JP2012149514A - Slope stabilization method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a slope stabilization method capable of effectively demonstrating pull-out resistance and deterrent force.SOLUTION: The slope stabilization method is for reinforcing a slope ground, a first drilling mechanism is set inside a steel pipe provided with a plurality of grout material discharge holes in a peripheral wall and also provided with a plurality of node projections, and the steel pipe is placed while drilling from a slope to a prescribed depth deeper than a slide surface. After placing is completed, a second drilling mechanism for performing drilling by an excavation diameter smaller than the steel pipe inner diameter is set inside the steel pipe, and drilling is performed further deeper than the distal end of the placed steel pipe by the second drilling mechanism. After the drilling is completed, a grout material is pressurized and injected into the drilled borehole, the grout material is injected in a jetting form from the grout material discharge holes in the steel pipe peripheral wall, a reinforcing bar is erected through the inside of the steel pipe inside the borehole to which the grout material has been injected, and a ground improvement body by the ground to which the grout material has been injected, the reinforcing bar and the steel pipe is formed.

Description

  The present invention relates to a slope stabilization method, and more particularly to a slope stabilization method for reinforcing a slope ground.

  The slope stabilization method is a method that suppresses landslides and stabilizes the cut and fill slopes. As shown in FIG. 18, the embankment slope is the slope 1 when embanked on the original slope 2, and the cut slope is the slope 3 newly formed by cutting the original slope 2. In this slope, the part of the slope surface layer where the surface layer is intended to be active (the part to be slid) is defined as a moving layer, and the part deeper than the moving layer is defined as a non-moving layer or a supporting layer. That is, as shown in FIG. 19, the slope is composed of a moving layer 4 having a weak ground and a non-moving layer 5 having a strong ground, and the moving layer 4 slides or collapses along a portion indicated by a dotted line due to an earthquake or other factors. Probability is high. For this reason, the slope stabilization work described above is performed. For slope stabilization work, (a) ground anchor work and (b) reinforced earth work by inserting reinforcing bars (for example, anchor bolts) are known.

As shown in FIG. 20, the ground anchor 6 in the ground anchor construction has three structural parts, that is, an anchor head 6a and an anchor free length part 6b having a length of 11 m, for example, an anchor fixing length part 6c having a length of 4 m, for example. Can be separated. The anchor head portion 6a is a portion that transmits the anchor force to the slope surface layer portion, and the anchor free length portion 6b is a portion that passes through the moving layer 4 to prestress the anchor head portion, 6 c is a portion that exerts an anchoring force built on the immovable layer 5. As a deterrent function, the ground anchor 6 transmits the anchor force obtained from the immovable layer 5 by the fixing length 6c to the anchor head 6a arranged on the slope surface using the free length 6b. Prestress is applied to the moving layer 4 from the slope surface layer through the pressure receiving structure (precast pressure receiving plate, method frame, retaining wall, etc.) 7-1 constituting 6a, and the sliding surface (boundary part of the moving layer / non-moving layer) ) And the moving layer 4 is forcibly suppressed. In the figure, 7-2 is the collapsed surface of the current state after the collapse, 7-3 is the slope after construction, 7-4 is a frame or lock net for the purpose of preventing peeling due to weathering of the slope surface, etc. The slope is fixed, 7-5 is cut and 7-6 is filled.
Such a ground anchor is provided with a fixing portion 6c in the immovable layer 5, so that when the depth becomes deeper, it may enter the other person's premises and may come into contact with the foundation of another structure and may not be used. There is.

Reinforcing earthwork by inserting reinforcing bars, as shown in Fig. 21, place 2 to 5m reinforcing bars 8 for ground reinforcement in an unstable part of the ground, and fix this to the whole ground (full length) with fixing material. It is intended to suppress ground deformation, and its structure and construction are simple. However, in the reinforced earth work by inserting reinforcing bars, the length per one is shortened, but the total cumulative length becomes long, which is uneconomical. In other words, in the rebar insertion work, peripheral frictional force cannot be taken for reasons such as drilling hole diameter, injection mode (mostly pressureless injection), etc. For this reason, a large number of small pitches must be placed, and as a result, the total accumulated length becomes equal to or greater than the ground anchor work. In addition, reinforced earthwork by inserting reinforcing bars has a limit of performance and construction at present of D29 deformed steel bar, L = 7m, and when the slip surface is deeper than L = 7m, and the required deterrence is high. In this case, the ground deformation cannot be effectively suppressed, and the construction method is located on the danger side.
Fig. 22 is a comparison table of required quantities for ground anchor work and rebar insertion work. Drilling hole diameter, length, pitch, number of steps, number of slopes per 10m of slope width, total extension per slope width of 10m and an example of construction schematic diagram Show.

  In order to improve the ground reinforcement effect and solve the problems of ground anchor work and rebar insertion work, the applicant proposed a slope stabilization method to reinforce the ground by forming a ground improvement body around the steel pipe material. (Patent Document 1). In this proposed slope stabilization method, (1) a plurality of grout material discharge holes are provided in the peripheral wall, and a drilling mechanism including a bit is accommodated in a steel pipe material having a plurality of node projections, and (2) The bit is ejected from the tip of the steel pipe material, and the steel pipe material is pushed while being drilled while drilling the slope ground. (3) After the placement, the hole drilling mechanism is recovered, and after the hole drilling mechanism is recovered, The grouting material is pressurized and injected into the grouting material, and the grouting material is ejected from the grouting material discharge hole to form a ground improvement body around the steel pipe material to reinforce the ground.

FIG. 23 is an explanatory view of the proposed slope stabilization construction method described above. (1) First, while drilling by a double tube dry drilling method using an eccentric diameter expanding bit (drilling bit) 2 The steel pipe material 1 having a plurality of grout material discharge holes on the peripheral wall is directly placed on the ground. (2) If the steel pipe material 1 is driven to a predetermined depth, after the drill bit 2 is reduced in diameter and stored in the steel pipe material 1, the drill bit such as the drill bit 2, inner rod 3, down-the-hole hammer 4, etc. Pull out the mechanism and collect it. (3) Next, if the single packer 201 of the injection packer device is disposed in the vicinity of the tip of the steel pipe material 1 and the grout material is injected under pressure from the grout injection pipe 202, the steel pipe material 1 and the peripheral wall of the steel pipe material The grout material is discharged from the formed grout material discharge hole. (4) Thereafter, when stepped pressure injection is performed using an injection packer device, the grout material is discharged from the grout material discharge hole and the grout column 31 is formed. (5) Finally, if the pouring device is placed at the mouth and the grout material is injected into the steel pipe material 1, the grout material is discharged from the grout material discharge hole 1 and extends over the entire length around the steel pipe material 1. A uniform grout pillar (ground improvement body) 31 is completed. That is, a composite pile in which the steel pipe material 1 and the grout column 31 are integrated is completed.
As a conventional technique, as shown in FIG. 24 (A), a drilling machine in which a self-drilling bolt 9a is arranged as a double-pipe drilling rod in a casing pipe 9b is used to drill a hole with the self-drilling bolt 9a. As shown in FIG. 24 (B), the casing tube 9b is driven into the inner hole 9c of the self-drilling bolt 9a and then injected into the casing tube 9b to a certain depth while being discharged from the tip. There is a method of drawing out and forming a small hole pile (Patent Document 2).

Japanese Patent Application No. 2007-87883 Patent 3927842

However, in the proposed method of Patent Document 1, the steel pipe material 1 having a diameter that can accommodate the drilling mechanism is drilled and punched to a sufficiently long length by a double pipe drilling method using a down-the-hole hammer or the like. Since it is assumed that the ground improvement body 31 made of a grout material is formed over the entire length of the steel pipe, there is a problem that it takes time for construction as compared with the reinforcing bar insertion work and is not economical.
Further, in the prior art of Patent Document 2, a self-drilling bolt 9a and a casing tube (outer tube) 9b that can withstand rotation / blow of a drilling hole are required, and the bit becomes a discarded bit, which is very expensive. . The outer tube is pulled out to a certain extent, but the edge between the outer tube and the ground is cut, and only the self-drilling bolt located deeper than the outer tube is fixed to the ground, so that sufficient peripheral friction force There was a problem that could not be taken.
As described above, the object of the present invention is to provide a deterrence effectively together with the pull-out resistance by compensating for the bending rigidity of the reinforcing bar without requiring the tension required for maintenance and management, even if the construction is not as long as the ground anchor. It is to provide a slope stabilization method that can be used.
Another object of the present invention is to enable a more effective reinforcement by taking a sufficiently large peripheral frictional force, resulting in a shorter total construction length and a more economical slope stabilization method. Is to provide.
Another object of the present invention is to prevent the reinforcing member assembly from being pulled out together with the casing tube when the casing tube is pulled out.

  The present invention is a slope stabilization method that reinforces the slope ground, the first drilling mechanism is set in a steel pipe having a plurality of grout material discharge holes on the peripheral wall and a plurality of node projections, and a slip surface from the slope. A step of driving the steel pipe while drilling to a predetermined depth below, a step of setting a second drilling mechanism for drilling with a drilling diameter smaller than the inner diameter of the steel pipe in the steel pipe after the completion of the driving, the second Further drilling a hole deeper than the drilled steel pipe tip by the drilling mechanism, and, after completion of the drilling, inserting a reinforcing bar into the drilled hole penetrating through the steel pipe, A step of pressurizing and injecting a grout material into the steel pipe, and ejecting the grout material from the grout material discharge hole of the steel pipe tip and the peripheral wall of the steel pipe, thereby forming a ground improvement body around the reinforcing bar and the steel pipe; .

According to the present invention, effective reinforcement can be performed while shortening the overall construction total length. That is, according to the present invention, a rebar made of deformed steel bar or the like can be used as the pulling resistance on the non-moving layer side, and it is possible to take a large peripheral frictional force in combination with a large hole diameter of the steel pipe part, Insufficient bending strength of reinforcing bars can be compensated by steel pipes.
According to the present invention, since it is possible to use a large-diameter rebar that was impossible with conventional rebar insertion work, it is possible to increase the deterrent force to be borne per construction, and accordingly the number of placements Can be reduced.
Moreover, steel pipes (and couplers for connecting steel pipes) are expensive, and if they are long, it takes time for drilling and placing, but according to the present invention, the steel pipe can be kept short and the construction time Can be shortened and the economy can be improved.
In addition, according to the present invention, since the joint rise prevention means for preventing the reinforcement member assembly from being pulled out together with the casing tube is provided, the reinforcement member assembly is prevented from being lifted up when the casing tube is pulled out. be able to. In addition, this makes it possible to reflect the design rebar length management and steel pipe installation position management more accurately and reliably in the construction.

It is a schematic explanatory drawing of the slope stabilization method of this invention. It is construction state explanatory drawing at the time of constructing a reinforcement assembly to a slope by the slope stabilization method of 1st Example. FIG. 2 is an explanatory diagram of a steel pipe of a first example. It is a block diagram of the front-end | tip part of a reinforcing material assembly. FIG. 3 is an explanatory diagram of a construction method of the first embodiment. It is explanatory drawing of a 1st modification. It is explanatory drawing of the coupler by which the antirust process of the 1st modification was carried out. It is explanatory drawing of the center riser of a 1st modification. It is explanatory drawing of the nut of a 1st modification. It is explanatory drawing of the bearing plate to which the antirust process of the 1st modification was performed. It is explanatory drawing of a 2nd modification. It is construction method explanatory drawing of a 2nd modification. It is construction state explanatory drawing at the time of constructing a reinforcement assembly to a slope by the slope stabilization method of 2nd Example. It is explanatory drawing of the steel pipe of 2nd Example. It is construction method explanatory drawing of 2nd Example. It is explanatory drawing of a 1st modification. It is a required quantity comparison chart of a prior art example and this invention method. It is cutting and embankment slope explanatory drawing. It is slope ground layer explanatory drawing. It is explanatory drawing of a ground anchor work. It is explanatory drawing of the reinforcement earthwork (rebar insertion work) by reinforcement insertion. It is a comparison table of required quantity of ground anchor work and reinforcement earthwork by inserting reinforcing bars (reinforcing bar insertion work). It is explanatory drawing of the slope stabilization construction method proposed. It is a prior art explanatory drawing.

(A) Outline FIG. 1 is a schematic explanatory view of a slope stabilization method according to the present invention, and shows a state after a reinforcing material assembly is constructed on a slope. In the figure, 11 is the moving layer, 12 is the non-moving layer, 13 is the sliding surface (boundary part of the moving layer and the non-moving layer), 14 is the falling surface after the collapse, 15 is the slope after construction, and 16 is the slope A frame for fixing the frame or lock net for the purpose of preventing peeling due to weathering of the surface layer, 17 is a cut portion, 18 is a filled portion, 20 is a reinforcement assembly is there.
The reinforcing material assembly 20 is a steel pipe 21 having a relatively short length L1 (for example, about 4 to 6 m) having a plurality of node projections, and a length arranged in the steel pipe so as to protrude from the tip of the steel pipe by a predetermined length. It has a rebar 22 such as a deformed steel bar of L2 (for example, a length of about 7 to 12 m) and a threaded rebar.
The construction method is as follows: (1) Double pipe drilling method (casing drilling method), drilling from the slope to deeper than the sliding surface 13 to a predetermined depth, and placing a casing pipe (not shown), (2) After drilling is completed, the hole drilling mechanism is recovered from the casing pipe. (3) After that, the reinforcing material assembly 20 is set in the casing pipe. (4) After the setting of the reinforcing material assembly 20 is completed, the steel pipe is placed in the steel pipe. A ground improvement body is formed around the reinforcing member assembly 20 by injecting the grout material under pressure to eject the grout material from the tip of the steel tube 21 and pulling out the casing tube.
(B) 1st Example FIG. 2 is a construction state explanatory drawing at the time of constructing a reinforcing material assembly on a slope by the slope stabilization method of the first example, and the same part as FIG. is doing. A slope 19 of about F200 to F500 is assembled on the slope 19 formed by cutting and embankment. The slope work 16 is fixed to the slope 19 by setting a mesh-shaped scraping frame and a slope frame of reinforcing bars in a grid pattern on the slope 19 and then spraying concrete. A construction part 16a for constructing the reinforcing member assembly 20 is formed at an appropriate position of the slope 16 by being positioned by a VU pipe and a void pipe.
The reinforcing member assembly 20 has a pipe-shaped steel pipe 21 and a reinforcing bar 22 arranged in the steel pipe so as to protrude from the tip of the steel pipe by a predetermined length. The length of the steel pipe 21 is relatively short L1 (for example, about 4 to 6 m). In the illustrated example, the thickness is 8.6 mm, the diameter is 114.3 mm, and a plurality of circular node projections 23 are formed at equal intervals on the outer periphery. Has been. As shown in FIGS. 3A and 3B, the node protrusion 23 is formed by bead welding so that the protrusion height becomes 2.5 mm or more. 3A is an enlarged cross-sectional view of the lower half of the steel pipe 21, and FIG. 3B is a cross-sectional view of the node protrusion.

In the illustrated example, the reinforcing bar 22 is a deformed steel bar having a diameter of 29 mm and a length L2 (for example, about 7 to 12 m), a threaded reinforcing bar, and the like (referred to as a threaded reinforcing bar). It is attached to the steel pipe 21 so as to protrude. FIG. 4 is a configuration diagram of the distal end portion of the reinforcing member assembly, (A) is a partially cutaway view of the reinforcing member assembly 20, and (B) is a front view of the reinforcing member assembly 20. FIG. The four auxiliary reinforcing bars 24 are attached to the steel pipe 21 by welding at intervals of 90 degrees so as to surround the reinforcing bars 22, and a cone-shaped tip metal fitting 29 is attached to the tip. The reinforcing bar ring 25 functions to connect the four auxiliary reinforcing bars 24 to each other and maintain a predetermined positional relationship. The auxiliary reinforcing bar 24 and the reinforcing bar ring 25 are connected by welding. The reinforcing bar system is formed by the reinforcing bar 22, the auxiliary reinforcing bar 24, and the reinforcing bar ring 25.
After placing the reinforcing member assembly 20 on the mouth side, the bearing plate 26 is fitted into the threaded reinforcing bar 22, and the nut 27 is screwed onto the male threaded portion of the threaded reinforcing bar 22 from above the bearing plate 26 and tightened. The bearing plate 26 is pressed against the frame work 16. A portion 28 surrounded by a dotted line is a hole drilled by a hole drilling machine to be described later.

FIG. 5 is an explanatory diagram of the construction method of the first embodiment. As for the outline of the construction, a steel pipe 21 with a node projection of length L1 (about 4-6m) is arranged to a depth of 13 or more on the sliding surface, and a reinforcing bar 22 of length L2 (about 7-12m) is arranged to a deeper position. Then, the grout material is ejected from the steel pipe 21 to form a ground improvement body.
That is, first, using a drilling machine (all hydraulic rotary percussion drill, etc.) 31, a double pipe using a casing pipe 32 (pipe that enters the hole with the bit so that it does not collapse into the drilling hole). Drill to the depth where the rebar is built by drilling method ((1) in Fig. 5 (A)). That is, for example, when the outer diameter of the cast steel pipe is φ114.3 mm, the casing pipe 32 is driven simultaneously while excavating a hole having a diameter of about φ146 mm by the casing drilling hole.
After drilling is completed, the hole drilling mechanism is recovered from the casing tube 32, and instead, a reinforcing material assembly comprising a steel tube 21 having a plurality of node projections and a reinforcing bar 22 arranged in the steel tube so as to protrude from the tip of the steel tube by a predetermined length The body 20 is set in the casing tube ((2) in FIG. 5A).
Next, the grout material 33 is pressurized and injected into the steel pipe 21, the grout material is ejected from the tip of the steel pipe, the grout material 33 is injected into the steel pipe and the bottom of the hole (base grouting), and simultaneously the casing pipe 32 starts to be pulled up. (Refer to (3) in FIG. 5B).
Thereafter, the grout material 33 is pulled around the reinforcing bar 22 and the steel pipe 21 by pulling out the casing pipe 32 while injecting the grout material 33 under pressure (skunking), and the ground improvement body is placed around the reinforcing material assembly 20. (See (4) of FIG. 5B).

The node projections 23 formed on the outer periphery of the steel pipe 21 significantly improve the load transmission performance of the ground and the reinforcement assembly 20, and the joint projection 23 allows the reinforcement assembly 20 to be shared when the casing pipe 31 is pulled up. The rise can be suppressed. In addition, the steel pipe can be installed at a predetermined depth in the design, and reliable construction can be performed so that the length of the reinforcing bar protruding from the steel pipe becomes a predetermined length.
According to the first embodiment, effective reinforcement can be performed while shortening the total construction total length. That is, according to the first embodiment, as the pulling resistance on the non-moving layer side, a reinforcing bar made of threaded reinforcing bar or deformed steel bar can be used, and a large peripheral friction force is taken in combination with a large hole diameter of the steel pipe part. In addition, the steel pipe can compensate for the lack of bending strength of the reinforcing bars.
In addition, according to the first embodiment, since it is possible to use a large-diameter rebar that was impossible with the conventional rebar insertion work, it is possible to increase the deterrent force to be borne per construction, and accordingly The number of placements can be reduced. Furthermore, steel pipes (and couplers for connecting steel pipes) are expensive, and when they are long, it takes time for drilling and placing, but according to the present invention, the steel pipe can be kept short and the construction time is shortened. Can be shortened and the economy can be improved. In addition, if only one coupler is used, it is possible to construct a steel pipe length of up to 12 m, and it is possible to suppress all slips that can be suppressed by this construction method, so there is no coupler or it is desirable to use about one .

First Modified Example FIG. 6 is an explanatory diagram of the first modified example, and the same reference numerals are given to the same parts as those of the first example of FIG. A first different point is that a long-shaped threaded reinforcing bar 22 is formed by coupling a deformed threaded steel bar subjected to a short rust treatment by a coupler 41 and attached to the steel pipe 21. A second different point is that a center riser 42 is attached to the threaded reinforcing bar 22 so that the steel pipe 21 and the threaded reinforcing bar 22 are in a predetermined arrangement state.
7A and 7B are a cross-sectional view and a side view of the lower half of the coupler 41 that has been rust-proofed, FIGS. 8A and 8B are a front view and a side view of the center riser 42, and FIG. ), (B) are a sectional view and a side view of the lower half of the nut 27. FIGS. 10A and 10B are a plan view and a cutaway side view of the bearing plate 26 subjected to the rust prevention treatment.

Second Modified Example FIG. 11 is an explanatory diagram of the second modified example, showing only the distal end portion of the reinforcing member assembly, and the same reference numerals are assigned to the same parts as the distal end portion of the first embodiment of FIG. is doing. A different point is that the auxiliary reinforcing bar 24 constituting the tip reinforcing bar system is bent toward the tip and opens larger than the outer diameter of the steel pipe 21. Since the steel pipe 21 of the first embodiment has the node protrusion 23, the rise of the casing pipe 32 during the recovery (see FIG. 5) is suppressed to some extent. In order to prevent this, a joint rise prevention means is provided at the tip of the steel pipe to prevent the reinforcing material assembly 20 from being pulled out together with the casing pipe being pulled out.
The tip rebar system of the second modified example includes four auxiliary reinforcing bars 24 welded to the tip of the steel pipe 21 and a reinforcing bar ring 25 that interconnects these auxiliary reinforcing bars and maintains a predetermined positional relationship. Is biased to bend radially outward. A cone-shaped tip metal fitting 29 is provided at the tip of the auxiliary reinforcing bar 24, and this tip fitting 29 is coupled with the urging of the auxiliary reinforcing bar 24 to the outside, and the casing tube 32 (see FIG. 5) is pulled out during construction. It functions so that the entire reinforcing material assembly is not lifted by being caught on the drilling wall as it moves. Further, the auxiliary reinforcing bar 24 and the reinforcing bar ring 25 have an effect of preventing the reinforcing member assembly 20 from sinking into the hole bottom when the reinforcing material assembly 20 is inserted.

FIG. 12 is an explanatory diagram of the construction method of the second modification, and shows only the tip portion.
First, using a drilling machine (all hydraulic rotary percussion drill, etc.), the drilling mechanism accommodated in the casing pipe 32 drills to the depth where the rebar is built and doubles the casing pipe 32 (FIG. 12A). Drilling is performed by causing the drill bit 33 to protrude from the tip of the casing tube 32 and rotating the drill bit via the drill rod 34.
Reinforcement consisting of a steel pipe 21 having a plurality of node projections and a reinforcing bar 22 arranged in the steel pipe so as to protrude from the tip of the steel pipe by a predetermined length after the drilling mechanism is recovered from the casing pipe 32 after the casing pipe 32 has been placed. The material assembly 20 is set in the casing pipe (FIG. 12B). In this state, the outward urging force of the auxiliary reinforcing bars 24 is pressed down by the casing tube 32.
Subsequently, the grout material is pressurized and injected into the steel pipe 21 to eject the grout material from the tip of the steel pipe, and the grout material is injected into the steel pipe and the bottom of the hole, and at the same time, the casing pipe 32 starts to be pulled up. Thereafter, the grout material is injected around the reinforcing bar 22 and the steel pipe 21 by pulling out the casing tube 32 while injecting the grout material under pressure, and a ground improvement body is formed around the reinforcement assembly. When the casing pipe 32 is pulled out, the auxiliary rebar 24 expands larger than the outer diameter of the steel pipe 21 due to the outward biasing force, as shown in FIG. As a result, as the casing tube 32 is pulled out, the tip fitting 29 is caught on the hole wall and functions so that the entire reinforcing material assembly does not float. That is, it is possible to prevent the joint assembly 20 from being pulled out together with the casing tube 32 being pulled out.

(C) 2nd Example FIG. 13: is a construction state explanatory drawing at the time of constructing a reinforcement assembly to a slope by the slope stabilization method of 2nd Example, and it is the same part as 1st Example of FIG. Are given the same reference numerals. The second embodiment is effective when a greater deterrent is required than the first embodiment. The difference is
(1) Use of a steel pipe 21 having a diameter of φ165.2 mm or more and a length L1 (= about 4 to 12 m) larger than that of the steel pipe of the first embodiment,
(2) On the outer periphery of the steel pipe 21, circular node protrusions 23 are formed at a first pitch, and a grout material discharge hole 51 with a check valve mechanism is formed at a second pitch on the peripheral wall;
(3) At the time of construction, drill with a down-the-hole hammer using the steel pipe 21 as a substitute for the casing pipe, and then drill the diameter in front of the cast steel pipe tip smaller than the inner diameter of the steel pipe (about φ140mm) ), And the point where the screw rebar 22 with a radius of 29mm to 51mm and a length of L2 (= 7 to 12m) is built.
It is.
14A is an enlarged view of the lower half section of the steel pipe 21, and FIG. 14B is a partially broken view in the longitudinal direction of the steel pipe 21 around the grout material discharge hole 51 with a check valve mechanism. As in the first embodiment, the node protrusions 23 are formed at the first pitch so that the protrusion height is 2.5 mm or more by bead welding as shown in FIG. 14 (A), and has a check valve mechanism. As shown in FIG. 14B, the grout material discharge hole 51 is formed by valve processing as shown in FIG. 14B, and is composed of a discharge hole 51a and a check valve 51b. When the grout is pressurized, the check valve 51b is It opens and the grout is spit out.

FIG. 15 is an explanatory diagram of the construction method of the second embodiment.
The steel pipe 21 is directly placed on the ground while drilling by the double pipe dry drilling method using the down-the-hole hammer 50 ((1) in FIG. 15A). In the double-pipe dry drilling method using a down-the-hole hammer, a drilling mechanism such as a drill bit 56, an inner rod 52, and a down-the-hole hammer 53 is accommodated inside the hollow steel pipe 21, and the drill bit is inserted into the tip of the steel pipe material. The hole is drilled by striking and rotating action.
When the steel pipe 21 is driven to a predetermined depth, the drilling mechanism such as the drill bit 56, the inner rod 52, and the down-the-hole hammer 53 is collected. After the completion of the steel pipe placement, another drilling mechanism 61 with a bit at the tip for drilling with a drilling diameter smaller than the inner diameter of the steel pipe 21 is set in the steel pipe, and further drilled deeper than the tip of the steel pipe. ((2) in FIG. 15A).
Then, after the drilling is completed, the drilling mechanism 61 is recovered, and then the grout material 33 is injected from the tip of the steel pipe 21 into the rebar drilling hole ((3) in FIG. 15B) for base grinding. Further, the grouting material is injected from the inside of the steel tube 21 through the grouting material discharge hole 51 provided in the peripheral wall of the steel tube (jet grouting) to form a sking routing ((4) in FIG. 15B). Next, the rebar 22 is built through the steel pipe 21 into the rebar hole in which the grout material has been previously injected. As a result, a ground improvement body is formed by the ground into which the grout material is injected, the reinforcing bars 22 and the steel pipe 21. In addition, as a ground condition, since the depth beyond a slip surface is assumed to be soft rock or more, the steel pipe length below the slip surface may be 1 to 3 m.
Steel pipes (and couplers for connecting steel pipes) are expensive, and if they are long, it takes time to drill and place, but according to the second embodiment, the steel pipe can be kept short and the construction time Can be shortened and the economy can be improved. Further, according to the second embodiment, since it is possible to use a large-diameter rebar that is impossible with the conventional rebar insertion work, it is possible to increase the deterrent force to be borne per construction, and accordingly The number of placements can be reduced.

First Modified Example FIG. 16 is an explanatory diagram of the first modified example, and the same parts as those of the second example of FIG. 13 are denoted by the same reference numerals. A first different point is that a long-shaped threaded reinforcing bar 22 is formed by coupling a deformed threaded steel bar subjected to a short rust treatment by a coupler 41 and attached to the steel pipe 21. The second different point is that the center riser 42 is attached to the threaded reinforcing bar 22 so that the steel pipe 21 and the threaded reinforcing bar 22 are in a predetermined arrangement state.

(D) Comparison with Conventional Example FIG. 17 is a chart showing the required quantity comparison between the conventional example and the method of the present invention. The drilling hole diameter, length, pitch, number of steps, number per 10 m slope width, total extension per 10 m slope width, and The construction schematic diagram is shown. In addition, as a necessary reinforcement for the same slope, (a) ground anchor work, (b) reinforced earth work by inserting reinforcing bars, and (c) the construction method of the present invention were compared. In order to stabilize slopes, ground anchors are the most economical, but with this method, ground anchors enter the basement of other adjacent sites. The construction method of the present invention can easily perform drilling and placing with a required length, and can obtain a reliable reinforcing effect while dramatically shortening the number of placements and the total length as compared with the reinforcing bar insertion work. Is possible.
According to the present invention, it is more economical than the slope stabilization method of Patent Document 1, and only the reinforcing bars inserted therein, the bending strength is enhanced, and the peripheral surface frictional force is obtained. It becomes.
According to the present invention, it is possible to upgrade the reinforcing steel reinforced soil, and since it is possible to use a large diameter and long reinforcing bar that was impossible with conventional reinforcing bar insertion work, the problem of the ground anchor is solved, and It can be applied sufficiently as an alternative to the ground anchor method.
According to the present invention, a reinforcing bar such as a deformed steel bar can be used as the pulling resistance on the stationary layer side, and at the same time, a large peripheral frictional force can be taken.
Although the steel pipe with a node and the coupler are expensive, according to the present invention, the length of the steel pipe can be suppressed to (depth at which the slip surface is generated + predetermined length), and economical construction is possible.
Further, according to the present invention, as a design method, the design in the rebar insertion method which is a well-known technique can be applied for the tension reinforcement, and the frame analysis of the head free end is performed for the bending reinforcement. It is possible to check the amount of deformation and the steel pipe stress. In other words, when the slope is stabilized, the length under the slip surface also changes depending on the required deterrence and the hardness of the ground, but according to the present invention, it is easy to calculate the diameter and length of the steel pipe and the reinforcing bar. Since it can be changed, extremely economical and efficient construction is possible.

13 Sliding surface (boundary part of moving layer / non-moving layer)
21 Steel pipe 33 Grout material 22 Reinforcing bar 50 Down the hole hammer 52 Inner rod 53 Down the hole hammer 56 Drilling bit 61 Drilling mechanism

Claims (1)

In slope stabilization method to reinforce slope ground,
A first drilling mechanism is set in a steel pipe having a plurality of grout material discharge holes on the peripheral wall and a plurality of node projections, and the steel pipe is driven while drilling from a slope to a predetermined depth deeper than the slip surface. ,
After the completion of driving, a second drilling mechanism for drilling with a drilling diameter smaller than the inner diameter of the steel pipe is set in the steel pipe,
Further drilling deeper than the tip of the placed steel pipe by the second drilling mechanism,
After completion of the drilling, the grouting material is injected under pressure into the drilled drilling hole, and the grouting material is injected from the grouting material discharge hole in the peripheral wall of the steel pipe.
Reinforcing the steel bar through the steel pipe in the hole into which the grout material was injected,
Forming a ground improvement body by the ground injected with the grout material, the reinforcing bar and the steel pipe;
Slope stabilization method characterized by that.

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