JP5156988B1 - Ground improvement method - Google Patents

Abstract

[PROBLEMS] By using a biodegradable resin as a material for a drain pipe, a drain material, a member connecting the drain material and the drain pipe in a ground improvement method for promoting consolidation of the ground, it is not necessary to treat it as an industrial waste, Providing economical and environmentally friendly ground improvement methods.
Drainage made of biodegradable resin in a ground improvement method in which drainage material 2 is installed in the vertical direction of ground 41 and drained through drainage pipe 1 connected to drainage material 2 to promote consolidation of ground 41. Pipe 1 is used. Since the drainage pipe 1 is disassembled, the work of removing the drainage pipe 1 after ground improvement can be omitted, and it is not necessary to dispose it as industrial waste. Furthermore, a biodegradable resin may be used for a drain material and a water collecting pipe joint that is a member that connects the drain material and the drain pipe, a connection member that connects the water collecting pipe and the drain material, a valve, an atmospheric pressure sheet, and the like.
[Selection] Figure 1

Description

  The present invention relates to a ground improvement method using a drain pipe made of a biodegradable resin in a ground improvement method for promoting consolidation of the ground.

  There are various vertical drain methods, horizontal drain methods, vacuum consolidation methods, etc. as consolidation and drainage methods to promote consolidation of soft ground.

  In the case of the vertical drain method, a load mating method is often used in combination with a sand mat in which drain pipes are laid on the upper part of the clay ground to be consolidated, and further embankment is loaded thereon to promote consolidation.

  In vacuum consolidation method, vertical drain is placed in the improved area of soft ground and then covered and sealed with an airtight sheet, and negative pressure is generated in the ground using a vacuum pump etc., promoting settlement of soft ground and increasing strength. Is intended.

  By the way, the applicant has developed a technique using a biodegradable plastic pipe for underground pipes used for ground injection and the like. Also, in the field of ground improvement methods, some techniques using biodegradable plastics for drain materials and sheet materials are known.

  For example, in Patent Document 1 by the applicant, a biodegradable plastic tube is embedded in the ground, and a material containing microorganisms as an active ingredient is filled or injected into the underground tube after the purpose has been achieved. Disclosed is a method for promoting the degradation of underground buried pipes in which the underground buried pipes are promoted to decompose at the same position in the ground.

  Similarly, in Patent Document 2 by the applicant, a cellulose resin is contained in a thermoplastic resin so as to be easily pulverized, and an easily pulverized underground pipe formed by using this resin as a material is disclosed.

  Patent Document 3 describes that in a horizontal drain construction method in which a drain material having water permeability is laid in the horizontal direction, the horizontal drain material having water permeability is made of a biodegradable material.

  In addition to this, in Patent Document 4, an upper surface of the improved ground is covered with an airtight sheet fixed in the periphery of the soft ground, and a reduced pressure region isolated from the periphery of the improved ground is created on the improved ground under which a vacuum pressure is applied. In the improvement method of soft ground, the case where a biodegradable material is used for an airtight sheet is described.

Patent No. 4019069 JP 2006-118631 A JP 2002-030646 A JP 2007-278008 A

  If conventional plastic is used in the pipe installed to collect and drain the groundwater drained through the drain in the above-mentioned loading consolidation method or vacuum consolidation method, it will remain in the ground even after ground improvement. Need to be removed. Furthermore, when excavating after ground improvement as a removal method and removing as residual soil, the plastic pipe is easily entangled with the excavator and the workability is lowered.

  The present invention is intended to solve such problems, and in the ground improvement method for promoting consolidation of the ground, drainage pipes and drain materials, as a material of the member connecting the drain material and the drain pipe, biodegradable resin is used. It is intended to provide an economical and environmentally friendly ground improvement method that does not require treatment as industrial waste.

  The present invention provides a biodegradable resin as the drainage pipe in the ground improvement method in which vertical drainage material is installed on a soft viscous ground and drainage is performed through a drainage pipe connected to the drainage material to promote consolidation of the ground. It is characterized by using the drainage pipe which consists of.

  In the ground improvement method that promotes consolidation of the ground, the drain pipe is decomposed over time by using the drain pipe made of biodegradable resin, so the work of removing the drain pipe after the ground improvement can be omitted. This eliminates the need for disposal as industrial waste.

  The biodegradable plastic used in the present invention is a polymer compound that is decomposed by microorganisms, preferably thermoplastic, and can be processed by conventionally known extrusion molding and has mechanical strength as an injection tube. preferable. Water-soluble plastics, particularly plastics that dissolve under alkaline conditions, are easily decomposed by living organisms and are preferred in the present invention.

  The chemical structure is (1) the main chain is aliphatic and has an ether bond or ester bond, (2) the main chain (or side chain) has a hydroxyl group or a carboxyl group, or (3) plastic. It is a plastic with good biodegradability by containing additives that induce and promote photodegradation and microbial degradation of starch, specifically starch-based, cellulose acetate-based, polylactic acid-based, aliphatic polyester-based, Examples thereof include biodegradable plastics such as polyvinyl alcohol. To these main raw materials, other polymer compounds such as plastics such as polyethylene and polypropylene, plasticizers, stabilizers, colorants and the like are added as necessary for the purpose of improving performance or imparting flexibility. You can also

  The compound (2) having a hydroxyl group or a carboxyl group is preferably an aliphatic compound. Specific examples of these biodegradable plastics include “Pionore” (aliphatic polyester of polyol and dicarboxylic acid) (Showa Polymer Co., Ltd. and Showa Denko Co., Ltd.), “ Examples of “Cell Green” (cellulose acetate, polycaprolactone) (Daicel Chemical Industries, Ltd.), “Lacty (lactic acid)” (Shimadzu Corporation), (2) “Poval” (polyvinyl alcohol) (stock) Examples of (Kuraray) and (3) include “Wonder Stern” (corn starch and polyethylene) (Wonder Corporation) and the like.

  By blending the above biodegradable plastics with high melting point biodegradable plastics such as polyhydroxybutyrate, polylactic acid, polyglycoside, etc., the processability is improved, and a woven fabric or non-woven fabric is used as a bag body. Can also be used. These main raw materials are decomposed in the soil by bacteria for, for example, about 90 to 300 days.

  Since biodegradable plastics is a surface reaction between the molded product and an enzyme that is metabolized from the body of microorganisms, the thicker the molded product, the longer the degradation time. On the other hand, when the injection material is alkaline, biodegradable plastics having an ester bond are susceptible to hydrolysis. Moreover, the injection | pouring ground exists in various different conditions, such as acidic to alkaline, or seawater infiltration, and also changes with injection | pouring of injection materials. Therefore, although the decomposition rate of the injection pipe cannot be generally stated, it can be said that the period of one year is sufficiently short when it is not excavated. In addition, when excavating after injection, it is preferable to use biodegradable plastics that are more brittle.

  The biodegradable plastics according to the present invention can be decomposed or reduced in strength by lowering the weather resistance as necessary. Especially when such an injection tube apparatus is used, an injection operation is performed. Considering the previous management, it is preferable to avoid exposure to direct sunlight for a long time or leaving it in the rain as much as possible.

  In the ground improvement method according to the present invention, it is desirable that the drain material and the member connecting the drain material and the drain pipe are made of biodegradable resin.

  The members that connect the drain material and the drain pipe here are, for example, a water collecting pipe, a water collecting pipe joint, a connecting member that connects the water collecting pipe and the drain material, a valve, an atmospheric pressure sheet, and the like in the vacuum consolidation method.

  If these members and drain materials are made of biodegradable resin, it is only necessary to remove the negative pressure device after the ground improvement, which improves work efficiency and greatly reduces industrial waste discharged from the site. Can do.

  In addition, the biodegradable resin used for the drain material and the member that connects the drain material and the drain pipe may be the same as the biodegradable plastics described above, and it retains the strength and durability required for each member. Just do it.

  Moreover, it is desirable that the biodegradable resin according to the present invention is a biodegradable resin having friability. A biodegradable resin having crushability can be easily pulverized or decomposed in the soil, and can be easily pulverized without tangling the drainage pipe to the blade of the excavator during ground excavation.

  For example, as a resin that contains cellulose fiber in a biodegradable resin and is easily pulverized, this resin is molded into a material pellet at a temperature of 300 ° C. or less by an extrusion molding machine or an injection molding machine, and used as a drain pipe.

  In the present invention, such cellulose fibers are kneaded into a thermoplastic resin at a moisture content of 5 to 40% and granulated. Alternatively, the cellulose fiber is kneaded with a thermoplastic resin in the presence of water whose moisture content of the cellulose fiber does not cut below the lower limit of 5%, and the obtained kneaded product is made in the range of 5 to 40% of the moisture content of the cellulose fiber. Grain.

  In the present invention, when cellulose fibers are used, it is important to fully consider the behavior of cellulose fibers during pellet production. Cellulose is a typical hydrophilic polymer substance that absorbs and desorbs moisture very much, and its properties change depending on the state of moisture absorption and desorption. That is, it swells and softens due to moisture absorption and becomes flexible and easily deformed, while it becomes keratinized and hardened by dehumidification, becomes brittle and difficult to deform.

  The reinforcing fiber used in the present invention is a vegetable fiber as described above, but it has a strong shearing force after defibration or directly in a thermoplastic resin in a molten or softened state at around 100 ° C. or higher. Knead uniformly while applying. Under these conditions, the plant fiber mainly composed of cellulose loses moisture and becomes completely dry, so that it becomes keratinized and becomes brittle. Therefore, when kneaded with a strong shearing force in this absolutely dry state, the cellulose fibers are pulverized until they are uniformly dispersed in the thermoplastic resin, so that the fibrous shape is not retained.

  This tendency is more conspicuous in the case of a thermoplastic resin having a high melting temperature or softening temperature, and is not only affected by the deterioration of the fibers during the kneading but also by the further deterioration of the fibers and carbonization. Sometimes. In order to avoid this state, a thermoplastic resin added with reinforcing fibers is molded by injection molding or extrusion molding using a mold.

  The consolidation of the ground according to the present invention can be promoted by a vacuum consolidation method using a negative pressure operating device (vacuum pump). For example, in addition to the drain pipe, a water collecting pipe, a water collecting pipe joint, a connecting member that connects the water collecting pipe and the drain material, a valve, an atmospheric pressure sheet, or the like can be used.

  For example, as one of the vacuum consolidation methods, a vertical drain is placed in an improved area of soft ground, then completely covered and sealed with an airtight sheet, and negative pressure is generated in the ground using a negative pressure operating device. There are things that promote the settlement of the sea and increase the strength.

  As a feature of the vacuum consolidation method, it is possible to obtain consolidation settlement and increase in strength in a short time compared to the loading embankment method. In addition, unlike the loading embankment method, the lateral movement due to the extrusion of the foundation ground does not occur, so the slip failure of the ground does not occur. Consolidation drainage of soft ground is performed by vertical drains, horizontal drains and effective water collection pipes, and there is certainty.

  When a drain pipe made of a biodegradable resin is used as a water collection pipe in the vacuum consolidation method, the drain pipe (collection pipe) needs to be strong enough to withstand the vacuum pressure.

  In the vacuum consolidation method, the pressure applied to the drain pipe and the water collection pipe is the pressure due to the exhaust from the vacuum pump. The maximum degree of vacuum is about 740 mmHg, and the effects of the present invention can be obtained if the physical properties required for the drain pipe and the water collecting pipe are the same as those of conventional plastics.

  Table 1 shows a comparison between resin examples in the present invention and conventional plastics. Biodegradable plastics made of aliphatic polyester and those made by mixing paper and lactic acid polymer for easy crushing were made. Since each has a tensile strength equal to or higher than that of conventional plastics and has the same heat deformation temperature, it can be easily processed, so it can be molded as a conventional drainage pipe or water collection pipe. Further, by further adding paper, the elongation decreases, so that it becomes difficult to entangle the excavator even after excavation after ground improvement.

  In addition to drainage pipes and drainage pipes, if the drainage pipe joints, connecting members connecting the drainage pipes and drain materials, valves, atmospheric pressure seats, etc. made of biodegradable resin are used, after the ground improvement, only the negative pressure operating device Can be removed, work efficiency is improved, and it is not necessary to dispose of it as industrial waste.

  Since the ground improvement construction method using the biodegradable resin according to the present invention is configured as described above, the following effects can be obtained.

 (1) Since drainage pipes made of biodegradable resin are used, it is possible to save the trouble of collecting drainage pipes after ground improvement. In addition, since it is not necessary to treat the sand mat sand as an industrial waste, an economical and environmentally friendly construction method can be provided.

 (2) When a drainage pipe made of biodegradable resin is used in the sand mat by the loading embankment method, the biodegradable pipe is decomposed and the sand mat can be reused. Or it becomes possible to dispose as construction residual soil.

 (3) For example, in the vacuum consolidation method, in addition to the drain pipe, a water collecting pipe, a water collecting pipe joint, a connecting member that connects the water collecting pipe and the drain material, a valve, a material made of biodegradable resin, etc. After the ground improvement, only the negative pressure operating device needs to be removed, the work efficiency is improved, and it is not necessary to dispose as industrial waste.

 (4) In the long term, it will be decomposed by microorganisms in the ground to become harmless substances such as water and carbon dioxide, and will not degrade workability even when excavating the ground like sewage works or shield construction.

 (5) When a biodegradable resin with friability is used, pulverization is easy, and it is possible to construct piles or construct structures on the improved ground in the short term. It will not be a hindrance, and the environmental impact can be eliminated by disassembling in the long term.

It is sectional drawing which showed roughly one Embodiment of the ground improvement construction method which used the drainage pipe which consists of biodegradable resin which concerns on this invention for the loading embankment method. FIG. 2 is a cross-sectional view showing a case where an upper structure is built in the embodiment of FIG. 1. 1 is a perspective sectional view schematically showing a vacuum consolidation method as one embodiment of a ground improvement method according to the present invention.

  Hereinafter, specific embodiments of the present invention will be described. Note that the present invention is not limited to the embodiments described below.

[Example 1]
FIG. 1 shows an embodiment in which a drainage pipe 1 made of a biodegradable resin according to the present invention is used for a loading embankment method 21. First, the drain material 2 is installed in the vertical direction of the existing ground. The drain material 2 is required to have a function of draining the water in the ground 41. For example, a pipe-like material or a belt-like material having excellent water permeability or sandy soil is used. Moreover, you may use the drain material 2 which consists of biodegradable resin.

  Next, the sand mat 23 is laid on the existing ground 41, and the biodegradable drain pipe 1 is installed in the horizontal direction around the middle of the sand mat 23. Furthermore, the embankment 22 is performed on the upper part of the sand mat 23, and the ground 41 is consolidated. By consolidating from the upper part of the ground 41, the water in the ground 41 can be collected from the drain material 2 to the drain pipe 1 and discharged to the ground.

  After sufficiently compacting the ground 41 and improving the ground, the embankment 22 and the sand mat 23 are removed and disposed of.

  In the present invention, since the drain pipe 1 embedded in the sand mat 23 is biodegradable, the excavator is not entangled when the ground 41 is excavated. Moreover, since the biodegradable drainage pipe 1 is decomposed into soil and water, it is possible to reuse the embankment 22 and the sand mat 23 used once. Alternatively, since the embankment 22 and the sand mat 23 can be disposed of as construction residual soil, the cost can be reduced as compared with the conventional method in which the embankment 22, the sand mat 23, and the drainage plastic pipe are disposed of as industrial waste. Work efficiency is also improved.

[Example 2]
FIG. 2 shows a case where the structure 42 is provided on the embankment 22 formed on the ground 41 in the embodiment of FIG. The loading consolidation method 21 shown here is the same as that in the first embodiment.

  After sufficiently consolidating the ground and improving the ground, piles 43 and the like are placed in order to build the upper structure 42 on the embankment 22. In this case, since the biodegradable drainage pipe 1 is friable even in the situation where the pile 43 is driven up to the sand mat 23, it is not necessary to remove the drainage pipe 1 when the pile 43 is driven, Construction is easy. After placing the pile 43, the upper structure 42 is built.

Example 3
FIG. 3 schematically shows a vacuum consolidation method as one of the ground improvement methods according to the present invention. A negative pressure sealing layer (impermeable layer) is created on the upper portion of the ground, and the imperviousness is created. This is a method of consolidation by air layer.

  The drain material 2 is installed in the vertical direction on the existing ground. The drain material 2 used here is a drain material 2a whose upper end portion is air-impermeable processed. As in the first and second embodiments, the drain material 2 needs to have a drainage function. For example, a pipe or belt-like material having excellent water permeability or sandy soil can be used.

  The drain material used in this construction method is impervious to the upper end, and by placing it on the ground in the vertical direction, the depth corresponding to the drained material that has been imperviously processed becomes an impervious layer. It is possible to consolidate the ground where the material is.

  A water collecting pipe 34 is attached to the tip of the drain material 2 via an airtight cap 33. From the water collecting pipe 34, the drainage pipe passes through the biodegradable drain pipe 1 which is a horizontal water collecting pipe to the negative pressure acting device 32.

  In order for the existing ground 41 to be consolidated and subsidized by dehydration by the vacuum pressure from the negative pressure operating device 32, the negative pressure seal layer is filled and adapted to the subsidence. After forming the negative pressure sealing layer, vacuum consolidation is performed by the negative pressure device 32.

  In the case of the vacuum consolidation method, in addition to the drain pipe 1, the drain material 2, the airtight cap 33, the water collection pipe 34, and the like can be made of a biodegradable resin. In this case, it is sufficient to remove only the negative pressure acting device after sufficient consolidation and ground improvement. The use of a biodegradable resin for the drain pipe 1 and drain material 2, the airtight cap 33 connecting the drain pipe 1 and the drain material 2, the water collecting pipe 34, etc. eliminates the need for removal because it decomposes into soil and water. The cost and labor required for removal can be greatly reduced.

1 ... biodegradable drainage pipe,
2 ... Drain material, 2a ... Drain material (impermeable processing)
21 ... Load consolidation method,
22 ... banking,
23 ... Sandmat,
31 ... Vacuum consolidation method,
32 ... negative pressure device (vacuum pump),
33 ... Airtight cap,
34 ... Catchment pipe,
41 ... Ground,
42. Superstructure,
43 ... Pile

Claims (4)

A biodegradable resin having crushability as the drainage pipe in the ground improvement method in which drainage pipes connected to the drainage material are drained through a drainage pipe connected to the drainage material in a soft viscous ground and drainage is promoted. The drainage pipe is installed in a sand mat laid on the upper part of the viscous ground, embankment is performed on the upper part of the sand mat, the ground is consolidated, and moisture in the viscous ground is transferred to the drain After the ground is improved by collecting and discharging the material from the drainage pipe, the ground and the sandmat are removed by excavating the drainage pipe in the sandmat while crushing the drainage pipe with the excavator. Improved construction method. A biodegradable resin having crushability as the drainage pipe in the ground improvement method in which drainage pipes connected to the drainage material are drained through a drainage pipe connected to the drainage material in a soft viscous ground and drainage is promoted. The drainage pipe is installed in a sand mat laid on the upper part of the viscous ground, embankment is performed on the upper part of the sand mat, the ground is consolidated, and moisture in the viscous ground is transferred to the drain After collecting and draining the material from the drainage pipe to the drainage pipe, the upper structure is formed on the embankment while leaving the drainage pipe made of the biodegradable resin having the crushability in the sand mat. A ground improvement method characterized by placing piles to build objects . The ground improvement construction method according to claim 1 or 2 , wherein the drain material and the member connecting the drain material and the drain pipe are made of biodegradable resin. The drainage pipe made of the biodegradable resin having friability is obtained by molding a biodegradable resin containing cellulose fiber as a raw material pellet at a temperature of 300 ° C. or less by an extrusion molding machine or an injection molding machine. The ground improvement construction method according to claim 1, 2, or 3.

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