JPH04228723A - Ground reinforcing net - Google Patents

Abstract

PURPOSE:To increase pull-out resistance of a net by forming a perforated sheet having projections at intersections with a thermoplastic resin and by heating and stretching it laterally and longitudinally so that the projections are made larger in thickness and width than the net part by a predetermined value. CONSTITUTION:A perforated sheet having projections 23 at intersections are formed with a thermoplastic elastomer resin using an emboss roll and so on. Then, the perforated sheet is heated and stretched in the lateral and the longitudinal directions so that the thickness of the projections 23 is made 1.5 to 20 times larger than net parts 221 and 222 and the width is made 1 to 10 times larger than the net part. By this, a ground reinforcing net with large pull-out resistance in the ground can be obtained.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure of a ground reinforcement network, and mainly relates to a stretched reinforcement network made of synthetic resin for use as a countermeasure against landslides on embankments.

0002

BACKGROUND OF THE INVENTION In recent years, the construction of housing has increased rapidly, and therefore residential areas are often developed with embankments. Furthermore, many roads are constructed using steep embankments at civil engineering construction sites. These embankments do not allow landslides at all,
For this reason, various measures have been taken. Among these, a widely adopted method is to place nets in layers in the embankment to prevent landslides and stabilize the embankment. Conventionally, meshes made of corrosion-resistant synthetic resin have been used, and meshes made of unstretched polyethylene or nonwoven filament have been used. However, when an unstretched polyethylene network is buried underground, the elongation rate of the network against tensile forces due to earth pressure, etc., that is, landslides, is extremely large, so it cannot be expected to be very effective as a reinforcing material for embankments. . On the other hand, although non-woven filament nets have a certain degree of tensile strength compared to the polyethylene, they still tend to elongate considerably. Therefore, in recent years, as a countermeasure to this problem, nets that are uniaxially or biaxially stretched and molecularly oriented have come to be used. As a guideline for embankment landslides, it is desirable to have nets buried in the soil that have a high resistance to pulling them out of the soil, but it is a fact that this has not been fully satisfied.

0003

[Problems to be Solved by the Invention] The present invention aims to solve these problems, and provides a synthetic resin net that has particularly strong and elongated properties and also has high resistance to being pulled out of the soil. The purpose is to

0004

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a synthetic resin net having the following structure. That is, it is a corrosion-resistant synthetic resin net that is buried in embankment to provide a soil reinforcement effect, and the net portion is stretched in at least one direction to orient the molecules, and the thickness of the intersection point of the net portion is The ground reinforcing net is 1.5 to 20 times the thickness of the net in the stretching direction, and the width at the intersection point is 1 to 10 times the width of the net in the stretching direction. Preferably, the net is biaxially stretched and oriented. As such synthetic resins, thermoplastic elastomer resins are preferably used, such as high density polyethylene and polypropylene.

[0005] The intersection points of the net portions are like protrusions formed when viewed from the entire net, and the thickness at the intersection points (the height of the protrusions) is the thickness of the net portions in the stretching direction. 1.5~
If it is 1.5 times or less, it will not have much effect on the resistance to being pulled out of the soil, while if it exceeds 20 times, the resistance to the soil will also decrease due to the flexibility of the protrusion. The same thing can be said about the width of the protrusion, and the width of the protrusion is 1 to 1 to the width of the net portion in the stretching direction.
It is best to set it to 10 times; anything less than this is not very effective.
Even if it exceeds 10 times, the pull-out resistance against the soil tends to exceed the strength of the net itself, and the effect is not substantially improved.

[0006]

[Function] In general, the means for stretching synthetic resin sheets is as follows:
First, a perforated sheet is formed, which is then stretched uniaxially under heat and, if necessary, biaxially under heat. This is passed through to form an embossed sheet, which is then uniaxially or biaxially stretched under heating, and is generally made by opening holes in the thin portions. However, when the molecules are oriented by this stretching, the thickness of the sheet is slightly reduced. As a landslide prevention measure, the effectiveness of the netting used in the embankment is largely related to its effectiveness, and the pull-out resistance of various materials is generally compared. This underground pulling resistance is the resistance (KN/m2) when the net is pulled out in the horizontal direction after it is buried in the soil and a top load (KN/m2) is applied to the net.
), which is not only the size of the mesh, but also
It is known that it is mainly proportional to the thickness of the mesh. In other words, the larger the area that crosses the soil during pulling out, the greater the pulling resistance.

However, when a synthetic resin sheet is stretched, especially when biaxially stretched, the net portion becomes considerably thinner than the original thickness of the sheet, and its resistance to soil becomes extremely small. On the other hand, it is inevitable that the thickness at the intersection of the net portions will be thinner than the original sheet shape, and therefore, by stretching the net, the resistance to pulling it out of the soil will be reduced. As mentioned above, this underground pull-out resistance is related to the thickness of the net buried in the embankment, but the thickness and width of the intersection points of the net parts are particularly related to the underground pull-out resistance. I understand. The present invention increases the resistance to being pulled out of the soil by specifically specifying the width and height of the intersection points of the net portions.

[0008] A preferred example of the method of manufacturing the ground reinforcing net in the present invention is as follows. That is, an embossing roll with grooves carved in a cross or diagonal pattern on the metal roll surface is used, the grooves of both rolls are aligned, and the molten synthetic resin is poured between the rolls. Then, an embossed sheet is formed in which the thick net portion formed by the groove and the thinner portion are formed between the net portion and the thick net portion formed by the groove. The net portion of this embossed sheet is stretched in the longitudinal direction to produce a ground reinforcing net. When the net to be manufactured is biaxially stretched, it is reheated after being uniaxially stretched, and then stretched in a direction perpendicular to the uniaxially stretching direction to form the net.
Alternatively, it is formed by simultaneously stretching in uniaxial and biaxial directions. In the present invention, in some cases, only one roll may be provided with grooves to form an embossed sheet with unevenness formed on one side. As mentioned above, the grooves are cut in a cross or diagonal pattern on the roll, but in order to facilitate stretching after forming the embossed sheet, the entire groove is inclined (preferably at 45 degrees). ) and engrave it.

Now, in manufacturing the ground reinforcing net of the present invention, a net having a desired cross-sectional shape can be obtained by forming recesses deeper than the depth of the grooves at the intersections of the grooves of the embossing roll. be. FIG. 1 is an enlarged plan view of the embossing roll, and FIG. 2 is an enlarged sectional view taken along line A--A in FIG. That is, concave grooves 21 and 22 are carved on the surface of the embossing roll 1, in this case criss-crossing, and a concave portion 4 deeper than the concave grooves 21 and 22 is formed at the intersection position 3. It is something to keep. Even when stretched uniaxially or biaxially, the thick part, that is, the protrusion formed by the recess 4, maintains almost its original shape in both thickness and width, and this provides resistance to pulling it out of the soil. It will be useful for improving.

0010

[Specific Examples] The ground reinforcement network of the present invention will be explained in more detail below with reference to the drawings. FIG. 3 shows the first embodiment of the present invention.
4 is a plan view of a biaxially stretched polypropylene ground reinforcing net, and FIG. 4 is a cross-sectional view taken along line BB in FIG. 3.

FIG. 5 shows a plan view of the embossed sheet before stretching, and FIG. 6 shows a cross-sectional view taken along line C--C in FIG. The method for manufacturing this embossed sheet was as explained in the previous section. That is, the polypropylene sheet 11 formed from the embossing roll, that is, the sheet before stretching, has mesh portions 121 and 12 formed by grooves on the roll.
2, the thickness T0 is 4 mm, the width W0 is 6 mm, and especially the thickness T1 at the protrusion 13 formed at the intersection position is 10
mm, and the width W1 was 6 mm (diameter here). Also, one side of these net portions 121 and 122 is 15 mm,
A thin portion 14 is formed surrounded by the net portions 121 and 122 .

However, the shape of the net 21 after biaxial stretching is such that the stretched net portions 221 and 222 have a thickness T2 of 1 mm,
The width W2 is 3 mm, and the thickness T3 of the protrusion 23 at the intersection point is 9.
．． 7 mm, and the width W3 was 5.5 mm, and despite the biaxial stretching, the thickness T3 and width W3 of the protrusions 23 were hardly deformed and remained as they were in the original sheet. Since there is almost no deformation at the intersection point, this portion remains as a protrusion after stretching, and this greatly contributes to the resistance to being pulled out of the soil. In the figure, reference numeral 24 indicates a mesh, which is formed by tearing the thin portion 14 described above during stretching to form a mesh.

FIG. 7 is a sectional view similar to FIG. 4 of a ground reinforcement network 31 according to a second embodiment of the present invention. This is an example in which grooves are formed only on one side of the embossing roll, and in this case too, protrusions 33 are formed at the intersection points, which has an effect on the resistance to being pulled out of the soil. 321 and 322 in the figure
indicates a mesh portion, and 34 is a mesh.

[0014]

[Effects] As described above, in the present invention, the thickness and width of the intersection of the mesh portions are set large in advance during stretching of the net, and even after stretching, a non-stretched portion is left at this portion, and as a result, the net A protrusion is constructed at the intersection of the sections, which increases the resistance to pulling out of the soil and prevents landslides on embankments, etc.

[Brief explanation of the drawing]

FIG. 1 is an enlarged plan view of an embossing roll.

FIG. 2 is an enlarged sectional view taken along line AA in FIG. 1;

FIG. 3 is a plan view of the ground reinforcement network according to the first embodiment of the present invention.

FIG. 4 is a sectional view taken along line BB in FIG. 3;

FIG. 5 is a plan view of the ground reinforcement network before stretching according to the first embodiment of the present invention.

FIG. 6 is a sectional view taken along line CC in FIG. 5;

FIG. 7 is a sectional view similar to FIG. 4 of a ground reinforcement network according to a second embodiment of the present invention.

[Explanation of symbols]

1... Embossing rolls 21, 22... Concave groove 3... Intersection position 4... Concave portion 11... Polypropylene sheet 121, 122... Net portions 13, 23, 33 before stretching... Protrusions 21, 31 ... Nets 221 , 222 , 321 , 322 after biaxial stretching ... Net section T0 after biaxial stretching ... Thickness W0 of the mesh section before stretching ... Width T1 of the mesh section before stretching ... Before stretching Thickness W1 at the intersection point Width T2 at the intersection before stretching Width W2 of the mesh after biaxial stretching Width T3 of the mesh after biaxial stretching Intersection after biaxial stretching Thickness at position W3 ‥‥ Width at the intersection position after biaxial stretching

Claims (2)

[Claims] Claim 1: A corrosion-resistant synthetic resin net buried in embankment to provide a soil reinforcing effect, wherein the net portions are stretched in at least one direction to orient the molecules, and the thickness at the intersection of the net portions is is 1.5 to 20 times the thickness of the net portion in the stretching direction, and the width at the intersection point is 1 to 10 times the width of the net portion in the stretching direction. network. 2. The ground reinforcing net according to claim 1, wherein said net is biaxially stretched and oriented.