JPS58526B2 - Renzokukihouhekinyoru Odakukakusanboushikouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a construction method for preventing the diffusion of water pollution caused by underwater civil engineering work using an open cell wall.

In recent years, as the necessity of ocean development has been recognized, underwater civil engineering work has been actively carried out.

However, during dredging work to remove contaminated sludge from the seabed, there is a risk that the sludge will spread into the surrounding sea area and cause pollution.

In order to prevent such pollution, conventional measures have been taken to surround the construction area with impassable or releasable sheets.

However, since the sheet does not allow water to pass through, a considerable amount of tension is required on the sheet to resist the tidal current, and as a result, the ropes or anchors used to install the sheet must be strong enough to be economical. It is also technically disadvantageous.

Recently, in order to solve this problem, a large number of jet ports 21 are formed in the air pressure pipe 20 as shown in FIG. A method has been proposed in which air is blown out and the rise of air bubbles 23 is used to cause an upward flow of water, and the polluted area A and the clean area B are separated by a wall caused by the upward flow.

24 is a float, and 25 is a weight.

However, if the sea is calm and there are no currents, this will not be a problem.
When there is a tidal current F, as shown in Figure 4, the bubbles 23 are pushed by the tidal current and hit the nets 22 that should originally guide the bubbles upward and weaken the flow force of the tidal current. Bubble cracking occurs, many small bubbles are generated, and the upward flow momentum is reduced.

Further, as shown in FIG. 5, the bubbles discharged from one jet port and the other jet ports coalesce or interfere with each other as they rise, which also causes turbulence in the upward flow.

This invention was proposed in order to solve the above-mentioned difficulties all at once.The purpose of this invention is to provide a simple means, but also a construction method that can provide a stable upward flow even in the presence of tidal currents and reliably prevent the spread of pollution. Our goal is to provide the following.

The present invention will be explained below with reference to embodiments shown in the drawings.
Reference numeral 1 denotes a pneumatic feed pipe connected to a pressure pump, and air jet pipes 2, 2 .・・・
The shutoff means is constructed by attaching a large number of upwards.

This blocking means is arranged in the lower part of the sea where the polluted area A and the clean area B are to be separated.

A sheet 3 is suspended from the pneumatic feed pipe 1, and a weight 4 is provided at the bottom of the sheet 3, which is fixed to the seabed.

Further, air jet pipes 2,2. . . . Nets 5 with a relatively large rotation are stretched on both sides, and the upper part of the nets 5 is kept stretched with a float 6.

In this way, the air ejection pipes 2, 2. If the bubbles 7 are discharged from ......, a bubble wall of an upward flow 8 will be generated along with the bubbles 7, and even if polluted seawater approaches this bubble wall, the upward flow will cause it to rise again. It can be returned to the polluted area A, preventing the spread of pollution.

In particular, in this invention, the air jet pipes 2, 2. …
Because the lengths of... are different, even if the bubbles 7 emitted from the short air jet tubes 2 spread to some extent as they rise, by increasing the length of the adjacent air jet tubes 2, the long air bubbles 7 Since the bubbles emitted from the ejection pipe 2 have a short distance to reach the sea surface, they spread less, so mutual interference and concentration of the bubbles 7 can be avoided.

Furthermore, the nets 5 are simply the air jet pipes 2, 2. It is used to prevent falls and support and fixation due to tidal currents.

In the conventional method, the upward flow would be disturbed by the tidal current, so a net with a small mesh size is required for reasons such as reducing the force of the tidal current, and as mentioned above, this has the disadvantage of causing the bubbles to break, which is undesirable. However, in this invention, since the upward flow is hardly affected by the tidal current F,
The nets 5 are simply air jet pipes 2, 2. Since it is sufficient to have the function of supporting and fixing..., it is sufficient to use a material with a large mesh, which has the advantage of preventing bubble cracking.

And since there is almost no resistance to the current, it is easy to set up nets 5.

In addition, since the air jet pipe 2 is arranged near the sea surface, unlike the conventional method where the upward flow weakens as it goes upward, the method of the present invention allows the pollution near the sea surface to spread rapidly. Water can be reliably returned to the polluted area A.

By the way, for the air jet pipe, it is preferable to use a light synthetic resin such as polyethylene or polypropylene, which has a low specific gravity because it floats and is easier to maintain upright. It may be a polyacid resin or a vinyl chloride resin with a large diameter.

Incidentally, the spread of contamination can be prevented even if the blocking means and the net are located at different locations.

For example, it is possible to arrange a blocking means on the upstream side of the tidal current and a net on the downstream side.

As described above, according to the present invention, a stable upward flow can be ensured, and therefore, even during construction under adverse conditions, it is possible to reliably prevent the spread of pollution.

[Brief explanation of the drawing]

FIG. 1 is a front view showing the configuration of the open cell wall of the present invention, FIG. 2 is a sectional view thereof, FIG. 3 is a sectional view of a conventional example, and FIG.
The figure is a sectional view showing the behavior of bubbles when there is a tidal current in a conventional example, and FIG. 5 is a front view thereof. 1...Pneumatic feed pipe, 2...Air jet pipe, 3...Sheet,
4... Weight, 5... Nets, 6... Float, 7...
Bubbles, 8...Updraft, A......area, B......area, F.......

Claims (1)

[Claims] 1. In order to cut off the polluted area and the clean area, a blocking means should be used in which a plurality of air jet pipes of different lengths are attached upwardly at intervals in the length direction of the air pressure pipe. A pollution diffusion prevention method using an open cell wall, which is disposed below the water and generates air bubbles from the air jet pipe. 2. The method for preventing pollution diffusion using an open cell wall according to claim 1, characterized in that nets are stretched on both sides of the air jet pipe.