JP2772992B2 - Civil engineering method using foamable resin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a civil engineering method for producing a resin foam having a uniform foaming state and compressive strength when foaming resin is foamed to a required shape on site to perform embankment, formation of artificial ground, road widening work, and the like.

[Prior art]

Attempts have been made in the past to make use of the lightweight properties of the foamed resin to fill in depressions or to make them a part of artificial ground. For example, a foamable resin is molded into a foam block having a predetermined shape at a factory, the foam block is piled up on an original ground to be embanked, and a concrete floor plate, a wall protection material and the like are stretched on the surface layer to finish. Further, a reinforcing material such as a reinforcing bar is arranged inside to improve the structural strength. When stacking foam in this way to form the ground,
A gap easily occurs between the foam blocks. Accordingly, Japanese Utility Model Laid-Open No. 63-81941, Japanese Utility Model Laid-Open No. 63-81942, and the like introduce a method of forming irregularities on the surface of a foam block and engaging the irregularities in order to eliminate the deviation. I have. However, the method of transporting the foamed block after foaming at the factory to the site and stacking the foamed block in a predetermined shape takes time and effort to transport and handle. For example, a large block of about 2 × 1 × 0.5 m is used as this type of block, but such a large block requires labor for transportation despite its light weight. In addition, the transportation is substantially as if carrying air, and there is much waste. In addition, as the size of the block becomes larger, it is necessary to prevent the formation of a gap between the block and the block that is laid flat by flattening the original ground on which the work such as embankment is to be performed. Further, Japanese Patent Application Laid-Open No. 47-19617 discloses that an unfoamed resin such as urethane, vinyl chloride, styrene or the like is sprayed on a depression or a roadbed, and then a foaming reaction is performed to fill the depression or the like. ing. However, the publication does not specifically teach how to foam the resin. However, simply foaming the resin often does not have the required contour on the resin body surface after foaming due to uneven foaming or the like. In addition, when foaming is performed at the free interface, the surface strength of the foam is not sufficient, and dents and the like easily occur when a tread pressure is applied.

[Problems to be solved by the invention]

The present inventors, as a method of forming the ground having the required strength while taking advantage of the on-site construction, as a method of forming foamed resin beads on the original ground partitioned by the formwork, heating the resin by heating gas A method for constructing artificial ground by foaming beads has been developed. Incidentally, when the ground is constructed by foaming the resin beads, uneven foaming of the resin beads tends to occur. As a result, defects such as generation of irregularities on the surface of the resin body after foaming and generation of internal cavities will occur. Such defects are:
It is presumed to be due to the fluctuation of the foaming atmosphere of the resin beads. Therefore, an object of the present invention is to form a resin foam ground having a uniform foam structure and a compressive strength by uniformly controlling the foaming atmosphere throughout the entire foaming process, thereby uniformly foaming the resin beads. And

[Means for Solving the Problems]

In order to achieve this object, the civil engineering method of the present invention sprays beads made of foamed resin directly on the original ground or through a fine-grained layer, and freely raises and lowers the formwork via a space above the beads. The pressure control valve provided in the formwork is opened and closed according to the pressure in the space. As the fine-grain layer, sand particles are typically used. However, if other inexpensive granular materials are available, they can be used instead of sand particles.

[Action]

For example, when styrene resin beads are heated and foamed, the foaming reaction proceeds according to a time-temperature curve as shown in FIG. That is, foaming is partially started at a temperature of about 30 ° C., but at this time, the foaming is very small, and the accompanying expansion and pressure rise are also small. As the temperature rises, foaming progresses rapidly,
The volume expansion and pressure rise are also steep. Then, at the end of foaming, the foaming reaction becomes slow again, and the volume expansion and the pressure rise become slow. As described above, since the speed of the foaming reaction fluctuates according to time and temperature, when foaming proceeds in a free atmosphere, a foam having a high porosity is obtained at a location where foaming is rapidly performed, and foaming is slow. A dense foam is obtained at the point where the process has progressed. As a result, the foam as a whole does not have a uniform structure and strength. In this regard, in the present invention, the pressure of the atmosphere is controlled in accordance with the progress of foaming. That is, at the stage where foaming is rapidly performed, the atmospheric pressure is increased. This allows
Although the foaming reaction is slightly suppressed, the porosity of the formed foam is reduced, and the strength is improved. On the other hand, when the foaming reaction is slow, the atmospheric pressure is reduced. This accelerates the foaming reaction and prevents the formation of a foam having an overly dense structure. Therefore, formation of the ground utilizing the advantages of the lightweight and the volume occupancy per unit weight, which are advantages of the resin foam, is performed. At the end of the foaming reaction, it is preferable to increase the atmospheric pressure. Thereby, the surface layer of the resin foam is densified, and a ground strong against treading pressure is formed. In addition, as the pressurization at this time, the form is lowered,
A method of pressing against the surface of the foamed resin can also be adopted.

【Example】

Hereinafter, the present invention will be described in detail with reference to the drawings by using an example applied to embankment of a depression. In the present embodiment, as shown in FIG. 1, a predetermined embankment is formed in a depression 2 formed in the original ground 1. At the bottom of the depression 2, a sand layer 4 in which a gas injection pipe 3 is embedded is provided. Both ends of the gas injection pipe 3 are supported by columns 5 and 6, and are maintained at a constant height from the bottom surface of the depression 2. Prop 5, 6
Is driven into the soil of the original ground 1 and acts as a pile. In addition, at least one of the supports 5,6
Is formed by a pipe, a part of which is opened inside the gas injection pipe 3, and is connected to the boiler 9 via the air supply pipe 7 and the air supply pump 8. Alternatively, the air supply pipe 7 may be connected to the gas injection pipe 3 by a separate piping system. On the sand layer 4, beads 10 of foamable resin such as styrene resin are sprayed. Then, a mold 12 is arranged above the resin beads 10 via an internal space 11. Formwork 12
Are provided with holes through which the columns 5, 6 are inserted, and can be moved up and down by appropriate means using the columns 5, 6 as guides. Reference numeral 13 denotes an exhaust pipe penetrating the mold 12 and opening into the internal space 11. The exhaust pipe 13 is provided with a pressure control valve 14 for adjusting the atmospheric pressure of the internal space 11 according to the progress of the foaming reaction. Next, a procedure for forming a ground with a resin foam using this apparatus will be described. A styrene resin having an average particle size of 0.9 mm was used as the resin beads. This resin starts a foaming reaction in relation to temperature and time as shown in FIG.
Expanded to about 30 to 45 times the foam, the density after foaming is about 0.01
It was 5 g / cm ³ . The depression 2 was a test excavation with a cross section of 1 m x 1 m and a depth of 80 cm. A gas injection pipe 3 having a diameter of 40 mm was placed in the depression 2 where the test was excavated, and the gas injection pipe 3 was buried in a sand layer 4 formed by spraying sand with a thickness of 60 mm. The columns 5 and 6 supporting the gas injection pipe 3 were driven into the ground of the depression 2 at a depth of 40 cm. Then, after the resin beads 10 having a thickness of 23 mm are sprayed on the sand layer 4, the mold 12 is inserted into the supports 5, 6, and the distance from the surface of the sand layer 4 to the lower surface of the mold 12 (hereinafter, this is referred to as The height of the formwork 12) was set to 30 mm. In this state, steam at a temperature of 100 ° C. is supplied from the boiler 9 to the gas injection pipe 3 via the air supply pump 8 and the air supply pipe 7 at a rate of 0.1 / min.
It was supplied at a flow rate of m ^3. Then, the height of the mold 12 and the pressure of the internal space 11 were varied as shown in FIG. 2 according to the elapsed time of the steam injection. At this time, as shown in FIG. 3, the height of the mold 12 and the opening of the pressure control valve 14 were adjusted on the basis of a program corresponding to a predetermined volume change after foaming of the resin beads. After blowing water vapor for 17 minutes, resin beads 10
Expanded from the surface of the sand layer 4 to a height of 70 cm. At this point, in order to make the surface of the resin foam dense, the mold 12 was lowered and the surface of the foamed resin was pressed. Next, the mold 12 was removed, and the formed resin foam was taken out of the depression 2 and cut in the vertical and horizontal directions, and the foaming state inside was observed. As a result, it was found that the foam had a substantially uniform foam structure in both directions.When a test piece was cut out from the foam and the compressive strength was measured,
Compressive stress value when giving 4% compressive strain is 1.5 ~ 2.0kg / c
m ² range. From this, it can be seen that the ground having a strength sufficiently larger than 0.5 kg / cm ^2, which is the average tread pressure applied when the vehicle is running, is obtained. In addition, the resin foam formed in the depression 2 has the pillars 5 and 6 disposed therein as a reinforcing material, so that most of the tread pressure by the traveling vehicle and the like is received by the pillars 5 and 6 and the solid ground is formed. Can be used. In addition, since the lower ends of the columns 5 and 6 are driven into the bottom surface of the depression 2, the resin foam is reliably secured at a predetermined position on the original ground 1. In the above embodiment, the embankment of the depression 2 is described as an example. However, the present invention can be applied to the creation of a sloping land, the expansion of the road width, and the like by the same method. In such construction, since one side of the resin foam is open, the columns 5, 6 for fixing the foamed resin at a predetermined position on the original ground are used.
Is more pronounced.

【The invention's effect】

As described above, in the present invention, when the resin beads are foamed on site to construct the ground, the height of the frame and the pressure of the internal space are adjusted in accordance with the foaming of the resin beads. . Therefore, the inside and outside of the foamed resin are in a substantially uniform foaming state, and the compressive strength is not locally reduced. Thus, according to the present invention, it is possible to easily construct a ground having sufficient strength to withstand tread pressure.

[Brief description of the drawings]

FIG. 1 is a view for explaining an embodiment in which the present invention is applied to embankment of a depression, FIG. 2 is a graph showing an example of a variation in height of a formwork and a pressure in an internal space, and FIG. Is a graph showing the relationship between temperature and time. 1… Original ground 2… Slope 3… Gas injection pipe, 4: Sand layer 5,6… Post, 7… Air supply pipe 8… Air supply pump, 9… Boiler 10… Resin Beads, 11 ... Internal space 12 ... Formwork, 13 ... Exhaust pipe 14 ... Pressure control valve

──────────────────────────────────────────────────続 き Continuation of the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) E02D 17/18 E02D 3/00 E01C 3/00

Claims (1)

(57) [Claims] 1. A foamed resin bead is sprayed directly or through a fine-grain layer on an original ground, and a formwork is arranged above and below the bead via a space so as to be movable up and down. A civil engineering method using a foamed resin, wherein a pressure control valve provided on the mold is opened and closed.