JP2008163720A - Draining material used for improvement method of soft ground such as landfill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fiber draining material which promotes subsidence of a soft ground by draining water content of the clay layer of the soft ground by a vertically arranged drain, which can stabilize the ground at an early stage by the ground subsidence by shortening the time without collapse or fracture, and which corrods naturally and does not harm environment. <P>SOLUTION: The fiber draining material 1 consists of an outer covering material 2 and a filler 3 of a core material. The outer covering material 2 is made of jute fiber woven cloth or non-woven fabric having permeability, and the filler 3 is made of a skin short length fiber of a shell of a coconut. The core material of the filler 3 is made of a short length fiber which is in a disentangled state, and the filler 3 is attached to the pervious outer covering material 2 made of the jute fiber woven cloth or non-woven fabric. The outer covering material 2 and the core material of the filler 3 attached to the inside of the outer covering material 2 are sewn and integrated together by a thread 5 of natural fiber such as a cotton thread in a plurality of positions of the outer covering material 2. Thus, the outer covering material 2 and the core material are made an extra-long fiber draining material 1. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention eliminates the bending of the vertical drain driven into the soft ground due to the consolidation and settlement of the soft ground when embankment is performed on the soft ground or when landfilling, and the permeability of the vertical drain is deteriorated. It is related with the improvement of the method of draining efficiently from a vertical drain and stabilizing a soft ground.

  When creating land or islands for land reclamation, the seabed or land formed by land reclamation is soft ground. When embankment is applied to such soft ground, it gradually begins to sink, and in some cases the land is lost. May end up. Therefore, in order to prevent such a situation, it is necessary to improve the soft ground by land reclamation and form land and islands without causing land subsidence.

  By the way, when the soil used for reclaiming the seabed or the sea is clayey, this clayey soil (hereinafter referred to as “clay”) has very poor water permeability. So, when landfilled with such poorly permeable clay, the islands and land are filled with water, and the water contained in the clay flows very slowly and is pushed out. It is very slow but the clay hardens. As the clay hardens, the ground height gradually decreases and the ground sinks. As the soft ground sinks in this way, the reclaimed land is gradually formed into a stable ground.

  However, if the landfill is made without taking any measures against the clay during the landfill construction, the subsidence of the soft ground will continue for a long period of 100 years or more. Such subsidence velocity is theoretically analyzed by Terzaghi's consolidation theory. This means that “the settlement time changes in proportion to the square of the thickness of the ground layer”. Therefore, when the thickness of the layer is halved, the settlement time has a relationship of ¼.

  Therefore, a method of improving the stable ground by subsidizing the soft ground at an early stage by subsidizing the drainage of the landfill instead of leaving the landfill as it is is being implemented. One of them is a vertical drain method using a sand drain (Vertical Drain method). For example, sand pillars are driven vertically into a 20 m thick clay layer by landfill at intervals of 2 m, and water is passed through the sand pillars as a water permeable layer that permeates the pore water contained in the gap clay layer. In this way, water contained in the clay layer is discharged, and the soft ground is subsidized at an early stage for stabilization. In this way, when sand pillars are erected on the clay layer, for example, at intervals of 2 m, the maximum drainage distance becomes horizontal in the clay layer, so that it becomes 1/10 of 20 m. Therefore, if it takes 100 years for water to escape at a thickness of 20 m, water will drain in 1 year of the square of 1/10. Therefore, it can be said that the vertical drainage method by sand drain is a very effective landfill construction method. However, when a perfectly shaped sand column as a sand drain could not be set up in a soft clay layer, a complete drainage passage could not be formed, which sometimes failed.

  Furthermore, a sand mat, which is a horizontal drainage material, has been conventionally known. The role of this sand mat is to increase the water permeability of the vertical drain material by quickly draining the water contained in the clay layer that has been raised on the soft ground through the vertical drain material further horizontally on the soft ground. It plays a role in promoting thick subsidence in soft ground. By the way, since the sand is spread over the entire area of the ground improvement target to a thickness of about 50 cm to 100 cm for sand mat use, the amount used is enormous. For this reason, problems such as depletion of resources and environmental destruction caused by sand collection have arisen, and on the other hand, obtaining high-quality sand has become difficult in recent years. For this reason, a decrease in the quality of sand and an increase in the cost of materials have been pointed out.

  As described above, since sand used in the sand drain method has become difficult to obtain from the viewpoint of resource protection or environmental protection, the vertical drainage method using sand drain has been replaced by a method using other drain materials. ing. That is, a water-permeable material that replaces sand has been produced and supplied in the factory, and has become a construction method using a prefabricated vertical drain (hereinafter referred to as “PVD”) material. In this PVD, what material can be used as a band-like water-permeable material is an important requirement.

  By the way, as one of the ground drainage methods for improving soft ground, a horizontal piece consisting of a sheet-like member with a high-strength anti-corrosion fiber layered at least on one side is laid on the soft ground. Then, a method for improving the soft ground in which the saddle shaped piece of the sheet-like member is penetrated and connected to the horizontal piece has been proposed (see, for example, Patent Document 1).

  Furthermore, as a fiber drain that is used as a drain to effectively drain pore water in soil and promote soil compaction in landfills, levee construction, etc. A plurality of core materials having a plurality of core materials are arranged in parallel, and this core material is integrally covered with a jacket material made of burlap to form a flat band, and the outer and outer jacket materials are sewn between adjacent core materials. A drain is disclosed (for example, see Patent Document 2).

  The PVD used for these vertical drainage methods needs to be shortened without breaking the drain length like a sand drain as the soft ground subsides. However, these do not take into account the idea of that point.

  On the other hand, the applicants, as a horizontal drain instead of the conventional sand mat, are not easily damaged by pressure such as embankment, either by remaining in the ground or decomposition and extinction due to corrosion in the ground depending on the choice of material. Has developed a horizontal drain that has an excellent water permeability / drainage function and can follow the distortion of the ground (see, for example, Patent Document 3).

  Furthermore, we have developed a horizontal drain material that has a high filter function because the jacket material has sufficient water permeability, and the filler made of the internal fiber mat has sufficient water permeability even under pressure. (For example, refer to Patent Document 4). However, since these are horizontal drain materials, it is not necessary to reduce the length of the drain along with the drainage as in the case of a vertical sand drain, and a situation in which the drain is further bent does not occur.

Japanese Patent Laid-Open No. 50-88810 Japanese Utility Model Publication No. 6-34413 Japanese Patent Laid-Open No. 10-140550 JP-A-11-172666

  The problem to be solved by the present invention is to drain the pore water contained in the clay layer of the soft ground in the landfill work by the permeability of the vertical drain arranged in the vertical direction in the soft ground, and to settle the ground of the soft ground Fiber drain material that can stabilize the ground early by shortening the length of the vertical drain without buckling or breaking following the land subsidence caused by drainage It is to provide a fiber drain material made of a natural material that does not harm the environment by corrosive decomposition.

  The means of the present invention for solving the above-mentioned problem is that, in the invention of claim 1, a jacket material having water permeability made of woven or non-woven fabric of burlap fibers, and a loosened material inherent in the jacket material. The coconut short fiber core material is in a state of being made of a long material formed by integrating the outer cover material with the filler core material at a plurality of locations on the outer cover material. It is a vertical fiber drain material for draining soft ground. Since the coconut fiber of the core material of the filler is in a loosened state, it is easily shrunk without resisting shrinkage of the length of the jacket material, resulting in the length of the vertical fiber drain material Can contract as the ground sinks in soft ground.

  According to a second aspect of the present invention, the coconut fiber core filler in the loosened state is formed by lengthening the coconut short fibers (i.e., coir) by shifting the fiber direction of the coconut fibers in a straight line. A vertical fiber drain material for water penetration of soft ground according to claim 1, which is integrated in a jacket material made of woven fabric or non-woven fabric. Since the fibers of the coconut fruit outer skin are contained in a straight shape in the longitudinal direction of the vertical fiber drain material, the water permeability is further improved and the core material can be more easily contracted.

  Further, according to a third aspect of the present invention, the jacket material made of burlap or non-woven fabric of burlap fibers is made of a double woven or non-woven fabric. Type fiber drain material. In this way, the jacket material has a double structure, which further increases the tensile strength of the fiber drain material, facilitates insertion into soft ground, and further improves the filter effect to improve the water permeability of the core material. It is said.

  As described in the above-mentioned means, the present invention provides a woven fabric of burlap fiber that is water-permeable and has a good filter effect as a filler of a core material made of a material obtained by loosening short fibers of coconut shells. In order to stabilize the soft ground by draining the water contained in the clay layer of the landfill site, the fiber drain is placed in the clay layer of the soft ground. When water is drained from above by vertical insertion and the surrounding water is drained from the capillarity formed between the fibers of the fiber drain, it is inserted into the soft ground along with the subsidence of the clay layer due to the drainage of the water. The length of the worn fiber drain is automatically shortened, and it is prevented from being bent like conventional PVD to deteriorate the water permeability, and the subsidence is promoted by draining the water contained in the soft ground at an early stage. Ground In addition, the fiber drain jacket material has a double structure, which improves the tensile strength of the fiber drain, improves the insertion performance to soft ground, and further improves the filter effect of the jacket material Thus, the invention of the present application exhibits an excellent effect that is not found in the past as a fiber drain, such as preventing deterioration of the water permeability of the core material of the filler over a long period of time.

  The best mode for carrying out the invention of the present application will be described below with reference to the drawings. The fiber drain material 1 of the means of the present invention is made of a woven or non-woven fabric of burlap fiber having a water-permeable covering material 2, and the core material of the filler 3 is made of coconut shell husk short fibers. The coconut shell husk short fibers of the core material of these fillers 3 are mounted in a water-permeable covering material 2 made of woven or non-woven burlap fibers in a loosened state. The outer cover material 2 and the core material of the filler 3 mounted in the outer cover material 2 are integrated by being sewn from a plurality of portions of the outer cover material 2 with natural fiber threads 5 such as cotton thread, The fiber drain material 1 is a long material. In this case, as shown in FIG. 1, the length of the long material of the fiber drain material 1 is such that the long outer covering material 2 is folded in half and the side end portion 4 thereof is made of natural fiber yarn 5 in the longitudinal direction. They are bound to form a cylinder, in which the core material of the filler 3 is mounted. The long material, which is the fiber drain material 1 formed in this way, has a belt-like outer shape having a rectangular cross section with a thickness of 9.0 mm ± 1.5 mm and a width of 90.0 mm ± 15.0 mm. Is formed. The length of the long material of the fiber drain material 1 depends on the depth of the soft ground to which the fiber drain material 1 is applied.

  In another embodiment, as shown in FIG. 2, the cross-sectional shape of the fiber drain material 1 of the present invention is such that two jacket materials 2 made of burlap or non-woven fabric of burlap fibers are stacked. In this way, by making the outer cover material 2 two layers, the filter performance is further improved, and fine soil particles from the soft ground into the core material of the coconut fruit which is the inner filler 3 It is assumed that clogging occurs and the water permeability of the core material of the filler 3 is not hindered.

  Further, since the coconut fruit outer fiber of the core material of the filler 3 is a short fiber, the gap between the capillaries formed between the fibers having a continuous length corresponding to the length of the fiber drain material 1. In order to further improve the water permeability, the short fibers of the core material that is the filler 3 are rearranged in the length direction, and the short fibers are sequentially shifted from each other. By arranging the short fibers in such a manner, the length of the fiber drain material 1 which is a long material can be easily reduced due to the consolidation settlement accompanying drainage of the soft ground. Like conventional PVD, kink (zigzag-shaped bending) is generated in soft ground, and it does not bend and deteriorate water permeability or buckle and break.

The tensile strength of the core material consisting of the short fibers of the coconut fruit of the filler 3 of the fiber drain material 1 of the present invention is 5 kN or more per fiber, and the permeability coefficient of the core material of the filler 3 is as shown in FIG. as shown in 3, it is about 1 × 10 ⁰ cm / s at a lateral pressure 50 kN / m ^2, is at the lateral pressure 200kN / m ² 2.5 × about 10 ^-1 cm / s. On the other hand, a conventional fiber drain in which, for example, four pipes twisted in a rope shape as a core material in a tubular body 2 of a jacket material 2 made of woven or non-woven fabric of double burlap fibers, for example, are contained. permeability of wood is, 1 × 10 ^-1 cm / s approximately at the lateral pressure 50 kN / m ^2, as shown in FIG. 4, a 1 × about 10 ^-2 cm / s in the side pressure 200 kN / m ^2, compared to Thus, the water permeability coefficient of the fiber drain material 1 of the present invention is about 10 times or more on average. 3 is a graph showing the relationship between the cell pressure (upload pressure) and the hydraulic conductivity of the fiber drain material 1 of the present invention, and FIG. 4 is a conventional fiber drain material having four rope-shaped core members. The vertical axis represents the hydraulic conductivity k (cm / s), and the horizontal axis represents the cell pressure (upload pressure) (kN / m ² ) of the clay layer. In addition, the value of i in these graphs indicates the hydraulic gradient.

  In the fiber drain material 1 of the present invention, after anchors are set on the soft ground with a known placement machine, the fiber drain material 1 is placed vertically in the soft ground while preventing twisting, and the upper end of the fiber drain material is placed on the soft ground. To protrude. Further, for example, the horizontal drain material of the above-mentioned Patent Document 3 or Patent Document 4 is arranged on the soft ground, and the projecting upper end of the fiber drain material 1 of the present invention placed vertically is connected to the soft ground. The pore water in the clay layer is permeated upward, and the permeated water can be drained horizontally by a horizontal drain material. When these constructions are completed, the embankment is loaded on the soft ground and the construction for draining is completed.

  The core material, which is the filler in the present invention, is applied with short fibers of coconut husk, but the filler is made of natural plant fibers in addition to the coconut husk short fibers. Needless to say, any fiber of burlap, cannabis, cocoon or other plant can be used as long as it rots and decomposes in the same years as the jacket material.

It is a schematic diagram which shows the cross section of the fiber drain material which has a single jacket material of this invention. It is a schematic diagram which shows the cross section of the fiber drain material which has a double jacket material of this invention. It is a graph which shows the water permeability coefficient of the fiber drain material of this invention. It is a graph which shows the water permeability coefficient of the conventional fiber drain material (four core materials).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fiber drain material 2 Jacket | cover material 3 Filler 4 Side edge part 5 Yarn which consists of natural fibers

Claims (3)

  A jacket material having water permeability made of woven or non-woven fabric of burlap fibers and a filler of a coconut fiber core material in a loosened state contained in the jacket material, and these jacket material and core material A vertical fiber drain material for water permeability of soft ground, characterized in that it is made of a long material that is formed by sewing and integrating the above filler at a plurality of locations on the jacket material.   The coconut fiber core filler in the unwound state is integrated into a jacket material made of woven or non-woven burlap fibers by shifting the fiber direction of the coconut fibers and stacking them in a straight line. The vertical fiber drain material for water permeability of soft ground according to claim 1, wherein   3. The vertical fiber drain material for water permeability of soft ground according to claim 1, wherein the jacket material made of burlap or non-woven fabric of burlap fibers is made of double woven or non-woven fabric.

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