JP2010031453A - Construction method for backfilling depression by dredging - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve an water quality environment of a depression which is formed by dredging, and also to provide a sea area where fishing can be performed. <P>SOLUTION: In this backfilling method, a slow-acting alkaline chemical and/or dredged soil are/is charged into the depression which is formed after the dredging. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a method for backfilling a depression formed by dredged water such as the seabed.

Conventionally, landfill work has been performed in which earth and sand are deposited in water to artificially create land. The main purpose of landfill in harbors is to obtain port land, factory land, airport land, and the like. As one of the construction methods for this landfill, there is a method in which sand mud or the like at the bottom of a harbor or river is pumped up together with water to form a blowout embankment in a landfill area through a pipe.

However, dredging large amounts of sand and mud at the bottom of harbors and rivers will form a wide range of depressions in the area. Since the water (seawater) in the depression is stagnant, dissolved oxygen is substantially lost and seafood cannot live. In addition, sand and mud containing organic matter from rivers, etc. accumulates in the depressions, eutrophication and abnormal plankton occurs, resulting in a red tide. In the process, a large amount of oxygen in the water is consumed, and a water mass (anoxic water mass) with extremely little dissolved oxygen is formed. In addition, since anaerobic bacteria such as sulfate-reducing bacteria occupy the anoxic water mass, hydrogen sulfide is generated, water containing hydrogen sulfide is produced, and when it rises to the sea level, it becomes blue tide. Due to this depression, red tides and blue tides were also generated. In addition, there was a situation where the bottom net fishing method could not be performed because the seabed was concave.

  The present inventor conducted various studies on the backfilling method for improving the water quality environment of the depression formed by these dredgings, and as a result, the present invention has been completed.

That is, the present invention is a method of filling a depression formed by dredging with a slow-acting alkaline agent and / or clay, and further, if necessary, branching objects.

According to the backfilling method of the present invention, the anaerobic sand mud in the depression has an acid property, and when the slow-acting alkaline agent is introduced into the depression, the sand mud that accumulates in the gaps of the slow-acting alkaline agent enters and is effectively removed It can be reconciled, reducing consumption of dissolved oxygen, eliminating the occurrence of red tides and blue tides, and shortening the period during which the depressions are refilled, and accordingly, it is possible to carry out bottom net fishing.
In addition, the slow-acting alkaline agent used is partly treated as industrial waste, but it can be used effectively, and the formed ground is also mixed with the slow-acting alkaline agent and the infused sand mud. So the ground strength is also improved.
Further, by introducing a branched object, sand mud and a slow-acting alkaline agent adhere to the branched part of the object, so that it does not deposit directly on the bottom of the water, so that the inside of the depression can be maintained in an aerobic atmosphere. Further, an effect of causing a turbulent flow in the water flow is also produced by the branched portion of the branched object, and a more aerobic atmosphere can be maintained.
In addition, since the branched objects are easily attached to seaweeds such as kelp and seaweed, and shellfish, the inside of the depression can be kept closer to the natural environment by natural force.

In the present invention, for example, a slow-acting alkaline agent is continuously added over a period of time to a depression after dredging in a coastal area.
Examples of the slow-acting alkaline agent include shellfish such as clams, clams, swordfish, turban shells and oysters, limestone, Oya stone, concrete fragments and the like. The shells can be used after the meat is removed, but those subjected to a baking treatment are preferable. Since the deposits such as meat pieces are incinerated by the baking treatment in this manner, the water quality is not deteriorated and the solubility in water is also improved.

The form of the slow-acting alkaline agent used in the method of the present invention is preferably solid. For example, small shellfish such as clams and clams are used as they are, or are broken into about 2 to 3 pieces. It is preferable to use oyster shells that are relatively large such as oyster shells by breaking them into 2-6 pieces.
Thus, when a slow-acting alkaline agent having a size of at least about 1 cm ² is introduced into the depression, a space is provided between adjacent slow-acting alkaline agents, and sand mud flowing from a river or the like is introduced into this space. Intrusion and contact area with slow-acting alkaline agent increase. And since the alkaline agent has a slow effect, it can neutralize the sand mud that exhibits the flowing acid over a long period of time.
Furthermore, according to the construction method of the present invention, when the slow-acting alkaline agent is used, the sand mud that has flowed in is mixed, so that the ground to be formed is also earth resistant.
In addition, instead of the slow-acting alkaline agent, the present invention throws in sandy soil such as dam lakes and rivers, or if a slow-acting alkaline agent and stagnant soil are used in combination and then alternately put, Since the mud is in a mixed state, the ground formed is also earth resistant.

Furthermore, the effect of the method of the present invention is further improved by introducing a branched substance in addition to the slow-acting alkaline agent and / or the clay. Examples of the branched objects used in the present invention include thinned trees, withered trees, synthetic resin trees (for example, Christmas trees) and the like. As a method of charging the branched object, when the specific gravity is smaller than water, a weight is added to sink, and the charging time is also charged simultaneously with the slow-acting alkaline agent and / or clay, or the slow-acting alkaline agent and / or soot is added. It is possible to adopt a method in which the soil and the branched object are alternately put in a certain period.

Although the construction method of the present invention depends on the width (area) of the depression, it can be achieved by continuously adding a slow-acting alkaline agent and / or clay over several years and laminating.

Claims (4)

A backfilling method characterized by introducing a slow-acting alkaline agent and / or clay into a depression formed after dredging. The backfilling method according to claim 1, wherein the slow-acting alkaline agent is solid. The backfilling method according to claim 1 or 2, wherein the slow-acting alkaline agent is continuously added. A backfilling method characterized by introducing a slow-acting alkaline agent and / or clay and a branched object into a depression formed after dredging.