JPS62197512A - Improving work for soft ground - Google Patents

Abstract

PURPOSE:To raise the efficiency of improving work by a method in which an expanded plastic material is provided on a sheet on soft ground, and a civil-work structure is constructed on the plastic material. CONSTITUTION:A felt-like nonwoven cloth sheet 2 having a thickness of about 2mm or more is laid on soft ground 1, an expanded plastic material 3, e.g., polyurethane foam, is directly provided on the sheet 2, and a civil-work structure, e.g., agricultural road, is constructed on the material 3.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to soft ground such as reclaimed land, reclaimed land, wetland, etc.
In particular, the present invention relates to a method for improving soft ground that provides holding power for civil engineering structures built on ultra-soft ground.

[Prior Art] Conventionally, the following methods are known as methods for improving soft ground.

(1) A method in which foamed plastic plates are stacked directly on soft ground to form a lightweight embankment base as an alternative to embankment, and to support civil engineering structures built on top of it (U.S. Patent No. 3)
．． No. 828.702).

(2) By interposing a sheet-like material between the soft ground surface and the exposed soil, the load of the exposed soil is absorbed by the sheet, which is held by frictional resistance due to the close contact structure between the sheet and the soft ground surface. Distributed support (Special Public Service Showa 4B)
-13885).

(3) A method in which a sheet-like material is spread over the soft ground surface, leveling is performed by sprinkling sand or artificial aggregate on top of it, and then a foamed plastic board is placed on top of it (Magazine "Foundation Construction J" 1988) January issue).

[Problems to be Solved by the Invention] However, in the construction method (1) above, the scaffolding becomes extremely unstable, especially when the ground is extremely soft, so the work of stacking foamed plastic plates on top of it becomes extremely difficult. It becomes difficult. In addition, uneven settling of each foamed plastic board is likely to occur, and to prevent this, the connection between each foamed plastic board must be made considerably strong, resulting in the problem of increased work burden.

In the case of method (2) above, when the ground is extremely soft,
There is a problem that the sheet-like material alone tends to lack supporting capacity, and cannot sufficiently support the load of heavy machinery such as dump trucks and bulldozers when discharging earth and sand, making construction difficult. Furthermore, since the weight of the spewed earth and sand is added to the weight of the civil engineering structures built on top of it, excessive settlement or uneven settlement is likely to occur, and the constructed civil engineering structures are also susceptible to damage due to this.

In the case of the method (3) above, similar to the method (2) above,
Heavy equipment is placed on top of the unfolded sheet material and leveling is performed by sprinkling out sand and artificial aggregate, so if the ground is extremely soft, it may not be able to support the load of the heavy equipment, making construction difficult. There's a problem. In addition, if leveling is performed by sprinkling sand or artificial aggregate, it will be easier to polish the foamed plastic board on top of it, but there will be a difference in weight between thick and thin areas of the sand or artificial aggregate layer. . That is,
In places where the sand or artificial aggregate layer is thick, the load on the soft ground increases, whereas in places where the sand or artificial aggregate layer is thick, the load on the soft ground is low, which causes irregular settlement. This unequal subsidence is
Especially when the ground is extremely soft, it tends to become large.

[Means for solving the problems] The means taken to solve the above problems will be explained with reference to FIG. 1, which corresponds to an embodiment of the present invention.
By laying the sheet-like material 2 on the surface of the soft ground ff1l, placing the foamed plastic material 3 directly on the sheet-like material 2, and constructing the civil engineering structure 4 on top of the sheet-like material 2, the above-mentioned method can be achieved. This problem was solved.

[Function] In the present invention, the sheet-like material 2 laid on the surface of the soft ground 1I11 functions to stabilize the level of the surface of the soft ground 1 through frictional resistance with the surface of the soft ground 1. When the soft ground 1 becomes extremely soft, the sheet-like material 2 does not have enough supporting power to support heavy machinery in a stable state.
It can provide enough support to support the work of light equipment and workers.

The foamed plastic material 3 provided on the sheet-like material 2 prevents excessive sinking due to its buoyancy and exerts sufficient supporting force for the civil engineering structure 4 to be constructed thereafter.

By the way, the foamed plastic material 3 is extremely lightweight and can be easily installed by using light equipment without the use of heavy machinery. The work can be sufficiently supported by the supporting force of the sheet-like material 2. Therefore, work can be carried out in a stable state, and construction can be carried out efficiently.

In addition, the foamed plastic material 3 is provided directly on the sheet-like material 2, and there is no need to throw out heavy earth and sand between the sheet-like material 2 and the foamed plastic material 3, so heavy machinery for this purpose is not required. Depending on the use and weight of the excavated soil, etc.
Excessive burden on the sheet-like material 2 can be prevented. Furthermore, since the lower surface of the foamed plastic material 3 contacts the soft ground 1 evenly through the sheet material 2, the load on the soft ground 1 is almost uniformly distributed over the entire area, and the foamed plastic material 3 Since partial subsidence is difficult to occur because it is blocked by the sheet-like material 2, uneven subsidence and excessive subsidence are extremely unlikely to occur.

Since the construction of the civil engineering structure 4 is carried out on a stable surface provided with the foamed plastic material 3, it can be carried out almost in the same way as ordinary work on the ground. In particular, the ground obtained by the construction method of the present invention has a supporting capacity of 1
Combined with the weight reduction achieved by the foamed plastic material 3, it becomes extremely stable, making it possible for civil engineering structures 4 to withstand ground subsidence.
It is possible to reliably prevent damage to the

[Example] Fig. 1 shows a case where a bird path is constructed as a civil engineering structure 4 using the construction method of the present invention.

In the figure, 1 is soft ground, and a sheet material 2 is laid on the surface of the soft ground.

Soft ground 1 means -axial compressive strength of 0.25 kg/cm2
Refers to the following soils, especially those with -axial compressive strength of 0.
Ground with a weight of less than 1 kg/cm2 is called ultra-soft ground.

As the sheet material 2, for example, a film or sheet of rubber or synthetic resin, a woven or knitted fabric such as a single layer of fabric, a nonwoven fabric made of short or long fibers, a net made of plastic or fibers, etc. can be used. can. Among them,
Woven fabrics, knitted fabrics, and long-fiber nonwoven fabrics (spunponds) are preferred because they can drain water that causes slippage with the surface of the soft ground 1, have high frictional resistance, and are easy to obtain with high strength.

It is preferable that the sheet material 2 has a tensile strength of 50 kg and 15 cm width so as to be able to withstand the tension that will be applied due to the load applied from above, and also have a tensile strength of 40% or more in order to prevent sudden breakage. It is preferable that the material has a modulus of elasticity.

The sheet-like material 2 not only supports the load from above, but also serves to protect the foamed plastic material 3 provided thereon from wood chips, tree roots, rocks, stones, etc. in the soft ground g11. From this point of view, the sheet-like material 2 is preferably a felt-like nonwoven fabric having a thickness of two or more layers.

The above-mentioned sheet-like material 2 can be brought into the site as a roll, pulled out and laid, or formed into a required area in advance and rolled out on the site, etc. to cover the soft ground 1.
laid on the surface. When using a plurality of sheet-like materials 2, it is preferable that their seams are firmly connected.

After laying the sheet-like material 2, the foamed plastic material 3 is provided directly on it.The foamed plastic material 3 may be provided by foaming plastic on the sheet-like material 2, for example, by foaming polyurethane in-situ. It is preferable to lay out pre-formed boards or blocks side by side, as it is easier to adjust their properties and height. When laying out boards or blocks, it is preferable to use one piece as much as possible. It is preferable that the size of each unit be at least 5cm thick, at least BOc width, and at least 180cm long, so that the boards or blocks can be laid out side by side, for example, in a grid. It is preferable to simply connect them to each other by piercing or the like, as this will strengthen the integrity of the whole and make it easier to prevent uneven settlement.

As for the material of the foamed plastic material 3, when it is made into a plate or block shape, polyurethane, polystyrene, polyethylene, polyvinyl chloride, etc. can be used, and whether it is an extrusion foam molded product or a bead foam molded product, It's okay.

The foamed plastic material 3 has the strength to support the load and has sufficient buoyancy against the soft ground 1.

The density is 10kg/m3 to 50kg/m3, the compressive strength in the thickness direction is 1kg/cm2 to 10kg/cm2, and the elastic modulus in the thickness direction is 30kg/cm2 to 200kg/cm.
2. The bending strength is preferably 1 kg/cm2 to 10 kg/cm2, and the water absorption rate is 10 MaoI to prevent the buoyancy from decreasing due to water absorption! %
The following are preferred. From this point of view, when using a plate or block shape as the foamed plastic board 3, an extruded foamed polystyrene board is optimal.

The height of the foamed plastic material 3 is determined based on the purpose and weight of the civil engineering structure 4 to be constructed thereon, the properties of the soft ground 1, etc.

In this embodiment, a farm road is constructed as a civil engineering structure 4 on the foamed plastic material 3 provided as described above. To further explain this, the foamed plastic material 3
After sprinkling sand 5 on top, an embankment 6 is applied, and a roadbed 7 made of chestnut or the like and a surface layer 8 made of asphalt or the like are further provided to form a farm road.

The sand 5 is for protecting the foamed plastic material 3 from stones, rocks, etc., and chestnuts, etc. contained in the embankment 6, and can be omitted if the embankment 6 does not contain a large amount of large stones, rocks, etc. Yes, the civil engineering structures 4 include roads other than farm roads, buildings, etc., as well as developed land.

FIG. 2 is an explanatory diagram of another embodiment, in which the foamed plastic material 3
is wrapped in a sheet-like material 2. This wrapping of the foamed plastic material 3 by the sheet-like material 2 is particularly useful when the foamed plastic material 3 is in the form of a plate or block. can be made strong and stable. Therefore, uneven settlement when the soft ground is extremely soft can be more reliably prevented. Furthermore, by integrating the foamed plastic materials 3, the dispersion and support effect of the vertical load is strengthened, so that the stacking height of the five foamed plastic materials 3 can also be reduced. Furthermore, since the upper surface of the foamed plastic material 3 is also covered with the sheet-like material 2, the upper surface of the foamed plastic material 3 can be protected from stones, rocks, etc., and by selecting the material of the sheet-like material 2, it is possible to prevent water from seeping in from the ground surface. It is also possible to protect the foamed plastic material 3 from gasoline and oil.

The foamed plastic material 3 may be wrapped in one sheet-like material 2, but it may also be wrapped in two upper and lower sheet-like materials 2. Also, if the stacked height of the foamed plastic material 3 is high, , only the lower part may be wrapped with the sheet-like material 2, or the whole may be wrapped in several stages.

Next, a concrete example of calculation is shown.

A trial calculation was made for the case of constructing a farm road by embanking on extremely soft ground. The local ground is originally a reservoir area, and -13
The area up to m is corroded, the area below -18 m is silite, and the soft layer continues up to 124 m. The ground data is shown in the table below.

The sheet-like material was a nonwoven fabric made of polyester long fibers, and the foamed plastic material was a plate-like extruded foamed polystyrene plate.

The properties of this polyester long fiber nonwoven fabric and extruded foamed polystyrene plate are as follows.

I used a 10m x 25cm piece made by cutting a 2m x 100cm original fabric at 25mm length and sewing them side by side.

Thickness 2.8■ Weight 300g/Peng 2 Tensile strength Vertical 75kg 15c layer width Width 65〃 Elongation Vertical 65% Width 65% Dimensions 10cm /c+s2 or more 5% strain bending strength 3
kg/c Layer 2 or more Moisture content 10voj)
The following are the results of trial calculations assuming that a farm road is constructed using sand with a thickness of 1 cm and a layer of sand on top of the mountain with a thickness of 25 cm.

(1) As in the construction method of the present invention, when sheet materials and foamed plastic materials are used together, the
It is calculated that layer C will sink, and the area equivalent to embankment is 30c.
m remains on the ground.

(2) If a 50 cm embankment is made by simply laying sheet-like materials, it is calculated that the embankment will sink by 42 cm when the consolidation settlement stabilizes, meaning that almost the entire embankment area will sink.

(3) If only a plate-shaped foamed plastic material is provided, not only will the settlement be greater than when a sheet-shaped material is used in combination, but it is expected that uneven settlement will occur from plate to plate.

[Effects of the Invention] According to the present invention, not only good workability can be obtained even on extremely soft ground, but also stable ground without uneven settlement can be easily obtained.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of one embodiment of the present invention, and FIG. 2 is an explanatory diagram of another embodiment. 1: Soft ground, 2: Sheet material, 3: Foamed plastic material, 4: Civil engineering structure.

Claims (1)

[Claims] 1) A method for improving soft ground, which is characterized by laying a sheet-like material on the surface of the soft ground, placing a foamed plastic material directly on the sheet-like material, and constructing a civil engineering structure on top of it.