JP2000117141A - Construction method for diluting salt concentration of dredged deposited soil and solidifying dredged deposited soil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove water contained in a weak layer while diluting salt concn. when dredged soil in sea sand is utilized as a building material to enable excavation and transport. SOLUTION: Fresh water is stagnated above dredged deposited soil and, while fresh water is forcibly sucked to the water suction point provided to the lower part of the deposited soil in a gravity direction through the introducing sand column 1 provided to the deposited soil, salt contained in the deposited soil is diluted. After the reduction of salt concn. is confirmed, the stagnation and supply of fresh water is stopped and the forcible suction from the water suction point 2 is continued to dry the deposited soil and a building material not generating turbid water and reduced in environmental pollution is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION The present invention relates to a construction method which considers the necessity of supply of construction materials, and is a method of measuring salt dilution and consolidation between dredged sediment soil particles and pore water.

2. Description of the Related Art Conventional techniques include a method of mixing and diluting fresh water before discharging dredged soil into a buried soil, and discharging the same.
The ion exchange method, the reverse osmosis membrane method, the distillation method, and the like are currently being performed. In the case of large quantities such as dredged soil and different permeability of sedimentary soil, none of them is economical. In addition, there are difficulties in excavating and transporting the dredged soil after salt dilution, and in some cases solidification methods have been adopted, but this is uneconomical. In particular, in the case of mixed dilution with fresh water, turbid water discharge is a problem.

[Problems to be solved by the invention] In a large amount like dredged soil,
Regardless of the magnitude of the permeability of the sedimentary soil, the salt concentration is set uniformly for a certain period of time, diluted and, at the same time, dried to a state where excavation and transportation can be carried out within a certain period, and the supply is economically measured as construction material. The present invention has been made because of the need.

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, first, salt is dissolved when mixed with fresh water, and it is considered that water containing salt present on the surface of soil particles and between soil particles may be replaced with fresh water. For that purpose, firstly, it is conceivable to increase the area in contact with fresh water. In order to artificially increase the area in contact with fresh water, it is necessary to provide a large number of small-diameter sand columns because the target is a layered dredged sediment with a different permeability, but this is uneconomical. Therefore, the sedimentary soil is cut radially from one water-conveying sand column to a place where there is no sand column, fresh water and sedimentary soil are brought into contact with a large area as much as possible, and the salt content is dissolved. Using the contact surface, water is collected on the water-conveying sand column in reverse. The water collected in the headrace column can naturally rise in the direction of gravity using the drain effect, but when sedimentary sand is used as construction material at an early stage, or when a landfill for dredged soil is reclaimed. In consideration of the above, a method of establishing a forced water absorption point under the dredged soil, making the dryness at an early stage by using negative pressure, and allowing excavation and transportation is possible.

According to the present invention, the initial salt concentration is 1500 p.
pm to 2000 ppm could be reduced to 150 ppm to 200 ppm, and excavation and transportation could be facilitated by drying.

[Example] We washed with water for the purpose of using sea sand as construction material at the gravel yard, but a lot of silt and turbid water were generated.
It is a method that we could not release as it was. Sea sand is deposited in the sedimentation basin, fresh water is retained in the upper part, a jet-type sand column is provided in the sedimentary soil layer, and a water absorption point is provided in the lower part of the sedimentary soil. Not
The salinity could be diluted. Over time, we also learned that the concentration could be further diluted. By stopping the water accumulation and making it dry, it became possible to excavate and carry out the sedimentary soil, and by repeating this, the supply of sea sand as construction material could be measured.

[Brief description of the drawings]

FIG. 1 is a conceptual view and a sectional view of a method of the present invention.

[Explanation of symbols]

 1. Introduced sand column 2. Water absorption point 3. Water absorption system

Claims (4)

[Claims] 1. The method according to claim 1, wherein the surface of the soil particles of the dredged sediment and the salt contained in the water interposed between the soil particles are transferred to a water absorption point provided in the lower part of the dredged sediment by allowing fresh water to remain on the upper part of the dredged soil.
It is forcibly guided through the introduced sand column, and measures the dilution of the salt concentration in the process. After the dilution, stop the replenishment of accumulated water and continue the forced suction to excavate and dry the dredged soil until it can be transported. It is. 2. The introduction sand column is an introduction path for guiding fresh water remaining on the upper part of the dredged soil to a water absorption point provided on the lower part of the dredged soil. It has wings radially. With this wing, the dredged soil is cut with jet water or air jet water, so that the contact area between fresh water and dredged soil can be increased. (Fig. 1) 3. The water absorption point is a system in which fresh water retained on the upper part of the dredged soil is forcibly sucked in water adhering to the surface of soil particles and pore water by utilizing a negative pressure through an introduced sand column. 4. After dilution of the salt concentration in the dredged soil, replenishment of the water in the upper part is stopped, the water in the dredged soil is forcibly sucked, and the dredged soil can be discharged without turbid water. In addition, the dredged soil can be dehydrated early,
It is characterized by being able to carry out excavation.