JPH0426007B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is applicable to the construction of marine platforms, artificial islands, etc., or to large seabed surfaces, where particles such as sand are dispersed in a fluid such as water and transported through pipes. It concerns the technique of sowing possible slurry.

<Conventional technology> For example, the technology of transporting slurry sand and filling it with ballast material such as sand into a concrete box submerged in water has been implemented in other places such as the Delta project in the Netherlands. has been done.

As shown in Fig. 11, the conventional filling technology is to create a bottomed structure A that has a plurality of ballast chambers a with a raised structure.
This method involves filling the inside with slurry sand.

Each of the ballast chambers a, b... is partitioned by a partition wall B, and a communication port C is opened at the upper end of each partition wall B so that the ballast chambers a, b... communicate with each other.

Then, a slurry transport pipe D is connected to the upper side wall of the ballast chamber a located at the outermost end to supply slurry.

In this method, the transported sand is deposited in the ballast chamber a, while the water used for transportation is discharged to the outside, and each ballast chamber a is sequentially filled with sand.

<Problems to be Solved by the Present Invention> The following problems remain in the above-mentioned filling technology of slurry sand.

That is, when the slurry is discharged from the transport pipe D into the ballast chamber a, the cross-sectional area of the transport path becomes larger than that of the transport pipe D.

As a result, sand begins to sink and accumulate, but as the amount of sand that accumulates increases, the distance from the sky becomes narrower.

As a result, a natural flow path commensurate with the flow velocity is formed between the top surface of the sand and the roof.

This natural flow path has an unstable shape, meandering while changing its direction to a place with low resistance, and finally blocks the outlet E.

<Object of the present invention> The present invention has been made in order to solve the above-mentioned problems, and it is possible to transport the slurry to a long distance without reducing the flow velocity and prevent clogging, and moreover, to efficiently transport particles in the slurry. The purpose is to provide a technique for sowing slurry that can be used to sow bodies.

<Example> Hereinafter, with reference to the drawings, the filling of a bottom-attached structure made of a box will be described as an example, but the same can be done for sowing on other wide seabeds.

First, a sowing device used for sowing the slurry will be explained.

<A> Sowing device (Fig. 2) The sowing device 1 has, for example, a semicircular cross section,
It is a tube with an open bottom.

Both ends of this tube are closed with side walls 11.

A throttle hole 12 is formed in the upper part of both side walls 11, respectively.

Further, a continuous sand settling port 13 is formed on the bottom surface of the tube.

A plurality of flow rate adjusting walls 4 are provided inside the sowing device 1.

A hole 5 is provided in the upper part of each flow rate adjusting wall 4, and the flow rate of the slurry can be adjusted by selecting the diameter of the hole 5.

Further, the sowing device 1 without the flow rate adjusting wall 4 may be used.

In short, it is sufficient if it is an open bottom body with aperture holes in the front and back.

[Method of arranging sowing device] (FIG. 1) This sowing device 1 is arranged on the ceiling side in each ballast chamber a of the bottoming structure A partitioned by a partition wall B.

For example, a transport pipe D extending from a slurry pump P that mixes and pumps sand 7 and water on the water side is connected to the throttle hole 12 of the sowing device 1 located at the outermost end (the left end side in FIG. 1). .

Furthermore, the throttle holes 12 of each sowing device 1 are arranged on the same line through the communication port of the partition wall B to form a communication structure.

Furthermore, if the ballast chamber a is large, a plurality of sowing devices 1 may be arranged in parallel as shown in FIG.

<B> Principle of sowing slurry When the fluid reaches a certain flow velocity (limit flow velocity), sand in the water rises to the surface and moves at the same speed as the fluid.

On the other hand, it is known that when the fluid reaches a critical flow velocity or less, sand begins to settle.

The slurry sowing technology according to the present invention rapidly increases the flow velocity of the slurry by rapidly decreasing the cross-sectional area of the enlarged slurry flow path from a certain point in the ballast chamber a. sand 7
The sand 7 is transported over long distances, and the sand 7 is successively sown into each ballast chamber a.

That is, when observing mainly the transportation speed of the slurry, it changes as follows.

[Flow Velocity in Transport Pipe] The flow velocity of the slurry transported from the slurry pump P is discharged into the ballast chamber a while maintaining approximately the flow velocity at the time of the start of transport in the transport pipe D having the same diameter.

[Change in flow velocity in the ballast chamber] The slurry transported through the transport pipe D is transferred to the transport pipe D through the settling port 13 of the sowing device 1.
The slurry is discharged into the space of the ballast chamber a, which has a large area compared to the cross section of the slurry, and the flow velocity of the slurry decreases below the critical flow velocity.

As a result, only the sand 7 starts to settle in the ballast chamber a.

In this state, the amount of settling sand 7 in the ballast chamber a gradually increases, and eventually the settled sand 7 blocks the sand settling port 13 in the space partitioned by the flow rate regulating wall 4.

From that moment on, the tube forming the sowing device 1 becomes the only channel for the slurry.

The cross-sectional area of this tube is extremely small compared to the cross-sectional area of the ballast chamber a, which was a flow path until just before.

Therefore, the transport speed of the slurry instantly increases beyond the critical flow speed.

As a result, the slurry is transported into the space partitioned by the next flow rate adjusting wall 4, and the sand 7 is precipitated, and filling progresses one after another. (FIG. 4) When the filling of the first ballast chamber a is completed, it is transported at high speed to the next ballast chamber a, and filling is performed in the same manner thereafter.

In this way, the reason why the slurry transport speed suddenly increases is that the slurry flow path instantly shrinks due to the sedimentation of the sand 7, which causes the slurry transport speed to increase naturally. This is not due to increased pressure.

The above steps are repeated to fill each ballast chamber a with sand 7.

[Experiment showing the relationship between sand flow velocity and deposition state] When the amount of sand 7 deposited increases and the sand settling port 13 is blocked, the flow velocity of the slurry naturally increases because
This is clear from the following experimental example.

That is, a plurality of model pipe bodies 2 each made of a transparent cylinder having a constant length are arranged in series.

Each model pipe body 2 is connected at the side with a hose 3.

Then, the slurry was pumped from the side of the outermost model tube 2, and the relationship between the flow velocity of the slurry and the state of accumulation of the sand 7 was tested.

There are two types of flow velocity conditions:

Flow rate condition: 1.5 to 2.0 m/sec Flow rate condition: 2.5 to 3.0 m/sec However, the above flow rate is the flow rate at the discharge port of the slurry pump P.

[Test Results] Under both flow rate conditions, the model pipe body 2 was once filled in a jet state.

The changes in the deposition state of sand 7 over time since then are as follows:
The flow velocity conditions are shown in FIGS. 5 to 7, and the flow velocity conditions are shown in FIGS. 8 to 10, respectively.

In the case of flow velocity conditions, the sand 7 is deposited sequentially from the inlet side to the outlet side because the blowing distance of the sand 7 is short.In the case of flow velocity conditions, the fine particles contained in the sand grain group are The particles were suspended and deposited near the outlet, and even smaller particles were transported to the next model pipe body 2.

The final deposition state of the sand 7 under the flow velocity conditions is as shown in FIGS. 7 and 10.

There is a slight difference in the final deposition state of sand 7 under both flow velocity conditions, but in both cases, sand 7 does not block the flow path inside the model pipe body 2. When the sand 7 was deposited stably, it was transported to the next model pipe body 2.

The above test results can prove that the flow velocity of the slurry supplied using the sowing device 1 described above decreases initially in the ballast chamber a due to the sudden increase in the cross-sectional area of the flow path.

Furthermore, when the accumulation of sand 7 progresses and the sand settling port 13 of the sowing device 1 is blocked, the cross section of the flow path in the sowing device 1 is rapidly reduced, and the flow velocity of the slurry is sufficiently increased. This can be proven.

<Effects> Since the present invention is as described above, the following effects can be expected.

(a) A sowing device is placed at the top of each ballast chamber of the bottoming structure.

When slurry is supplied through this sowing device, the flow velocity initially decreases due to the difference in cross-sectional area of the channels, and sand accumulates.

When the accumulated sand reaches the point where it blocks the bottom opening of the sowing device, the cross-sectional area of the flow path within the ballast chamber is rapidly reduced to a very small cross-sectional area.

As a result, the flow rate of the slurry increases from a certain moment, allowing it to be transported to the next ballast chamber at high speed.

Therefore, even after one ballast chamber is sufficiently filled with sand, the slurry can be transported to a long distance without reducing the flow velocity, and the filling operation can be carried out in a large number of ballast chambers in succession.

(b) As mentioned above, when the cross section of the slurry flow path suddenly decreases from a certain moment, the flow velocity of the slurry naturally increases to a velocity higher than the critical flow velocity.

Therefore, clogging of sand within the sowing device can be reliably prevented.

(c) Since a large amount of sand can be sown over a wide area without blocking the slurry flow path, the occurrence of unfilled spaces in the ballast chamber can be suppressed.

Therefore, sufficient weight can be given to the bottom-wearing structure.

(d) It can be used not only for stuffing into structures that land on the bottom, but also for sowing various solids into a wide water bottom.
The scope of use is wide.

[Brief explanation of drawings]

Fig. 1: An explanatory diagram showing the state of stuffing the bottom into the bottom structure, Fig. 2: An explanatory diagram of an embodiment of the sowing device, Fig. 3: A sectional view of - in Fig. 1, Fig. 4:
Explanatory diagram showing the transportation state of slurry in the sowing device, Figures 5 to 10: Using a model pipe body,
Explanatory diagram of the test results for the state of sand accumulation, Part 1
Figure 1: An explanatory diagram of the conventional filling technology. 1... Sowing device, 2... Model pipe body, 7...
Sand, 12... throttle hole, 13... sand settling port, A... bottom landing structure, B... bulkhead, a... ballast chamber.

Claims (1)

[Claims] 1. Slurry transported through a pipe is first discharged into a space with a larger cross-section than the cross-section of the pipe and is allowed to settle, and the cross-sectional area of the space is gradually reduced due to the precipitation, and from a certain moment, the cross-section of the space of the flow channel is suddenly reduced. A slurry sowing method in which the transport speed of the slurry is increased to a speed at which particles in the slurry float by decreasing the amount of slurry, and the process of discharging the slurry into the next large cross-sectional area is repeated. 2. A pipe body that communicates with and connects to the tip of a transport pipe that transports slurry, and both ends of this pipe body are closed with side walls with holes for slurry passage, and the bottom of the pipe body is open. A sowing device used for sowing slurry, characterized by: