KR102296412B1 - Method of filling void space with polyurthane foam for emergency treatment - Google Patents

Abstract

The present invention relates to a small-scale underground cavity reinforcement method for reinforcing the cavity by filling the cavity by injecting a filler into the underground cavity. In the present invention, it is characterized in that polyurethane foam, which is an intumescent material, is used as a filler.
The present invention comprises the steps of filling the cavity by injecting polyurethane foam into the cavity formed underground, expanding and curing the cavity, and laminating the soil on the filling portion formed by the polyurethane foam to form a cover portion. And it is possible to further strengthen the bearing capacity of the cavity by installing a plurality of meshes in the cavity, or by supporting the poles.

Description

Method of reinforcing underground cavities using polyurethane foam for mine damage prevention emergency measures

The present invention relates to a cavity reinforcement method for reinforcing the ground or closing the cavity by filling a cavity in the ground, particularly a cavity connected to the surface in a mine area, with a filler.

1 is a schematic diagram of the ground subsidence of the mine area. Referring to FIG. 1 , when ore such as coal or limestone is mined, a mine cavern called a so-called goaf is formed at the location where the ore was mined. Over time, the cavity expands upward due to various causes, or the ground above the cavity relaxes, and eventually the surface collapses.

In particular, in the case of limestone mines, this problem is more serious. Limestone is easily soluble in groundwater. Groundwater flows in and fills the mines in the abandoned mine, and the limestone is melted by the groundwater, increasing the risk of ground collapse at the top of the cavity.

Also, even if it is not a mine or an abandoned mine, cavities often occur in the ground due to various reasons. As shown in the photo of FIG. 2 , a cavity that can cause a safety accident is formed at a considerable depth even on a hiking trail. In order to prevent safety accidents due to these cavities, reinforcement of the cavities is required.

The size of the community varies widely. There are cases where it is local as shown in the photo of FIG. 2, but there are cases where it appears in a wide range, such as subsidence of the ground. For large cavities, full-scale ground stabilization construction should be performed using cement, aggregate, grout, etc., but for small cavities, reinforcement should be performed at a level sufficient to prevent safety accidents in consideration of economic feasibility and efficiency.

In particular, small-scale cavities are sporadically distributed and most often occur in places where infrastructure such as roads and electricity are not provided. Therefore, it is very difficult to transport aggregate or grout material. This is because aggregates or grout materials are difficult to transport due to their large weight or volume. Also, transportation cost is a bigger problem than material cost. Moreover, heavy equipment such as a pump car is needed to fill them in the cavity, but there is a problem that it is not easy for such heavy equipment to enter a mountainous area or a small abandoned mine.

Accordingly, a method for simply reinforcing small cavities scattered in remote areas where roads and electricity are not provided is required.

An object of the present invention is to provide a reinforcement method capable of filling small cavities formed in the ground such as mine cavities very simply and economically using polyurethane foam fillers to solve the above problems.

The method for reinforcing an underground cavity using a polyurethane foam for a first aid project for mine damage prevention according to the present invention for achieving the above object includes: filling the cavity by spraying the polyurethane foam into the cavity formed underground to expand and harden; and laminating soil on the filling part formed by the polyurethane foam to form a covered soil part.

In the present invention, in order to ensure stable construction of the filling part, and to secure support for external load after filling, a net may be further installed. That is, further comprising the step of installing a mesh in the cavity in a state spaced upward from the bottom of the cavity, it is possible to form the filling part on the mesh.

In one example of the present invention, the mesh and the filling part may be alternately stacked in a vertical direction to form a multi-stage.

In addition, the rim portion of the mesh may be fixed to the surface of the outside of the cavity, or the mesh may be completely inserted into the cavity to fix the mesh to the inner wall of the cavity.

In an example of the present invention, at least one lateral support traversing the cavity is installed to be spaced apart from the bottom of the cavity, and the filling part may be formed on the support. In particular, it is preferable that a plurality of the lateral supports are arranged in a direction crossing each other.

In one embodiment of the present invention, it is preferable to install at least one longitudinal support supported on the bottom or inner wall of the cavity and disposed in the vertical direction, and the filling part is formed on the longitudinal support.

Also, in another example of the present invention, after arranging at least one lateral support disposed in the transverse direction on the longitudinal support, after installing the mesh on the lateral support, it is preferable to form the filling part on the mesh. .

In the present invention, the polyurethane foam can be used as rigid or flexible, and the rigid and flexible polyurethane foams are alternately laminated, or the flexible polyurethane foam is first laminated, and then the rigid polyurethane foam is laminated thereon. can

According to the present invention, by injecting and expanding polyurethane foam, which is an intumescent material, for underground cavities requiring reinforcement such as mining, tunnels, ground depressions, groundwater closed wells, etc. Compared to that, it has the advantage of being very easy to construct and economical.

In particular, in the case of remote mountainous areas, infrastructure such as roads is not sufficient to apply the filling method using concrete, aggregate, etc., but in the case of polyurethane foam, it is light and the volume before expansion is very small.

In addition, polyurethane foam is chemically stable even in acidic and alkaline environments, so it has the advantage of being able to minimize the secondary environmental impact after construction even in an underground space where groundwater exists.

In addition, polyurethane foam has weak strength compared to concrete, but is not rapidly destroyed, and is advantageous in maintenance.

1 is a view simulating the subsidence of the ground in the mine mining cavity.
2 is a photograph of a small-scale underground cavity.
3 is a schematic diagram of a first embodiment of the present invention;
4 is a schematic diagram of a second embodiment of the present invention;
5 is a schematic flowchart of a small-scale underground cavity reinforcement construction method according to a third embodiment of the present invention.
6 and 7 are diagrams for explaining the third embodiment.
8 is a view for explaining the longitudinal support and the transverse support.
9 is a view viewed from above after the installation of the mesh.
10 is a photograph taken of the work process of spraying the polyurethane foam into the cavity through the spray gun.
11 is a photograph of a state in which a mesh is installed after filling the lower cavity with polyurethane foam to the middle.
12 is a photograph of filling the upper part of the cavity by filling the polyurethane foam again on the mesh in FIG. 11 .

An object of the present invention is to fill and reinforce an underground cavity. Here, the underground cavity includes a cavity formed downward from the surface, as well as a cavity extending downward from the underground tunnel again.

The above cavities may be formed for various reasons, and in the present invention, there is no separate limitation with respect to the cause of the formation of the cavities. am. The cavity is formed vertically or inclined. Although the present invention can be applied to a horizontal cavity, the horizontal cavity has less risk of a safety accident than a vertical cavity or an inclined cavity, so a vertical cavity or an inclined cavity will be described as an example.

In addition, the present invention can prevent contamination of groundwater and aquatic ecosystems by injecting and sealing fillers into conduits such as closed groundwater wells or small-scale waterways not managed in mines, wastewater pipes, and wastewater pipes.

The point that the research team of the present invention focused on in reinforcing the underground cavity is the ease of construction and economic feasibility. As described above, the area where the cavity is generated in the abandoned mine or underground is mainly located in the remote mountainous area, so it is not easy to transport the equipment. Therefore, small cavities occurring in these areas should be able to be constructed with minimal equipment and logistics.

In addition, we focused on a method that can safely reinforce the cavity without using heavy and bulky materials such as aggregate. The solution to these problems came down to material selection. That is, in the present invention, an intumescent material is used to fill the cavity. More specifically, in the present invention, polyurethane foam is used.

Polyurethane foam is manufactured using polyurethane and a foaming agent.

Polyurethane is a generic term for urethane-bonded (-NHCOO-) polymer compounds made by combining an alcohol group (OH) and an isocyanate group (NCO). Polyurethane is a type of plastic and has the characteristics of being tough and resistant to chemicals. It is used in electrical insulators, structural materials, foam insulation materials, foam cushions, and elastic fibers. Because of its elasticity, it is also used as a substitute for rubber.

A blowing agent is a generic term for a substance that creates bubbles by mixing with plastic or rubber. There are two types of blowing agents: chemical blowing agents and physical blowing agents. Chemical foaming agents use the activity of isocyanate groups to react with water to form carbon dioxide and foam. Physical blowing agents form bubbles by entraining a gas or generating heat of reaction using a decomposing or evaporative blowing agent.

Polyurethane foam is obtained by mixing two components: isocyanate (isocyanate) or methylene diphenyl diisocyanate (DMI) (component A) and polyol resin (component B). The two components are labeled A for isocyanate and B for polyol in the foam mix. When these components are mixed and mixed, they swell and, depending on the components, the volume expands to approximately 30 times the original liquid state. Polyurethane foam is inert once fully expanded and dried, and molecules are cross-linked to maintain their shape regardless of external environmental conditions such as temperature changes, and they are not decomposed and are semi-permanently preserved. . In particular, polyurethane foam has the advantage that necessary physical properties such as density and strength can be strengthened by additionally adding additives.

In the present invention, by injecting and expanding the polyurethane foam into the underground cavity, it is intended to fill the cavity. Polyurethane foam is effective for cavity filling as it expands about 30 times compared to its original volume as an expandable material as described above. In addition, the raw material state has the advantage of being light and easy to transport compared to aggregate or cement in a liquid state.

The first embodiment, which is the most basic form of the present invention, is to fill the small cavity (c) by spraying polyurethane foam as shown in FIG. 3 . If the cavity (c) is not deep, the polyurethane foam is sprayed from the bottom surface of the cavity (c) to expand. The polyurethane foam filled in the cavity (c) is referred to as the filling part (10). However, while spraying and expanding the polyurethane foam in stages, the upper surface of the filling part 10 reaches only a certain height of the upper part of the cavity (c). The upper part of the cavity (c) is completely filled by filling the filling part (10) with soil to form the covering part (20).

Forming the cover portion 20 in the present invention is also for the purpose of preventing the polyurethane foam filling portion 10 from harming the surrounding landscape by being exposed to the outside, but technically it is to prepare for a fire. Although polyurethane foam has been described above, there are various advantages in physical properties, but harmful gas may be generated when burned. This is to prevent harmful gas from being discharged from the polyurethane foam filling part 10 in response to a forest fire, etc. by forming the covering part 20 using soil. In addition, even if it is not a wildfire or a big fire, it is desirable to form a cover part on the upper part to prevent deformation in an unexpectedly high temperature environment.

In the first embodiment shown in Figure 3, since the cavity is not deep, the cavity is completely filled with polyurethane foam, but if it is a deep cavity, it is uneconomical to completely fill the cavity with polyurethane foam, and the effectiveness is not large. As previously described, the present invention does not permanently and completely reinforce the cavity like a full-scale ground reinforcement method using a grout material. More fundamentally, reinforcement using grout materials is not easy for small cavities located in remote mountainous areas, and even if possible, it is uneconomical compared to efficiency. In other words, it is enough to reinforce the small cavity to a level that can prepare for a safety accident using polyurethane foam. This view is also applicable to the case of deep cavities. That is, it is uneconomical and inefficient to fill all the deep cavities with polyurethane foam. Therefore, in the second embodiment of the present invention, when the cavity is deep, filling is performed only from the top of the cavity, not from the bottom of the cavity. This can be easily achieved because polyurethane foam is used as the filling material. This will be described in detail.

4 shows an example of filling the empty road according to the second embodiment of the present invention. As shown in FIG. 4 , in the present invention, polyurethane foam was filled only from the middle part of the cavity (c) to the upper part to form the filling part 11, and the soil part 21 was formed by laminating soil thereon. Polyurethane foam is sprayed like shotcrete. When polyurethane foam is sprayed toward the inner wall of the cavity (c), the polyurethane foam is hardened while attached to the inner wall surface. And if polyurethane foam is gradually sprayed toward the central part of the cavity based on the polyurethane foam attached to the inner wall, the filling part 11 can fill the cavity (c) without being supported on the bottom surface. Moreover, since the inner wall surface of the cavity (c) is not flat and curved, the polyurethane foam expands to fill the curvature of the inner wall of the cavity (c). Accordingly, it is possible to prevent the filling part 11 from being separated downward due to the frictional force between the outer surface of the filling part 11 and the inner wall of the cavity c. In particular, in the case of an inclined cavity as shown in FIG. 4 , since the filling part 11 is inclined with respect to the gravity direction and a part of the filling part 11 is supported on the inner wall of the cavity, it is possible to more effectively prevent the filling part from leaving. Even in the case of a vertical cavity, the filling part will not be easily separated downward due to the frictional force between the filling part and the inner wall of the cavity. Moreover, in the case of a small cavity to which the present invention is applied, it is unlikely that a heavy load such as a vehicle will be applied thereon. Since this is mainly to prevent safety accidents caused by a fall, the filling unit only needs to be able to support the weight of a person. Even if the polyurethane foam is partially filled as in this embodiment without completely filling the cavity, a weight of about 100 kg will be able to withstand by the frictional force and some supporting force between the polyurethane foam and the inner wall of the cavity.

In the first and second embodiments described above, the cavity was reinforced only by the filling part formed of polyurethane foam and the covering part laminated on the upper side of the filling part. In the third and fourth embodiments to be described below, by installing a mesh, it is possible to not only facilitate spraying of the polyurethane foam, but also to further increase the bearing capacity for the load applied to the filling part.

Fig. 5 is a schematic flowchart of the third embodiment.

Referring to FIG. 5 , in the method for reinforcing a small-scale underground cavity according to the third embodiment, first, a longitudinal support 31 and a transverse support 32 are installed in the cavity (c), respectively. The longitudinal support 31 is supported on the bottom surface (FIG. 6) or the inner wall (FIG. 7) of the cavity c, as shown in FIG. 6 or FIG. 7, and is disposed in the vertical direction. Here, the up-down direction includes a vertical direction and means an angle close to the approximately vertical direction even if it is not vertical. Although only one longitudinal support 31 may be installed as shown in the drawing, a plurality of longitudinal supports 31 may be disposed depending on the embodiment.

The transverse support 32 is coupled to the longitudinal support 31 , and is disposed in a horizontal direction or at an angle close to the horizontal direction. Although only one circumferential support 32 may also be disposed, a plurality of them may be disposed to cross each other, for example, in a cross shape as shown in FIG. 8 . Of course, the lateral supports may be arranged parallel to each other without intersecting each other.

The longitudinal support 31 and the transverse support 32 are for supporting the filling part 12 disposed thereon. According to an embodiment, only a plurality of longitudinal supports 31 may be installed to support the filling part 12, and as in this example, the longitudinal support 31 and the transverse support 32 are included in the filling part 12. can support Unlike the above-described embodiments, in this embodiment, the filling part 12 can be more firmly supported by installing a support structure under the filling part, and even if a load is applied on the filling part, the filling part 12 is separated to the lower part. I never do that.

After installing the longitudinal support 31 and the transverse support 32 , the mesh 40 is installed. The form viewed from the top after the mesh 40 is installed is shown in FIG. 9 . The mesh 40 is inserted into the central portion of the cavity (c), the rim is fixed to the outside of the cavity (c), that is, on the ground surface. The part inserted into the cavity (c) rests on the transverse support (32). As a whole, the mesh 40 is disposed along the inner wall of the cavity.

The reason for installing the mesh 40 is two. First, it is because the polyurethane foam can be easily fixed. When filling polyurethane foam from the middle rather than the bottom of the cavity, it must be sprayed from the inner wall of the cavity and extended to the center. because it's done Of course, since the transverse support 32 is installed at the lower part of the mesh 40, polyurethane spraying may be easier.

In addition, when the net 40 is installed and then fixed on the ground, the net acts as a support for the filling part, so that the bearing capacity for the load is further increased. In this embodiment, the net 40 is fixed to the ground by using the nail 50, but depending on the embodiment, after inserting the entire net into the cavity, the net may be fixed to the inner wall of the cavity.

And the net may be installed only one, or a plurality of meshes may be arranged to be spaced apart from each other along the height direction of the cavity. When a mesh is installed in multiple stages and polyurethane foam is sprayed, the polyurethane foam and the mesh are alternately arranged. In other words, a plurality of meshes are spaced apart from each other and inserted into the filling part. If a plurality of meshes are installed, the bearing capacity for the load is reinforced that much, and when spraying polyurethane foam, the fixable area increases and spraying becomes easier.

As described above, after installing the longitudinal support 31 and the transverse support 32 and the mesh 40, polyurethane foam is sprayed as in the previous embodiments to form a filling part, and finally the soil is laminated This completes the reinforcement of the cavity by forming a covered soil part.

In the fourth embodiment, one or a plurality of nets are installed as in the third embodiment, but unlike the third embodiment, the support is not installed. Therefore, a detailed description will be omitted.

On the other hand, in the present invention, instead of the support, a method of filling the three-dimensional network structure in which the wires are bundled in the lower part of the cavity first, and then filling the polyurethane foam thereon may be adopted. The three-dimensional network structure has a large volume but small weight because there are many voids inside the thin wire. For example, it is possible to use a form such as a commercially available iron scrubber, or a network structure having a smaller density than an iron scrubber. The network structure may be integrally formed, but may be filled with a plurality of network structures in the shape of a small lump.

10 to 12 are photographs showing an actual cavity reinforcement process. As shown in Fig. 10, in the present balgo, polyurethane foam is filled to the lower region or middle region of the cavity using a spray gun, etc., and a mesh is installed as shown in Fig. 11 . After that, as shown in FIG. 12 , it is a photograph of filling the upper part of the cavity by filling the polyurethane foam again on the mesh. Covering and planting can be carried out later.

A key feature of the present invention is that reinforcement is performed using polyurethane foam fillers in areas requiring reinforcement by fillers, such as abandoned mines, sinkholes, and ground depressions. Polyurethane foam is very useful to replace fillers such as aggregate and cement used in existing underground cavities. First, it is 1/50 times lighter than concrete and, of course, has good portability. The fact that the construction can be carried out by manpower in remote areas where no roads have been established is a great advantage in terms of the simplicity and economic feasibility of construction. Furthermore, the damage to vegetation is minimal because construction is possible without opening a road for the transport of equipment.

And it can be applied to a large cavity because its volume expands by about 30 times that of the raw material depending on the composition ratio. It is also impervious and resistant to erosion, so it is excellent for application to underground cavities where groundwater exists.

In addition, polyurethane foam is chemically very stable. When eroded by acidic and alkaline environments, the effect is limited to the surface and does not affect the structure of the final expanded foam. Since it does not react with groundwater, etc., there is an advantage that there is no secondary environmental pollution after construction.

However, the strength of polyurethane foam is weaker than that of cement, concrete, and grout, which are conventional reinforcing materials. However, the strength problem is compensated for by the deformation characteristics of polyurethane foam. That is, when polyurethane foam is applied with a vertical force, half of the load moves horizontally. When a load is applied beyond the compressive strength, creep phenomenon occurs, causing a gradual deformation rather than an abrupt failure, so rapid collapse can be prevented.

In addition, in the present invention, in order to supplement the load bearing capacity of the polyurethane foam, the net can be installed singly or in plurality, and furthermore, the bearing capacity for the load can be supplemented by installing a longitudinal support and/or a transverse support in the lower part.

Above all, when polyurethane is used, economical efficiency is excellent. That is, it can be constructed at a cost of about 30-60% compared to concrete construction.

On the other hand, the polyurethane foam used in the present invention can use both hard and soft. Considering economic feasibility, it is possible to alternately spray hard and soft polyurethane foam, or to construct a soft polyurethane foam on the lower side and a rigid polyurethane foam on the upper side.

The unexplained reference number g indicates the ground.

c: cavity, g: ground
10, 11, 12: filling part
20, 21, 22: covered part
31: longitudinal support, 32: transverse support
40: net
50: nail

Claims (12)

Filling the cavity by injecting polyurethane foam into the cavity formed underground to expand and harden; and
Including; stacking the soil on the filling part formed by the polyurethane foam to form a covering part;
At least one transverse support traversing the cavity is installed to be spaced apart from the bottom of the cavity, and after installing the mesh on the transverse support, the rim of the mesh is fixed to the surface of the outside of the cavity, the mesh Forming the filling part on top,
The mesh and the filling part are alternately stacked in the vertical direction to form a multi-stage, the mesh is completely inserted into the cavity, and the mesh is fixed to the inner wall of the cavity,
A plurality of the transverse supports are arranged in a mutually intersecting direction, and at least one longitudinal support is supported on the bottom or inner wall of the cavity and disposed in the vertical direction, and the filling part is formed on the longitudinal support,
The polyurethane foam can be used in rigid or flexible, and the rigid and flexible polyurethane foams are alternately laminated, or the flexible polyurethane foam is first laminated, and then the rigid polyurethane foam is laminated thereon, characterized in that A small-scale underground cavity reinforcement method. delete delete delete delete delete delete delete delete delete delete delete

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