JP7497254B2 - How to repair slopes - Google Patents

Description

This invention relates to a method for repairing a slope that repairs a void formed on a slope on which a slope protection structure is installed.

Slope protection work (stabilization measures) on sloping land (embankments, natural ground, etc.) is carried out to prevent the erosion and collapse of the slope. A commonly used method of protection is to install slope protection structures made of concrete or other materials on the slope. For example, one such concrete slope protection structure has a lattice-shaped reinforced concrete slope frame, the inside of which is covered with vegetation or mortar spraying.

When the ground loosens due to more rain than expected or groundwater, the soil behind the slope protection structure can flow out, creating a gap between the slope protection structure and the ground. A construction method has been proposed to fill the gap that has formed between the existing sprayed mortar slope and the ground by filling it with a fluid grout material (see, for example, Patent Document 1). In Patent Document 1, the fluid grout material used is a plastic FM grout mainly made of cement, fly ash, slag, or fly ash and cement, or a slag-based plastic grout mainly made of slag and cement.

Japanese Patent No. 6106836

In the method of Patent Document 1, when the void has a complex three-dimensional shape, the fluid grout material may not fill the void properly. In addition, because the grout material containing cement is relatively heavy, there is a risk that the grout material may slide along the slope, and the method lacks long-term stability.

The present invention has been proposed in consideration of the above problems associated with the conventional technology, and aims to provide a method for repairing slopes that allows for more reliable sealing of voids and has excellent long-term stability.

In order to overcome the above problems and achieve the intended purpose, a method for repairing a slope according to the present invention includes the steps of:
A repair method for filling a void formed on a slope on which a slope protection structure is provided, comprising the steps of:
Inserting a steel bar into an insertion hole formed in the ground constituting the void;
A solidification material is injected into the insertion hole to fix the steel bar to the ground;
injecting a urethane material into the void and foaming the urethane material in the void, thereby filling the void with the resulting polyurethane foam;
The gist of the invention is that a fastening material is attached to the tip of the steel bar protruding from the polyurethane foam to the front side, and the polyurethane foam is sandwiched between the fastening material and the ground.

The slope repair method of the present invention allows for more reliable sealing of voids with polyurethane foam, and the polyurethane foam that fills the voids has excellent long-term stability.

FIG. 2 is a schematic perspective cutaway view showing a slope repaired by the repair method according to the embodiment of the present invention. FIG. 2 is a schematic perspective view showing a slope repaired by the repair method of the embodiment, cut at a position different from that in FIG. 1 . FIG. 2 is a schematic perspective view showing an enlarged view of a main portion of a slope repaired by the repair method of the embodiment. 1 is a schematic perspective view showing a portion of a slope before a void is formed. FIG. FIG. 2 is an explanatory diagram showing the arrangement of steel bars in the repair method of the embodiment. FIG. 4 is an explanatory diagram showing a repair process according to the repair method of the embodiment. FIG. 4 is a main part explanatory diagram showing a repair process according to the repair method of the embodiment. FIG. 4 is a main part explanatory diagram showing a repair process according to the repair method of the embodiment.

Next, a preferred embodiment of the slope repair method according to the present invention will be described below with reference to the attached drawings.

Figures 1 and 4 are schematic perspective views showing a slope 10 on which a slope protection structure 12 is provided. Figure 4 shows the slope 10 before a void S (see Figures 1 to 3) is formed, and Figure 1 shows the slope 10 after the void S formed therein has been restored by the repair method of the embodiment. The slope protection structure 12 of the embodiment is composed of slope frames 14 that are provided to intersect the slope 10 vertically and horizontally, and sprayed concrete 16 that is provided to cover the slope 10 between the slope frames 14. In addition, the slope protection structure 12 of the embodiment has the vertical and horizontal intersections of the slope frames 14 held in place by anchors 18 fixed to the ground.

The repair method for filling the void S in the embodiment and repairing the slope 10 will be described in order. In the embodiment, the void S is formed on the back side of the area including the slope protection structure 12's slope frame 14 and the sprayed concrete 16 due to the runoff of the surface soil on the slope 10 (see Fig. 6(a) and Fig. 7(a)). First, a through hole 20 is formed in the position corresponding to the void S in the sprayed concrete 16 using a boring machine such as a core drill (see Fig. 7(b)). An insertion hole 22 is formed in the bottom surface of the void S in the slope 10 using a boring machine through the through hole 20 (see Fig. 7(c)). A steel bar 24 is inserted from the through hole 20 into the insertion hole 22 (see Fig. 7(d)), and a solidifying material 26 such as cement milk or mortar is injected into the insertion hole 22 to fix the steel bar 24 to the ground J (see Fig. 7(e)). At this time, the steel bar 24 is arranged so that its head protrudes from the through hole 20 to the front side of the sprayed concrete 16.

The steel bars 24 may be general-purpose products such as threaded reinforcing bars and deformed steel bars, and among these, threaded reinforcing bars are preferred because general-purpose nuts 36 can be used as fastening materials. The steel bars 24 may have a nominal diameter in the range of D19 to D32. As described later, since the polyurethane foam 28, which is the filler, is lightweight, it is possible to use steel bars of D19, which is a thin class for civil engineering applications. The steel bars 24 are preferably arranged at intervals of 1.0 m to 2.0 m (1 bar/1.0 m ² to 1 bar/4.0 m ² ) corresponding to the voids S, more preferably at intervals of 1.5 m to 2.0 m (1 bar/2.25 m ² to 1 bar/4.0 m ² ), because this can prevent the ground J from collapsing and properly support the polyurethane foam 28, which is the filler. In addition, the steel bars 24 are preferably arranged in a staggered pattern, because this can prevent the ground J from collapsing and properly support the polyurethane foam 28, which is the filler (see FIG. 5 ). Furthermore, it is preferable to set the depth of insertion of the steel bars 24 into the ground J to a range of 2 m to 5 m, since this can prevent the ground J from collapsing and adequately support the polyurethane foam 28 that is the filler. The conditions for the steel bars 24 described above are set appropriately depending on the hardness (N value) of the ground J, the size of the void S, the density of the polyurethane foam 28 to be filled, and the like.

The size (caliber) of the insertion hole 22 is set larger than the diameter of the bar-shaped steel 24 to be inserted, and is preferably set, for example, to 3 to 5 times the diameter of the bar-shaped steel 24, since this makes it easier to inject the solidification material 26 into the insertion hole 22 into which the bar-shaped steel 24 has been inserted. The depth of the insertion hole 22 may be adjusted to the insertion depth of the bar-shaped steel 24 described above.

The size (caliber) of the through hole 20 is set to be larger than the diameter of the steel bar 24 that passes through the through hole 20. Here, it is preferable to set the size of the through hole 20 larger than the size of the insertion hole 22, as this makes it easier to fill the void S with the polyurethane foam 28. If the through hole 20 is set large, when the nozzle 30 for injecting the polyurethane foam 28 is inserted into the void S from the through hole 20 through which the steel bar 24 passes (see Figures 8(a) and (b)), the nozzle 30 can be directed up, down, left, or right. This makes it easier to fill the void S with the polyurethane foam 28.

After injecting the solidifying material 26 into the insertion hole 22 into which the steel bar 24 has been inserted (see Figs. 6(b) and 7(e)), the urethane material M is injected from the through hole 20 through the nozzle 30 so as to be sprayed into the void S (see Figs. 8(a) and (b)). At this time, it is advisable to inject the urethane material M into the lower part of the void S from the through hole 20 opened at a position corresponding to the lower part of the void S. The urethane material M injected into the void S foams and expands within the void S, thereby filling the void S with polyurethane foam 28 without any gaps (see Fig. 8(c)). The polyurethane foam 28 is a so-called on-site foamed polyurethane foam, which is formed by mixing liquid A (polyol) and liquid B (isocyanate) on-site and spraying it with a spray foaming machine to form a polyurethane foam.

The degree to which the polyurethane foam 28 has filled the void S can be confirmed in various ways, such as by checking whether the polyurethane foam 28 has leaked out from through-holes 20 other than the through-hole 20 through which the nozzle 30 passes, or by viewing the void S with a microscope through the through-hole 20. For example, when the urethane material M is injected from the bottom of the void S, if the polyurethane foam 28 leaks out from the through-hole 20 corresponding to the top of the void S, it is clear that the polyurethane foam 28 has filled up to the top of the void S.

A rigid polyurethane foam with high compressive strength is used as the polyurethane foam 28, and a closed cell structure is preferable because it is water impermeable. It is also preferable to use a lightweight polyurethane foam 28 with a density in the range of 20 kg/ ^m3 to 60 kg/ ^m3 . The conditions for the polyurethane foam 28 described above are set appropriately depending on the size of the void S and the load of the slope protection structure 12 covering the void S.

Next, after removing excess polyurethane foam 28 that has leaked from the through hole 20, the through hole 20 is blocked with a shielding material 32 such as mortar, and the surface side of the polyurethane foam 28 protruding from the sprayed concrete 16 is covered with the shielding material 32 (see FIG. 8(d)). The tip of the bar-shaped steel 24 protruding from the through hole 20 is passed through a hole formed in the plate 34, and the plate 34 is set on the surface of the sprayed concrete 16 so as to cover the through hole 20. A nut 36 is attached as a fastening material to the tip of the bar-shaped steel 24 protruding from the plate 34 and tightened (see FIG. 8(e)). As a result, the polyurethane foam 28 is sandwiched between the fastening material 36 and the ground, and the repair of the slope 10 is completed (see FIG. 6(c)).

According to the above-mentioned method for repairing the slope 10, the installation of the steel bars 24 fixed to the ground J can suppress the sliding of the sprayed concrete 16 (slope protection structure 12) and the polyurethane foam 28 filling material. In addition, since the polyurethane foam 28 adheres to the steel bars 24 that penetrate it, the sliding of the sprayed concrete 16 (slope protection structure 12) can be suppressed. In this way, according to the above-mentioned method for repairing the slope 10, the installation of the steel bars 24 can stabilize the slope 10 for a long period of time.

The polyurethane foam 28 is lightweight (has a smaller weight per unit volume) compared to cement-based fillers such as mortar, so it is possible to suppress sliding from the ground J and reduce the load applied to the slope protection structure 12. Furthermore, because the polyurethane foam 28 is lightweight, it is possible to reduce the number of steel bars 24 installed and to shorten the insertion depth (anchored length) of the steel bars 24 into the ground J. Therefore, according to the above-mentioned method for repairing the slope 10, it is possible to reduce the effort required to install the steel bars 24 and to reduce the difficulty of installing the steel bars 24, improving the workability of repairing the slope 10 and contributing to reducing the scale of construction and the construction period.

According to the above-mentioned method for repairing the slope 10, the polyurethane foam 28 is foamed in the voids S, so that the polyurethane foam 28 can be filled without gaps in the voids S having a complex three-dimensional shape. In addition, even if the voids S must be filled in several times with a cement-based filler, the polyurethane foam 28 can be filled fewer times. Moreover, since the polyurethane foam 28 takes a very short time to harden compared to a cement-based filler, it is possible to significantly shorten the construction period. The density and compressive strength of the polyurethane foam 28 can be easily adjusted for each site by adjusting the reaction such as the foaming ratio. This allows the physical properties such as density and compressive strength to be appropriately set according to conditions such as the weight of the slope protection structure 12, and the slope 10 can be more suitably stabilized. Since the polyurethane foam 28 is chemically stable, the bar-shaped steel 24 is less likely to rust when covered with the polyurethane foam 28, and it is possible to easily meet the double rust prevention standard required for the maintenance and management of the bar-shaped steel 24.

Because the urethane material M foams and expands, even if the urethane material M is poured into the void S from the bottom, it expands toward the top of the void S, allowing the polyurethane foam 28 to be filled from the bottom to the top of the void S without any gaps. In addition, adverse effects on the ground J when the urethane material M is injected, such as scraping the ground J, can be avoided. Furthermore, by injecting the urethane material M into the void S by spraying, adverse effects on the ground J when the filler is injected, such as scraping the ground J, can be more appropriately avoided.

By covering the surface of the polyurethane foam 28 that is exposed through the through holes 20 in the sprayed concrete 16 with a shielding material 32, the polyurethane foam 28 can be protected from sunlight, exhaust gases, and other factors that have a negative effect on the polyurethane foam 28. Therefore, the slope 10 can be stabilized for a long period of time.

By forming the through hole 20 that penetrates the sprayed concrete 16 with a larger diameter than the insertion hole 22, it becomes easier to insert the nozzle 30 through the through hole 20 and inject the urethane material M into the void S. In particular, the direction of the nozzle 30 inserted through the through hole 20 can be easily changed up, down, left, and right, allowing the urethane material M to be more appropriately injected into the void S.

A model case was set up with the conditions shown in Table 1, and the required conditions for the steel bars were compared between an example in which polyurethane foam was used as the filler and a comparative example in which mortar was used as the filler. The results of the comparison are shown in Table 2.

As shown in Table 2, it can be seen that the number of steel bars required is significantly smaller in the embodiment using polyurethane foam as the filler than in Comparative Examples 1 and 2 using mortar as the filler. In addition, by comparing the embodiment with Comparative Example 1, it can be seen that the anchorage length of the steel bars is significantly shorter in the embodiment. According to the NEXCO construction standard, the interval between adjacent steel bars is required to be about 1.0 m to 1.5 m (about 1 bar/ ² m2). For example, if the steel bars are arranged at 1.0 m intervals, 184 bars can be arranged, and if the steel bars are arranged at 1.5 m intervals, 65 bars can be arranged. From this, the embodiment meets the NEXCO construction standard, while Comparative Example 1 has an interval of about 0.6 m, which falls outside the standard. Here, according to the NEXCO construction standard, the length per steel bar is required to be about 2.0 to 5.0 m, but even in Comparative Example 1, which has an anchorage length of the steel bars that is just about 5.0 m, Comparative Example 1 does not meet the bar interval standard.

(Example of change)
The present invention is not limited to the above, and may be implemented as follows, for example.
(1) In the examples, the existing sprayed concrete remains, but the repair method disclosed herein can be applied even if the covering work that covered the slope, such as the existing sprayed concrete or vegetation works, has been lost due to collapse or the like.
(2) When repairing voids where covering work has been lost, it is a good idea to apply covering work such as sprayed concrete or vegetation work to the front side of the polyurethane foam as a shielding material.

10 Slope, 12 Slope protection structure, 20 Through hole, 22 Insertion hole, 24 Steel bar,
26 Solidification material, 28 Polyurethane foam, 32 Shielding material, 36 Nut (fastening material),
S Vacant space, J Ground, M Urethane material

Claims (4)

A repair method for filling a void formed on a slope on which a slope protection structure is provided, comprising the steps of:
Inserting a steel bar into an insertion hole formed in the ground constituting the void;
A solidification material is injected into the insertion hole to fix the steel bar to the ground;
injecting a urethane material into the void and foaming the urethane material in the void, thereby filling the void with the resulting polyurethane foam;
A method for repairing a slope, comprising the steps of: attaching a fastening material to the tip of the steel bar protruding from the polyurethane foam to the front side; and sandwiching the polyurethane foam between the fastening material and the ground. The method for repairing a slope according to claim 1, in which the urethane material is injected from the bottom of the void. The method for repairing a slope according to claim 1 or 2, in which the front side of the polyurethane foam is covered with a shielding material. The insertion hole is drilled through a through hole penetrating the slope protection structure covering the void,
4. The method for repairing a slope according to claim 1, wherein the urethane material is injected into the void from the through hole, which is formed to have a larger diameter than the insertion hole.

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