Tension structure of ground anchor, and fastening method of ground anchor

Abstract

To make it possible to easily carry out from a confirmation test through fastening in a ground anchor.SOLUTION: A tension structure of a ground anchor comprises an anchor plate (13), an anchor head (14), a wedge (15), a tension jack (21), a ram chair (22), a push-in jack (23), and a holder (24) holding the wedge (15). The holder (24) holds the wedge (15) so that the wedge (15) is arranged coaxially with a tension material (12). When the holder (24) is pressed by the push-in jack (23), the holder (24) moves toward the anchor head (14) side and the wedge (15) engages with the anchor head (14). When the tensioning force by the tension jack (21) is released while the wedge (15) is engaged with the anchor head (14), the released tension causes the wedge (15) to bite into the anchor head (14).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a tensioning structure for a ground anchor and a method for fixing the ground anchor. [Background technology]

[0002] In the construction of ground anchors, a confirmation test is conducted to check the quality of the ground anchor before it is fixed. In the confirmation test, in order to prevent the wedge from affecting the tendons, etc., a predetermined tension is applied to the tendons by a tensioning jack without setting the wedge on the anchor head and tendons (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2002-242438 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned conventional method, it is necessary to remove the tension jack used in the confirmation test, then set the wedge in the anchor head and the tension material, and then set the tension jack again. Here, because the tensioning device including the tension jack is heavy in weight, frequent installation and removal of the tension jack is a burden on the workers.

[0005] In view of the above, an object of the present invention is to provide a ground anchor that can be easily carried out from confirmation testing to installation. [Means for solving the problem]

[0006] The present invention is a tensioning structure for a ground anchor comprising: an anchor plate; an anchor head through which a tension member is inserted; a wedge that engages with the anchor head and presses the anchor head against the anchor plate by the tension of the tension member; a tensioning jack that applies tension to the tension member; a ram chair that is interposed between the tensioning jack and the anchor plate and supports the tensioning jack; a push-in jack that is disposed within the hollow ram chair; and a holder that is disposed between the push-in jack and the anchor head in the axial direction of the tension member and holds the wedge, wherein the holder holds the wedge so that the wedge is coaxial with the tension member, and when the holder is pressed by the push-in jack, the holder moves toward the anchor head and the wedge engages with the anchor head, and when the tension caused by the tensioning jack is released with the wedge engaged with the anchor head, the released tension causes the wedge to bite into the anchor head. Effect of the Invention

[0007] According to the tensioning structure of the ground anchor and the fixing method of the ground anchor of the present invention, the process from confirmation testing to fixing can be easily carried out. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing a tensioning structure of a ground anchor according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is an exploded view of the tensioning device and ground anchor. [Figure 3A] This is a view of the ram chair and the push jack as viewed in the axial direction from the anchor plate side. [Figure 3B] FIG. 2 is a cross-sectional view of the ram chair and the pusher jack. [Figure 4] FIG. 2 is a cross-sectional view of the anchor head. [Diagram 5] FIG. 4 is a cross-sectional view showing a holder, a wedge, and an elastic member. [Figure 6]FIG. 2 is a cross-sectional view showing the tensioning device and ground anchor set in the ground. [Figure 7] 13 is a cross-sectional view showing a state in which the holder is pressed by a push-in jack. FIG. [Figure 8] 8 is a cross-sectional view showing a state in which the pressure applied by the push-in jack is released from the state shown in FIG. 7. FIG. [Figure 9] FIG. 11 is a cross-sectional view showing a state in which the ground anchor has been fixed by releasing the tension applied by the tension jack in the second embodiment. [Figure 10] FIG. 2 is a view of the anchor head support as viewed in the axial direction from the holder side. [Figure 11] 11 is a diagram showing a state in which the movement restricting member has slid radially outward from the state in FIG. 10 . [Figure 12] FIG. 11 is a cross-sectional view showing a holding state of the anchor head in the restriction release position. [Figure 13] 13 is a cross-sectional view showing a state in which the anchor head has been moved from the state shown in FIG. 12. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of a tensioning structure for a ground anchor according to the present invention will be described with reference to the accompanying drawings.

[0010] [First embodiment] Fig. 1 is a diagram showing a tensioning structure of a ground anchor 10 according to a first embodiment of the present invention, a part of which is a cross-sectional view. The ground anchor 10 is installed in the ground G for the purposes of landslide prevention, ground stabilization, structure stabilization, and the like. The ground anchor 10 includes an anchor body (not shown) provided in the ground G, an anchor head 11 provided near the ground surface, and a tendon 12 connecting the anchor body and the anchor head 11. The ground anchor 10 connects the anchor body and the anchor head 11 with a high-strength tendon 12, and stabilizes the ground G etc. by utilizing the tensile force of the tendon 12. The tendon 12 is a PC steel strand, but may also be a PC steel bar or continuous fiber reinforcement.

[0011] The anchor head 11 includes an anchor plate 13 that contacts the ground surface of the ground G, an anchor head 14 that is installed on the anchor plate 13, and a wedge 15 that engages with the anchor head 14. The wedge 15 presses the anchor head 14 against the anchor plate 13 by the tension (pulling force) transmitted from the tendon 12 to the wedge 15. Usually, a plurality of tendons 12 are arranged in the anchor head 14, and in this embodiment, two tendons 12 are illustrated. However, the number of tendons 12 may be one, or three or more.

[0012] The tension of the tendon 12 is applied by a tensioning device 20 . The tensioning device 20 includes a tensioning jack 21 that applies tension to the tension member 12, a ram chair 22 that is interposed between the tensioning jack 21 and the anchor plate 13 and supports the tensioning jack 21, and a push-in jack 23 that is disposed within the ram chair 22. The tensioning device 20 also includes a holder 24 that is arranged between the pushing jack 23 and the anchor head 14 in the axial direction of the tension member 12 and holds the wedge 15, an anchor head support 25 (a member on the anchor head side) that is sandwiched between the ram chair 22 and the anchor plate 13, and an elastic member 26 that is sandwiched between the holder 24 and the anchor head support 25. In the following description, unless otherwise specified, the axial direction means the axial direction of the tendon 12.

[0013] FIG. 2 is an exploded view of the tensioning device 20 and the ground anchor 10. 1 and 2, the tensioning jack 21 is a center hole jack having a through hole 21a at the center that passes through the tensioning jack 21 in the axial direction. The tensioning jack 21 has a jack main body 31 and a movable part 32 that moves in an axial direction relative to the jack main body 31. The tensioning jack 21 is of a hydraulic type.

[0014] In the tensioning jack 21, one axial end of the jack body 31 is supported by the ram chair 22. The movable part 32 extends from the other axial end of the jack body 31 in the opposite direction to the anchor plate 13. A pulling head 32a that holds the tension member 12 by wedging action is provided at the end of the movable part 32. The tendon 12 is inserted through the through hole 21a and fixed to the movable part 32 by the pulling head 32a.

[0015] 3A is a view of the ram chair 22 and the pusher jack 23 as viewed in the axial direction from the anchor plate 13 side. FIG. 3B is a cross-sectional view of the ram chair 22 and the pusher jack 23. The ram chair 22 is formed hollow. The ram chair 22 includes a cylindrical portion 33 provided so as to surround the tendon 12 from the periphery, and a bottom wall portion 34 provided at the end of the cylindrical portion 33 on the tension jack 21 side. The bottom wall portion 34 abuts against one axial end of the jack body portion 31 and receives a reaction force against the pulling force of the tension jack 21. The bottom wall portion 34 is disk-shaped, and a hole 34a through which the tendon 12 passes is provided in the center of the bottom wall portion 34. The tubular portion 33 has a cylindrical shape and extends in the axial direction from the peripheral edge of the bottom wall portion 34. The tendon 12 passes through the center of the tubular portion 33.

[0016] The pushing jack 23 is disposed inside the cylindrical portion 33 and is supported in the axial direction by the inner surface of the bottom wall portion 34. The pushing jack 23 extends in the axial direction from the bottom wall portion 34 along the inner circumferential surface of the cylindrical portion 33 toward the anchor plate 13. A pressing plate 35 capable of coming into contact with the holder 24 is provided at the axial end of the pushing jack 23. The pressing plate 35 is disc-shaped and fits along the inner circumferential surface of the cylindrical portion 33. A hole 35a through which the tension member 12 passes is provided in the center of the pressing plate 35. The push jack 23 expands and contracts in the axial direction by hydraulic pressure supplied to the hydraulic pressure supply unit 23a.

[0017] 1 and 2, the anchor plate 13 is provided with a hole 13a through which the tendon 12 passes. FIG. 4 is a cross-sectional view of the anchor head 14. 1, 2 and 4, the anchor head 14 has a cylindrical shape and is arranged so as to overlap the anchor plate 13 from the outside. The anchor head 14 has a plate abutment surface 14a that abuts against the anchor plate 13, a wedge insertion surface 14b that is the surface opposite to the plate abutment surface 14a, and a tapered hole 14c into which the wedge 15 and the tendon 12 are inserted. The plate abutment surface 14a and the wedge insertion surface 14b are parallel to each other. The tapered hole 14c has a tapered shape in which the inner diameter becomes smaller from the wedge insertion surface 14b toward the plate contact surface 14a.

[0018] 1 and 2, the anchor head support 25 is cylindrical and larger than the anchor head 14. The anchor head support 25 has a plate side end surface 25a that abuts against the anchor plate 13, and a ram chair side end surface 25b that faces the ram chair 22. The plate side end surface 25a and the ram chair side end surface 25b are parallel to each other.

[0019] Further, at the center of the anchor head support 25, there are provided an anchor head fitting hole 25c into which the anchor head 14 fits, and an escape hole 25d having a smaller diameter than the anchor head fitting hole 25c. Further, the anchor head support 25 has a stepped portion 25e that is recessed in an annular shape in the axial direction at the peripheral edge portion of the ram chair side end face 25b.

[0020] The anchor head fitting hole 25c is provided in the plate side end face 25a, and the relief hole 25d is provided in the ram chair side end face 25b. The anchor head fitting hole 25c and the relief hole 25d are arranged coaxially. The tendon 12 and the wedge 15 pass through the anchor head fitting hole 25c and the relief hole 25d. The depth of the anchor head fitting hole 25c is equal to the axial thickness of the anchor head 14. A peripheral portion 25f of the relief hole 25d protrudes radially inward from the outer circumferential surface of the anchor head 14. As a result, the peripheral portion 25f abuts against the wedge insertion surface 14b of the anchor head 14 in the axial direction, and prevents the anchor head 14 housed in the anchor head fitting hole 25c from slipping out in the axial direction.

[0021] The ram chair 22 is connected to the anchor head support 25 by engaging the axial end of the cylindrical portion 33 with the step portion 25e. The ram chair 22 presses the anchor head 14 against the anchor plate 13 via the anchor head support 25.

[0022] FIG. 5 is a cross-sectional view showing the holder 24, the wedge 15, and the elastic member 26. As shown in FIG. 1, 2, and 5, the holder 24 includes a holder body portion 24b having a hole portion 24a through which the tendon 12 passes, and a flange portion 24c protruding radially outward from the holder body portion 24b. The holder body portion 24b has a holding surface 40 that faces the wedge insertion surface 14b of the anchor head 14 in the axial direction. The surface of the holder 24 opposite the holding surface 40 is a pressed surface 24e that is pressed by the push jack 23. The pressed surface 24e faces the pressing plate 35 of the push jack 23.

[0023] The holder 24 is disposed within the ram chair 22 between the anchor head 14 supported by the anchor head support 25 and the pressure plate 35 of the pusher jack 23 .

[0024] The holder body 24b has a cylindrical shape extending in the axial direction of the tendons 12. The holes 24a are provided in the center of the holder body 24b. The number of holes 24a is the same as the number of the tendons 12. The flange portion 24c is provided on the pressed surface 24e side of the holder main body portion 24b in the axial direction. The flange portion 24c is annular and surrounds the holder main body portion 24b.

[0025] 5, the holding surface 40 is provided with a wedge seat 24f that is recessed in the axial direction relative to the end surface 40a of the holding surface 40. The wedge seat 24f is a circular recess as viewed in the axial direction. The wedge seat 24f is provided so as to overlap the hole 24a as viewed in the axial direction, and is disposed in a coaxial positional relationship with the hole 24a.

[0026] A magnet 41 is embedded in the bottom surface of the wedge seat 24f. The holding surface 40 holds the wedge 15 by the magnetic force of the magnet 41. The magnet 41 is annular and arranged coaxially with the hole 24a. The magnet 41 is provided on the bottom surface of the wedge seat 24f, on the periphery of the hole 24a.

[0027] An inner circumferential portion 41a of the annular magnet 41 constitutes a part of the hole 24a, and the tension member 12 passes through the inner circumferential portion 41a. The inner circumferential portion 41a has a larger diameter than the inner diameter of a portion of the hole 24a that is closer to the pressed surface 24e than the inner circumferential portion 41a.

[0028] The wedge 15 is a cylindrical body having a tapered shape corresponding to the tapered hole 14c of the anchor head 14. At the center of the wedge 15, an insertion hole 15a through which the tendon 12 is inserted is provided. The wedge 15 includes a pair of divided bodies 15b, 15c formed by dividing the circular wedge 15 into a plurality of parts in the radial direction when viewed in the axial direction. The wedge 15 is formed into a cylindrical body by combining the pair of divided bodies 15b, 15c.

[0029] The wedge 15 is attached to the retaining surface 40 by fitting one axial end 15d into the wedge seat 24f. The magnet 41 on the retaining surface 40 abuts against the one end 15d and holds the wedge 15 by magnetic force. The wedge 15 is positioned within the wedge seat 24f by fitting the one end 15d into the inner periphery of the wedge seat 24f. The wedge 15 is held so as to surround the tendon 12 from the periphery. The wedge 15 projects axially from the retaining surface 40 towards the anchor head 14 .

[0030] When the wedge 15 is held by the wedge seat 24f, the insertion hole 15a and the hole 24a of the holder 24 are coaxially positioned. The tendon 12 is inserted through the insertion hole 15a of the wedge 15 and the hole 24a of the holder 24, and passes through the center of the insertion hole 15a and the hole 24a. In this state, the tendon 12 and the insertion hole 15a of the wedge 15 are in a coaxial positional relationship. In other words, the holder 24 holds the wedge 15 so that the wedge 15 and the tendon 12 are arranged coaxially.

[0031] The elastic member 26 is annular and surrounds the holder main body 24b from the outer periphery side. The elastic member 26 is attached to the holder main body 24b by fitting the inner periphery of the elastic member 26 into the outer periphery of the holder main body 24b. One axial end 26 a of the elastic member 26 is received in a flange portion 24 c of the holder 24 . The other axial end 26b of the elastic member 26 protrudes axially toward the anchor head 14 beyond the holding surface 40. The elastic member 26 is made of an elastomer having rubber elasticity, for example, rubber.

[0032] Here, the confirmation test and fixing of the ground anchor 10 by the tensioning device 20 will be described. FIG. 6 is a cross-sectional view showing a state in which the tensioning device 20 and the ground anchor 10 are set in the ground G. 6, the holder 24 is supported by the tendons 12 as the tendons 12 are inserted into the holes 24a of the holder body 24b. When the ground G is a slope or a vertical wall, the tendons 12 support the holder 24 against gravity through the holes 24a. The holes 24a function as support holes that support the holder 24.

[0033] In the state shown in FIG. 6, the holder 24 is axially movable between the pushing jack 23 and the anchor head 14 so as to slide on the tendon 12 . 6, a part of the wedge 15 is inserted into the tapered hole 14c of the anchor head 14. In this state, the other end 26b of the elastic member 26 abuts against the ram chair side end surface 25b of the anchor head support 25, thereby regulating the axial position of the holder 24.

[0034] In detail, the elastic member 26 regulates the axial position of the holder 24 so that an axial gap D is formed between the outer circumferential surface of the wedge 15 and the inner circumferential surface of the tapered hole 14c. Because the wedge 15 and the tapered hole 14c are tapered, when the gap D is formed, a radial gap is also formed between the wedge 15 and the tapered hole 14c. In this manner, by regulating the amount of insertion of the wedge 15 into the tapered hole 14c by the elastic member 26, unnecessary contact between the wedge 15 and the tapered hole 14c is avoided.

[0035] In the state shown in Fig. 6, the tensioning jack 21 is driven to pull and extend the movable part 32 (Fig. 1) in the direction of arrow T, thereby performing a confirmation test to confirm the quality of the ground anchor 10. In the confirmation test, the tensioning jack 21 extends the tension member 12, and a predetermined amount of tension is applied to the tension member 12. When the confirmation test is completed, the tension of the tension member 12 is released, and the tension member 12 contracts to its original state.

[0036] During the confirmation test, the tendon 12 expands and contracts, which may cause axial displacement or vibration of the tendon 12, which may cause the wedge 15 to move. In the tensioning device 20, the holder 24 supports the wedge 15, which prevents the wedge 15 from strongly hitting the components around the wedge 15, such as the tendon 12 and the tapered hole 14c. More specifically, even if the holder 24 moves axially as the tendon 12 expands and contracts during the confirmation test, the gap D is secured by the elastic member 26. This prevents the wedge 15 from coming into strong contact with the tapered hole 14c, and prevents the wedge 15 from engaging with the tapered hole 14c.

[0037] In this way, in the tensioning device 20, the wedge 15 is appropriately supported by the holder 24, so that the confirmation test can be performed with the wedge 15 set in the tendon 12. Therefore, there is no need to repeatedly attach and detach the tensioning device 20 for the confirmation test, and the confirmation test can be easily performed.

[0038] FIG. 7 is a cross-sectional view showing a state in which the holder 24 is pressed by the push-in jack 23. As shown in FIG. After the confirmation test, the anchoring process for anchoring the ground anchor 10 in the ground G is carried out. In the fixing process, the tensioning jack 21 is driven to pull the tension member 12, and a predetermined amount of tension for fixing is applied to the tension member 12. During the fixing process, the pushing jack 23 is driven to push the holder 24 axially toward the anchor head 14, causing the wedge 15 to engage with the tapered hole 14c.

[0039] More specifically, as the pushing jack 23 pushes in the holder 24, the other end 26b of the elastic member 26 comes into contact with the ram chair side end face 25b of the anchor head support 25. As the amount of pressure increases, the pushing jack 23 compresses and deforms the elastic member 26 between the flange portion 24c and the ram chair side end face 25b, moving the holder 24 toward the anchor head 14. As a result, the gap D (FIG. 6) decreases. When the pressing amount (push amount) of the push-in jack 23 is further increased, the gap D (FIG. 6) becomes zero and the wedge 15 engages with the tapered hole 14c. In this state, the compression amount C (FIG. 7) of the elastic member 26 is equal to the length of the gap D. When the wedge 15 engages with the tapered hole 14c, the wedge 15 is pressed against the outer periphery of the tendon 12 by a wedging action.

[0040] In the anchoring process, the tensioning force by the tensioning jack 21 is released with the wedge 15 engaged with the tapered hole 14c. Then, the wedge 15 is pulled toward the ground G by the force of the tendon 12 which is trying to contract, and bites deeper into the tapered hole 14c. As a result, the tendon 12 is fixed to the anchor head 14 with a predetermined amount of tension applied, and the ground anchor 10 is anchored to the ground G.

[0041] In the fixing process, the pulling force acting on the wedge 15 from the tendon 12 when the wedge 15 bites into the tapered hole 14c is greater than the holding force of the wedge 15 by the magnet 41. Therefore, in the fixing process, the wedge 15 is automatically released from the holding surface 40 by the force of the tendon 12.

[0042] FIG. 8 is a cross-sectional view showing a state in which the pressure applied by the push-in jack 23 has been released from the state shown in FIG. After the tension of the tensioning jack 21 is released and the ground anchor 10 is fixed, the pressure plate 35 of the pushing jack 23 is retreated and the pressure on the holder 24 by the pushing jack 23 is released. In this state, the compressed elastic member 26 returns to its original length. The holder 24 is pushed by the restoring force of the elastic member 26 and displaced toward the push-in jack 23. The wedge 15 may automatically come off the holding surface 40 due to the restoring force of the elastic member 26.

[0043] As described above, according to the first embodiment to which the present invention is applied, the tensioning structure of the ground anchor 10 includes the anchor plate 13, the anchor head 14 through which the tension member 12 is inserted, the wedge 15 that engages with the anchor head 14 and presses the anchor head 14 against the anchor plate 13 by the tension of the tension member 12, the tensioning jack 21 that applies tension to the tension member 12, the ram chair 22 that is interposed between the tensioning jack 21 and the anchor plate 13 and supports the tensioning jack 21, the push jack 23 that is disposed within the hollow ram chair 22, and the holder 24 that is disposed between the push jack 23 and the anchor head 14 in the axial direction of the tension member 12 and holds the wedge 15. The holder 24 holds the wedge 15 so that the wedge 15 is coaxially disposed with the tension member 12, and when the holder 24 is pressed by the push jack 23, the holder 24 moves toward the anchor head 14 and the wedge 15 engages with the anchor head 14. When the tension applied by the tensioning jack 21 is released with the wedge 15 engaged with the anchor head 14, the released tension causes the wedge 15 to bite into the anchor head 14. According to this configuration, a confirmation test can be performed by applying tension to the tension member 12 by the tensioning jack 21. A holder 24 that holds the wedge 15 is provided. When the holder 24 is pressed by the pushing jack 23, the wedge 15 engages with the anchor head 14. When the tension by the tensioning jack 21 is released in this state, the wedge 15 bites into the anchor head 14. Therefore, after the confirmation test, the ground anchor 10 can be fixed by simply operating the pushing jack 23 and the tensioning jack 21 without removing the tensioning jack 21. In addition, during the confirmation test, the holder 24 appropriately supports the wedge 15, so that the wedge 15 can be prevented from hitting the tension member 12 and the like strongly, and damage to the wedge 15 and the tension member 12 can be prevented. Therefore, the process from the confirmation test to the fixing of the ground anchor 10 can be easily performed.

[0044] Moreover, the holder 24 holds the wedge 15 by magnetic force, and when the wedge 15 bites into the anchor head 14 by tension, it separates from the holder 24 against the magnetic force. According to this configuration, the wedge 15 can be easily held by magnetic force, and when fixed, the wedge 15 can be automatically released from the holder 24 by utilizing tension.

[0045] The holder 24 also has a hole portion 24a through which the tension member 12 passes and a retaining surface 40 facing the anchor head 14, and the wedge 15 is retained on the retaining surface 40, and a magnet 41 that retains the wedge 15 is provided on the retaining surface 40 on the peripheral portion of the hole portion 24a. According to this configuration, the wedge 15 can be held on the holding surface 40 with a simple structure by the magnet 41 provided on the periphery of the hole 24a through which the tendon 12 passes.

[0046] In addition, an elastic member 26 is provided which is sandwiched between the holder 24 and the anchor head support 25. The elastic member 26 forms an axial gap D between the wedge 15 and the anchor head 14. The pushing jack 23 compresses and deforms the elastic member 26 in the axial direction via the holder 24, thereby engaging the wedge 15 with the anchor head 14. According to this configuration, an axial gap D is formed between the wedge 15 and the anchor head 14 by the elastic member 26 between the holder 24 and the anchor head support 25, which prevents the wedge 15 from coming into contact with the anchor head 14 during the confirmation test and prevents damage to the wedge 15 and the tension member 12. In addition, when fixing the anchor, the elastic member 26 is compressed and deformed by the push-in jack 23, allowing the wedge 15 to engage with the anchor head 14.

[0047] Furthermore, the holder 24 has a holder main body portion 24b through which the tension member 12 passes, and a ring-shaped flange portion 24c protruding radially outward from the holder main body portion 24b, and the elastic member 26 is ring-shaped and surrounds the holder main body portion 24b from the outer circumferential side, and one axial end 26a of the elastic member 26 is received by the flange portion 24c. According to this configuration, the annular elastic member 26 is provided so as to surround the holder body 24b through which the tendon 12 passes, so that the axial force acting on the holder 24 can be evenly received by the annular elastic member 26. This makes it possible to prevent contact between the wedge 15 and the anchor head 14. Also, the elastic member 26 can be appropriately supported by the flange portion 24c and the holder body 24b.

[0048] In addition, the holder 24 has a hole portion 24a as a support hole portion through which the tension member 12 passes, and is supported by the tension member 12 via the hole portion 24a, and the wedge 15 is held on the peripheral portion of the hole portion 24a so as to surround the tension member 12. According to this configuration, the holder 24 can be supported with a simple structure by the tendon 12 passing through the hole 24a. In addition, since the wedge 15 is held on the periphery of the hole 24a so as to surround the tendon 12, the wedge 15 can be arranged coaxially with the tendon 12. This makes it easy to engage the wedge 15 with the anchor head 14.

[0049] Moreover, in the method of fixing the ground anchor 10, a confirmation test is performed in which the tensioning jack 21 is used to tension the tension material 12 by a specified amount, and then the push-in jack 23 is used to press the holder 24 toward the anchor head 14 to engage the wedge 15 with the anchor head 14, and thereafter the tensioning force from the tensioning jack 21 is released, and the released tensioning force causes the wedge 15 to bite into the anchor head 14. According to this method, after the confirmation test, the ground anchor 10 can be fixed by simply operating the pushing jack 23 and the tensioning jack 21, without removing the tensioning jack 21. Furthermore, during the confirmation test, the holder 24 appropriately supports the wedge 15, which prevents the wedge 15 from hitting the tension member 12 or the like too hard, thereby preventing damage to the wedge 15 and the tension member 12. Therefore, the process from the confirmation test to the fixing of the ground anchor 10 can be easily carried out.

[0050] [Second embodiment] A second embodiment to which the present invention is applied will be described below with reference to Figures 9 to 13. In this second embodiment, parts configured similarly to the first embodiment are given the same reference numerals and descriptions thereof will be omitted. The second embodiment differs from the first embodiment in that an anchor head support 250 includes a movement restricting member 251.

[0051] Fig. 9 is a cross-sectional view showing a state in which the tension of the tensioning jack 21 is released to fix the ground anchor 10 in the second embodiment. Fig. 9 corresponds to the state of Fig. 8 in the first embodiment in the second embodiment. In the second embodiment, an anchor head support 250 is provided in place of the anchor head support 25 of the first embodiment.

[0052] FIG. 10 is a view of the anchor head support 250 as viewed in the axial direction from the holder 24 side. 9 and 10, the anchor head support 250 is sandwiched between the ram chair 22 and the anchor plate 13. The anchor head support 250 holds the anchor head 14 on the anchor plate 13 side.

[0053] The anchor head support 250 comprises a cylindrical support body 225 larger than the anchor head 14 , a movement restricting member 251 that restricts the movement of the anchor head 14 , and a fastener 252 that fastens the movement restricting member 251 to the support body 225 .

[0054] The support body 225 has an anchor head fitting hole 225c (anchor head storage hole) into which the anchor head 14 fits. The anchor head fitting hole 225c is a round hole provided in the center of the support body 225, and passes through the support body 225 in the axial direction. The depth of the anchor head fitting hole 225c is equal to the axial thickness of the anchor head 14. The support body 225 has a plate-side end face 225a that abuts against the anchor plate 13, and a holder-side end face 225b that faces the holder 24. The plate-side end face 225a and the holder-side end face 225b are parallel to each other. A step 225e is provided on the peripheral edge of the holder-side end face 225b, where the peripheral edge of the holder-side end face 225b is recessed in an annular shape in the axial direction.

[0055] The ram chair 22 is connected to the anchor head support 250 by engaging the axial end of the cylindrical portion 33 with the step portion 225e. The ram chair 22 presses the anchor head 14 against the anchor plate 13 via the anchor head support 250.

[0056] 10, the holder side end surface 225b is annular and provided around the anchor head fitting hole 225c when viewed in the axial direction. The movement restricting member 251 is disposed on the holder side end surface 225b. The movement restricting members 251 are provided as a pair facing each other across the anchor head fitting hole 225c when viewed in the axial direction. The movement restricting members 251 are plate-shaped members disposed along the holder side end surface 225b. The movement restricting members 251 are slidable along the holder side end surface 225b.

[0057] FIG. 11 is a diagram showing a state in which the movement restricting member 251 has slid radially outward from the state shown in FIG. 9 to 11, the movement restricting member 251 is slidable in the radial direction R of the anchor head support 250 on the holder side end surface 225b. The movement restricting member 251 has a fixing hole 251a penetrating the movement restricting member 251 in the plate thickness direction. The fixing hole 251a is an elongated hole extending in the radial direction R. The fixing holes 251a are provided such that a pair of the fixing holes 251a are spaced apart from each other in the circumferential direction of the anchor head support 250. An inner periphery 251b of the movement restricting member 251 in the radial direction R is shaped like a circular arc that fits along the outer periphery of the anchor head fitting hole 225c.

[0058] The fastener 252 is inserted through the fixing hole 251a and fixed to the holder side end surface 225b. The fastener 252 is, for example, a bolt that is inserted through the fixing hole 251a and screwed into a screw hole (not shown) in the holder side end surface 225b.

[0059] 9, an end surface 251c of the movement restricting member 251 on the holder 24 side is a surface against which the other end 26b of the elastic member 26 abuts when the push-in jack 23 pushes in the holder 24, for example. The end face 251c may be provided with a countersunk hole (not shown) for accommodating the head 252a of the bolt of the fastener 252. The countersunk hole is an elongated hole that fits along the fixing hole 251a. This allows the head 252a to be prevented from contacting the elastic member 26, and the end face 251c to be appropriately abutted against the elastic member 26. The end surface 251c corresponds to the portion of the ram chair side end surface 25b (FIG. 8) in the first embodiment that comes into contact with the elastic member 26.

[0060] The movement restricting member 251 is movable between a restricting position where the movement of the anchor head 14 housed in the anchor head fitting hole 225c is restricted and a restricting release position where the restriction is released. 9 and 10 show a state in which the movement restricting member 251 is in the restricting position. In the restricted position, the inner circumferential portion 251b of the movement restricting member 251 protrudes into the anchor head fitting hole 225c. In this state, the inner circumferential portion 251b abuts against the wedge insertion surface 14b of the anchor head 14, and the movement restricting member 251 engages with the anchor head 14, thereby restricting the movement of the anchor head 14 in the direction of the arrow T. Here, the direction of the arrow T is the pulling direction when tension is applied to the tension member 12 by the tensioning jack 21, and is the opposite direction to the biting direction of the wedge 15 due to the released tension.

[0061] In the restricted position, the outer end of the fixing hole 251a in the radial direction R abuts against the fastener 252. From this state, the fastener 252 is loosened and the movement restricting member 251 is moved outward in the radial direction R, whereby the movement restricting member 251 can be moved to the unrestricted position shown in Fig. 11. In the unrestricted position, the inner end of the fixing hole 251a in the radial direction R abuts against the fastener 252. In addition, in the unrestricted position, the fastener 252 is re-fastened.

[0062] 11, the inner circumferential portion 251b of the movement restricting member 251 has moved to the outside of the anchor head fitting hole 225c. In this state, the inner circumferential portion 251b does not abut against the wedge insertion surface 14b of the anchor head 14, and the engagement of the movement restricting member 251 with the anchor head 14 is released. Therefore, the anchor head 14 is able to move in the direction of the arrow T.

[0063] The tensioning jack 21 applies a predetermined tension to the tension member 12, pushes the wedge 15 into the anchor head 14, and then releases the tension from the tensioning jack 21, completing the setting of the ground anchor 10. In this case, when the tension is released, the tension member 12 shrinks due to the biting of the wedge 15, etc., so the tension after setting may be smaller than the above-mentioned predetermined tension. For this reason, a setting load confirmation test may be conducted to confirm the actual setting load (tension) at the time of setting.

[0064] Fig. 12 is a cross-sectional view showing a state in which the anchor head 14 is held in the restriction release position, and Fig. 13 is a cross-sectional view showing a state in which the anchor head 14 has moved from the state in Fig. 12. Here, an example of the procedure of the fixing load confirmation test will be described. Fig. 9 shows a state in which the tension of the tensioning jack 21 has been released and the ground anchor 10 has been fixed. In the state shown in Fig. 9, the worker loosens the fastening device 252 (Fig. 10), moves the movement restricting member 251 from the restricting position (Figs. 9 and 10) to the release position (Figs. 11 and 12), and refastens the fastening device 252. The worker can access the fastening device 252 and the movement restricting member 251 from, for example, an access opening (not shown) provided in the cylindrical portion 33 (Fig. 9) of the ram chair 22, and change the position of the movement restricting member 251. In Fig. 9, the wedge 15 is inserted into the anchor head 14 to a position where the end face on the holder 24 side is substantially flush with the wedge insertion surface 14b. In Fig. 8 of the first embodiment, the wedge 15 may also be inserted into the anchor head 14 to a position where the end face is substantially flush with the wedge insertion surface 14b.

[0065] Next, the tensioning jack 21 pulls the tensioning material 12 in the direction of the arrow T, and tension is applied to the tensioning material 12 to confirm the anchoring load. The tensioning material 12 does not displace in the axial direction until the tensioning material 12 reaches the fixed tension. However, when the applied tension exceeds the fixed tension, the tensioning material 12 displaces in the direction of the arrow T, and the anchor head 14 displaces together with the tensioning material 12 in the direction of the arrow T. That is, when the tensioning material 12 applies the tension to the tensioning jack 21 exceeds the fixed tension, the anchor head 14 lifts up from the anchor plate 13 as shown in FIG. 13. In FIG. 13, the anchor head 14 lifts up from the anchor plate 13 by a displacement δ. The operator creates a graph showing the relationship between the load of the tensioning material 12 and the axial displacement of the tensioning material 12 during the anchoring load confirmation test, and determines the load at the time when the displacement changes (when the anchor head 14 lifts up from the anchor plate 13) as the actual anchoring load at the time of anchoring. Thereafter, the tension force of the tension jack 21 is released, and the anchoring load confirmation test is completed, and the tendon 12 contracts and is anchored again.

[0066] As described above, according to the second embodiment to which the present invention is applied, there is provided the anchor head support 250 that holds the anchor head 14 on the anchor plate 13 side, and the anchor head support 250 includes a movement restricting member 251 that engages with the anchor head 14 to restrict movement of the anchor head 14. The movement restricting member 251 is movable between a restricting position where it restricts movement of the anchor head 14 in the direction opposite to the biting direction of the wedge 15 due to the released tension (the direction of arrow T), and a restriction release position where it releases this restriction. According to this configuration, the anchor head support 250 is provided with a movement restricting member 251, and by setting the movement restricting member 251 to a restricting position, it is possible to restrict the anchor head 14 from moving in the opposite direction to the biting direction of the wedge 15. Therefore, when performing a confirmation test or when the wedge 15 is caused to bite into the anchor head 14 to fix the ground anchor 10, unnecessary movement of the anchor head 14 can be restricted, making it easier to perform the confirmation test and fixing work. Furthermore, by setting the movement restricting member 251 to the restriction release position, the anchor head 14 becomes movable in the direction opposite to the biting direction of the wedge 15. When performing an anchoring load confirmation test, the movement restricting member 251 is set to the restriction release position, and tension is applied to the tension member 12 by the tensioning jack 21. Then, when this tension exceeds the anchoring load, the anchor head 14 moves together with the tension member 12 in the direction opposite to the biting direction of the wedge, and the anchor head 14 floats up from the anchor plate 13. In this way, after the ground anchor 10 is fixed, simply by moving the movement restricting member 251 to the restriction release position, the anchor head 14 becomes movable in the direction opposite to the biting direction of the wedge 15. Therefore, there is no need to remove the ram chair 22 and the tensioning jack 21, etc., to perform the fixing load confirmation test, and the fixing load confirmation test can be easily performed.

[0067] In addition, the anchor head support 250 has a support body 225 with an anchor head fitting hole 225c that stores the anchor head 14, and the support body 225 has a holder side end face 225b facing the holder 24 around the anchor head fitting hole 225c, and the movement restricting member 251 moves between the restricting position and the unrestricted position by sliding on the holder side end face 225b. According to this configuration, the position of the movement restricting member 251 can be easily switched between the restricted position and the unrestricted position with a simple structure in which the movement restricting member 251 is slidably moved on the holder side end surface 225b.

[0068] Also provided is an anchor head support 250 that holds the anchor head 14 on the anchor plate side, and the anchor head support 250 includes a movement restricting member 251 that engages with the anchor head 14 to restrict movement of the anchor head 14. The movement restricting member 251 is movable between a restricting position where it restricts movement of the anchor head 14 in the direction opposite to the biting direction of the wedge 15 due to tension, and a restricting release position where it releases this restriction, and before the wedge 15 is bitten into the anchor head 14 by the released tension, the movement restricting member 251 is in the restricting position, and after the wedge 15 is bitten into the anchor head 14 by the released tension, the movement restricting member 251 is in the restricting position, and the tensioning jack 21 is used to pull the tensioning material 12 to check the fixed load of the tensioning material 12. In this method, the movement restricting member 251 is in the restricting position before the released tension causes the wedge 15 to bite into the anchor head 14. Therefore, when conducting a confirmation test or when fixing the ground anchor 10, unnecessary movement of the anchor head 14 can be restricted, making it easier to perform the confirmation test and fixing work. In addition, after the released tension has caused the wedge 15 to bite into the anchor head 14, the movement restricting member 251 is set to the restriction release position, and the tensioning jack 21 is used to pull the tension material 12 in the direction opposite to the biting direction of the wedge 15, thereby checking the anchoring load of the tension material 12. For this reason, there is no need to remove the ram chair 22, the tensioning jack 21, etc., in order to perform the anchoring load confirmation test, and the anchoring load confirmation test can be easily performed.

[0069] Although one embodiment of the present invention has been described above, the present invention is not limited to the specific embodiment, and various modifications and changes are possible within the scope of the spirit of the present invention described in the claims unless otherwise specifically limited in the above description. For example, the configuration of the above-mentioned embodiment can be appropriately added or deleted, and the configuration of one embodiment can be applied to another embodiment. Furthermore, the effects of the above-mentioned embodiment are merely examples of the effects resulting from the present invention, and do not mean that the effects of the present invention are limited to the above-mentioned effects. In the above first embodiment, the elastic member 26 is described as being sandwiched between the holder 24 and the anchor head support 25 as a member on the anchor head side, but the present invention is not limited to this. For example, when the anchor head support 25 is not provided, the elastic member 26 may be sandwiched between the holder 24 and the anchor head 14 as a member on the anchor head side. In the above first and second embodiments, the anchor head 14 is supported by providing the anchor head support 25, 250, but the ground anchor 10 can be fixed without providing the anchor head support 25, 250. In this case, since there is no member that restricts the movement of the anchor head 14 in the direction opposite to the biting direction of the wedge 15, after the ground anchor 10 is fixed, the tensioning jack 21 can be used to pull the tensioning jack 21 to perform a fixing load confirmation test. However, by providing the anchor head support 25, 250 as in the above first and second embodiments, it is possible to suppress the movement of the anchor head 14 in the direction perpendicular to the tensioning jack 21, thereby suppressing friction between the anchor head 14 and the tensioning jack 21 and suppressing the floating of the anchor head 14, so it is preferable to provide the anchor head support 25, 250. The configuration of the second embodiment is even more preferable because the anchor head support 250 is equipped with a movement restricting member 251, which, when in the restricting position, can restrict the floating of the anchor head 14, and by setting the movement restricting member 251 to the unrestricted position after fixing, a fixing load confirmation test can also be performed. In the above second embodiment, the movement restricting member 251 is described as sliding on the holder side end surface 225b, but the present invention is not limited to this. For example, a hole penetrating from the outer periphery of the support body 225 to the anchor head fitting hole 225c, and a slide member (movement restricting member) slidably inserted into this hole may be provided. The position where the slide member engages with the engagement part on the outer periphery of the anchor head 14 may be defined as the restricting position, and the position where the slide member disengages from the engagement part on the outer periphery of the anchor head 14 may be defined as the unrestricted position. [Explanation of symbols]

[0070] 10: Ground anchor 12: Tensile material 13: Anchor plate 14: Anchorhead 15: Wedge 21: Tension Jack 22: Ram Chair 23: Push Jack 24: Holder 24a: Hole (support hole) 24b: Holder body 24c: Flange part 25: Anchor head support (part on the side of the anchor head) 26: Elastic member 26a: one end 40: Holding surface 41: Magnet 225: Support body 225b: Holder side end face 225c: Anchor head fitting hole (anchor head storage hole) 250: Anchor head support (part on the side of the anchor head) 251: Movement restriction member D: Gap

Claims

1. the tensioning jack is disposed between the tensioning jack and the anchor plate and supports the tensioning jack; a push-in jack is disposed within the hollow ram chair; and a holder is disposed between the push-in jack and the anchor head in the axial direction of the tensioning material and holds the wedge; The holder holds the wedge so that the wedge is coaxially disposed with the tendon; When the holder is pressed by the pushing jack, the holder moves toward the anchor head and the wedge engages with the anchor head, A tensioning structure for a ground anchor in which, when the tensioning force by the tensioning jack is released with the wedge engaged with the anchor head, the released tensioning force causes the wedge to bite into the anchor head.

2. The holder holds the wedge by magnetic force; The tensioning structure of a ground anchor according to claim 1 , wherein the wedge separates from the holder against the magnetic force when the wedge bites into the anchor head due to tension.

3. The holder has a hole through which the tendon passes and a holding surface facing the anchor head, and the wedge is held by the holding surface; The tensioning structure of a ground anchor according to claim 2 , wherein a magnet for holding the wedge is provided on the periphery of the hole on the holding surface.

4. An elastic member is provided between the holder and a member on the anchor head side, The elastic member forms an axial gap between the wedge and the anchor head, The tensioning structure of the ground anchor according to claim 1, wherein the pushing jack compresses and deforms the elastic member in the axial direction via the holder, thereby engaging the wedge with the anchor head.

5. The holder includes a holder body portion through which the tension member passes, and an annular flange portion protruding radially outward from the holder body portion, 5. The tensioning structure of a ground anchor according to claim 4, wherein the elastic member is annular and surrounds the holder body from the outer periphery, and one axial end of the elastic member is received in the flange portion.

6. The holder includes a support hole through which the tendon passes, and is supported by the tendon via the support hole, The tensioning structure of a ground anchor according to any one of claims 1 to 5, wherein the wedge is held on the peripheral portion of the support hole portion so as to surround the tendon.

7. An anchor head support is provided to hold the anchor head on the anchor plate side, The anchor head support includes a movement restricting member that engages with the anchor head to restrict movement of the anchor head, 2. The tensioning structure of a ground anchor according to claim 1, wherein the movement restricting member is movable between a restricting position where the movement of the anchor head in a direction opposite to the biting direction of the wedge due to the released tension force and a restricting release position where the restriction is released.

8. The anchor head support includes a support body having an anchor head storage hole for storing the anchor head, The support body has a holder side end surface facing the holder around the anchor head receiving hole, The tensioning structure for a ground anchor according to claim 7 , wherein the movement restricting member is moved to the restricting position and the released position by sliding on the holder side end surface.

9. A method for fixing a ground anchor using a tensioning structure of a ground anchor comprising: an anchor plate; an anchor head through which a tensioning material is inserted; a wedge that engages with the anchor head and presses the anchor head against the anchor plate by the tension of the tensioning material; a tensioning jack that applies tension to the tensioning material; a ram chair that is interposed between the tensioning jack and the anchor plate and supports the tensioning jack; a push-in jack that is disposed within the hollow ram chair; and a holder that is disposed between the push-in jack and the anchor head in the axial direction of the tensioning material and holds the wedge, A method for fixing a ground anchor, comprising the steps of: performing a confirmation test in which the tensioning jack is used to tension the tension material by a predetermined amount; then using the push-in jack to press the holder toward the anchor head and engage the wedge with the anchor head; and then releasing the tension from the tensioning jack and allowing the wedge to bite into the anchor head with the released tension.

10. An anchor head support is provided to hold the anchor head on the anchor plate side, The anchor head support includes a movement restricting member that engages with the anchor head to restrict movement of the anchor head, The movement restricting member is movable between a restricting position where the movement of the anchor head in a direction opposite to a biting direction of the wedge due to the tension force is restricted and a restricting release position where the restriction is released, The movement restricting member is in the restricting position before the wedge is caused to bite into the anchor head by the released tension force, 10. The method for fixing a ground anchor according to claim 9, further comprising the steps of: causing the wedge to bite into the anchor head by the released tension; placing the movement restricting member in the restriction release position; and pulling the tension material with the tensioning jack to check the fixing load of the tension material.

Images