WO2008084900A1

WO2008084900A1 - Soil nail anchor

Info

Publication number: WO2008084900A1
Application number: PCT/KR2007/003356
Authority: WO
Inventors: Lee Keun Park
Original assignee: Lee Keun Park
Priority date: 2007-01-08
Filing date: 2007-07-11
Publication date: 2008-07-17
Also published as: KR100704774B1

Abstract

Disclosed is a soil nail anchor for slope reinforcement construction. Spikes having an acute edge are tightly inserted into the inner wall of a reinforcing bore by the pressure of supplied grout, so that a body of the soil nail anchor can be stably anchored. A bore wall protection pipe is coupled to an upper end of the body, so that the inner wall of the reinforcing bore can be prevented from collapsing toward an upper cap, and that the reinforcing bore can be filled with grout after the process of anchoring the body.

Description

Description SOIL NAIL ANCHOR

Technical Field

[1] The present invention relates to a soil nail anchor for slope reinforcement construction. Background Art

[2] The present invention relates, in general, to a soil nail anchor for slope reinforcement construction, and more particularly, to a soil nail anchor for slope reinforcement construction, in which spikes having acute edges are tightly inserted into the inner wall of a reinforcing bore by the pressure of supplied grout, thereby stably anchoring a body of the soil nail anchor, and in which a bore wall protection pipe is coupled to an upper end of the body, thereby preventing the inner wall of the reinforcing bore from collapsing toward an upper cap, and filling the reinforcing bore with grout after the process of anchoring the body.

[3] In general, when civil engineering work is done for residences, industrial parks, or industrial infrastructure such as railroads, highways, and tunnels, natural steep slope topography is used, or artificial steep slope topography is formed by, for instance, excavation work.

[4] Slopes formed naturally or artificially are exposed to dangers such as separation, collapse, etc. due to various factors such as soil pressure, wind pressure, water pressure, and earthquakes.

[5] Hence, in order to prevent the cutoff, collapse, etc. of the slopes, a variety of slope reinforcing methods such as a soil nailing method, a rock bolting method, and a permanent anchoring method are used.

[6] Among the slope reinforcing methods, the soil nailing method is adapted to perform slope leveling, to bore a plurality of reinforcing holes from an upper portion to a lower portion of the slope at regular intervals, to spray compressed air or high-pressure water to eliminate foreign materials such as soil remnants in the reinforcing holes, to insert a nail (called a deformed bar) into each reinforcing hole, fill the reinforcing holes with grout (a mixture of cement, water, and sand), and to install a plate at the entrance of each reinforcing hole. In this method, nails are sequentially inserted into the respective reinforcing holes up to the lower portion of the slope, the reinforcing holes are grouted, and then superficial planting or shotcrete spraying is performed on the slope, thereby completing the slope reinforcement construction.

[7] However, the traditional soil nailing method cannot stably reinforce the slope, because the nail structures and the grout are merely fitted in the reinforcing holes by insertion of the nail structures and then injection and curing of the grout. Further, this soil nailing method has a problem in that the construction period is long, because the grout is injected into the upper reinforcing holes of the slope and is cured for five to seven days, and then the nails and the grout are inserted and injected into the lower reinforcing holes.

[8] In order to solve the problem of the traditional soil nailing method, a soil nail structure, which is capable of reducing a slope reinforcement construction period and enhancing tension resistance by applying an anchoring method to the soil nailing method, has been proposed.

[9] Such a soil nail structure, in which the anchoring method is applied to the soil nailing method, is disclosed in Korean Patent No. 10-0448037 (hereinafter, referred to as "Cross-Reference 1"), entitled "Soil Nail Structure and Soil Nailing Method for Slope Reinforcement Construction."

[10] As in FIGS. 12 and 13, Cross-Reference 1 is characterized in that, in the soil nail structure for slope reinforcement construction, in which a nail 1 is inserted into a hole 3 bored in a rock and then grout is poured into the hole and hardens, the nail has a leading end thereof screwed to an anchor body 18, and is turned to expand anchor blades 16 of the anchor body such that the anchor blades are pressed against or stuck into the inner wall of the blind end of the bored hole 3, so that the nail body applies tensile force to the nail 1 installed in the rock.

[11] However, Cross-Reference 1 makes use of a screwing force for the purpose of the coupling of the anchor body 18 and the nail 1, and the spreading of the anchor blades 16 of the anchor body. To this end, separate tools are used to form a thread in the nail 1 and apply the screwing force. Hence, productivity and construction convenience are reduced.

[12] More specifically, for the purpose of construction, a boring machine bores the rock first. Then, the anchor body 18, in which the nail 1 is screwed, is inserted into the bored hole 3, and the nail 1 is turned using a rotating tool. At this time, since it is nearly impossible to manually operate the rotating tool, a pneumatic rotating tool is used to expand the anchor blades 16. Thus, when constructed, a separate rotating tool must be used in addition to the boring machine.

[13] Further, the boring process and the process of anchoring the soil nail structure are subject to interruptions in construction because two types of installing tools are required. Construction is thus inconvenient in terms of process flow.

[14] In particular, when anchored to the inner wall of the bored hole 3, the anchor blades

16 scrape down the inner wall of the bored hole 3 in a direction in which they are bent and spread by a tapered body 14, so that the anchoring force of the anchor body 18 is reduced. Further, as in FIG. 10, the ends of the anchor blades 16, which are inserted into the bored hole 3, are in a horizontal plane, which faces the entrance of the bored hole 3. For the reason, when tensile force is applied to the anchor body 18, it acts in a direction perpendicular to the horizontal plane of the end of each anchor blade 16. The tensile force, which is applied in a direction perpendicular to the horizontal plane, is concentrated on the superficial part of the inner wall of the bored hole, so that the inner wall in front of the anchor blades 16 collapses. Accordingly, the anchoring force of the anchor body 18 is lost, and thus it is difficult to maintain the tensile force.

[15] Meanwhile, Korean Patent Application No 10-2005-0023887, (hereinafter, referred to "Cross-Reference 2") entitled "Earth Anchor Structure," has been proposed.

[16] As in FIGS. 14 through 16, Cross-Reference 2 is characterized in that, in the earth anchor structure, which is inserted into a bored hole 100 and expanded toward an inner wall of the bored hole, and thereby assists in the anchoring of a tensile material, an anchor cap 16 is installed on one side of an anchor body 14 to which steel wires 10 are coupled, in that expansion anchors 20 are installed between the anchor cap 16 and the anchor body 14 to thus protrude in a radial direction due to resilient force of springs 18 such that the anchor cap 16 acts as a support for supporting the expansion anchors 20 against the tensile force of the steel wires, and in that a locking tool 22 is surrounded by the expansion anchors 20 such that it is inserted into the anchor body 14 and maintains and releases the inserted state to permit radial protrusion.

[17] Cross-Reference 2 is directed to providing the earth anchor structure, which is adapted to use a steel wire material (steel wire) as the tensile material, compared to Cross-Reference 1, which uses only the nail (deformed bar) as the tensile material, which sufficiently secures binding rigidity of the expansion parts and the anchor body, and which makes it more convenient to expand the expansion parts in the bored hole, thereby enabling simple construction.

[18] However, according to Cross-Reference 2, each expansion anchor 20, which is in contact with the inner wall of the bored hole 100 in a horizontal direction, has a wide cross section, and is expanded toward the inner wall of the bored hole 100 depending on the resilient force of the corresponding spring 18. As such, the expansion anchors 20 maintain the contacted state without being stuck deep into the inner wall of the bored hole 100, so that the anchoring force of the anchor body 14 is not positively exerted. Further, when external force stronger than the resilient force of the springs 18 is applied in the anchoring process, the expansion anchors 20 retreat from their original positions.

[19] The locking tool 22 is provided to release the locked state of the expansion anchors

20. Thus, the locking tool 22 is adapted such that the locked state of the expansion anchors 20 can be released by the manual operation of a worker or when the insertion of the anchor body 14 is completed. However, it is impossible in practice for the worker to manually operate a heavy head rod 40, the diameter of which has ranges from 12 mm to 15 mm and the length of which ranges from 12 m to 30 m, corresponding to the depth of the bored hole, and thereby release the locking tool 22.

[20] Further, as in FIG. 11, the end of each expansion anchor 20, which is stuck into the inner wall of the bored hole 100, is flat in a horizontal direction, and thus is aligned with the entrance of the bored hole 100. For the reason, when the tensile force is applied to the anchor body 14, it acts in a direction perpendicular to the horizontal plane at the end of each expansion anchor 20. The tensile force, which is applied in a direction perpendicular to the horizontal plane, is concentrated on a superficial part of the inner wall of the bored hole, so that the inner wall in front of the expansion anchors 20 collapses. Accordingly, as in Cross-Reference 1, it is difficult to maintain the anchoring force of the anchor body 14, and in most cases, reconstruction must be carried out.

[21] Consequently, Cross-References 1 and 2 have the following problems in that:

[22] the anchor blades 16 or the expansion anchors 20, as means for anchoring the nail anchor structure, fail to secure more stable and firm anchoring force in the process in which they are inserted into and anchored to the inner wall of the bored hole 3 or 100;

[23] the inner wall in front of the anchor blades 16 or the expansion anchors 20 collapses due to the improper structure of the anchor blades 16 or the expansion anchors 20 when the tensile force is applied to the anchor body 18 or 14, and the anchoring force is lost, so that reconstruction must be carried out; and

[24] the anchor blades 16 or the expansion anchors 20 are expanded using a separate tool, such as a pneumatic rotating tool or a locking tool 22, and the grout is supplied into the bored hole 3 or 100 using the grouting machine, so that continuity and the convenient constructability between the anchoring processes are reduced.

[25] The reference numbers used for the Cross-References 1 and 2 are limited to those indicated by the detailed description of the invention, and so they must be distinguished from those used for the main parts of the present invention. Disclosure of Invention Technical Problem

[26] Accordingly, the present invention has been made in an effort to solve the problems occurring in the related art, and an object of the present invention is to provide a soil nail anchor for slope reinforcement construction, in which spikes having an acute edge are tightly stuck into the inner wall of a reinforcing bore by the pressure of supplied grout, thereby stably anchoring the body of the soil nail anchor, and propagating a tensile force applied to the body deep into the inner wall by means of an upper rake face of the acute edge of each spike, and in which a bore wall protection pipe is coupled to an upper end of the body, thereby preventing the inner wall of the reinforcing bore from collapsing toward an upper cap due to the propagation of the tensile force when the tensile force is applied to the body of the soil nail anchor, and filling the reinforcing bore with grout after the process of anchoring the body to thereby perform the slope reinforcement construction in a more stable, economical manner.

[27] The configuration of the present invention for accomplishing the object will be described in detail with reference to the accompanying drawings.

Advantageous Effects

[28] As described above in greater detail, the present invention has the following advantages. The spikes 20 can be stuck into the inner wall of the reinforcing bore 200 with stronger force derived from the propellant force of the piston head 70 supplied with the grout supply pressure, be easily stuck into the inner wall of the reinforcing bore 200 due to the acute edge 21 thereof defined by the upper inclined face 21a and the lower inclined face 21b, and minimize the collapse of the superficial part of the inner wall by allowing the tensile force, which is applied to the body 10 by the upper rake face 21a of the acute edge 21 of each spike, to propagate to the deep part of the inner wall of the reinforcing hole.

[29] The bore wall protection pipe 90 is coupled to the upper end of the body 10, thereby preventing the inner wall of the reinforcing bore from collapsing toward the upper cap 50 due to the propagation of the tensile force to the ground around the spikes 20. Thereby, even in the state in which the grout is not cured, the tensile force required by a design can be realized, so that the ground can be protected from major deformation occurring in the early stage after the reinforcing hole 200 is excavated, regardless of a hardening period from 5 days to 7 days in which the grout is hardened.

[30] The grout, which is supplied from the mounting holes 11 in succession of the process of anchoring the body 10, can be charged into the reinforcing bore 200, so that slope reinforcement construction can be carried out in a more rapid, stable, economical manner.

Brief Description of the Drawings

[31] FIG. 1 is an exploded perspective view illustrating an embodiment of the present invention;

[32] FIGS. 2, 3 and 4 are sectional views illustrating the operation of the present invention;

[33] FIG. 5 is a top plan view illustrating the operation of spikes of the present invention;

[34] FIG. 6 is a sectional view illustrating the constructed state of the present invention; [35] FIG. 7 is an exploded perspective view illustrating another embodiment of the present invention;

[36] FIG. 8 is a sectional view illustrating another embodiment of the present invention;

[37] FIG. 9 is a view illustrating the state of a reinforcing hole when tensile force is applied to a soil nail anchor of the present invention;

[38] FIG. 10 is a view illustrating the state of a reinforcing hole when a tensile force is applied to an existing soil nail anchor of Cross-Reference 1;

[39] FIG. 11 is a view illustrating the state of a reinforcing hole when a tensile force is applied to an existing soil nail anchor of Cross-Reference 2;

[40] FIG. 12 is a perspective view for explaining an existing soil nail anchor of Cross-

Reference 1;

[41] FIG. 13 is a sectional view for explaining the operation of an existing soil nail anchor of Cross-Reference 1; and

[42] FIGS. 14 through 16 are views illustrating an existing soil nail anchor of Cross-

Reference 2.

[43] <Description of Reference Numbers of Main Parts in the Drawings>

[44] 10: body, 11: mounting hole, 12: seating recess, 12a: screw hole,

[45] 13: external thread, 14: internal thread, 15: step,

[46] 16: pressing chamber, 17: screw hole, 18: mounting hole

[47] 20: spike, 21: acute edge, 21a: upper inclined face,

[48] 21b: lower inclined face, 22: arcuate inclined face

[49] 22a: arcuate vertical face, 23: slide groove, 24: ball bearing groove

[50] 30: stopper, 31: fixing bolt, 40: ball bearing, 50: upper cap,

[51] 51: spiral-threaded hole, 52: external thread, 53: through-hole,

[52] 54: fastening hole, 55: tapered hole, 56: wedge, 60: cylinder,

[53] 61: partition, 62: injection pipe, 63: sealing ring,

[54] 64: grout supply hose, 70: piston head, 71: conical surface,

[55] 72: guide hole, 73: sealing ring, 80: lower cap,

[56] 81: fastening hole, 82: fixing hole, 83: guide pin,

[57] 84: fastening nut, 85: fixing pin, 86: thread

[58] 90: bore wall protection pipe, 91: internal thread

[59] 100: nail, 101: spiral thread, 102: steel wire

[60] 200: reinforcing bore

Best Mode for Carrying Out the Invention

[61] FIG. 1 is an exploded perspective view illustrating a first embodiment of the present invention. FIGS. 2, 3 and 4 are sectional views illustrating the operation of the present invention. FIG. 5 is a top plan view illustrating the operation of spikes of the present invention. FIG. 6 is a sectional view illustrating a constructed state of the present invention.

[62] The soil nail anchor of the present invention comprises:

[63] an upper cap 50, which has a spiral-threaded hole 51, to which a nail 100 is coupled, in the center thereof, a pair of through-holes 53 facing each other in the diametrical direction of the spiral-threaded hole 51, and an external thread 52 in an outer circumferential surface thereof;

[64] a bore wall protection pipe 90, which has an internal thread 91 in the lower inner circumferential surface thereof and prevents the inner wall of a reinforcing bore 200 from collapsing around the upper cap 50;

[65] a body 10, which includes: an external thread 13, to which the internal thread 91 of the bore wall protection pipe 90 is screwed, in the upper outer circumferential surface thereof; an internal thread 14, to which the external thread 52 of the upper cap 50 is screwed, in the upper inner circumferential surface thereof; a pressing chamber 16, which extends from the internal thread 14 on the border of a step 15; a plurality of mounting holes 11, which radially communicates with and is perpendicular to the pressing chamber 16 and has an arcuate shape when viewed from the top; a plurality of seating recesses 12, each of which is located under the center of a respective mounting hole 11 ; a plurality of ball bearings 40, which are screwed into mounting holes 18, each of which extends from the bottom of the body to the bottom of each mounting hole 11, around the seating recesses 12; and a plurality of screw holes 17, which is formed in the bottom of the body;

[66] a plurality of spikes 20, each of which has an arcuate shape when viewed from the top so as to have the same shape as a respective mounting hole 11, and includes: a slide groove 23 and a ball bearing groove 24, both of which are formed in the bottom thereof; an arcuate inclined face 22 and an arcuate vertical face 22a, both of which are continuously formed on an inner side thereof; and an acute edge 21, which is defined by an upper rake face 21a and a lower rake face 21b on an outer side thereof;

[67] a plurality of stoppers 30, which are coupled to respective seating recesses 12 of the body 10 by fixing bolts 31, and are inserted into the slide grooves 23 of the spikes 20 upper ends thereof so as to stop outward movement of the spikes 20;

[68] a cylinder 60, which includes: an injection pipe 62, an upper end of which is inserted into the through-holes 53 of the upper cap 50 in the bore wall protection pipe 90 such that a grout supply hose 64 is coupled thereto, and a lower end of which is screwed to a partition wall 61; and a sealing ring 63, which is coupled in the middle of an outer circumferential surface thereof, and which is inserted into the pressing chamber 16 of the body 10;

[69] a piston head 70, which includes: a guide hole 72 in the center thereof; a conical surface 71, which is inclined toward a vertex in a downward direction; and a sealing r ing 73, which is coupled to an upper outer circumference of the piston head, and which is inserted into the pressing chamber 16 of the body 10;

[70] a lower cap 80, which includes: a guide pin 83 coupled with? a fastening nut 84 at the center thereof; and a plurality of fixing holes 82 aligned with the screw holes 17 formed in the bottom of the body; and

[71] a plurality of fixing pins 85, which are inserted into the fixing holes 82 of the lower cap 80 and are then screwed into the screw holes 17 of the body 10, each of which includes an external thread 86 fixing the lower cap 80 to the bottom of the body 10 at an upper end thereof, and sticks the body 10 into the bottom of the reinforcing bore 200.

[72] In the present invention constructed as described above, the grout is supplied to the pressing chamber 16 inside the body 10 at high pressure, and the spikes 20, each of which has an acute edge 21, are stuck into the inner wall of the reinforcing bore 200, so that the body 10 of the soil nail anchor is anchored fast to the lower end of the reinforcing bore 200.

[73] The tensile force applied to the body 10 is propagated deep into the inner wall of the reinforcing bore 200 by the upper rake face 21a of the acute edge 21 of each spike 20. The bore wall protection pipe 90 is coupled to the upper end of the body 10, and then, when the tensile force is applied to the body 10 of the soil nail anchor, the inner wall of the reinforcing bore 200 is prevented from collapsing toward the upper cap by the propagation of the tensile force. The grout pushed out of the mounting holes 11 in the process of anchoring the body can be put in from the bottom to the entrance of the reinforcing bore 200. Hereinafter, the configuration of the present invention will be described in greater detail together with the anchoring process.

[74] First, as for the process of assembling the present invention, the upper cap 50 is fastened to the internal thread 14 of the upper inner circumferential surface of the body 10 by screwing.

[75] The upper cap 50 is rotated using a separate fastening tool (not shown), so that the external thread 52 thereof is fastened to the internal thread 14. After protrusions on the bottom of the fastening tool are inserted into a pair of fastening holes 54 in the top of the upper cap 50, the fastening tool is turned in a screwing direction using a handle thereof. When the bottom, or the lower end, of the upper cap 50 is placed on the step 15, the upper cap 50 is no longer turned. Thereby, the process of fastening the upper cap is completed.

[76] When the process of fastening the upper cap 50 is completed, the bore wall protection pipe 90 is fastened to the external thread 13 of the body 10 by screwing.

[77] When the process of fastening the bore wall protection pipe 90 is completed, the cylinder 60 is inserted from the bottom of the body 10 until the injection pipe 62 passes through any one of the through-holes 53 drilled in the upper cap 50 to come into contact with the bottom of the upper cap 50.

[78] Then, the piston head 70 is inserted from the bottom of the body 10 with the flat top thereof facing the cylinder 60 until the flat top thereof comes into contact with the bottom of the cylinder 60.

[79] When the processes of inserting the cylinder 60 and the piston head 70 are completed, the guide pin 83 at the center of the lower cap 80 is fastened with the fastening nut 84. The upper end of the guide pin 83 is adjusted so as to be located in the mouth of the guide hole 72 of the piston head 70, and then the screw holes 17 of the body 10 are aligned with the fixing holes 82 of the lower cap 80. Then, the external threads 86 of the fixing pins 85 pass through the respective fixing holes 82 in the lower cap 80 to be screwed to the screw holes 17 in the body 10.

[80] After the lower cap 80 is fastened to the bottom of the body 10 using the fixing pins

85, the spikes 20 are inserted into the respective mounting holes 11, which are radially formed in the outer circumferential surface of the body 10.

[81] The spikes 20 are inserted such that the arcuate inclined faces 22 thereof are in contact with the conical surface 71 of the piston head 70, and then the stoppers 30 are inserted into the seating recesses 12. Continuously, the fixing bolts 31 are bolted to screw holes 12a. Thereby, the assembly of the present invention is completed.

[82] The present invention, assembled as described above, couples the nail 100 to the upper cap 50 in a manner such that a spiral thread 101 of the nail 100 is screwed to the spiral-threaded hole 51 of the upper cap 50, couples the grout supply hose 64 to the injection pipe 62, and is inserted and anchored in the lower end of the reinforcing bore 200. Hereinafter, the anchoring process of the present invention will be described in detail.

[83] When a worker inserts the body 10 of the soil nail anchor of the present invention, which is coupled to the leading end of the nail 100, from the entrance to the lower end of the reinforcing bore 200, the soil nail anchor moves down to the lower end of the reinforcing bore 200 due to the insertion accelerating force applied by the worker and the self-weight of the body 10, and is then stopped when the fixing pins 85 are stuck into the bottom of the reinforcing bore 200, as in FIG. 2.

[84] As in FIG. 6, the reinforcing bore 200 is bored such that the lower end thereof is inclined so as to be lower than the entrance thereof, so that the worker can easily insert the nail 100 and the body 10.

[85] When the process of fixing the body 10 to the lower end of the reinforcing bore 200 is completed, a grouting supply apparatus (not shown) is operated to supply the grout to the grout supply hose. [86] The grout supplied at high pressure is introduced into the injection pipe 62 via the grout supply hose 64. The grout passing through the injection pipe 62 enters the space under the partition wall 61 of the cylinder 60, and the piston head 70 is gradually lowered from the pressing chamber 16 by the grout supply pressure.

[87] As soon as the piston head 70 is lowered, the spikes 20 are pushed out of the mounting holes 11, and then move toward the inner wall of the reinforcing bore 200. Now, the process in which the piston head 70 is lowered to force the spikes 20 to move outward will be described.

[88] In the state in which the arcuate inclined faces 22 of the spikes 20 are in contact with the conical surface 71 of the piston head 70, the diameter of which is relatively small, as in FIG. 2, the piston head 70 begins to be lowered by the grout supply pressure, as in FIG. 3, and finally the arcuate inclined faces 22 of the spikes 20 come into contact with the conical surface 71 of the piston head 70, the diameter of which is relatively large. Thereby, the spikes 20 are gradually pushed outward from the mounting holes 11. Continuously, the conical surface 71 of the piston head 70 goes through the arcuate inclined faces 22 of the spikes 20 as in FIG. 4, and thus the arcuate vertical faces 22a of the spikes 20 comes into contact with the upper outer circumferential surface of the piston head 70, which is not indicated by a reference number. At that time, the outward movement of the spikes 20 is stopped.

[89] The piston head 70, which is lowered by the grout supply pressure, is gradually moved in a vertical downward direction without swinging by the guide pin 83 inserted into the guide hole 72, and then comes into contact with a disc of the guide pin 83, which is not indicated by any reference number, at the lower end thereof. At that time, the downward movement is stopped.

[90] As described above, the piston head 70 is lowered by the grout supply pressure, and thereby the spikes 20 come out of the mounting holes 11 to be anchored to the inner wall of the reinforcing bore 200. Thus, the spikes 20 are propelled by the piston head 70 receiving the grout supply pressure, so that they can be more powerfully stuck into the inner wall of the reinforcing bore 200, and particularly, can be easily inserted into the inner wall of the reinforcing bore 200 by the acute edge 21, which is defined by the upper and lower rake faces 21a and 21b of each spike 20.

[91] Each spike 20 moves outward while naturally sliding on the bottom of the corresponding mounting hole 11 by means of the corresponding ball bearing 40, which is in contact with the ball bearing groove 24 in each spike. Then, the spikes 20 stop moving outward when the arcuate vertical faces 22a thereof come into contact with the upper outer circumferential surface of the piston head 70. Afterwards, although the grout supply pressure is applied, the spikes 20 are caught by the stoppers 30, each of which contacts the slide groove 23 at the top thereof, thereby maintaining a stopped state.

[92] The opposite ends of each ball bearing groove 24 have spherical concavities, each of which is deeper than a semicircular groove along which the ball bearing 40 slides. In the state in which the spikes 20 are retreated into the body 10, each ball bearing 40 is brought into close contact with the deep spherical concavity of the outer end of the corresponding ball bearing groove 24 by a spring (not shown), which is elastically installed in the respective ball bearing. Thus, even if an external force is applied when the soil nail anchor is transported for the purpose of installation, the ball bearings inhibit the movement of the spikes 20 so as to prevent the spikes 20 from coming out of the mounting holes 11. When the outward movement of the spikes 20 is completed, each ball bearing 40 comes into close contact with the deep spherical concavity of the inner end of corresponding ball bearing groove. Thus, even if an external force is applied, the ball bearings inhibit the movement of the spikes 20 so as to prevent the spikes 20 from being pushed into the mounting holes 11.

[93] After the body 10 is anchored to the lower end of the reinforcing bore 200 by the spikes 20, the grout continues to flow out from the mounting holes 11, and thus fills the reinforcing bore 200 from the lower end to the upper end thereof.

[94] When the filling of the reinforcing bore 200 with the grout is completed, a plate is installed on the upper end, the entrance, of the reinforcing bore 200, and the entrance- side end of the nail 100 is anchored. Then, the ground is stably reinforced by applying a tensile force.

[95] The tensile force applied to the body 10 in the anchoring process is propagated deep into the inner wall of the reinforcing bore 200 by the upper rake face 21a of the acute edge 21 of each spike 20. The bore wall protection pipe 90, which is coupled to the upper end of the body 10, not only prevents the inner wall of the reinforcing bore from collapsing toward the upper cap 50 due to the tensile force that is transmitted to the superficial part of the inner wall of the reinforcing bore around the spikes 20 when the nail 100 is subjected to tension, but also firmly supports the ground. Thereby, the tensile force required by a design is secured, so that a stable reinforcement structure is obtained.

[96] The upper rake face 21a of each spike 20 is inclined toward the inner wall of the reinforcing bore with respect to the acute edge 21, so that the tensile force is directed in a direction perpendicular to the upper rake face 21a, so that it is propagated deep into the inner wall of the reinforcing bore that the upper rake face 21a faces, so that the risk of collapse of the superficial part of the inner wall of the reinforcing bore is minimized.

[97] According to the configuration of the present invention, the configuration of the upper cap 50 for coupling the nail 100 as the tensile member can be modified in order to use the tensile member as at least one steel wire member 102, as in FIGS. 7 and 8. To this end, the upper cap 50 is provided with several tapered holes 55, and a wedge 56 fixing one end of each steel wire member 102 is inserted into each tapered hole 55. [98] In other words, the upper cap 50 can be configured so as to be able to selectively use either a nail 100 or a steel wire member 102 inserted into the reinforcing bore 200.

Claims

[1] A soil nail anchor for slope reinforcement construction, in which an upper cap

(50) is screwed to an inner circumference of a body (10), a lower cap (80) is coupled to a bottom of the body, and several spikes (20) are radially mounted inside an intermediate portion of the body, thereby anchoring the body (10) to an inner wall of a reinforcing bore (200), characterized in that: the upper cap (50) has a pair of through-holes (53) facing each other centered around a spiral-threaded hole (51), into which a nail (100) is coupled; the body (10) includes an external thread (13) in an upper outer circumference thereof, and a pressing chamber (16), which extends from an internal thread (14) in a border of a step (15); a plurality of mounting holes (11) radially communicates with and is perpendicular to the pressing chamber (16) and has an arcuate shape when viewed from above; a plurality of seating recesses (12) is formed under a center of the respective mounting holes (11); a plurality of ball bearing (40) is screwed into mounting holes (18), each of which extends from the bottom of the body to a bottom of each mounting hole (11), around the seating recesses (12); and a plurality of screw holes (17) is formed in the bottom of the body; each spike (20) has an arcuate shape when viewed from above so as to be identical in shape to the respective mounting hole (11) and includes: a slide groove (23) and a ball bearing groove (24), both of which are formed in a bottom thereof; an arcuate inclined face (22) and an arcuate vertical face (22a), both of which are continuously formed on an inner side thereof; and an acute edge (21), which is defined by an upper rake face (21a) and a lower rake face (21b) on an outer side thereof; the external thread (13) of the body (10) is screwed to a bore wall protection pipe (90), which prevents the inner wall of the reinforcing bore (200) from collapsing toward the upper cap (50); a plurality of stoppers (30) is coupled to the respective seating recesses (12) by fixing bolts 31, such that upper ends thereof are inserted into the slide grooves (23) in the spikes (20) so as to stop outward movement of the spikes (20); a cylinder (60) is inserted into the pressing chamber (16), in a manner such that an injection pipe (62), an upper end of which is inserted into the through-holes (53) of the upper cap (50) in the bore wall protection pipe (90) such that a grout supply hose (64) is coupled thereto, is screwed to a partition wall (61) and such that a sealing ring (63) is coupled thereto in a middle of an outer circumferential surface thereof; a piston head (70) is inserted into the pressing chamber (16) of the body (10) in a manner such that a guide hole (72) is formed in a center thereof, such that a conical surface (71) is formed at a lower end thereof, and such that a sealing ring (73) is coupled on an upper outer circumferential surface thereof; and the lower cap (80) is fixed to the bottom of the body (10) by fixing pins (85) stuck into a bottom of the reinforcing bore (200) in a manner such that a guide pin (83) is coupled by a fastening nut (84) at a center thereof and such that a plurality of fixing holes (82) is formed.