JP4801412B2 - Sand cover method using three-dimensional structure net - Google Patents

Description

  The present invention relates to a sand-capping method using a three-dimensional structure net, and covers a soft mud layer in the bottom in a sand-capping method performed to improve the bottom sediment composed of a soft mud layer deposited on the bottom of a coastal sea area, a lake or the like. As described above, the present invention relates to a sand covering method using a three-dimensional structure net in which a three-dimensional structure net having a predetermined rigidity is developed and laid, and a sand-covering layer placed so as to have a predetermined thickness can be stably held thereon.

  The conventional sand-capping method, in which sand-covered sand is thrown into the bottom sludge as it is laid, causes the sand to be buried in a soft sludge layer, resulting in problems such as excessive sand input and the sea area. There is a known problem that when the water is rough, the layers of the sand cover and the bottom sludge are reversed, and the sludge is exposed to the bottom of the water. In order to solve these problems, a sand covering method or the like is generally performed in which a sheet is laid on the bottom sludge to support the sand covering and suppress the bottom sludge, and the sand is covered thereon.

  However, the work of laying the sheet on the entire surface to cover the sand is large-scale, and the sheet may be turned over or torn, so maintenance to maintain the completely sand-covered state is also lacking. I wo n’t.

  On the other hand, a sheet made of water-impermeable synthetic resin or synthetic rubber is mostly used for the sheet, and in that case, it is expected to deteriorate the biological environment of algae and various low-lying organisms spreading on the bottom sludge surface. The In view of the above problems, a sand surface stabilization structure made of a semi-permeable structure has been proposed (Patent Document 1).

  The semi-transparent structure disclosed in Patent Document 1 is a mat-like body having a predetermined thickness in which a synthetic resin or metal filament forms a large number of random loops and maintains a state of being entangled in a loofah shape. Thus, the rigidity of the wire itself and the mat shape in which the wire is entangled in the shape of a loof is ensured such that it is not deformed by the influence of waves, tidal currents, etc. received on the sea bottom.

  Since this mat is characterized in that the bottom of the water is stabilized without covering sand, the specific gravity of the mat becomes small when the filaments constituting the loofah-like structure are made of synthetic resin or the like. In order to stabilize the laid mat, an expanded metal or the like that functions as a weight is used as a core material in the mat.

  Moreover, the invention disclosed in Patent Document 2 has been proposed as a method for solving the problems of the conventional sand-capping method. In this construction method, instead of the conventional rubber sheet, a soil retaining material layer constituted by laminating granular materials such as shellfish waste paper, cement latency, coal ash, or slag is provided, and sand covering is performed thereon. It is like that. In this construction method, the soil retaining material constituting the soil retaining material layer is in a state of being intricately fitted, the gap between them is filled with soft mud soil, a strong soil retaining material layer is formed, and the sand covering layer and It is designed to prevent the soft mud layer from turning over and the mud layer from blowing up to the upper layer.

See JP-A-9-235713. See JP-A-5-5304.

  By the way, the stabilization structure disclosed in Patent Document 1 is based on a loofah-like structure in which the filaments constituting the mat-like semi-permeable structure are formed in an irregular loop shape when laid on the bottom of the water. The purpose of this is to attenuate the energy of ocean currents and waves that flow on the surface, and to stabilize when laid on the bottom of the water. it can. However, since the thickness and rigidity of the mat itself are large, it is difficult to maintain continuity when laid on the bottom of the water, and it is necessary to fix with a spike member or the like.

  Moreover, in the sand-capping method disclosed in Patent Document 2, it is difficult to form a soil retaining material layer having a uniform layer thickness, and therefore, soft mud in the lower layer may be ejected in the thin layer portion. In addition, although it is possible to lay the net bag-like body in layers, in that case, it is difficult to keep the individual bag-like bodies continuously and form a layer.

Thus, in the case of the sand-capping method, it is necessary to hold the sand layer at a predetermined layer thickness and to be able to stably lay the sheet-like body on the soft mud, and even after construction, near the bottom of the water It is necessary to have a structure that can stably hold the sand-covering and sheet-like bodies even under the influence of waves and tidal currents.
Therefore, the object of the present invention is to solve the above-mentioned problems of the prior art, and can be stably laid to a soft level at the time of laying, and the net member can be more securely held by the sand covering thrown thereon. An object of the present invention is to provide a sand-capping method using a three-dimensional structured net.

  In order to achieve the above-mentioned object, the present invention is formed by warp knitting to form a mesh-like front and back base material and connecting yarns that connect these base materials with a predetermined interval. A three-dimensional structure in which the size of the mesh is different between the front and back sides, and the connecting yarn is stretched between the string portion that forms the first mesh of the substrate on one side of the front and back and the string portion that forms the second mesh of the other substrate In the whole or a part of the string part, the connecting thread is stretched from the string part on the first mesh side to the plurality of string parts on the second mesh side, whereby the first mesh side And a three-dimensional structure net in which a predetermined continuous three-dimensional space shape is formed in the string portion forming the second mesh, and the three-dimensional string portion constituting the first mesh and the second mesh is folded. Then, touch the surface of the bottom mud soil and stretch the mesh in the direction of the net deployment to a predetermined scale. Is secured in close contact with the bottom mud surface, the bottom mud is filled into the three-dimensional space from the second mesh side, laid on the bottom mud surface, and further covered from the upper surface side of the three-dimensional structure net. Sand is thrown in to fill the three-dimensional space on the first mesh side with the sand-covered sand, and then the sand-covered sand is deposited on the three-dimensional structured net to a predetermined layer thickness.

  Preferably, the first mesh uses a three-dimensional little net having a mesh size larger than that of the second mesh.

Alternatively, the the said first network, said second network and is set to equal correct eyes fit dimensions, mesh position with the first network formed on the front side of the green body, which is formed on the back side of the green body it is preferable that the second mesh is utilized conformation nets which are arranged offset about 1/2 of the fit said purpose.

  At this time, it is preferable that the three-dimensional structure net is laid and stretched in a developing direction from a mesh size of the mesh in a folded state to a predetermined size mesh, and is in close contact with the submarine mud.

  According to the present invention, a large mesh and a small mesh are provided on the front and back surfaces of the three-dimensional structure net stretched and expanded so as to have a predetermined mesh size and laid on the submarine mud. Due to the structure of the net space with sufficient rigidity formed in the net, it is easy to lay the net when carrying out the sand-capping method, and it is possible to close the sand-covered mud surface by adhering to the bottom mud surface. There is an effect that it is possible to stabilize the sand cover filled and deposited in the eye space.

  Hereinafter, as the best mode for carrying out the sand covering method using the three-dimensional structure net of the present invention, the following examples will be described with reference to the accompanying drawings.

[3D structure net]
Hereinafter, the configuration of the three-dimensional structure net used in the present invention will be described with reference to FIGS. In addition, although this three-dimensional structure net is based on using the three-dimensional structure net which acquired patent 348289, it has the characteristic in the laying process in the sand-covering method.

  FIG. 1 is a perspective view schematically showing a three-dimensional structure net A according to an embodiment knitted with synthetic fiber yarns, drawn in the direction of arrow T and deployed to form a planar body. FIG. 2 is an enlarged plan view showing the initial knitted state of the three-dimensional structure net, an enlarged plan view of the planar net shown in FIG. It is a partially expanded sectional view of the net along the XX sectional line and YY sectional line of (a) and (b).

  1 to 4, reference numerals 1 and 2 in the drawings respectively indicate a substrate having a mesh shape on the front and back sides, and reference numerals 11 and 21 indicate string portions that form the meshes 12 and 22 on the front and back sides, respectively. Reference numeral 3 denotes a connecting yarn for connecting the front and back substrates 1 and 2 with a predetermined interval. Further, the connecting yarn 3 forms a three-dimensional structure net A having a required thickness and a high porosity. In this embodiment, a known thermoplastic synthetic resin such as high-density polyethylene or polypropylene can be appropriately used as the material of the thread of the three-dimensional structure net.

  In the three-dimensional structure net A of this embodiment, one of the front and back substrates 1, 2, for example, the mesh 12 of the substrate 1 is formed larger than the mesh 22 of the other substrate 2, and the large mesh as the first mesh of the one substrate 1 is formed. 12 and the string portion 21 forming the small mesh 22 as the second mesh of the other substrate 2 are stretched over the connecting yarn 3 to create a gap that allows ventilation and water flow. A solid string portion 4 is formed inside. The three-dimensional string portion 4 is small in whole or in part by connecting the connecting thread 3 from the string portion 11 on the large mesh 12 side to the plurality of string portions 21 on the small mesh 22 side. On the mesh 22 side, a three-dimensional shape having a width for holding a small mesh 22 in the string portion is formed.

  In addition, since the three-dimensional structure net A is initially knitted, the string portions 11 and 12 are densely knitted, so that the net space S is almost closed as shown in FIG. The direction width is in a fully folded state. In this state, since the bulk volume of the three-dimensional structure net A is significantly smaller than that during deployment, it can be easily carried into the site.

  A feature of the shape of the three-dimensional structure net is that in all or a part of the three-dimensional string portion 4, the connecting portion of the connecting thread 3 is inclined to both sides when viewed from the large mesh 12 side and the string on the small mesh 22 side. By spanning over the portion 21, the cross section is knitted to form a substantially hollow three-dimensional shape having a three-dimensional void inside such as a substantially triangular shape, a substantially inverted triangle shape, a substantially trapezoidal shape or a substantially inverted trapezoidal shape. A space surrounded by 4 is a point where a net space S is formed. Thereby, the spanning part of the connecting thread 3 inclined on both sides in the three-dimensional string portion 4 can perform the function of supporting the load in the thickness direction, and can retain the shape when receiving a surface load as a net. It has become. Further, the three-dimensional string portion 4 is formed so that the three-dimensional gap formed by the inclined connecting thread 3 forms a tunnel shape that is continuous in the knitting direction and / or the knitting width direction, and is in a sufficient communication state. Can do. Specifically, as the planar shape, it is continuous in the knitting direction in a zigzag shape by being alternately knotted with the adjacent string portions on both sides for each required interval in the knitting direction. The substantially hexagonal polygonal meshes 12 and 22 are formed.

  Furthermore, the connecting yarn 3 is stretched between the corresponding stitch rows of the string portions 11 and 21 of the front and back base materials 1 and 21, and all or a part of the connecting yarn 3 of the three-dimensional string portion 4 is knitted. From the string portion 11 on the large mesh 12 side, the plurality of (for example, two) or more string portions 21 on the small mesh 22 side are slanted on both sides, whereby a substantially hollow three-dimensional shape That is, a three-dimensional shape having a three-dimensional void inside is formed. The code | symbol 13 has shown the knot part of the string parts 11 and 11, 23 has shown the knot part of the string parts 21 and 21. FIG.

  About the ratio of the magnitude | size of the large mesh 12 of one base 1, and the small mesh 22 of the other base 2, it can set arbitrarily arbitrarily for both the knitting direction and the knitting width direction. In addition to the case where one of the large stitches 12 corresponds to a plurality of small meshes 22 in the knitting direction and the knitting width direction, the proportion of the large meshes 12 is the plurality of small meshes 22 (however, the larger ones are large). It can also be set so as to correspond to more than the number of meshes. By setting in this way, warp knitting becomes easy.

  As shown in the yarn configuration diagram shown in FIGS. 3 and 4, in the knitting direction, the number of knitting courses for one mesh 12 of the large base 1 on the front and back sides, that is, two adjacent string portions 11, The number of knitting courses from the knot part 13 between 11 to the next knot part 13 is twice the number of knitting courses for one small mesh 22 of the other substrate 2, that is, the large mesh 12 is twice the small mesh 22 Further, in the knitting width direction, the mesh 12 having the large base 1 on the front and back sides is one for the two meshes 22 having the small base 2 on the other side, that is, the width is doubled. Is formed. Although not shown, in the knitting direction, the number of knitting courses for one large mesh 12 on one side 1 of the front and back becomes the number of knitting courses for three small meshes 22 on the other base 2. Further, in the knitting width direction, it is possible to perform knitting so that one large mesh 12 corresponds to two small meshes 22. Further, in the case of this embodiment, one of the small meshes 22 of the other base 2 is knitted so as to correspond to the approximate center of the large mesh 12 of the base 1 on the front and back sides. , 22 is stretched over the entire circumferences of the meshes 12, 22 so that the net space S formed inwardly forms a substantially funnel shape. Is formed.

  As a result, the three-dimensional string portion 4 around the net space S has a substantially hollow three-dimensional shape such as a substantially triangular cross section having a three-dimensional void inside the entire circumference, and this three-dimensional shape is continuous in a tunnel shape. Thus, it can be supported in a balanced manner against the compressive load in the thickness direction. In addition, since the three-dimensional string portion 4 having a three-dimensional shape is continuous in a tunnel shape over the entire net, the structural stability and the effect of preventing the collapse are further increased, and the internal three-dimensional voids are covered as described later. It can function as a filling space for filling materials such as sand and a distribution space for ventilation, water flow, and the like. In the three-dimensional shape of the three-dimensional string portion 4, as shown in FIGS. 3 and 4, the angle α formed by the spanning portion of the connecting thread 3 inclined to both sides from the string portion 11 on the large mesh 12 side is 45 °. If the knitting is performed by setting the size of the mesh and the thickness of the net so that the cross section of about 75 °, particularly preferably around 60 °, is almost a regular triangle, the structure stability is the best. However, it is not limited to the above-mentioned angle depending on the thickness of the net required according to the application, the size of the mesh, and the yarn used.

  The above-described large mesh 12 and small mesh 11 are made the same size mesh, and the arrangement of the mesh is set so as to be shifted by a half width of the mesh between the substrate 1 and the substrate 2, The same function as the three-dimensional shape of the large mesh 12 and the small mesh 11 described above can be exhibited.

[Sand covering method using 3D structure net]
Hereinafter, the Example which applied the three-dimensional structure net | network mentioned above to the sand covering method is described. FIG. 5 is a partial cross-sectional view of the water bottom 30 showing the completed state of the sand-capping method. As shown in the figure, in the sand covering method using the three-dimensional structure net of the present invention, the three-dimensional structure net A is laid on the surface of the soft mud 30 in the bottom of the construction area where the sand covering work is performed. Part of the small mesh 22 side of the lower surface of the mesh is buried in the mud 30 and the mud 31 is clogged from the mesh 22 side into the mesh space S, and in this state, a good quality sand cover 35 is formed on the net from the net upper surface side to a predetermined layer thickness. The sand-covering work is completed. For this reason, the mesh 22 on the lower surface of the three-dimensional structure net A is clogged with the mud 31 and the mesh 12 on the upper surface is reliably filled with the sand covering 34, and the mud 30 on the bottom of the water and the sand covering 35 can be reliably separated. While the mud 30 eruption phenomenon and the like can be reliably blocked, the three-dimensional structure net A is rich in ventilation and water permeability. Therefore, methane gas and spring water generated in the case of the mud 30 close to sludge are free from the three-dimensional structure net A. It passes through and can be discharged through a permeation path (not shown) formed in the sand cover 35.

  The thickness of the three-dimensional structure net A used in the sand-capping method of this embodiment is preferably about 30 to 50 mm, and the mesh size of the small mesh 22 on the lower surface depends on the thickness of the net, for example, the opposite side of the turtle shell is 10 to 15 mm. Similarly, the mesh size of the large upper surface is preferably about 30 to 45 mm.

[Laying three-dimensional structure net-sand covering process]

  A series of steps of the sand covering step for laying the three-dimensional structure net A on the bottom mud and covering the surface of the three-dimensional structure net A will be described with reference to FIGS. 6 and 7. In this embodiment, the width of the original fabric of the three-dimensional structure net A is 2 m, and the plane dimension in the fully expanded state (2 m × n rows) × the total length in a state where the mesh is expanded in the stretching direction is taken into consideration. It is preferable to set the initial number of mats to be laid. FIG. 6 is an explanatory diagram showing a mat laying state schematically showing one row in the unfolded state, one row in the mat unfolding adjacent to the one row, and the mat in the folded state. In the developed three-dimensional structure net A, it is preferable to connect adjacent portions with a binding material such as a string as necessary. As the binding material, each mat can be used with the passage of time after laying by using a string made of natural fiber material or biodegradable resin fiber material, or a soft iron wire (wire, wire) that easily corrodes in seawater. The connection part is released, and it becomes close to a state where a single material is laid. For this reason, even when a coastal disaster is caused by a large wave during a typhoon, etc., it is sufficient to cause damage to the extent that a single mat is partially washed away. Stop by work. For this reason, there exists an advantage that the maintenance cost in the case of considering a disaster etc. is also small.

  Hereinafter, the laying procedure of the three-dimensional structure net A will be described with reference to FIGS. First, the three-dimensional structure net A in a folded state is laid down at a place to be laid while maintaining a roll shape of a predetermined length and grounded, and one end is fixed to the mud surface 30 with a fixing member (not shown) such as a pin member. (See FIG. 7 (a)). As shown in FIG. 7 (b), the free end from this state is stretched in the T direction so that the mesh is, for example, the distance between opposite sides of the mesh 12 on the upper surface of the turtle shell shape (for example, the mesh is meshed). If it is about 10 mm in a folded state, it is stretched to a turtle shell shape that is expanded to about 50 mm, which is about 5 times the mesh width, and the expanded state is maintained. Then, as shown in FIG. 7C, by pressing the three-dimensional structure net A against the surface of the mud 30, the three-dimensional structure net A can be brought into close contact with the mud 30 so that the mud enters from the mesh of the lower surface. .

  Furthermore, by putting sand at a time so that the high-quality sand-covering sand 35 extends over a thin layer as shown in FIG. 7 (d) or a predetermined layer thickness as shown in FIG. 7 (e), Sand 34 is filled in the mesh 12 on the upper surface of the three-dimensional structure net A, and the bottom mud 30 and the covering sand 35 are configured so that the bottom mud 30 and the covering sand 35 mesh with each other with the three-dimensional structure net A as a boundary. Can be completely shut off. The sand covering 35 is deposited to a thickness of about 50 to 200 cm depending on the construction site. However, since the three-dimensional structure net A has sufficient rigidity to support the vertical load, the three-dimensional structure net A is on the mud surface. Holds securely.

  In addition, as the sand-covering sand deposited on the three-dimensional structure net A, there is an advantage that the stability of sand-covering can be achieved by using high-quality sand, ore slag having a large specific gravity.

The perspective view which showed a part of three-dimensional structure net | network used for the sand covering method of this invention. FIG. 2 is a partially enlarged cross-sectional view illustrating a state in which the three-dimensional structure net illustrated in FIG. 1 is expanded from a folded state to a predetermined size and developed. FIG. 3 is a cross-sectional view of a yarn configuration shown along the XX cross-sectional line and the YY cross-sectional line shown in FIG. FIG. 3 is a cross-sectional view of a yarn configuration shown along the XX cross-sectional line and the YY cross-sectional line shown in FIG. The fragmentary sectional view which showed typically the sand covering method construction completion state. The perspective view which showed typically the process of laying a three-dimensional structure net | network. Construction sequence explanatory drawing schematically showing a procedure for laying a three-dimensional structure net and further covering sand.

Explanation of symbols

1, 2 Base 3 Linking thread 4 Solid string part 11, 21 String part 12 Large mesh (first mesh)
22 Small mesh (second mesh)
30, 31 Mud 34, 35 Covered sand A Three-dimensional structure net S Net space

Claims (4)

  By warp knitting, it is formed by a mesh-like front and back base material and connecting yarns that connect these base materials with a predetermined interval, and the front and back base mesh sizes are different between the front and back sides. In all or a part of the three-dimensional string portion in which a connecting thread is stretched between the string portion forming the first mesh of one substrate and the string portion forming the second mesh of the other substrate, the connection The yarn is stretched from the first mesh side string portion to a plurality of second mesh side string portions, thereby forming the first mesh side and the second mesh side. A three-dimensional structure net in which a predetermined continuous three-dimensional space shape is formed in the string portion, with the three-dimensional string portion constituting the first mesh and the second mesh folded, is grounded on the bottom mud surface, By stretching the mesh in the direction of net deployment, a predetermined mesh is secured and the surface of the submarine mud is secured. And filling the three-dimensional space into the three-dimensional space from the second mesh side and laying it on the surface of the three-dimensional structure net, and then adding sand covering from the upper surface side of the three-dimensional structure net. A sand-covering method using a three-dimensional structure net, wherein the three-dimensional space on a mesh side is filled with the sand-covering sand, and then the sand-covering sand is deposited up to a predetermined layer thickness.   2. The sand-capping method using a three-dimensional structure net according to claim 1, wherein the first mesh has a mesh size larger than that of the second mesh. Said first network, said second network and is set to equal correct eyes fit dimension, and the first mesh formed on the front side of the green body mesh position, the second formed on the back side of the green body 2. The sand covering method using a three-dimensional structure net according to claim 1, wherein the mesh is arranged with a difference of about 1/2 of the mesh.   The three-dimensional structure net is stretched and laid in a deployment direction from a mesh size of the mesh in a folded state to a predetermined size mesh, and is closely attached to the submarine mud. Sand-capping method using a three-dimensional net.

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