JPS5911005B2 - Slope embankment construction method - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for constructing a sloped embankment body.

In the conventional construction technology for sloped embankments, the slope IJ −
After the caisson embankment body is towed and installed, the caisson embankment body is towed and installed, and the earth and sand transport vessel is brought alongside the embankment body to be transported by grab-back or other means, and transported by machinery. The method used is to inject filler soil into the bulkhead from the top of the caisson embankment.

Therefore, the slope reinforced concrete 1 for the slope embankment had no choice but to be constructed as cast-in-place reinforced concrete after the completion of the construction.

However, since the sea areas where wave-dissipating seawalls and wave-dissipating breakwaters, etc. will be constructed are almost always areas with rough waves, cast-in-place concrete in the sea area where breakwaters, etc. will be constructed is recommended.
Construction should be completed in as short a time as possible, and the development of some kind of rapid construction method is desired.

The method for constructing a sloping levee body of the present invention satisfies the above-mentioned requirements and significantly saves labor for on-site offshore construction. It is characterized by a process of building in a box-building yard, and a process of injecting a suspension of water and sand from an inlet provided in advance in the embankment body after launching, towing, and installation.

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

FIG. 1 shows a wave-dissipating levee as a type of sloping levee 1.

In the present invention (/c), as shown in FIG. The structure was built in a box yard as an integral structure with the caisson, and prior to launching, the front opening of the embankment was covered with a temporary steel plate lid 1'.
It will be sealed by attaching a caisson, and after being launched, it will be towed to the site in the same way as a normal caisson.

When building a box in a dry dock, the superstructure is also built at the same time as a box in the dry dock, so the drainage may become too deep when leaving the dock. A floater 5 is used as shown.

Alternatively, the auxiliary lifting method of a hoist ship may be used instead.

Immediately after the coulson is installed on the leveled surface of the 7'ζ foundation stone prepared in advance at the planned installation location of the embankment body, the filling work is started immediately.

As shown in Figure 2, temporary soil is placed on the seabed in advance.
I'll keep it.

It is preferable to embed a rectangular steel pipe (gas pipe) 6 in the hole 3 of the sword concrete υ-1/plate 4 as a filler sand injection [1 or surplus water discharge 1].

The packed sand is transported through pipes using a method similar to a normal bomb dredger, in which a suspension of water and sand with a volumetric sand content of about 10% is pumped.

According to the present invention, as shown in FIG.
The filling sand material 9 temporarily placed on the seabed is suctioned, the pressure is increased by a small star point/fiber 10 on the barge T, and the concrete slab 4 is transported through a flexible hose 11 to the slope concrete slab 4.
The water is injected into the inside of the caisson bulkhead through the lower hole 3 of the caisson wall, respectively; the surplus water is drained from the upper hole 3 through the hose 12.

In another embodiment of the present invention, as shown in FIG. 4, a cargo ship γ' is used as the barge 7, and the cargo ship γ' is placed alongside, and a sand pump with a cutter is suspended directly into the hold. 1. It is more convenient to take out the slurry while adding water by spraying water.

With this filling method, variations in the sand content in the slurry can be tolerated over a wide range.

Furthermore, if the surplus water is allowed to flow back, there is no risk of the surplus water contaminating the seawater.

The experimental results of the present invention are shown below.

For the sloping embankment filling experiment, a scale acrylic model was torn apart.
A device for supplying slurry with a sand content of approximately 10% was also prepared, and the experiment was carried out in an experimental tank with the positional relationship between the seawater level and the embankment body suited to the actual situation.

According to Froude's law of similarity, the model dimensions, practical injection pipe diameter, flow rate, flow rate, etc. are as shown in the table below.

Regarding the first section of the sloping embankment, the entrance is at the bottom,
Advantageously, the outlet is provided at the top.

If it were the other way around (injecting from above and discharging from below the slope),
After a certain height -L is filled, the sand suspension is directly discharged from the drainage outlet, and no sand is deposited on the top of the slope, proving that the filling condition is defective. It was done.

If the drainage outlet is provided above the slope, the drain will be filled satisfactorily, leaving almost no unfilled space.

Even in experiments with multiple drainage ports, good results were obtained that were not significantly different from those with one drainage port.

Therefore, the strainer in the stop and reverse flow process diagram shown in FIG. 5d is considered to be almost unnecessary as there is no need to reverse flow to compensate for the remaining space in practice.

After Ejin, the injection port can be closed with concrete, etc.

Since the experimental results were satisfactory, we attempted simultaneous injection of multiple fields as the next step.

For this reservoir, it is necessary to provide a communication hole 13 in the upper part of the caisson partition wall 2, an example of which is shown in FIG.

Slurry for the model in Figure 5. Time to break a sweat is 23 minutes.
Other conditions were as shown in Table 1 above, except that the average sand content of the slurry was 11.2%, and the average density of the filled sand was 1.83.
Met.

The sand used in the experiment had a uniform particle size due to model scale limitations, so this is about this level, but in practice, sand with an appropriate particle size distribution is used, so the filling density is even higher. I think it will get better.

The partition wall communication hole 13 is provided at the -7 section of the partition wall 2, and its size is sufficient as it is almost the same as the cross-sectional area of the inlet.
It is not large enough to significantly affect the design of the caisson components.

The present invention can also be used to construct an enclosure for a marine farm.

In order to cultivate Taneichi production resources as a cultivation fishing technology, it is necessary to raise and establish a wide variety of fish and shellfish on marine farms.

To do this, as shown in Figure 7, a submerged embankment 14 is required in the area outside the farm.
However, recent research has shown that in order to raise fish eggs, fry, and other larvae, it is necessary to constantly pump fresh high-nutrient seawater containing Blank 1 into the farm. is desirable, and it is considered that the latest technology is to utilize the natural energy of the deep density stratified fluid movement (internal waves) containing such high nutrients, and the inclined submerged levee 14 is suitable for this purpose.

Using conventional port construction technology, this type of sloping levee with a caisson structure could not be installed underwater as a submerged levee.

The reason for this is C because it was not possible to construct reinforced concrete on the ceiling slope underwater.

In the present invention, first, a dome caisson is lowered from a land yard using a hoist ship 15, or is made in a dry dock or box building yard, launched and towed to the installation site sea area, and then a hoist Installed by ship 15.

After that, filler sand is injected from the slurry supply system into the caisson through a flexible pipe, and a submerged embankment with the required weight is completed.

Because a caisson is a gigantic piece, no matter how great the capacity of a modern crane ship is, it is impossible to sink it as a complete embankment body, but if the construction method of the present invention is used, it will work with the crane during the sinking. Only by reducing the load through buoyancy balance will construction work become possible.

Needless to say, the inside of the caisson is empty during installation work.

By using this method, it is possible to plan the outer enclosure of a deep-water marine farm with a considerable embankment height.

If this were to be made of rubble or concrete blocks, the width of the sloping embankment body would be extremely wide, requiring an enormous amount of construction cost.

In addition, when taking in high-density lower seawater containing high nutrients, it is desirable for the slope to have an accurate dimension and shape to prevent stratified fluid movement, that is, waves traveling up the slope. Type C was extremely rough for an upstream slope, and the introduction of highly nutrient-rich seawater was insufficient.

At the same time, the dam body made of concrete blocks and rubble has large gaps, and the action of waves sucks out highly nutrient-rich seawater to the outside, making the lower part of the interior of the farm calm enough to be suitable for seed cultivation. I couldn't.

According to the present invention, such drawbacks can be eliminated.

Incidentally, many experiments with sand filling for sloped embankments have been carried out mainly at 20 degree inclinations, but 10 degree and 5 degree inclinations have also been tested, and it has been shown that construction can also be carried out at 0 degree, that is, completely horizontal. has been confirmed in experiments.

In fact, the looser the diagonal angle, the easier the filling construction will be.

A slightly technical explanation of this is as follows.

As shown in Figures 5b and 5c, the slurry passing through the inlet and inside the box naturally creates a waterway in search of the line of least resistance in the latter stage of injection, as if it were a natural river. However, at this time, there is resistance in the flow path, and the pump side must bear the friction head loss.

Naturally, the angle of inclination also increases the head loss.

Therefore, there is naturally a limit to the mutual distance between the injection pipe and the discharge pipe, and there is a significant relationship between the flow rate of the slurry and the particle size of the sand to be discharged. From the top of the caisson's pressure resistance, the distance between the injection pipe and the discharge pipe is:
In the case of a 20 degree oblique embankment, it is preferably around 8 m, but in the case of a horizontal embankment, it corresponds to about Iom.

In the method of the present invention, even a relatively small hoist ship can be installed on the seabed mound in a completely submerged state due to the buoyancy balance, like the submerged embankment of the marine farm in the above embodiment. It will also be possible to build your body.

(Not shown) In response to modern demands for deep-water port structures, the dimensions of embankment structures are becoming increasingly gigantic, and the boxyard facilities that manufacture them are having difficulty meeting their size. This is the actual situation, and one way to deal with it is to stack it in multiple stages.

The slurry injection method of the present invention allows for the construction of a sub-loaded caisson as a "covered" caisson, ie, a caisson with an integral ceiling reinforced concrete slab.

As described above, the "method for constructing a dike body" of this invention can be constructed more easily even when the angle of obliquity is gentle, and as a caisson with a lid, it can be applied to various port structure construction methods that were previously unthinkable. can be considered.

In the above embodiments, only sand was used as the filling material, but gravel or the like having a particle size larger than sand may also be used as the material for the pond.

According to the present invention, it is possible to omit the on-site pouring of the upper cover concrete as in the past, and the upper cover concrete is manufactured as one piece under careful construction management within the caisson yard. Upper cover concrete with satisfactory strength can be obtained.

In addition, even when towing from a caisson yard, since the upper cover concrete is prefabricated, there is no need to worry about seawater inflowing, which is convenient when there is no caisson yard near the site and the vessel must be towed from a distant yard. .

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the completed state of the inclined embankment, Figs. 2 and 3 are explanatory diagrams of the method of the present invention, Fig. 4 is an explanatory diagram of another embodiment of the present invention, and Fig. 5 a to d are injection experiments. Explanatory drawing, Fig. 6 An explanatory drawing of the first experimental model, Fig. γ (This is an explanatory drawing of the ri marine farm.・・・
...hole, 4...slanted conch 1 roux 1, version, 5
...Floater, 7'...Ship, 8
... Submersible sand pump, 9 ... Sand filler, 10 ... Booster pump, 11 ...
... Flexible pressure pump, 12 ... Hose, 13 ... Communication hole, 14 ... Inclined submerged embankment, 15 ... Hoist ship.

Claims (1)

[Claims] 1. The process of constructing the levee body in an almost closed box-like construction yard using the slope concrete slab of the levee body as the caisson and the grandchild of the levee body, and after launching, towing, and installing the levee body, the injection port was prepared in advance in the levee body. 1. A method for constructing a slope embankment comprising the step of injecting a suspension of water and sand.