JPH0459403B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for covering soft underwater ground with sand, and more specifically, when spreading sand through a conduit onto the underwater ground such as a sludge layer, The present invention relates to a sand-covering method that allows the sand to land softly on the soft ground at the bottom of the water, thereby achieving good sand-covering.

[Prior art]

In recent years, there has been an increasing trend in the use of a sand-covering method for regenerating and purifying soft underwater ground, such as a sludge layer on the ocean floor, by spreading sand over it.

Generally speaking, as shown in Figure 3, this sand-covering method involves transporting sand from a sand carrier 1 to a grab bucket 2 through a conduit such as a tremie pipe 3 onto soft ground 8 on the water bottom.
As shown in FIG. A construction method is adopted in which the sand is spread by using a sand pipe 7 as a conduit and guiding it onto the soft ground 8 at the bottom of the water.

However, the above construction method has a problem in that it is not possible to control the descending speed of the sand S particles when they land on the soft underwater ground 8 to cause them to land softly.

That is, when sand S is introduced from the grab bucket 2 in FIG. 3 through the tremie pipe 3, the lowering speed increases as the amount of sand in the tremie pipe 3 increases, especially when the water depth is shallow. The sediment becomes a clod flow, and the arrow F appears on the soft soil of the water bottom soft ground 8.
The problem is that you get completely absorbed in it.

Furthermore, even when the sand S in the form of slurry is guided and spread by the sand pipe 7 in Fig. 4, the descending speed cannot be suppressed, and the flow speed causes the soft soil to scatter as shown by the arrow F, causing the sand to spread. This has the disadvantage that it prevents the S from landing softly.

[Purpose of the invention]

The present invention was made in order to solve the problems in the conventional sand-covering method, and it controls the descending speed of the sand flow in the conduit, uniformly mixes water and sand, and softens the water bottom. The purpose of this method is to enable sand to be evenly spread over soft ground at the bottom of the water without sand sinking into the ground, and to carry out sand-covering work efficiently.

[Structure of the invention]

The present invention is directed to a sand-covering method for soft ground under water, in which sand is introduced from above the water surface through a conduit to the soft ground under water, and the sand is spread while discharging compressed air from the lower end of the conduit upwardly within the conduit. Constructed by spraying.

〔Example〕

The details of the present invention will be explained below with reference to the drawings. Figure 1-A is for explanation of the main part of Example 1 showing the state in which sand capping work is being performed using the sand capping method of the present invention. FIG.

Embodiment 1 shown in Fig. 1-A is an application of the present invention to the sand-covering method for soft underwater ground 8 in the conventional example shown in Fig. 3. Identical parts are indicated by the same part number, and water surface L
Sand S is guided into the tremie pipe 3 from the sand carrier 1 above by a grab bucket 2 using the tremie pipe 3 as a conduit, and the sand S is spread on the soft ground 8 on the water bottom, but in this embodiment 1, As shown in Figures 1-B and 1-C, an annular compressed air discharge pipe 11 having a large number of air discharge holes 12 on its lower surface is disposed at the lower end of the tremie pipe 3, and the sand carrier 1 Compressed air A from air compressor 9 above
The sand S is discharged upward into the tremie pipe 3 through the compressed air discharge pipe 11, while the sand S is discharged into the soft underwater ground 8.
We are trying to guide the people in spreading the information.

As a result, the descending speed of the sand S introduced into the tremie tube 3 by the grab bucket 2 is controlled by the rise of the compressed air A, and the air bubbles of the compressed air A rise in the tremie tube 3, causing the sand to descend. S and water are mixed in a complex manner and uniformly mixed.

Note that the descending speed of the sand S in the tremie tube 3 can be changed depending on the amount of compressed air A discharged from the compressed air discharge tube 11.

Next, Example 2 in FIG. 2 shows a case where the present invention is applied to the conventional example in which the sand S shown in FIG. 4 is made into a slurry and sand-covering work is performed. The same parts are indicated by the same part numbers, but a compressed air discharge pipe 11 similar to that shown in FIG. The same function as in the first embodiment is provided by guiding and scattering the sand S onto the soft underwater ground 8 via the sand pipe 7 while discharging it into the water.

Here, in the second embodiment, an air discharge port 13 for releasing the compressed air A is provided at the top of the sand pipe 7.

In the present invention, as a device for releasing compressed air A from the lower end of a conduit such as the tremie pipe 3 or the sand feeding pipe 7 into the conduit, the above embodiment 1 is used.
The shape and structure of the compressed air discharge pipe 11 of 2 and 2 are not limited, and any device may be used.

〔Effect of the invention〕

As explained above, in the sand-covering method for soft ground on the water bottom of the present invention, when sand from above the water surface is guided onto the soft ground on the water bottom through the pipe, the flow velocity of the downward flow of sand in the conduit is reduced. In addition to being easy to measure, a uniform mixture of the descending sand and water can be obtained, allowing the sand to land softly on the soft ground at the bottom of the water.

As a result, a uniform and good sand covering layer is efficiently formed on the soft underwater ground such as a sludge layer, and the thickness of the sand covering layer becomes uniform, so the amount of sand used can be reduced, making it economical. be.

[Brief explanation of drawings]

Figure 1-A is an explanatory side sectional view of the main part of Example 1 showing the state in which sand-covering work is being performed using the sand-covering method of the present invention, and Figure 1-B is Figure 1-A. Fig. 1-C is a cross-sectional view taken in the X-X direction of Fig. 1-B, and Fig. 2 is a state in which sand-covering work is being performed in Embodiment 2 of the present invention. FIGS. 3 and 4 are explanatory side sectional views of essential parts showing states in which different conventional sand-covering works are being performed, respectively. 3...Tremy pipe, 7...Sand pipe, 8...Soft water bottom ground, 9...Air compressor, 11...Compressed air discharge pipe, A...Compressed air, L...Water surface, S
……sand.

Claims (1)

[Claims] 1. In the sand-covering method for soft ground on the water bottom, in which sand is introduced from above the water surface through a conduit onto the soft ground on the water bottom, the sand is spread while releasing compressed air from the lower end of the conduit upward into the conduit. Sand-covering method for soft ground under water.