JP4557668B2 - Civil engineering drainage - Google Patents

Description

  The present invention relates to a civil engineering drainage material, and more particularly to a civil engineering drainage material suitable mainly as an artificial vertical drainage material for ground improvement at a large depth.

In recent years, land reclamation of the ocean and lakes has been actively carried out in charge of the redevelopment of the land, but so far, mainly sand and sand etc. have been used to improve the ground of so-called ultra-soft ground with extremely high water content. As a drainage consolidation method using natural water permeable materials, sandpile construction has been mainly carried out, but development of artificial drainage materials is required against the background of depletion of sea sand and rising prices. However, it is not uncommon for vertical depth drainage materials mainly for ground with a high water content to have a consolidation settlement rate of more than 50%, and the drainage materials are subject to compression and bending deformation of 50% or more in the soil. Is not uncommon.
By the way, many artificial vertical drainage materials have been proposed in which the peripheral surface of a plastic core material is covered with a water-permeable material. There are roughly two types of composite integrated structures of the core material and the water-permeable material in the artificial drainage material proposed so far.
One is a type in which the core material is simply covered with a water-permeable material as described in Patent Document 1, and the core material and the water-permeable material are slidable with respect to each other. is there. The other is a type in which the core material and the water-permeable material are fixed and integrated by durable water-resistant adhesion over a part or the entire surface, as described in Patent Document 2 or Patent Document 3.

However, since both types have the following problems, they are not actually used as a deep vertical drainage material. Usually, these strip-shaped drainage materials are commercialized in the form of rounded as long objects, but the former non-adhesive drainage materials are not stripped because the core material and the permeable filter material are not integrated. When rolling a long product of the above, the core material and the filtering material show separate behavior, and there is a drawback that the coated filtering material is partially crumpled or wrinkled. When earth pressure is applied to the drainage material, the coated filter material in the portion may be easily deformed by the action of the earth pressure, causing problems such as reducing the water cross-sectional area of the drainage material. Further, in this type, there is a problem that the operation becomes incomplete due to the sliding between the core material and the filter material in the operation of gripping the tip portion with a mandrel and placing it in the soil.
In addition, the latter durable adhesive type drainage material has no problems in the production of drainage material, and has the advantage of excellent handling performance and initial performance until the end of placing in the soil, but as a vertical drainage material for large depths. When used, of course, a high level of consolidation settlement occurs in the ground, which causes a high level of axial compression on the drainage material, which causes the drainage material to bend significantly. Since the filter medium and the filter medium are firmly bonded partly or entirely with a highly water-resistant durable adhesive, as shown in FIG. 7, the filter medium is subjected to a high tensile action on the outer peripheral surface side of the arm bending portion. There was a problem that No. 3 caused a breakage or perforation phenomenon and could not function as a filter medium.

In order to reduce the breakage of the water-permeable material at the time of such bending, the core material and the water-permeable material are joined with an elastic adhesive, and a buffering role is introduced between the water-permeable material and the core material. Has been proposed. Furthermore, in Patent Document 5, the water-permeable material and the core material are bonded with an adhesive whose adhesive strength is reduced by contact with water. It is disclosed that the water-permeable material is released from the core material by contact with the base material and prevents breakage during bending.
However, the former is highly effective when the ground is relatively small and the degree of bending is small, but sufficient effects cannot be obtained in a situation where the bending exhibits a large bending exceeding the deformation limit of the adhesive. In the latter case, as in the case where the filter medium and the core material are not bonded, when the earth pressure is applied to the drainage material in the soil, the covered filter medium in the portion is easily deformed by the action of the earth pressure. It causes problems such as reducing the cross-sectional area of drainage material. Further, the adhesive is greatly affected by water or humidity, because it leads to the release of the permeability material and core material, installation and storage in the field was very difficult say the Most problems.
Japanese Patent Publication No.2-222168 JP-A-63-67321 JP-A-1-207515 JP-A-5-106217 JP-A-5-79032

  The problem of the present invention is to solve the above-mentioned problems of the prior art, and the core material and the filter medium do not slide when being placed in the soil, and the filter medium does not break due to bending, and the handling property is improved. An object of the present invention is to provide a civil engineering drainage material that is good and can maintain drainage over a long period of time.

As a result of earnestly examining the above problems, the present inventors firmly fixed and integrated the core material and the filter medium until the end of the drainage material production, transportation, storage, and placement in the soil, and after being installed in the soil The inventors have found that the above-mentioned problems can be achieved by preferentially lowering the strength from the core material by biodegradation and the like, and have reached the present invention.
The invention claimed in the present application in order to achieve the above object is as follows.

(1) The length of the peripheral surface of the belt-shaped plate-shaped core material having independent protrusions in which a large number of irregularities using polycaprolactan have an inter-core distance of 10 to 20 mm and a protrusion height of 2 to 15 mm is made of aliphatic polyester. In a structure that is covered with a water-permeable filter material made of a fiber nonwoven fabric, and at least a part of a portion where the water-permeable filter material and the belt-like plate-shaped core material are in contact with each other, the aliphatic polyester is: D-lactic acid polymer, L-lactic acid polymer, D-lactic acid and L-lactic acid copolymer, D-lactic acid and hydroxycarboxylic acid copolymer, L-lactic acid and hydroxycarboxylic acid copolymer A polymer and a polymer selected from a copolymer of D-lactic acid, L-lactic acid and hydroxycarboxylic acid, or a blend of two or more selected from these polymers, and the structure is allowed to stand at 48 ° C. for 5 days. The above after composting Civil drainage material relationship between elongation at break B of the the elongation at break A of the aqueous filtration media strip-shaped plate-like core material characterized in that it is a A> B.
( 2 ) The material drainage material for civil engineering according to ( 1 ), wherein the strip-shaped plate-shaped core material has a material thickness of 0.4 to 0.8 mm and a molding thickness of 4 to 8 mm.

According to the civil engineering drainage material of the present invention, since it is integrated with the belt-like plate-like core material and the water-permeable filter material in the standard state, a strong adhering state is obtained, and the handleability is excellent, and after being embedded in the soil Since the belt-like plate-like core material is preferentially deteriorated in strength, the water-permeable filter material is hardly damaged by earth pressure or deformation, and long-term drainage can be maintained.
Therefore, the civil engineering drainage material of the present invention is extremely useful as a vertical depth drainage material in which compression and bending forces act on the drainage material. Moreover, since it has the above characteristics, it is highly useful as a vertical drainage material for low depth and a horizontal drainage material in addition to a vertical depth drainage material, and greatly contributes to various ground improvements.

The present invention will be described below.
As shown in FIG. 1, for example, as shown in FIG. 1, the civil engineering drainage material of the present invention has a circumferential surface of a strip-shaped plate-like core material 2 having a large number of irregularities and is coated with a water-permeable filter material 3. It is a structure (drainage material 1) having an adhesion point 4 to which at least a part of a portion where the belt-like plate-like core material 3 is in contact with each other is fixed, and the water-permeable filter material 3 and the belt-like plate-like core material 2 include The relationship between the breaking elongation A of the water-permeable filter material 3 and the breaking elongation B of the belt-like plate-like core material 2 after the structure is composted at 48 ° C. for 5 days is A> B, preferably A> B × 1.3, more preferably A> B × 2.5 is used.
By using the permeable filter material and the belt-like plate-like core material constituting the structure, the permeable filter material can be used even when stress is generated in the soil due to ground degradation or curvature. Since a part of the belt-like plate-shaped core material buckles or collapses before it is damaged by stress, it is possible to prevent stress from concentrating on the water permeable filter material, thereby reducing the stress on the water permeable filter material and The filter medium can be prevented from being damaged, and the long-term drainage by the water-permeable filter medium can be maintained. On the other hand, when the elongation at break B of the band-shaped plate-shaped core material is equal to or higher than the elongation at break A of the water-permeable filter medium (A ≦ B), the stress applied to the drainage material due to earth pressure or deformation Before the stress applied to the water-permeable filter material is alleviated and the water-permeable filter material is damaged, the drainage property of the water-permeable filter material cannot be maintained.

In the present invention, the elongation at break A and B of the water-permeable filter material and the strip-shaped core material after the structure is composted for 5 days at 48 ° C. are measured by the following methods.
First, after adjusting the temperature of the composting treatment according to JIS K-6437 to 48 ° C. and allowing the sample to stand for 5 days, the sample is taken out and washed with simple water so that no force is applied to the sample. After removing the mud, it is dried in an environment of 20 ° C. and 65% RH for 24 hours while avoiding direct sunlight. Thereafter, it is cut into a length of 20 cm and a width of 3 cm. At this time, when the strip plate core and the water-permeable filter material are easily peeled without physical damage other than deterioration due to composting, the peeled strip plate core and the water-permeable filter material are each stretched and stretched. Subject to degree test. When there is a possibility of physical damage, a test piece having a length of 20 cm and a width of 3 cm is cut out for collecting a test piece of the strip-shaped plate core material and the water-permeable filter material, respectively, and the strip-shaped plate core material and the water-permeable material are cut out. The strip-shaped plate-like core material after removing the water-permeable filter material by a method such as cutting off the water-permeable filter material other than the joint point with the filter material is used as a test piece, and the water-permeable filter material is also other than the joint point. A strip-shaped plate-shaped core material removed by a method such as cutting is used as a test piece. The conditions in the tensile strength / elongation test are a sample width of 3 cm, a grip interval of 100 mm, a tensile strength / elongation of 10 mm / min, and the elongation at the first peak appears as the breaking elongation.

The belt-like plate-like core material used in the present invention is not particularly limited as long as it is approximately flat and elongated and has a large number of irregularities. As the material, it is preferable to select a material that causes a decrease in strength in the soil. For example, a material that can be thermoformed with polyvinyl alcohol, polylactic acid, cellulose, or the like is used. Moreover, the material thickness of the strip-shaped plate-shaped core material is generally 0.4 to 0.8 mm, more preferably 0.6 to 0.7 mm, in view of the high ground pressure of the deep ground, The molding thickness is about 4 to 8 mm, more preferably about 6 to 7 mm because it is necessary to secure a large drainage pipe (drainage cross-sectional area) in terms of the high water content ratio of the deep ground.
An example of the concavo-convex shape formed on the belt-like plate-like core material is shown in FIG. 2, but the concavo-convex shape is not limited to these. The convex portion may or may not be perforated. The independent protrusion shape is preferably used because a high drainage pipe line is obtained. The distance between the cores of the independent protrusions is preferably 10 to 20 mm, but it is desirable to determine the distance comprehensively in consideration of the material thickness, the molding thickness, and the like of the belt-like plate-like core material. The width of the belt-like plate-like core material is preferably about 10 cm and the length is about 100 to 200 m and can be rolled. The height of the protrusion is preferably 2 to 15 mm.

Examples of the water-permeable filter material used in the present invention include various non-woven fabrics such as spunbond, thermal bond, resin bond, and spunlace, and composite sheets thereof, in terms of separation performance of soil particles. A nonwoven fabric made of long fibers is preferably used.
The single yarn denier of the constituent fibers of the nonwoven fabric is generally 1 to 5 dtex, more preferably 2 to 4 dtex, and a basis weight of 30 to 200 g / m ² , more preferably 40, in terms of soil particle separation performance and earth pressure durability. It is good to set it to -120 g / m < ² >.
It is preferable that the degree of dispersion of the fiber arrangement is higher, and it is more desirable that the arrangement is substantially evenly distributed in the vertical, horizontal and diagonal directions. Also, as the material is needed use a polyester fiber in terms of strength degree.
Among polyester fibers, D-lactic acid polymer, L-lactic acid polymer, D-lactic acid and L-lactic acid copolymer, D-lactic acid and hydroxycarboxylic acid copolymer, L-lactic acid and hydroxy An aliphatic polyester which is a copolymer selected from a copolymer of carboxylic acid and a copolymer of D-lactic acid, L-lactic acid and hydroxycarboxylic acid, or a blend of two or more selected from these polymers. In addition to high strength, it is more preferably used from the viewpoint of reducing the environmental load because it is finally decomposed in the soil after the drainage function is completed.

By using a material that is not biodegradable or a material that is more durable in the soil as compared to a strip-like plate-like core material as a water-permeable filter material, The relationship between the breaking elongation A and the breaking elongation B of the strip-shaped plate-like core material can be A> B, and the object of the present invention is achieved. That is, when a material having high durability in soil, such as polyester, is used for the water-permeable filter material, it exhibits biodegradability such as polylactic acid, PVA, polybutyric acid, poly-ε-caprolactone, and cellulose as a belt-like plate-like core material. Material can be used.
When polylactic acid is used as the water-permeable filter material, the object of the present invention can be achieved by selecting a material having a high biodegradation rate such as polybutyric acid or poly-ε-caprotactone as the belt-like plate-like core material. Furthermore, the biodegradation rate can be adjusted not only by selecting the material but also by adjusting the thickness and shape.
In the civil engineering drainage material of the present invention, the portion where the belt-like plate-like core material 2 and the water-permeable filter material 3 are in contact with each other is a convex portion existing in many places on the belt-like plate-like core material 2 as shown in FIG. The adhesion point 4 between the apex and the permeable filter material 3 is referred to. In the present invention, all or a part of these adhesion points 4 are bonded, and the belt-like plate-like core material 2 and the permeable filter material 3 are fixed. Say things. These bonding methods are not particularly limited, such as thermal bonding and use of an adhesive resin. However, when an adhesive resin is used, a resin having biodegradability such as PVA or cellulose is preferable from the viewpoint of reducing environmental load. .

The manufacturing method and effect of the civil engineering drainage material of this invention are demonstrated using FIG.3, FIG.4 and FIG.5.
FIG. 3 is an explanatory view showing an example of a method for producing a drainage material according to the present invention. The strip-shaped plate-like core material 2 was continuously fed out by the guide roll 6, and the adhesive 5 was applied to the tops of the convex portions on both the front and back surfaces of the strip-like plate-like core material 2 by the roll coater 7, and then wound separately. The permeable filter material 3 is continuously supplied to the surface of the band-shaped plate-like core material 2 by the filter material coating device 8, and the permeable filter material 3 is continuously provided so as to surround the peripheral surface of the band-shaped plate-like core material 2. Then, the overlapped portion of the coated water-permeable filter material 3 is fixed by the adhesive extruded by the adhesive extrusion device 9 and further supplied to the drying device 10 by the press roll 13 and dried. Then, a long drainage material 1 guided by the guide roll 6 and rounded is obtained.

FIG. 4 is an explanatory view showing a use state of the civil engineering drainage material of the present invention at the time of placement, and FIG. 5 is an explanatory view showing a state at the time of consolidation settlement after placement. In addition, 11 in FIG. 4 shows embankment, 12 shows a ground surface. The drainage material 1 is supplied to the driving machine, and is drawn into the soil in a state where the tip is gripped by the mandrel of the driving machine and is driven in the vertical direction.
According to the civil engineering drainage material of the present invention, the belt-like plate-like core material 2 and the water permeable filter material 3 are firmly integrated by the adhesive material until the drainage material is manufactured, transported, and placed. In addition, problems such as misalignment and breakage of the filter medium, and poor handling properties do not occur, and rational manufacture, transportation, and placement are possible. Further, the drainage material 1 embedded in the soil has a predetermined relationship between the belt-like plate-like core material 2 and the water-permeable filter material 3, so that the belt-like plate-like core material 2 preferentially buckles and collapses after placement. Therefore, even if the stress on the water permeable filter material 3 is reduced and the consolidation settlement proceeds as shown in FIG. Can take a stable structure by deformation of the belt-like plate core. As a result, the water-permeable filter material can withstand long-term burial without damaging and maintain a high drainage function.

Hereinafter, the present invention will be described by way of examples. In addition, the measurement and evaluation in an example were performed by the following method.
(1) Weight per unit (g / m ² )
According to the method prescribed in JIS-L-1906, three test pieces measuring 20 cm in length and 25 cm in width are sampled per 1 m width of the sample, the mass is measured, and the average value is obtained by converting the mass per unit area. .
(2) Elongation at break after 5 days at 48 ° C. Composting treatment Adjusted to 48 ° C. by composting treatment according to JIS K-6437, and removed the sample (drainage material) that was allowed to stand for 5 days. After washing with water and removing excess mud, it is dried in an environment of 20 ° C. and 65% RH for 24 hours while avoiding direct sunlight.
Thereafter, it is cut into a length of 20 cm and a width of 3 cm. At this time, if the strip plate core and the permeable filter material are easily peeled without physical damage other than deterioration due to composting, the peeled strip plate core and the permeable filter material are each stretched and stretched. Subject to degree test. When there is a possibility of physical damage, test pieces each having a length of 20 cm and a width of 3 cm are cut out for collecting test pieces of the belt-like plate-like core material and the water-permeable filter material. When the strip-like core material is used as a test piece, the water-permeable filter material other than the joining point is removed by a method such as cutting off and used for the test. Similarly, the water-permeable filter material is removed by a method such as cutting a strip-shaped core material other than the joining point, and subjected to a test. The conditions in the tensile strength / elongation test are a sample width of 3 cm, a grip interval of 100 mm, a tensile strength / elongation of 10 mm / min, and the elongation at the first peak appears as the breaking elongation.

(3) Change in shape of water-permeable filter material during bending The state of breakage of the water-permeable filter material was confirmed by visual observation when the drainage material after 5 days of composting was pushed and bent. That is, a drainage material sample having a width of 10 cm and a length of 20 cm in which the peripheral surface of the belt-like plate-shaped core material is coated with a water-permeable filter material and the apex portions of the convex portions where these two materials are in contact with each other are fixed with an adhesive material. After adjusting at 48 ° C. by composting treatment according to JIS-K-6437, taking out the sample that was allowed to stand for 5 days, performing simple water washing so that force is not applied to the sample, and removing excess mud, After drying in an environment of 20 ° C. and 65% RH for 24 hours while avoiding direct sunlight, it is compressed and bent at a rate of 1 mm / min under a side pressure of 5 kg · f / cm ² , and a water permeable filter material The damage state of was observed.
(4) Permeability evaluation after deformation From the sample subjected to the compression bending test in (3) above, a water permeable filter material was taken out in accordance with (2), and the inner diameter was 10 cm in accordance with JIS-A1218 constant water level permeation test. Under the condition of 10 cm, the water permeability in the direction perpendicular to the surface of the spunbond was measured to measure the water permeability coefficient.

[ Comparative Example 5 ]
As shown in FIG. 6, the belt-like plate-like core material 2 has a thickness of 0.6 mm, a convex portion apex diameter D of 5 mm, a height of 6 mm, a convex portion core distance L of 20 mm, and a melting point of 61 ° C. The melt viscosity at 185 ° C. is 2600 Pa. s is an independent concavo-convex molded core material made of polycaprolactan, and as a water-permeable filter material, a single yarn denier 2 dtex made of polyethylene terephthalate, a basis weight of 50 g / m ² , and a spunbond nonwoven fabric with a thickness of 0.18 mm A strip-shaped drainage material having a width of 10 cm was prepared in which the entire surface of the three vertices in a row of the above-described independent concavo-convex-molded strip-shaped core material and the portion where the spunbonded nonwoven fabric was in contact with each other were fixed with an acrylic adhesive.

[Example 1 ]
In Comparative Example 5 , a polylactic acid spunbonded nonwoven fabric having a single yarn denier of 2 dtex, a basis weight of 50 g / m ² and a thickness of 0.18 mm manufactured by the following method was used as a water-permeable filter material, and a PVA resin was used as an adhesive material Produced a strip-shaped drainage material having a width of 10 cm in the same manner as in Comparative Example 5 .
Polylactic acid spunbonded nonwoven fabric has a melting point of 170 ° C. and an MFR value of 10 g / min. Polylactic acid [D / L copolymerization ratio (molar ratio) = 1.3 / 98.7] thermoplastic resin, extrusion temperature After spinning at 215 ° C., spinning a filament group using a 1540-hole spinneret, pulling using a high-speed airflow traction device, receiving a wire mesh web conveyor with a moving suction device, and creating a web, The web was obtained by partial thermocompression bonding at a pressure of 50 kg / cm using a thermocompression roll in which an engraving roll and a smooth roll were combined.

[Comparative Example 3]
In Comparative Example 5 , the belt-shaped plate-shaped core material is made of a thermoplastic resin made of vinyl chloride having a thickness of 0.6 mm, a vertex diameter D of the convex portion of 5 mm, a height of 6 mm, and a convex portion core distance L of 20 mm. Similar to Comparative Example 5 , except that a concavo-convex molded core material was used and a spunbond nonwoven fabric having a single yarn denier of 2 dtex made of polypropylene, a basis weight of 50 g / m ² , and a thickness of 0.35 mm was used as the water permeable filter material. A drainage material having a width of 10 cm was produced.

[Comparative Example 4]
In Comparative Example 3, a band-like width was obtained in the same manner as in Comparative Example 3 except that a single-filament denier 2 dtex made of nylon 6 and a spunbond nonwoven fabric having a basis weight of 50 g / m ² and a thickness of 0.35 mm were used as the water-permeable filter material. A 10 cm drainage material was produced.

[Comparative Example 1]
In Comparative Example 5 , a strip-shaped drainage material having a width of 10 cm was produced in the same manner as in Comparative Example 5 except that the thermoplastic resin-like uneven core material used in Comparative Example 3 was used as the belt-like plate-like core material. .
[Comparative Example 2]
In Comparative Example 1, a strip-shaped drainage material having a width of 10 cm was produced in the same manner as in Comparative Example 1 except that the spunbonded nonwoven fabric used in Example 2 was used as the water-permeable filter material.

Physical properties of the strip-like core material and the water-permeable filter material constituting the drainage material used in Example 1 and Comparative Examples 1 to 5 , and the strip-like plate-like core material after composting the drainage material for 5 days at 48 ° C The physical properties of the permeable filter material were measured, and the results are shown in Table 1.
From Table 1, in the drainage material obtained in Example 1 and Comparative Examples 3 to 5, in the bending test after 5 days of composting, a part of the belt-like plate-like core material was buckled or cracked, and the permeable filtration It was confirmed that the material was not damaged and the water permeability was maintained. On the other hand, in the drainage materials obtained in Comparative Examples 1 and 2 , it was confirmed in the bending test that the water-permeable filter material failed to follow the bending and was damaged.
Moreover, from the measurement result of the water permeability coefficient, in the drainage materials obtained in Example 1 and Comparative Examples 3 to 5, the water permeability of the water permeable filter material after 5 days from composting was maintained. The water permeable filter material was damaged, and the water permeability coefficient could not be measured. This result shows that the drainage material of the present invention has an ideal function as a deep vertical drainage material.

  The drainage material for civil engineering of the present invention is excellent in handleability before being buried in the soil, and after embedding in the soil, the belt-like plate-like core material is preferentially deteriorated in strength, and the permeable filter material due to earth pressure or deformation Therefore, it is extremely useful as a vertical drainage material for large depths where compression or bending force acts on the drainage material. In addition, it has high utility value as a vertical drainage material for low depths and a horizontal drainage material, and greatly contributes to various ground improvements.

It is a structural cross-sectional schematic diagram of the civil engineering drainage material which shows an example of this invention. It is a schematic diagram which shows an example of the strip | belt-shaped plate-shaped core material used for this invention. It is a schematic diagram which shows an example of the manufacturing apparatus of the drainage material for civil engineering of this invention. It is a construction drawing in which a drainage material for civil engineering is placed and embankment is performed. It is a schematic diagram showing a deformation | transformation of the drainage material for civil engineering by consolidation of the ground after placement. It is the schematic diagram of the strip | belt-shaped plate-shaped core material used for the Example. It is a schematic diagram showing the curved state after placement of the conventional drainage material.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Drainage material, 2 ... Concave-molding strip-shaped plate-shaped core material, 3 ... Water-permeable filter material, 4 ... Adhesion point, 5 ... Adhesive, 6 ... Guide roll, 7 ... Roll coater, 8 ... Filter material coating apparatus, 9 DESCRIPTION OF SYMBOLS ... Adhesive extrusion apparatus, 10 ... Drying apparatus, 11 ... Filling, 12 ... Ground surface, 13 ... Press roll, D ... Convex vertex diameter, L ... Convex center distance.

Claims (2)

Polycaprolactan many uses irregularities center distance 10 to 20 mm, the peripheral surface of the strip-shaped plate-shaped core material having independent projection is the height 2~15mm projections, the long-fiber nonwoven fabric consisting of an aliphatic polyester In which the aliphatic polyester is D-lactic acid , wherein the aliphatic polyester is coated with a water-permeable filter material, and at least a part of the portion where the water-permeable filter material and the belt-like plate-like core material are in contact with each other is fixed. A polymer of L-lactic acid, a copolymer of D-lactic acid and L-lactic acid, a copolymer of D-lactic acid and hydroxycarboxylic acid, a copolymer of L-lactic acid and hydroxycarboxylic acid, And a polymer selected from a copolymer of D-lactic acid, L-lactic acid and hydroxycarboxylic acid, or a blend of two or more selected from these polymers, and the structure is composted at 48 ° C. for 5 days. The water permeability after Civil drainage material relationship between elongation at break A of the over wood and elongation at break B of the band-shaped plate-like core material characterized in that it is a A> B. 2. The civil engineering drainage material according to claim 1 , wherein the strip-shaped plate-shaped core material has a material thickness of 0.4 to 0.8 mm and a molding thickness of 4 to 8 mm.

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