JPH05187012A - Method of ground surface-coarse drainage construction - Google Patents

Abstract

PURPOSE:To improve a poor subsoil by using a drainage material enabling stabler supply than a sand mat and having high drainage capacity. CONSTITUTION:After drain material 1 are placed, drainage materials 10 are laid on the ground surface of a poor subsoil E, and soil covering is executed by using a part of a banking material and a banking 3 is formed. Consolidation due to settlement is generated in the poor subsoil E in response to a change with time by the loading load of the banking 3, and soil water rises on the ground surface through the drain materials 1, infiltrates into the drainage materials 10 and is discharged to the periphery of an improvement area from the peripheries of the drainage materials 10. The drainage materials 10 are formed in three layer structure, in which a core material simultaneously having pressure resistance and water infiltrating properties is held between a pair of permeable layers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground surface layer drainage method for draining underground water leaching to the surface of the ground due to consolidation settlement of soft ground to the outside.

[0002]

2. Description of the Related Art As a method for improving soft ground, there are a vertical drain method and a method combining a drain method and an embankment method. In these construction methods, the drain material is vertically driven into the soft ground by a drain material placing machine, and the underground water is discharged to the surface of the ground by utilizing the capillary phenomenon of the drain material to achieve the consolidation and subsidence of the ground. In addition, in the method of using embankment together, the earth pressure of the embankment is also applied to further promote drainage of underground water.

In any of the construction methods, it is necessary to discharge the underground water spouting on the surface of the ground to the outside of the improved area. Therefore, a sand mat is spread over the ground surface of the improved area to a predetermined thickness, and the water flowing out to the surface of the surface is improved. Is guided to the inside of this sand mat and drained to the outside through the sand particle gap. As a material for such a sand mat, sea sand or mountain sand having high water permeability is used.

[0004]

However, recently, it is difficult to secure a large amount of good quality sand, and the material cost and transportation cost increase depending on the construction site.
The profitability was low. On the other hand, although attempts have been made to use non-woven fabric as a drainage material to replace sand mat, the non-woven fabric has the advantage of being flexible and rich in workability, but the cross-section of water flow can be extremely reduced due to the loading load such as embankment, It was not suitable as a drainage material because the penetration of fine particles such as clay would cause clogging at an early stage and reduce the water permeability.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a ground surface layer drainage method using a drainage material capable of more stable supply than sand mat and having a high drainage capacity.

[0006]

To achieve the above object, the present invention comprises a substantially flat plate-like core material having both pressure resistance and water permeability, and a water-permeable layer disposed on both surfaces of the core material. The drainage material provided is spread over the soft ground surface, and the drainage material is covered with soil.

Further, according to the present invention, a drainage material having a substantially flat plate-like core material having both pressure resistance and water permeability and water-permeable layers disposed on both surfaces of the core material is provided with a required tensile strength. While laying on the soft ground surface through the water permeable sheet,
The drainage material is covered with soil.

It is desirable that the water permeable layer comprises a filter layer for preventing clogging of the core material and a filter protection layer for protecting the filter layer.

Further, the drainage material preferably has a flexible portion in which the core material is roughly arranged.

[0010]

According to the above construction, the permeable layer absorbs the underground water, and the water is drained to the outside through the inner core material having water permeability. Since this core material has a required pressure resistance and also serves as a compressive strength member, it is possible to sufficiently secure a cross section of water even if earth pressure is applied to the drainage material.

When the ground is extremely soft, a water-permeable sheet having a required tensile strength is laid on the ground, and drainage material is spread on the water-permeable sheet to prevent uneven settlement of the drainage material. You can In any of the above cases, the drainage material is covered with soil to ensure trafficability.

Further, since the water-permeable layer is composed of a filter layer for preventing clogging of the core material and a filter protective layer for protecting the filter layer, sediment particles leading to clogging of the core material. Is removed by the filter layer, and a filter protection layer is interposed between the filter layer and the earth and sand to protect the filter layer from mechanical deterioration. Further, since the drainage material has a flexible portion in which the core material is roughly arranged, the drainage material can be bent into a roll shape by the flexible portion, which is convenient not only for transportation but also for drainage. It is easy to punch with a mandrel when placing the material, and damage to the core material can be minimized.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a construction procedure of a ground surface layer drainage method according to an embodiment of the present invention. First, as shown in (a), a large number of drain materials 1 are placed in the improved area of the soft ground E by the vertical drain method. afterwards,
As shown in (b), the drainage material 10 is provided on the ground surface of the soft ground E.
After laying, the soil is completed by covering the soil with, for example, a part of the embankment material and then raising the embankment 3. Trafficability on the soft ground E is secured when the soil covering work is completed. Under the load of the embankment 3, the underground water is discharged along the drain material 1 and the drainage material 10 to the drainage groove 4 side excavated outside the site, as shown by the arrow. Then, the soft ground E causes consolidation settlement as shown in (c) according to the change with time, and the ground is improved.

FIG. 2 shows a construction procedure of the ground surface layer drainage method according to another embodiment of the present invention. In this example,
Compared with the first embodiment, the only difference is that the water permeable sheet 20 having the required tensile strength is laid on the soft ground E in advance and then the drain material 1 is placed. By doing this, even if the ground E is extremely soft,
It is possible to prevent uneven settlement of the drainage material 10 and reliably secure trafficability. 1 and 2, the drain material 1 is driven between the drainage materials 10 of the unit, but the drain material 1 may be arranged so as to punch out the drainage material 10. Good.

As shown in FIG. 3, the drainage material 10 includes a core material 12 having pressure resistance and water permeability between a pair of water permeable layers 14.
The core material 12 has a thickness of 30 to 50 mm, and the width is, for example, a distance corresponding to the driving interval of the drain material 1, although the thickness depends on the required water flow conditions. .

The core material 12 is made of a material that can maintain a continuous space while maintaining its cross-sectional dimension against a load such as earth pressure. For example, the water-passing performance is 10 ¹ to 10 ² cm.
/ S and a structure having a pressure resistance of about 10 t / m ² is selected. Examples of such a structure include a loofah structure-like structure, an open-cell porous high-strength member (resin-molded product formed in a sponge shape), or a plate material having a corrugated cross section.

The water permeable layer 14 is composed of a filter layer 14a and a filter protective layer 14b which are provided in contact with the core material 12. As the filter layer 14a, a flexible sheet having a filter function such as non-woven fabric or woven fabric is used, and a mesh corresponding to the target soil is set. For example, in the case of clay such as silt, 4 to 200 μm is used, and in the case of sandy soil such as sand, 0.3 to 1.2 mm is adopted.

The filter protection layer 14b is the filter layer 14
a is prevented from directly contacting the ground or the embankment layer to prevent mechanical deterioration of the filter layer 14a. A mesh made of synthetic resin or the like is used as the filter protection layer 14b.
On the side of the drainage material 10 which is disposed on the lower surface and contacts the ground, it is preferable to use a material having a smaller water permeability coefficient than the one disposed on the upper surface of the drainage material 10 in consideration of edging with clay.
Also, regarding the mechanical strength, the tensile strength is 50 to 100.
It is desirable to have a width of about kg / 3 cm. The filter protection layer 14b may be omitted in consideration of soil conditions and the like.

If the core material 12 is, for example, a corrugated core material made of plastic as shown in FIG. 4, it has strength and rigidity against compression, and at the same time, it is possible to secure a continuous water passage space in the corrugated cross section direction. It can be provided with flexibility such that it can be wound into a roll and carried. Then, at the time of laying, the drainage materials 10 adjacent to each other may be developed into a sheet shape having a predetermined width and length, and the adjacent drainage materials 10 may be connected to each other by the clip joint 6. Alternatively, as shown in FIG. Also, if the cloth hinges 7 on the back side are integrally connected, the joint portions of the core members 12 serve as hinges, which can be rolled and carried and deployed.

If, for example, a structure having a loofah structure is used as the core material 12, the core material 1 cannot be wound due to its rigidity. Therefore, as shown in FIG.
If the flexible portions 12a in which the 2 are roughly arranged are provided at appropriate intervals in the longitudinal direction of the drainage material 10, the drainage material 10 will be provided with the flexible portion 1
2a can be folded in order and rolled into a roll,
Easy to handle. At this time, if the water-permeable layer 14 provided on the flexible portion 12a has an extra length, the water-permeable layer 14 is easier to handle and the water-permeable layer 14 is less damaged.

Further, as shown in FIG.
A block of 10 to 10 cm square (as a matter of course, other appropriate shape and size may be taken) may be set as one unit, and the flexible portions 12a may be arranged so as to be arranged in a grid.
By doing so, it becomes easy to drive the drain material 1 such as a plastic board drain material into the drainage material 10 and join it, as described later. In addition, drainage material 1 with a mandrel
Even if 0 is punched out, the damage to the drainage material 10 can be minimized for one unit of block.

The continuity between the drain material 1 and the drainage material 10 is such that the upper end of the drainage material 1 protruding in a row on the ground surface is exposed at the edge of the drainage material 10, and the drainage material 10 is removed by the metal stitcher 5 or the like. It can be maintained by fixing it to the surface, or the drain material 1 may be directly driven into the drainage material 10 and joined as described above. At this time, sand only partially near the joint between the drain material 1 and the drainage material 10,
It is also possible to promote drainage by inserting a material having a large coefficient of permeability such as granular resin or fiber material. Further, the drainage members 10 are connected to each other in the width direction by the clip joints 6 to maintain their integrity. Further drainage material 1
The length of 0 is set to a transportable length, for example, a length that can be rolled and carried around.

In order to further promote the drainage, it is desirable to install the underdrain under the spread drainage material 10 at appropriate intervals, but at this time, the box culvert 30 as in the conventional case is used. In place of the structure in which the perforated pipe is installed along with the gravel material and the core material 12 of the present embodiment is filled through the water permeable layer 14 as shown in FIG. Compared with the underdrain using, the pressure loss when soil water flows in is greatly reduced, and the drainage efficiency can be improved.

In the above embodiments, the present invention is applied to the method in which the vertical drain method and the embankment method are used in combination, but the invention can also be applied to each method alone.

[0025]

As described above in detail with reference to the embodiments, in the ground surface drainage method according to the present invention, the drainage material to be spread is stably supplied by factory production as compared with the case where the conventional sand mat is spread. Therefore, it is highly economical and stable in quality.

Further, the permeable layer absorbs underground water, and drains to the outside through the inner core material having water permeability.
Since this core material has the required pressure resistance and doubles as a compressive strength member, it is possible to secure a sufficient cross-section for water flow even if earth pressure is applied to the drainage material, and it is possible to optimize the design according to the soil quality, loading load, etc. At the same time, the trafficability can be secured when the drainage material is covered with soil. When the ground is extremely soft, it is possible to prevent uneven settlement of the drainage material by laying a water-permeable sheet having the required tensile strength on the ground and laying the drainage material on it. Not only that, the trafficability can be secured more reliably.

Further, since the water-permeable layer is composed of a filter layer for preventing clogging of the core material and a filter protection layer for protecting the filter layer, earth and sand particles leading to clogging of the core material. Is removed by the filter layer, and a filter protection layer is interposed between the filter layer and the earth and sand to protect the filter layer from mechanical deterioration.

In addition, since the drainage material has a flexible portion in which the core material is roughly arranged, it can be bent at the flexible portion into a roll shape, which is convenient for transportation. Not only that, punching with a mandrel at the time of placing a drain material is easy, and various excellent effects such as damage to the core material can be minimized.

[Brief description of drawings]

1 (a) to 1 (c) are explanatory views showing a construction procedure of a soft ground improvement method according to an embodiment of the present invention and a temporal change after the construction.

2 (a) to (c) are explanatory views showing a construction procedure of a soft ground improvement method according to another embodiment of the present invention and a temporal change after the construction.

FIG. 3 is a sectional view of an essential part of the drainage material of the present invention.

FIG. 4 is a partially enlarged perspective view showing the connection relationship between the drainage material and the drain material of the present invention.

FIG. 5 is a partially enlarged perspective view showing another embodiment of the drainage material of the present invention.

FIG. 6 is a partially cutaway perspective view showing the drainage material of the present invention.

FIG. 7 is a sectional view of an underdrain to which the drainage material of the present invention is applied.

[Explanation of symbols]

 1 drain material 3 embankment 10 drainage material 12 core material 12a flexible part 14 water permeable layer 14a filter layer 14b filter protection layer 20 water permeable sheet E soft ground

Claims (4)

[Claims] 1. A drainage material comprising a substantially flat plate-like core material having both pressure resistance and water permeability, and a water-permeable layer disposed on both surfaces of the core material is spread over a soft ground surface and the drainage is performed. Ground surface drainage method characterized by covering the material with soil. 2. A water-permeable sheet having a required tensile strength for a drainage material comprising a substantially flat plate-like core material having both pressure resistance and water permeability and water-permeable layers disposed on both surfaces of the core material. A ground surface layer drainage method characterized by covering the drainage material with soil while covering it on a soft ground surface. 3. The water permeable layer comprises a filter layer for preventing clogging of the core material and a filter protective layer for protecting the filter layer. Ground surface drainage method described in 2. 4. The ground surface layer drainage method according to claim 1, wherein the drainage material has a flexible portion in which the core material is roughly arranged.