.

〔Example〕

Next, the present invention will be explained in detail using illustrated examples.

Figures 1 to 4 show an example of a composite caisson consisting of a large caisson and a small caisson used in carrying out the present invention. A support beam 7 extending parallel to the side wall 6 of the large caisson 1 and a support beam 9 extending parallel to the left and right side walls 8 of the large caisson 1 are integrally constructed and fixed, and are integrally attached to the inner lower part of each side wall 6, 8 of the large caisson 1. Small concrete caissons 2A, 2B are fitted into the areas defined by the protrusions 10 and the support beams 7, 9 so as to be arranged alternately in the circumferential direction of the large caisson 1. 2
A step part 11 for supporting the lid plate is integrally provided in B,
The stepped portion 11 has an insert 1 having an internal thread.
2 is embedded and fixed, and the periphery of a steel lid plate 4 is placed on the upper surface of the stepped portion 11 via a rubber sealing material 13, and the insert 1 is inserted through the lid plate 4.
The lid plate 4 is fixed to the small caisson 2A, 2B by a bolt 14 screwed into the small caisson 2. Further, the lid plate 4 is provided with a cylindrical opening 3, and the opening 3
A locking flange 15 is integrally provided on the upper outer periphery of.

A plurality of pressure beams 16 are placed on the upper surface of each small caisson 2A, 2B, and center hole jacks 17 are placed on both ends of each pressure beam 16.
The lower end of the steel anchor rod 18 inserted through the center hole of the center hole jack 17 is locked to the inner protrusion 10 of the support beam 7 or the support beam 9 or the large caisson 1, and
A nut 20 that engages with the hollow piston 19 of the center hole jack 17 is screwed onto the upper end of the nut 8 .

Among the many small caissons lined up along the peripheral wall of the large caisson 1, openings 3 in some of the small caisson 2A lined up every other small caisson.
A closing plate 22 provided with a sealing material 21 is placed on the opening 3, and a bolt 24 inserted between the clip 23 and the closing plate 22, which engages the flange 15 on the outer peripheral edge of the opening 3, closes the closing plate. 22 is tightened and fixed to the opening 3, and the other end of an air supply hose 26 whose one end is connected to a compressed air supply source is connected to the air supply port 25 provided in the closing plate 22. There is.

When submerging the caisson, use the air supply hose 26.
Compressed air is supplied from the hose 26 to the lower part of the lid plate 4 of each small caisson 2A connected to the lid plate 4, the closing plate 22, the small caisson 2A, and the pressurizing beam 16 due to the pressure of the compressed air. , center hole jack 17, steel anchor rod 1
The large caisson 1 is supported via 8.

Next, in this state, by extending the center hole jack 17 attached to each of the other small caisson 2B, the small caisson 2B is press-fitted into the soft ground using the large caisson 1 as a reaction force support. In this case, the earth and sand in the small caisson 2B are discharged from the opening 3 of the small caisson 2B. Note that the earth and sand may be discharged with the lid plate 4 of the small caisson 2B removed. Further, all the small caissons 2B may be press-fitted at the same time, or the small-sized caissons 2B may be press-fitted one by one.

Next, remove the closing plate 22 attached to the small caisson 2A, and attach the closing plate 22 to the opening 3 attached to the small caisson 2B.
Compressed air is supplied from the air supply hose 26 to the lower part of the lid plate 4 at B, and the pressure of the compressed air causes
The large caisson 1 is supported via the lid plate 4, the closing plate 22, the small caisson 2B, the pressure beam 16, the center hole jack 17, and the steel anchor rod 18.

Next, in this state, by extending the center hole jacks 17 attached to each of the other small caisson 2A, the small caisson 2A is press-fitted into the soft ground using the large caisson 1 as a reaction force support. In this case, the earth and sand in the small caisson 2A are discharged from the opening 3 of the small caisson 2A. Note that the earth and sand may be discharged with the lid plate 4 of the small caisson 2A removed. Further, all the small caissons 2A may be press-fitted at the same time, or the small-sized caissons 2A may be press-fitted one by one.

When press-fitting the small caissons 2A and 2B using the center hole jack 17, the center hole jack 17 is extended while the nut 20 is engaged with the upper end of the hollow piston 19, and then the center hole jack 17 is shortened. After that, Natsuto 2
0 to the upper end of the hollow piston 19 is repeatedly performed.

Next, move the nuts 20 screwed onto each steel anchor rod 18 upwards, and tighten the large caisson 1.
subsidence on soft ground due to natural settlement or loading. In addition, in this case, each small caisson 2
Excavate and discharge the earth and sand in the area surrounded by A and 2B.

Next, small caisson 2B by the above-mentioned means
The press-fitting of the small caisson 2A, and the sinking of the large caisson 1 are repeated as many times as necessary.

Large caisson 1 and small caisson 2A, 2B
After sinking to a certain depth, using large caisson 1 as a reaction force support, each small caisson 2
Press in A and 2B to reach the supporting ground (hard ground). In this case, each small caisson may be press-fitted at the same time, or one or more small caissons may be press-fitted one at a time.If the large caisson does not sink naturally, no pneumatic support force must be applied to the small caisson. Good too.

As shown in Figure 5, small caisson 2A, 2B
A spacer 27 is placed between the upper end surface of the pressure beam 16 and the pressure beam 16.
By press-fitting the small caissons with the caisson interposed, the upper end surfaces of the small caisson 2A, 2B are positioned near the lower edge of the protrusion 10 of the large caisson 1, and then the upper outer surface of the small caisson 2A, 2B and the large caisson A hardening agent such as mortar or a chemical solution is injected between the blade and the inner surface of the cutting edge to harden the earth and sand therebetween.

The curing agent may be injected through an injection hole drilled in the upper part of the small caisson, or may be injected from between the upper end of the small caisson and the protrusion 10.

Next, support beams 7, 9 and ridges 10 of the large caisson 1 are shaved to expose the reinforcing bars, foundation reinforcing bars are connected to the reinforcing bars, foundation concrete 28 is poured as shown in Figure 6, and each small caisson 2A, 2
The upper part of B is integrally connected to the large caisson 1, and the small caissons 2A and 2B are used as the foundation of the large caisson 1.

In addition, after the caisson sinking construction is completed, the pressure beam 1
6. Remove the center hole jack 17, steel anchor rod 18, etc. The cover plate 4 may be removed, or may be used as part of the foundation without being removed.

When carrying out this invention, the number of small caissons arranged in one large caisson may be increased or decreased compared to the case shown in the drawings, and the number and arrangement of small caissons to which air pressure is applied may be set as appropriate. It's okay. In addition, large caisson 1 and small caisson 2
In order to prevent earth and sand from flowing into the large caisson 1 from between the large caisson 1 and the lower surfaces of the support beams 7 and 9 and the ridges 10 of the large caisson 1 and the outer peripheral surfaces of the small caisson 2A and 2B, A sealing material may be provided on each small caisson 2A, 2B.
may be surrounded by temporary enclosure walls each having a height above the water level, and the temporary enclosure walls may be mounted on the support beams 7 and 9 and the ridges 10 of the large caisson 1,
Alternatively, the sealing material and a temporary enclosure wall may be used together.

When large caisson 1 and each small caisson 2A, 2B are to be sunk until reaching a certain depth in soft ground, these caissons may be sunk at the same time, or the small caisson is sunk after large caisson 1 is sunk. The operation of lowering the caisson may be repeated as many times as necessary, or the operation of lowering the large caisson after lowering the small caisson may be repeated as many times as necessary. Further, if the caisson sinks further and the caisson no longer sinks naturally, it is not necessary to provide the small caisson with support force by pneumatic pressure.

〔Effect of the invention〕

According to this invention, a plurality of small caissons 2A and 2B are arranged along the peripheral wall inside the large caisson 1,
Cover plates 4 are fixed to some of the small caissons, compressed air is supplied between the cover plates 4 and the soft ground 5, and while earth is being removed from some of the other small caissons, the large caissons 1 and each Since the small caissons 2A and 2B are lowered to a certain position on the soft ground, the large caisson 1 can be lowered to a certain position on the soft ground while suppressing the rapid sinking of the large caisson 1 by the support force due to air pressure. Moreover, it can be easily settled without causing heaving or boiling, and furthermore, since the inside of the large caisson 1 is divided into small sections by the small caissons 2A and 2B, the earth can be removed easily and safely. I can do it. In addition, by appropriately setting the number of small caissons to which air pressure is simultaneously applied or the air pressure, etc., it is possible to control the large caisson 1 to an appropriate sinking speed. The inclination of the large caisson 1 can be easily corrected by applying air pressure only to the small caisson on the sinking side, or by press-fitting an appropriate amount of small caisson to which the air pressure is applied. After the small caissons 2A and 2B are sunk to a certain depth, each small caisson is press-fitted using the large caisson 1 as a reaction force support, and then the small caisson and large caisson are connected, so the foundation concrete 28 is poured. When installing, the work can be carried out safely by using a small caisson as an earth retaining wall.
Furthermore, small caissons 2A and 2B are replaced with large caisson 1.
This has the effect that it can also be used as a supporting foundation.

[Brief explanation of drawings]

The drawings show a composite caisson consisting of a large caisson and a small caisson used for carrying out the present invention, in which Fig. 1 is a plan view, Fig. 2 is a sectional view taken along the line A-A in Fig. 1, and Fig. 3 is a cross-sectional view taken along line A-A in Fig. The figure is an enlarged longitudinal sectional front view of the floor plate attachment part and the cover plate attachment part, and FIG. 4 is an enlarged front view showing the vicinity of the center hole jack. FIG. 5 is a longitudinal sectional front view showing a state in which a small caisson has been press-fitted to a predetermined position using a spacer, and FIG. 6 is a longitudinal sectional front view showing a state in which foundation concrete has been poured into the caisson. In the figure, 1 is a large caisson, 2A and 2
B is a small caisson, 3 is an opening, 4 is a cover plate, 5 is a soft ground, 7 and 9 are support beams, 10 is a ridge, 1
2 is an insert, 13 is a rubber sealing material, 14 is a bolt, 15 is a locking flange, 16 is a pressure beam, 17 is a center hole jack, 18 is a steel anchor rod, 19 is a hollow piston, 20 is a nut, 21 22 is a sealing material, 22 is a closing plate, 23 is a clip, 24 is a bolt, and 26 is an air supply hose.

Claims (1)

[Claims] 1 A plurality of small caissons 2A and 2B are arranged along the peripheral wall inside the large caisson 1, and the cover plates 4 are fixed to some of the small caissons, and the cover plates 4 and the soft ground 5 are fixed.
After compressed air is supplied between the large caisson 1 and each small caisson 2A, 2B to sink to a certain position on the soft ground, each small caisson is press-fitted using the large caisson 1 as a reaction force support, and then A caisson sinking method in soft ground characterized by combining a small caisson and a large caisson.