JPS6354092B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for preventing the swelling of dredged and reclaimed mud, which prevents the volume of the mud immediately after the reclaiming from swelling more than the volume before dredging, when the dredged mud containing a large amount of silt and clay is reclaimed by a pump ship. It is something. When reclaiming dredged mud with a high content of silt and clay,
In the case of rapid construction using conventional construction methods, there are many cases in which the volume of mud immediately after the completion of reclamation is more than twice the volume before dredging, and as a result, there are cases in which even half of the planned dredged volume could not be accommodated in the landfill, and There are many cases in which the land has been contained by raising the level of the seawall or rebuilding the embankment behind the seawall. Furthermore, even in the case of slow construction with a reclamation period of 3 to 10 years, the volume change rate is approximately 1.6 times or less. In this way, the reclaimed ground created using dredged mud with a high content of silt and clay undergoes ground improvement work after the completion of the reclamation, and the present invention suppresses the volume change of the mud during the reclamation work process, This is a swelling prevention method that eliminates the need for raising the level of the reclaimed land embankment or rebuilding the embankment, as well as omitting the initial stages of ground improvement work to be carried out after the completion of the reclamation work. The content of the invention will be explained below with reference to the drawings. FIG. 1 shows the planar shape of a reclaimed land for explaining the method of preventing swelling of dredged reclaimed mud of the present invention, and shows the reclaimed seawall 1.
When dredged mud water from a pump ship flows into a landfill surrounded by a tank, a flocculant is injected by a chemical injection device 3 at an arbitrary position of the mud drain pipe 2. The flocculant is used to coagulate fine soil particles in mud and increase the water permeability of sediment deposited in a landfill. A drainage pocket 4 is provided in the landfill before the start of the landfill work, and a permeable mat pipe 5 and a coarse filter 6 are laid toward the drainage pocket. The water-permeable pine pipe and the coarse-grained filter conduct the seepage water from the accumulated mud into the drainage pocket. The drainage pocket is
It is surrounded by a diversion embankment 7 that detours the residual amount of permeated water and an adsorption filter 8 that allows it to pass through, and the permeated water and residual water flowing into the drainage pocket are pumped up by a drainage pump 9 and drained. The spillway 10 drains excess water after the end of the landfill work when the drainage pump is no longer used. FIG. 2 shows an arbitrary cross-section of a reclaimed land according to the method of the present invention, where there is sedimentary mud 12 flowing from the mud drain pipe 2 on the original ground 11 of the reclaimed land, and the surplus water flows into the reclaimed land. The water permeates into the permeable pine pipe 5 placed on the original ground. One end of the permeable mat pipe is connected to the coarse filter, and the permeated water is drained into the drainage pocket 4.
They are starting to gather together. The coarse filter medium 6 is constructed by stacking coarse filter media in a mesh bag or the like. FIG. 3 is a sectional view showing how the water-permeable pine pipe of the present invention is laid. In the process of loading the water-permeable pine material 14 on the work barge 13 and sequentially laying it, the coarse filter material 15 is transferred to the transporter 16. The coarse filter material is sent to the enclosure frame 17 and dropped onto a water-permeable mat, and the coarse filter material is sealed and closed within the water-permeable mat by the bonding machine 18. FIG. 4 is a sectional view of a water-permeable mat tube formed by enclosing a coarse filter medium in the water-permeable mat. The water-permeable mat may be a water-permeable sheet with voids suitable for allowing permeate water to pass through. The seepage water has a flocculant injected into it, so it passes through the gaps in the granulated mud created by the agglomeration of fine particles, and due to the adsorption effect of the mud, it is clear water with a small amount of suspended solids, and it is not disposed of in a landfill. The permeable pine will not become clogged during the process. FIG. 5 is a schematic diagram illustrating that in the present invention, the reclaimed mud is subjected to the consolidation action by its own weight consolidation and seepage water pressure. In addition to the pressure due to its own weight expressed as underwater weight, B is the water level difference H between the landfill and the drainage pocket.
This indicates a state in which the consolidation rate is increased by the infiltration water pressure 16 generated in the accumulated mud, and the hydraulic conductivity k (Kg/min) of the reclaimed mud, which is related to the consolidation rate, is the consolidation load P. (Kg/cm ² ), there are test examples shown in Table 1.

[Table] From Table 1, the mud piled with flocculant added has a higher hydraulic conductivity than the case without additive in the range of small consolidation load P. This means that it is possible to rapidly consolidate soft mud piled with flocculants added during the landfill process to a certain consolidation level using seepage water pressure. It is necessary to fully understand the types of chemicals, the addition rate of chemicals, and the osmotic consolidation characteristics of the deposited mud. FIG. 6 is a cross-sectional view of an adsorption filter for reducing the amount of suspended solids in the residual water that does not become percolated water, out of the residual water generated by separation from the accumulated mud, and guiding it to the drainage pocket. A pre-treatment filter plate 20 with a permeable pine or a permeable sheet as a water-permeable surface is arranged on the upper part of the foundation embankment 19, and a retaining pile 22 is installed on the downstream side of the pre-treatment filter plate 20.
This is a two-stage filtration device configured by holding an adsorption filter body 21 held at 3 and having an adsorption filter body 21 stacked with coarse filter media in a mesh bag between the two. The surplus water flowing into this adsorption filter is
Since a flocculant is added to the sludge pipe, the suspended solids are mainly flocculated particles and contain only a few fine particles. Therefore, the suspended solids adhere to the water-permeable mat surface of the pre-treatment filter plate, and the low concentration surplus water flows into the adsorption filter body. The amount of suspended solids is further adsorbed and reduced in the adsorption filter, and the amount of suspended solids (SS) in wastewater becomes 20 to 50 ppm, which satisfies general wastewater standards. When the amount of suspended solids in the surplus water flowing into the adsorption filter becomes excessive at the end of the landfill work, a water flow control device will be installed upstream of the adsorption filter to reduce the amount of suspended solids through physical measures. . In addition, floating substances adhering to the surface of the water-permeable mat of the pre-treatment filter plate are removed by sweeping them downwards in a timely manner.

[Brief explanation of the drawing]

FIG. 1 shows the planar shape of a landfill site for explaining the method for preventing swelling of dredged and landfill mud of the present invention, in which 1 is a landfill revetment, 2 is a mud drain pipe, 3 is a chemical injection device, 4 is a drainage pocket, 5 is a water permeable pine pipe, 6 is a coarse filter, 7 is a diversion embankment, 8 is an adsorption filter, 9 is a drainage pump, and 10 is a spillway. Fig. 2 shows a construction cross section of a reclaimed land according to the method of the present invention, in which 1 is a landfill revetment, 2 is a sludge pipe, 4 is a drainage pocket, 5 is a permeable pine pipe, 6 is a coarse filter, and 7 is a construction site. 9 is a diversion embankment, 9 is a drainage pump, 10 is a spillway, 11 is a reclaimed land, and 12 is sedimentary mud. FIG. 3 is a cross-sectional view showing how the water-permeable pine pipe of the present invention is laid. 15 is a coarse filter material, 16 is a water-permeable pine material,
1 is a transporter, 17 is an enclosure table, and 18 is a joining machine. FIG. 4 shows a cross-sectional view of the water-permeable mat tube, in which 14 indicates a water-permeable mat material, and 15 indicates a coarse filter material. FIG. 5 is a schematic diagram showing that the reclaimed mud is subjected to its own weight consolidation and consolidation due to osmotic water pressure. In the figure, 12 is the direction of the settled mud and 16 is the direction of the osmotic water pressure. FIG. 6 is a sectional view of an adsorption filter for treating residual water, in which 19 is a foundation embankment, 20 is a pretreatment filter plate, 21 is an adsorption filter, 22 is a holding stake, and 23 is a fence board.

Claims (1)

[Scope of Claims] 1. A section in a landfill having a spillway is partially partitioned by a diversion embankment whose lower part is composed of a coarse-grained filter to form a detour, and an adsorption filter is used in this section. The landfill is further partitioned to form a drainage pocket section, and one end of a permeable pine pipe containing a coarse filter medium is connected to the coarse filter body at the lower part of the diversion embankment, and is placed on the original ground within the landfill. By injecting muddy water with a flocculant added into the ground during the discharge process of dredged mud, surplus water from the landfill can easily pass between the deposited soil particles, and flow through the permeable pine pipes and coarse-grained filter into the drainage pocket. The water level inside the drainage pocket is kept low by driving the drainage pump installed inside the drainage pocket, and the osmotic pressure acting on the accumulated soil particles due to the difference between the water level in the landfill and the water level in the drainage pocket and the dead weight of the accumulated soil particles are reduced. A method for preventing swelling of dredged and reclaimed mud, which is characterized by rapidly sinking a layer of accumulated soil particles. 2. The method for preventing the swelling of dredged and reclaimed mud as set forth in claim 1, wherein the adsorption filter is one in which coarse-grained filter media in mesh bags are piled up between a pretreatment filter plate and a holding pile held on a shelf board. .