JPS6134534B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for constructing a caisson embankment such as a breakwater.

The caisson-type hybrid levee is a typical structural type of breakwater or revetment. A method for constructing this type of gravity structure is generally performed in the following steps.

(i) Loading of rubble by stone-loading ships, gatsuto ships, etc. (ii) Leveling of rubble mounds by divers (iii) Towing and installation of individually manufactured caisson boxes (iv) Filling with sand and construction of superstructures Construction (v) Installation of foot protection blocks, cover blocks, etc. Of the above work steps, (ii), the method of constructing rubble mounds, relies heavily on divers, and furthermore, diving work is subject to constraints such as sea conditions and water depth. is often received. In general, work that does not significantly affect the efficiency of the diver is limited to a depth of -20 to -25 m, and it is said that workability is extremely poor and impractical at depths greater than that.

In particular, the target water depth for deep-water structures such as offshore artificial island construction projects that have been called for in recent years is -30
Since the mounds are as deep as -50m, when constructing a caisson-type hybrid embankment in such sea areas, it becomes difficult to construct mounds using conventional methods by divers.

In addition, conventional methods for installing caissons include using push barges to slowly sink them while injecting water, but the current situation is that high precision cannot be expected because the caissons are shaken by waves.

Especially when it comes to large caissons, the added weight is large, making it difficult to control the floating body, and even if large work vessels are introduced, installation accuracy becomes a problem.

On the other hand, the problem with gravity-type structures in deep water is the bearing capacity of the mound. The allowable soil bearing capacity of mounds created using conventional construction methods is usually around 40 to 50 t/m ² in many cases.

When the water becomes deep, the influence of the bearing capacity of the soil on wall stability increases. In other words, the minimum width of the embankment required for wall stability is determined by the bearing capacity of the ground. Therefore, increasing the bearing capacity of the mound by even a small amount will lead to lower construction costs, but at present, only the above-mentioned values are adopted in conventional methods.

In addition, in recent years, in order to construct breakwaters in deep water areas, a method of constructing breakwaters in which multiple caissons are stacked in several tiers has been proposed. Since the bonding takes place below the sea surface, sufficient bonding is not possible.

The present invention is intended to improve the above-mentioned problems and drawbacks, and the method for constructing a caisson embankment of the present invention includes a step of forming a roughly leveled rubble mound, and a step of forming a caisson embankment on the rubble mound. A step of installing a work boat with an installation spud using the spud, a step of suspending the caisson from the work boat, and a step of sinking the caisson to a predetermined height from the rubble mound and installing a work boat on the underside of the caisson. The process consists of a step of injecting mortar into the lower base fabric (canvas) from which mortar leaks through the mesh, thereby filling the gap between the lower surface of the caisson and the rubble mound, and a step of removing the spud-equipped work boat. It is characterized by

Embodiments of the present invention will be described below with reference to the drawings.

In the present invention, the rubble thrown in by a stone carrier or the like is first processed by a rubble leveling machine to reduce the surface unevenness by 30 to 30 mm.
It is roughly leveled to about 50 cm, and a catamaran boat 2 with spuds for installing a caisson is towed and installed on top of this rubble mound 1. The catamaran 2 with spouts mainly includes a hull 3, a girder 4 for suspending a caisson,
It consists of a spud 5, and is equipped with a hydraulic jack for raising and lowering the spud 5, and a hoist placed on the girder 4 for suspending the caisson.

Installation of the catamaran 2 with spuds is carried out in the following steps. That is, after guiding the caisson to the planned installation position, the spud 5 is lowered and water is injected into the hull 3 in order to maintain the stability of the entire hull.

By controlling the amount of water injected, the vertical load applied to the spud can be arbitrarily determined.
Normally, considering a vertical load of about 300 to 400 tons, it is possible to maintain stability against waves of about 1 meter, but if a too large vertical load is applied, it will exceed the limit that can be supported by the mound. Therefore, it is desirable that the load acting on each spud with a diameter of about 1 m be constant at about 100 to 130 tons.

After the catamaran 2 with spouts is installed at a predetermined position in this way, the lower caisson 7, which has a ventilation tower 6 formed on its upper part manufactured at a floating dock or a land yard, is towed and guided to the catamaran with spouts. do. Next, as shown in Figure 1, the lower caisson 7
The upper part of the vessel and the girder 4 are connected with a wire 8, and a desired amount of seawater, which has been adjusted and injected into the hull section 3, is transferred into the lower caisson 7 by a pump. Next, the first
While the lower caisson 7 is being held in the state shown in the figure, the upper caisson 9, which has been towed separately as shown in Fig. A recess 1 formed on the upper surface of the lower caisson 7 by pouring water to the extent that a load is applied.
The upper caisson 9 is lowered until it touches the ground at 0.

After the upper caisson 9 is grounded on the lower caisson 7, the seawater in the upper and lower caisson is pumped up again into the hull 3, as shown in FIG.
Raise the lower caisson until the connecting surface is above the sea. At this time, the floating height, displacement amount, pump operation, etc. are controlled so that the hanging load hardly changes.

The upper and lower caissons are integrated with the connecting surfaces exposed to the atmosphere. The integration can be done by connecting them with cast-in-place concrete, or by fixing one end of the PC steel bar 11 to the lower caisson 7 in advance and connecting the PC steel bars between the upper and lower caissons with a coupler to prestress them. It is also possible to introduce and integrate. In addition, in order to improve the accuracy when grounding the upper caisson to the lower caisson, not only the recess 10 but also a guide pipe (not shown) is installed in the lower caisson 7 to ensure that the upper and lower caissons are grounded securely.
It is possible to connect with PC steel rod 11.

After the upper and lower caissons have been completely integrated, as shown in Fig. 4, the seawater that had been returned to the hull 3 is poured into the lower caisson 7 again, and the seawater is lowered to a predetermined height (installation depth). ), and while holding the caisson with anchors and mooring cables (not shown) thrown into the surrounding seabed, the caisson lower base cloth (canvas) 12 was previously attached to the lower part of the lower caisson 7. concrete or mortar is poured into the tank from the sea. The injection hole should be installed in advance on the caisson bulkhead, etc.

Next, when the concrete poured into the lower caisson base fabric 12 has sufficient strength to hold the caisson, the lower caisson 7 is filled with sand, etc. using a pump or the like using the ventilation tower 6, and then the upper caisson 9 is filled with sand, etc. The caisson was then filled in and the superstructure was constructed as usual, and then the hoist that was suspending the caisson was gradually loosened, the spud was lifted with hydraulic jacks, and the catamaran with the spud was separated from the caisson. and completed the caisson embankment.

The initial strength of concrete is sufficient to support the vertical load of the caisson, so it is sufficient to develop around 1 kg/cm ² . Therefore, it only takes a few hours to maintain the caisson in a floating state until the caisson installation is completed. In addition, when it is desired to further shorten the required time, it is possible to adjust by adding a curing accelerator or the like.

Thereafter, the water in the hull section 3 is drained, floated, and the catamaran 2 is removed, completing the two-stage caisson as shown in FIG.

The effects of the present invention are listed below.

(1) Positioning is carried out in a floating state using a catamaran with spuds and an existing caisson, allowing for quick and accurate positioning.

(2) By providing a ventilation tower, it is possible to facilitate the installation of a covered caisson. In addition, after being submerged, the aeration tower can be used as a drainage pipe using the filling method.

(3) By using buoyancy and repeating drainage, the load on the spud can be kept constant.

(4) Since buoyancy is used, even large caissons can be installed with a small lifting load.

(5) Since the gap is filled with concrete etc. while the caisson is floating, there is no need to level the top of the mound and the height of the caisson top can be set accurately.

(6) Since finishing the top of the mound by mechanical leveling is sufficient, construction can be carried out in deep water areas where diving work is difficult.

(7) Since the lower end of the caisson and the rubble are integrated using concrete or mortar leaked through the mesh of the canvas, the bearing capacity of the ground can be increased compared to conventional methods, and construction costs can be reduced. .

(8) Since the buoyancy of ordinary caissons and caisson with lids can be adjusted as desired, they can be sunk with high precision.

(9) Since the upper caisson and lower caisson are connected above sea level, the strength of the connection can be sufficiently increased.

[Brief explanation of the drawing]

Figure 1 is an explanatory plan view of the catamaran, Figures 2 to 6
Each figure is a process explanatory diagram of the method of the present invention. 1... Rubble mound, 2... Catamaran, 3... Hull, 4... Girder, 5... Spud, 6...
Ventilation tower, 7... lower caisson, 8... wire,
9...Upper caisson, 10...Recess, 11...Steel rod, 12...Caisson lower base fabric.

Claims (1)

[Scope of Claims] 1. A step of forming a roughly leveled rubble mound, a step of installing a work boat with a spud for installing a caisson on the rubble mound using the spud, and a step of hoisting the caisson by the work boat. The caisson is lowered to a predetermined height from the rubble mound, and mortar is injected into the lower base fabric (canvas) from which the mortar leaks through the mesh provided on the lower surface of the caisson. A method for constructing a caisson embankment, comprising the steps of: filling a gap between the lower surface and the rubble mound; and removing the spudded work boat. 2. A step of forming a roughly leveled rubble mound, a step of installing a work boat with a spud for installing a caisson on the rubble mound using the spud, and a step of suspending the lower caisson by the work boat, A step of placing the upper caisson on top of the lower caisson, a step of floating the lower caisson and the upper caisson together and connecting them with their connecting surfaces exposed above the sea surface, and a step of moving the upper and lower caissons to the rubble. Mortar is injected into the lower base fabric (canvas) which sinks to a predetermined height from the mound and leaks through the mesh provided on the lower surface of the lower caisson, thereby creating a gap between the lower surface of the lower caisson and the rubble mound. 1. A method for constructing a caisson embankment, comprising the steps of: filling the work boat with spuds; and removing the spud-equipped work boat.