Description of the Prior Art A ground anchor (also known as an earth anchor) has been widely used in timbering methods for preventing the collapse of ground while excavation work is performed for the purpose of constructing buildings or other structures on the ground surface.

There are a variety of different types of ground anchors, such as the compression, the tension, or the ground pressure types.

The ground anchor of the tension type has been most widely used, however, tension members cannot be removed from the anchor. Because the ground pressure anchor type is restrained by applying point anchoring ground pressure, its removal from the ground is very difficult.

Furthermore, the tension type anchor is reduced in anchoring power by the tension fissure of a grout body, and the ground pressure type anchor is applied only on bedrock capable of the point anchoring ground pressure.

In general, when the ground anchor is inserted in an excavated anchor hole on the ground surface, tension members, such as steel wires, are used to secure the anchoring power. The anchoring power stabilizes a soil sheathing wall installed on an excavated surface for safety in construction work during deep excavation. However, after construction, if tension members are left in the excavated hole and another building is built on the ground near them, the tension members obstruct the construction work, and moreover, a construction fee for removing the tension

members is added.

To solve those problems, an example of a ground anchor which is capable of disassembly is disclosed in Korean Publication No. 96-4273. However, the ground anchor of the prior art has several problems, namely, that the number of components is relatively large, a manufacturing cost is increased and assembly and construction work are complicated considerably. Furthermore, tension members cannot be removed from the ground anchor without using a draw-bench.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a ground anchor overcoming the above enumerated difficulties.

It is another object of the present invention to provide a ground anchor from which tension members are easily removed and which is applied to any type of ground.

It is a further object of the present invention to provide a ground anchor which allows ease in manufacturing and assembly.

It is still another object of the present invention to provide a ground anchor which can be inserted into even a small anchor hole.

To achieve the above objects, this invention provides a ground anchor assembled as follows: a support is situated on a cylindrical body; a wedge case seats on the support, a wedge is inserted into the wedge case; a cover puts on the front end portion of the body; and, a bolt is fastened to the wedge.

The body has an annular stepped portion at the lower end of the inner circumference and a wire insertion hole. The support, which is made of a thermoplastic resin, has a heating member buried therein and a cable connected to the heating member. The cable passes through the wire insertion hole of the body and extends outward. The wedge case has a plurality of semicircular grooves formed on the tapered inner circumference at equal intervals and the wedge has a plurality of semicircular grooves formed on the inversely tapered outer circumference. The semicircular grooves of the wedge have the same number with that of the wedge case and are grooved in the opposite direction to that of the wedge case. Tension members are caught tight in spaces between the semicircular grooves of the wedge

case and the wedge.

According to the present invention, because the ground anchor tightly catches all tension members using only one wedge, the wedge case can be made in a small size, and further, the size of a hole for anchoring it is reduced, thereby making excavation work comfortable and reducing excavation costs considerably.

Other objects and benefits of the present invention will become apparent upon consideration of the following written description taken in conjunction with the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS Understanding that these drawings depict only typical embodiments of the invention and are, therefore, not to be considered limiting of its scope, the invention will be described with additional specificity and detail through use of the accompanying drawings in which: Figure 1 is a partially exploded view of a ground anchor according to the present invention; Figure 2 is a partially cut front view of a support; Figure 3 is a plan view of an anchor body in which a wedge case and a wedge are positioned; Figure 4 is a longitudinal sectional view of the anchor body in which tension members are caught tightly; Figure 5 is a longitudinal sectional view of the anchor body when a thermoplastic resin is pyrolized; and, Figure 6 is a longitudinal sectional view of the anchor body when a wedge gripping to the tension members is released by pyrolysis.

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail hereinafter with reference to the accompanying drawings, wherein the same reference characters designate corresponding parts throughout several views. It is to be understood that these drawings depict only typical embodiments of the invention and are, therefore, not to be

considered limiting of its scope.

Referring now to Figure 1, a ground anchor according to the present invention essentially comprises a body 1, a support 2, a wedge case 3, a wedge 4 and a cover 5.

The body 1, which is formed in a cylindrical shape, has an annular stepped portion 11 formed on the lower end of the inner circumference, a wire insertion hole 12 formed on the stepped portion 11 in an axial direction, an inner threaded portion 13 for coupling a reinforcing member of a concentric circle with the stepped portion 11, an outer threaded portion 14 formed on an outer surface of an upper portion, and a tension member hole 15 for inserting tension members. The tension member hole 15 is to connect a hose made of a polyethylene resin, for the prevention of the intrusion of foreign matters such as grout material, earth or sand. The reinforcing member is to improve the frictional force between the anchor body and concrete poured into an anchor hole in the ground surface.

The support 2 sits on the stepped portion 11 of the body 1. The support 2 includes thermoplastic resin 21, a heating member 22 buried in the thermoplastic resin 21 and a cable 23 connected to the heating member 22. The cable 23 of the support 2 passes through the wire insertion hole 12 of the body 1 and extends outward.

One of the properties of the thermoplastic resin 21 is that it is kept in a solid state at room temperature, but melted or vaporized by pyrolysis when high heat is applied to the thermoplastic resin 21. The resin with the above properties comprises MC nylon (Trade name) of the polyamide group, polyacetal resin and polycarbonate resin.

The heating member 22 is adhered to the lower end of the thermoplastic resin 21 or buried in the thermoplastic resin 21 by putting it in the mold when the thermoplastic resin 21 is cast in a mold. The heating member 22 buried in the thermoplastic resin 21 serves as a heat source to pyrolyze the thermoplastic resin 21.

The cable 23 extending outward is connected to an external power supply so as to serve an electric current through the cable 23 to the heating member 22.

The support 2 has an outer diameter equal to an inner diameter of the body 1 and an inner diameter equal to an outer diameter of the lower portion of the wedge case 3. Therefore, the support 2 is positioned tightly between the body 1 and the

wedge case 3, so that the thermoplastic resin 21 is prevented from coming out through a gap between the body 1 and the wedge case 3, though compressed under high pressure.

That is, since the thermoplastic resin 21 is situated without the gap between the body 1 and the wedge case 3, the thermoplastic resin 21 can stand even a severe anchoring load transmitted through the tension member and cannot break out through the gap.

The support 2 also has insulating plates 24 on the upper and lower surfaces of the thermoplastic resin 21. The insulating plates 24 isolate electrically the heating member 22 from the stepped portion 11 of the body 1 and a bottom surface of the wedge case 3, which are made of metal. Therefore, when the heating member 22 is electrically charged to remove the tension members from the ground anchor, the ground anchor is prevented from a leak of electricity so that it can be used without a waste of electricity and preventing an accident from electric shock. However, it will be understood that it is not essential in the present invention.

The reason is as follows: when the heating member 22 is initially charged with electricity, the thermoplastic resin 21 around the heating member 22 is melted by the pyrolysis and flows out so that the melted thermoplastic resin 21 blocks up the contact surfaces between the body 1 and the heating member 22, and between the heating member 22 and the wedge case 3, thereby insulating them from each other.

Moreover, the remainder, not undergoing pyrolysis, also functions as an insulator. Therefore, the insulating plates 24 are not essential, but used for providing a more excellent insulating effect.

Returning to Figure 1, when the support 2 is decreased in volume by pyrolysis, the wedge case 3, which restrains the tension members placed between the wedge case 3 and the wedge 4 in the body 1, sinks down, and thereby the gripping force on the tension members is reduced and the tension members can be removed from the ground anchor.

The wedge case 3, which has an outer diameter equal to the inner diameter of the body 1, has a stepped portion 31 formed on the lower portion of the wedge case 3 and a jaw portion 32 formed on the lower end portion of the wedge case 3 and the

front end of the stepped portion 31. The stepped portion 31 of the wedge case 3 has an outer diameter equal to the inner diameter of the stepped portion 11 and is closely inserted into the stepped portion 11. The jaw portion 32 has a flat surface to be in close contact with the upper surface of the support 2.

The wedge case 3 further includes a plurality of tapered holes 33 formed on the upper portion, and a plurality of semicircular grooves 34 formed at predetermined intervals along the circumference of the tapered holes 33.

The wedge 4 of an inverse cone shape for pressing outward all tension members located in the semicircular grooves 34 has a plurality of tapered portions 41 arranged at the same intervals with the tapered holes 33 of the wedge case 3, and a plurality of semicircular grooves 42 formed in the same number with the semicircular grooves 34. The semicircular grooves 42 are grooved in the opposite direction to the semicircular grooves 34. Therefore, when the wedge 4 is inserted into the wedge case 3, the semicircular grooves 34 and 42 form almost a circular shape, and the tension members are fastened tightly between the semicircular grooves 34 and 42.

The wedge 4 further has a neck portion which protrudes from the upper center portion and has a spiral groove 43 on its inner surface.

When the tension members are tightly inserted between the wedge case 3 and the wedge 4, a cover 5 which has an inner threaded portion 52 is coupled to the outer threaded portion 14 of the body 1. The cover 5 serves to stabilize the wedge 4 inserted in the wedge case 3, and to prevent the wedge 4 from following the wedge case 3 when the support 2 is decreased in volume by the pyrolysis of the thermoplastic resin 21, and thereby the wedge case 3 sinks downward. Furthermore, the cover 5 can prevent foreign matters such as soil, pebbles, or dry leaves from intruding into the front end portion of the body 1 until the tension members are removed from the anchor after inserting the anchor into the anchor hole in the ground surface.

In order to prevent instability of the tension members by movement of the cover 5 and the wedge 4 fastened to the cover 5, a bolt 6 is inserted through a hole 51 formed on the center portion of the cover 5 and coupled to the spiral groove 43 of the neck portion.

The cover 5 also has a head portion 53, in which the head of the bolt 6 is

placed, and has an inner diameter larger than the diameter of the head of the bolt 6, thereby the bolt is easily inserted into the hole 51.

A low elastic ring 7 is placed under the head of the bolt 6. When the wedge 4 is fixed to the cover 5 with the bolt 6 and the bolt 6 is pulled toward the tension direction by the tension members with the tension force, the low elastic ring 7 provides the bolt 6 with some space to move in the tension direction, thereby maintaining an initially strong gripping power to the tension members by the wedge 4. The low elastic ring 7 is situated on the bottom of the head portion 53 with a space for moving the ring 7, when the ring 7 is compressed by the tension force.

Referring to Figure 4, the process of assembly for inserting the tension members into the anchor body will be described in detail.

The support 2 with the cable 23 at the rear portion of the support 2 is inserted into the body I and sits on the stepped portion 11. At this time, the cable 23 is inserted into the wire insertion hole 12 and connected to a coated lead wire (e) with a length longer than that of the anchor hole in the ground surface. The wedge case 3 is located on the support 2 inserted in the body 1.

In the meantime, the tension members (a) having the same number with the semicircular grooves 34 and 42 are inserted through the tension member hole 15 and the stepped portion 31 of the wedge case 3, and then, each tension member (a) is situated in each groove 34.

The wedge 4 is inserted into the wedge case 3 in a way that the location of each semicircular groove 42 of the wedge 4 is corresponded to the semicircular groove 34 of the wedge case 3. When the wedge 4 is tensioned in the direction of insertion, a load greater than the anchoring load of the tension members is applied to fasten the tension members (a), and then, the cover 5 puts on the front end portion of the body 1.

At this time, it is stable as the bottom of the cover 5 is contacted to the upper surface of the wedge 4 closely. If the cover 5 is not in contact with the wedge 4, there is a possibility that the wedge 4 will move toward the cover 5, and thereby the gripping power to the tension members is weakened.

The bolt 6 with the low elastic ring 7 under the head thereof is inserted into the hole 51 of the cover 5, to be coupled to the spiral groove 43 of the wedge 4. The

space in the hole 51 in which the bolt 6 is inserted and a space of a portion where the cover 5 is connected to the body 1 is waterproofed by injecting a sealing material (8a).

At the rear portion of the tension members, a rigid plastic conduit (c) covers all the tension members (a). A front end portion of the rigid plastic conduit (c) is pushed through the tension member hole 15 into the stepped portion 31, so that the rigid plastic conduit (c) is located between the stepped portion 31 and the tension members (a). At this time, the outer surface of the front end portion of the rigid plastic conduit (c), which is coated with a sealing material (8b), is inserted into the stepped portion 31, and being scratched with an inner surface of the stepped portion 31. The sealing material (8b) prevents a permeation of water along the outer surface of the rigid plastic conduit (c), thereby preventing corrosion of the tension members in contact with the semicircular grooves 34 and 42 and the rigid plastic conduit (c). If the tension members are corroded, the corroded portions of the tension members stick to the wedge case 3 and the wedge 4, and thereby, the tension members are not removed from the ground anchor.

On the outer surface of the rigid plastic conduit (c), a C-shaped ring (b) and a cylindrical reinforcing member (d) are inserted. The front end of the reinforcing member (d) is coupled to the inner threaded portion 13 of the body 1, thereby the C- shaped ring (b) is pressed by the coupling portion between the reinforcing member (d) and the inner threaded portion 13. The C-shaped ring (b) pressed by the reinforcing member (d) is fastened tightly and caught between the tension member hole 15 and the rigid plastic conduit (c) to function as a water-stopper. The C-shaped ring (b) with waterproofing function provides a safety to the support 2, the wedge case 3 and the tension members (a) caught in the wedge case 3, and is not affecte by the pyrolysis of the support 2 when the electric current flows through the cable 23.

Referring to Figures 5 and 6, a method for removing the tension members from the ground anchor will be described in detail.

When the lead wire (e) drawn toward an external anchor (not shown in the drawings) is connected to the external power supply serving a flow of electricity, the heating member 22 is heated so that the thermoplastic resin 21 is pyrolyzed. The thermoplastic resin 21 in contact with the heating member 22 is melted or vaporized by

the pyrolysis and flowed outward.

At this time, the wedge case 3 is pulled down by the tension force of the tension members (a), and the pyrolyzed thermoplastic resin 21 is pressed down, and enters into a space of the wire insertion hole 12 in which the cable 23 is inserted, and then, remains stagnant in the bottom space of the body 1. The thermoplastic resin 21 is decreased in volume as much as the outflow amount, and the wedge case 3 sinks down as much as the reduced height of the thermoplastic resin 21. However, the wedge 4 keeps in its original position without moving down along the wedge case 3 because the wedge 4 is fixed to the cover 5 which is coupled to the body 1 by the bolt 6.

According to the above function, the distance between the wedge case 3 and the wedge 4 becomes wider and the gripping power to the tension members between the semicircular grooves 34 and 42 is gradually weakened. When the gripping power of the semicircular grooves 34 and 42 falls short of the tension force of the tension members, the tension members (a) begin to slide in the direction of the contraction of the tension members (a) from the semicircular grooves 34 and 42.

When the contractile force according to the anchoring load of the tension members (a) extends beyond the gripping power of the semicircular grooves 34 and 42, the tension members (a) slide out instantaneously and stop in the rigid plastic conduit (c).

The tension members (a) stopped in the rigid plastic conduit (c) can then be easily pulled out by human power without using any heavy equipment such as a draw-bench or a crane.

In the case of removing tension members with no tension force from the ground anchor, the tension members are removed by applying a predetermined tension force through a tensioning device.

Those skilled in the art will readily recognize that these and various other modifications and changes may be made to the present invention without strictly following the exemplary application illustrated and described herein, and without departing from the true spirit and scope of the present invention, which is set forth in the following claims.