JPH09228798A - Cable bolt and excavated ground reinforcing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the sticking strength to a filler so as to stabilize the circumferential natural ground by forming a non-circular unique sectional form in which each adjacent strand being in face contact with each other, and forming a center space, recesses and the like. SOLUTION: Four to nine pieces of strands 2... are stranded while recess parts 5... are formed between adjacent strands 2 and a space 3 is formed at a central part in the axial direction, thereby providing a stranded steel wire 1. In a cable bolt with the stranded wire 1, each strand 2 is brought into face contact with the adjacent strand 2 and formed in a non-circular unique shape such as almost trapezoidal shape or Z shape. The size of the space 3 in the center is made 6mm or more with the inscribing circle diameter used as a reference, and the stranded pitch is made 5-20 times of the wire diameter. On the outer surface part becoming the surface layer recesses 4 each having a step difference of 0.2-1.0mm is formed while the depth of recesses 5 is made 1mm or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground reinforced structure called a cable bolt used for a tunnel, a side wall of a mine tunnel or a large underground cavity, a ground for strengthening an excavated ground, or a pile for preventing a fall, and a ground reinforced structure for the structure. The excavation ground strengthening method.

[0002]

2. Description of the Related Art An outline of ground reinforcement method for side walls and ceilings in tunnels, mines, etc. is schematically shown in FIGS. Further, FIG. 5 shows a cable bolt construction procedure. The excavator 8 drills a hole 9 having a diameter of 50 to 70 mm and a depth of several to several tens of meters in the tunnel 6 and the underground cavity 7 (see FIG. 5 (A)), and a cable and / or a reinforcing steel material 10 is bored in this hole. It is inserted deeply and the gap between the perforation 9 and these steel materials 10 is filled with a filler (mortar, paste, etc.) 11 (see FIG. 5B). If the filler 11 solidifies, the steel material 10 and the filler 1
1 and 1 are integrated to complete the cable bolt 21 and / or the lock bolt 22, and these play the role of piles to strengthen the ground. 3 shows a state in which the cable bolt 21 and the lock bolt 22 are arranged in the tunnel 6 or the tunnel, and FIG. 4 shows that the cable bolt 21 and the lock bolt 22 are filled with a filler around the perforation 9 and the steel material 10. Each completed state is shown, and in FIG. 5, a drilling hole 8 is drilled in the tunnel 6 and the underground cavity 7 by the excavator 8, and the filling material 11 is filled in the drilling hole 9.
Shows a series of steps for filling the cable and inserting the cable.

To further explain a conventional cable bolt construction example, the following two methods are known. One of them is the pre-injection method shown in FIG. 6, which is a method in which the cable is inserted after the hole is filled with the filler. Another is a post-injection method, which is not shown, and is a method in which the cable is first inserted and then the filler is filled. The pre-injection method is
In FIG. 6, the filling agent 11 is filled into the perforation 9 by first inserting the filling material hose 12 to the back of the perforation 9, injecting the filling material 11 in order from the back, and gradually pulling out the hose 12 from the filled portion. While trying to fill completely. In the post-injection method, the filler is injected from the entrance side of the perforation to the back with the cable inserted. In this case, the filler is generally injected under pressure by a pump.

[0004]

According to the pre-injection method shown in FIG. 6, it is difficult to completely fill the filler with the formation of air pockets at the innermost portion of the perforations, and it is difficult to confirm whether the filler has been completely filled. However, there is a problem in that it is difficult to insert a flexible cable into the depth of the perforation because the filler is semi-rigid and the perforation locally collapses. Further, in a place where there is a lot of spring water, the filler is affected by water to change its composition, which causes a problem in strength as a pile.

On the other hand, in the latter post-injection method, in addition to the above-mentioned problems of the pre-injection method, incomplete filling of the filler due to air pockets is caused by incorporating an air bleeding hose into the cable.
The problem of difficulty in confirming the complete filling of the filler is solved for the time being. Also, with respect to spring water, there is no problem that the inside of the hole becomes positive pressure due to the seal at the hole entrance, and the spring water can be suppressed. Furthermore, as shown in FIG. By using the cable composed of the air bleeding hose 13 that is bundled along the above, the spring water during the injection of the filler can be discharged from the air bleeding hose 13, so there is no problem.

However, such a PC steel strand 10
In the case where the air bleeding hose 13 is externally attached to the hose 13, the hose 13 occupies a part of the surface of the PC steel stranded wire 10 and hinders the adhesive strength between the PC steel stranded wire 10 and the filler. Became a 10-year-old PC strand with a long time
There was a problem that it relaxed and came out.

On the other hand, FIG. 8 shows a wire rope which has been conventionally used as a ground reinforcing wire in a part thereof. This is a hose built-in type in which a plurality of twisted wires 14 are twisted around a hose 15. It is a rope, and this hose 15 can be used for venting air. However, in this case as well, the structure is such that a large-diameter hose having a considerable wall thickness is built-in, so the outer diameter of the rope becomes thicker, for example, a hose-built-in type that can withstand a load equivalent to PC steel wire φ15.2 mm. In the case of a rope, the finished outer diameter is as large as 26 mm, and it is necessary to increase the perforation diameter, which is economically disadvantageous. Also, since the rope itself has a weak stiffness, it is not practical because it is predicted that it will be difficult to insert when there is a risk of deep piercing or collapse.

The present invention has been made in order to solve the above problems, and therefore, the main object of the present invention is to make full use of the advantages of the filler post-injection method. This contributes to the formation of a cable bolt that retains high strength due to.

Another object of the present invention is to provide the cable bolt itself with a function of venting air and a function of confirming the complete filling of the filler, which contributes to the improvement of the reliability for strengthening the ground and the long perforation. The aim is to rationalize construction methods and promote high economic efficiency with the realization of smaller size and smaller diameter.

Still another object of the present invention is to improve workability and transportability by utilizing a steel stranded wire as a core material, and to improve the adhesion of the core material and the filler to improve the strength of the cable bolt. The aim is to improve the number and to reduce the number of castings.

[0011]

The present invention has the following configuration to achieve the above object. That is, according to the present invention, the steel is formed by twisting the strands having 4 to 9 strands into one layer to form a valley between adjacent strands, and forming a space penetrating in the axial direction in the central portion. A cable bolt having a stranded wire as a core wire, in which each element wire has a non-circular irregular cross-sectional shape such as a trapezoidal shape and a Z shape, which are in surface contact with each other and are made of steel stranded wire. In this case, it is characterized in that it has irregularities on the outer surface portion which becomes the surface layer.

According to the present invention, in the cable bolt described in the preceding paragraph, the space in the central portion of the steel stranded wire has a size of φ6 mm or more based on the inscribed circle diameter, and the element in the steel stranded wire is The unevenness of the outer surface of the wire is 0.2 to 1.0 or more, and the depth of the valley portion between the adjacent wires is 1 mm or more. The present invention is also characterized in that in the cable bolt described in the preceding paragraph, the twist pitch of the steel stranded wire is 5 to 20 times the stranded wire diameter.

According to the present invention, the wires having 4 to 9 wires are twisted together to form a valley between adjacent wires, and a space penetrating in the axial direction is formed at the center. A cable in which each element wire has a non-circular cross-sectional shape such as a trapezoidal shape or a Z shape, which are adjacent to each other in surface contact with each other, and the core wire is made of a steel stranded wire having unevenness on the outer surface portion as a surface layer A method of strengthening the ground around a drilling site by means of bolts, in which a long hole with a predetermined diameter and length is drilled in the ground around the drilling site by a drill, One or more of the wires were loosely inserted, and with the rear end of the wire slightly protruding outside the long hole, the hole entrance around the steel strand was closed with a sealant and then penetrated into the sealant. Press the room temperature solidifying filler into the slot through the filler injecting hose, and press Therefore, based on the fact that the excess room temperature solidifying filler is discharged after the air is discharged through the central space of the steel strand in the long hole, the filling of the room temperature solidifying filler into the long hole is completed. Then, by stopping the press-fitting of the room temperature solidifying filler, the cable bolt formed by firmly bonding and integrating the room temperature solidifying filler layer around the core wire made of one or more steel stranded wires is formed in the long hole. It is characterized by being installed to serve as a pile and strengthening the ground around the excavation site.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be specifically described below with reference to the accompanying drawings. 1 shows a steel strand for cable bolts according to an embodiment of the present invention, the steel strand 1 shown in the drawing is made by twisting strands 2 made of, for example, six steel wires in one layer. , A steel stranded wire having an inscribed imaginary circle and a cross section of which is generally in the shape of a flowering peony is formed. Each strand 2 of this steel strand 1 has the same shape, and non-circular irregular shapes adjacent to each other in surface contact with each other such that a valley 5 is formed between adjacent wires, for example, a generally trapezoidal shape. And the outer surface that becomes the surface layer when the steel stranded wire 1 is formed,
The structure has concaves and convexes, for example, concave portions 4 which are provided at regular intervals in the longitudinal axis direction.

The number of the wires 2 is not limited to six as long as the desired strength of the cable bolt and the predetermined cross-sectional area of the space 3 can be obtained. However, trapezoidal (deformed) processing of the wire becomes difficult as the number of wires decreases, so four or more wires are desirable. Further, the number of strands is preferably 9 or less because the stranding machine for twisting the strands becomes complicated and large as the number of strands increases.

The above-mentioned strands 2 having a substantially trapezoidal shape are shown in FIG.
As shown in (A), the trapezoid bottom side is on the outside, and the trapezoid top side is on the inside.
In the steel strand 1 thus constructed, a space 3 penetrating in the axial direction is formed in a central portion surrounded by the individual strands 2. The space 3 has a substantially regular hexagon that is substantially inscribed in one virtual circle. On the other hand, since the recessed portion 4 provided at the bottom of the trapezoid is provided to enhance the adhesiveness with the filler layer that is adhered and integrated around the steel strand 1, it is deep and has a short interval. It goes without saying that it is very effective.
However, as the depth becomes deeper, the tensile strength of the wire decreases, so it is preferable to make it 1 mm or less as described later, and to make the bottom rounded from the viewpoint of avoiding stress concentration.

Further, the shorter the twist pitch of the stranded wire 1 is,
The adhesion between the steel stranded wire and the surrounding concrete layer is improved, and the hollow stranded wire structure is stable, but if the length is shortened, the tensile strength decrease rate of the stranded wire as a collective load is large and the productivity is high. Therefore, the ratio of the twist pitch to the wire diameter is preferably 5 times or more. The twisting stability of the stranded wire becomes worse as the wire diameter becomes larger, and 20 times is the upper limit for reliably maintaining the hollow shape.

A method of strengthening the excavated ground by using the steel strand 1 having the above-mentioned structure will be described below with reference to FIG. 2 showing an example of the method of the present invention. A long hole 9 having a predetermined diameter and length, for example, a diameter of φ42 mm and a length of 10 m is bored in the ground 15 around an excavation site such as a tunnel or an underground cavity, and a steel stranded wire is provided in the long hole 9. One or a plurality of 1 are loosely inserted and positioned with the tip close to the bottom of the long hole 9, and the steel strand 1 has a length such that the rear end of the steel strand 1 slightly projects out of the long hole 9. Disconnect.

With the wire 1 slightly protruding from the steel,
After the sealing material 16 made of a rubber plug or the like is fitted into the hole inlet around the steel strand 1 to seal the hole inlet, the sealing material 1
The tip portion of the filler injecting hose 12 is inserted into the hole formed in 6 to expose the tip opening of the hose 12 into the elongated hole 9.
Next, a room temperature solidified filler 11 such as mortar is pressed into the elongated hole 9 through a filler injecting hose 12 by a filler pump (not shown).

As the mortar is gradually pressed into the long hole 9, the air in the hole is replaced and discharged through the space 3 of the steel strand 1 to the outside of the long hole 9, so that the mortar can be injected smoothly. Moreover, air is not accumulated in the long hole 9 at all, and complete filling is possible. Following the discharge of the air in the holes, the mortar reaching the bottom of the holes is discharged through the space 3. This discharge confirms that the filling of the mortar into the hole 9 is complete, so the operation of the filler pump is stopped, the press-in of the mortar is stopped, and the room temperature solidification of the mortar is awaited. The mortar solidifies with the passage of a considerable time, and the mortar layer is fixed and integrated around the steel strand 1.
This mortar layer densely enters the recesses 4 and the valleys 5 of the steel strand 1 during the solidification process, so that the mortar layer and the steel strand 1 are firmly and securely fixed to each other. Thus, the cable bolts 21 formed by firmly and integrally integrating the room temperature solidifying filler layer 11 made of mortar around the core wire made of one or more steel strands 1 are densely cast in the elongated holes 9. It is possible to strengthen the ground around the excavation site by sufficiently performing the role of a pile.

[0021]

Embodiments of the present invention will be described below with reference to the accompanying drawings. The breaking load of the conventional cable bolt is 261 when the hose external PC steel wire φ15.2 mm.
It is about kN and about 274 kN with a wire rope with a built-in hose. Therefore, the breaking load in this example is the stranded wire φ of PC steel.
It was set to 261 kN, which is equivalent to the guaranteed load of 15.2 mm. This example is shown below.

A 6-strand hollow steel stranded wire was produced as follows. Hard steel wire rod SWRH62B, φ10, and SWR
After heating H82B, φ9, φ8 at 900 ° C for 3 minutes,
Lead patenting at 70 ° C for 1 minute. Then HCl
After pickling and surface treatment under the conditions of × 20 minutes and zinc phosphate × 10 minutes, wire drawing is performed with 6 dies using a trapezoidal carbide tip (reduction rate of each die: 17%). The concave portions 4 are processed on the surface by a rolling method using convex and flat rollers. Subsequently, the cage type stranded wire machine was used to perform stranded wire processing, and Fig. 1
A 6-strand hollow steel wire having the dimensions of φa, φb, and φc shown in (A) was manufactured. Here, φa represents the outer diameter of the hollow steel stranded wire, φb represents the diameter of a circle inscribed in the central space 3, and φc represents the diameter of a circle passing through the bottom of the valley 5.

From the hard steel wire rod SWRH62B, φ10, the test No. Experiment Nos. 1 to 8 were also made from hard steel wire rod SWRH82B, φ9. Experiment No. 9 from hard steel wire SWRH82B, φ8. 10 were produced.
The results are shown in Table 1 below. In Table 1, as the depth of the recess 4 is deeper, that is, as the φc value (index of the depth of the valley between the strands) is smaller, the adhesion with the mortar is improved, but it can be seen in Experiment No. 1. , The φc value is 1
At 8 mm, that is, when the depth of the valley portion 5 is 0.5 mm, sufficient adhesion strength to mortar is not obtained. Experiment N
o. In No. 2, the same is true when the depth of the recess 4 is 0.15 mm.
From this, the depth of the valley portion 5 between the strands 2 is 1 mm or more, and the depth of the recess 4 is 0.2 mm or more, which is a condition for obtaining a desired adhesion strength to mortar. The breaking load decreased when the depth of the recess 4 was 1.0 mm.

[0024]

[Table 1]

After the mortar is completely filled in the perforations 9, the mortar is discharged to the outside through the air venting space 3 (conventionally a hose), so that the mortar is completely filled without any air pocket. Although it can be confirmed whether or not it was carried out, the fluidity in the space 3 of the mortar was examined as an index for this evaluation. The fluidity deteriorated when the space diameter b became φ4 mm, and clogging occurred depending on the state of the mortar. φ6 mm
Then, this blockage does not occur. Therefore, the diameter of the space 3 is φ6
mm or more is preferable.

Regarding the twist pitch, the shorter the twist strength, the higher the adhesion strength with the mortar, but when the ratio of the twist length (pitch) to the twisted wire diameter was 6.3, the breaking load was decreased.
The rigidity is evaluated by the amount of bending when a load of 2 kg is placed at the center with both ends as free fulcrums with a span of 1 m, but it is possible to confirm that the rigidity is sufficient compared to the conventional technology. did it.

[0027]

As described above in detail, according to the present invention, the cross-sectional shape of the strand of the steel stranded wire is a non-circular irregular shape such as a trapezoid and a Z shape, which have valleys and are in surface contact with each other. As a result, a space for bleeding air and confirming filling of the filler is formed in the center of the steel stranded wire in a reliable and stable state, and it can be used as a post-injection type element member having many advantages. As a result, the filling agent such as mortar can be completely filled, and the confirmation of the complete filling is easy, and the reliability of the performance as the cable bolt is increased.

Further, according to the present invention, since a space is formed in the steel strand itself and the filling rate of the steel material supporting the strength is improved, a core wire having a high breaking load can be obtained from a steel strand having a small diameter. To be For this reason, the diameter of the hole drilled in the ground is small, and the construction cost is low and it is economical. Further, since the rigidity of the wire is improved from the steel wire, the wire can be easily and reliably inserted even if the length of the hole is long, and even if a local collapse occurs in the hole, it can be inserted deep into the hole. It greatly contributes to improving the reliability of work.

The present invention also has a structure in which the strands are provided with valleys and irregularities having appropriate values in order to exert their characteristics, so that the adhesive strength between the steel strand and the filler around it is high. As a result, the strength of the cable bolt is improved, and the ground around the excavation site can be effectively stabilized. In addition, the number of cables to be laid can be reduced, and economic advantages such as lengthening of cable bolts can be expected.

[Brief description of drawings]

FIG. 1 shows a steel stranded wire for a cable bolt according to an embodiment of the present invention, (A) is a cross-sectional view, and (B) is a partial external view.

FIG. 2 is an explanatory diagram of an example of the method of the present invention.

FIG. 3 is an explanatory diagram of two examples of a conventional ground strengthening method.

FIG. 4 is an explanatory diagram of an example of a conventional ground strengthening method.

FIG. 5 is a diagram of a conventional cable bolt construction procedure.

FIG. 6 is an explanatory diagram of a conventional filler pre-injection method.

FIG. 7 shows a first example of a conventional steel wire for cable bolts,
(A) is a sectional view and (B) is a partial external view.

FIG. 8 shows a second example of a conventional steel wire for cable bolts,
(A) is a sectional view and (B) is a partial external view.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Steel stranded wire 2 ... Elemental wire 3 ... Space 4 ... Recess 5 ... Valley 9 ... Perforation 11 ... Filler 12 ... Filler injecting hose 15 ... Ground 16 ... Sealing material

Front Page Continuation (72) Inventor Tadashi Ninomiya 2-3 Kandajimachi, Chiyoda-ku, Tokyo Obayashi Corporation Tokyo Head Office (72) Inventor Satoru Amano 2-3 Kandaji-cho, Chiyoda-ku, Tokyo Stock Company Obayashi Tokyo Head Office (72) Inventor Jun Yamamoto 2-3 Kandajimachi, Chiyoda-ku, Tokyo Obayashi Tokyo Head Office

Claims (5)

[Claims] 1. A steel comprising strands of 4 to 9 strands, which are twisted into one layer to form a valley between adjacent strands and to form a space penetrating in the axial direction at the center. A cable bolt having a wire as a core wire, in which each wire has a non-circular cross-sectional shape such as a trapezoidal shape or a Z shape, which are adjacent to each other in surface contact, and when a steel stranded wire is formed. A cable bolt characterized in that it has irregularities on the outer surface which is the surface layer. 2. The space at the center of the steel strand is
The cable bolt according to claim 1, which has a diameter of 6 mm or more based on the inscribed circle diameter. 3. The step of the unevenness of the outer surface of the strand of the steel strand is 0.2 to 1.0 or more, and the depth of the valley between adjacent strands is 1 mm or more. The cable bolt described in 2. 4. The cable bolt according to claim 3, wherein the twist pitch of the stranded steel wire is 5 to 20 times the stranded wire diameter. 5. The strands of 4 to 9 strands are twisted into one layer to form a valley between adjacent strands, and a space penetrating in the axial direction is formed in the central portion of each strand. However, with a cable bolt having a non-circular cross-sectional shape such as a trapezoid and a Z shape, which are adjacent to each other in surface contact, and which has a stranded steel wire in the core wire having a concavo-convex outer surface portion as a surface layer, What is claimed is: 1. A method of strengthening the ground around an excavation site, comprising the step of drilling a long hole of a predetermined diameter and length in the ground around the excavation site, and
With more than one book inserted loosely and with its rear end protruding slightly out of the long hole, seal the hole entrance around this steel stranded wire with a sealant, and then inject the filler through the sealant. The room temperature solidifying filler is press-fitted into the long hole through the hose, and the press-fitting causes air to be discharged through the central space of the steel strand in the long hole, and then the excess room temperature solidifying filler is discharged. Based on the fact that the completion of the filling of the room temperature solidifying filler into the long holes is confirmed, the cold solidification of the room temperature solidifying filler is stopped by stopping the press-fitting of the room temperature solidifying filler. Reinforcement of excavated ground with cable bolts characterized by strengthening the ground around the excavation site by providing a cable bolt, which is formed by firmly adhering and integrating the filler layer, in the long hole to function as a pile. Method.