Support structure, rock bolts, and method for installing a support structure

Abstract

To produce desired displacement.SOLUTION: A rock bolt 2 comprises a rod-shaped member 51 that moves relative to an anchoring material 3 in accordance with the deformation of the natural ground 101 or that extends in accordance with the deformation of the natural ground 101, a sleeve member 8 that generates a first resistance force against the deformation of the natural ground 101, a ring member 6 that has an inner diameter larger than an outer diameter of the rod-shaped member 51 and has a ring through hole 63 through which the rod-shaped member 51 is inserted, and is positioned a predetermined distance away from the sleeve member 8 on an opening side of a drilled hole 104 to maintain its position relative to the anchoring material 3 in response to the deformation of the natural ground 101, and a precast member 7 that is positioned between the sleeve member 8 and the ring member 6 and faces the sleeve member 8. When the sleeve member 8 moves toward the opening of the drilled hole 104 in accordance with the deformation of the natural ground 101, the sleeve member 8 presses the precast member 7, thereby crushing the precast member 7 to generate a second resistance force different from the first resistance force.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a support structure, a rock bolt, and a method for providing a support structure.

Background Art

[0002] Structures constructed by excavation such as tunnels have a structure for resisting the pressure and deformation of the ground in which the structure is provided. Such a structure is called a support structure. The support structure includes a filling material such as mortar filled in a hole provided in the ground, and a rock bolt embedded in the filling material. The rock bolt generates stress against the deformation of the ground and supports the ground by the stress.

[0003] The rock bolt generates a support force due to its rigidity and resists the overburden pressure and the displacement of the tunnel. For example, during deep tunnel excavation, the overburden pressure and the displacement of the tunnel tend to be large. When using a highly rigid rock bolt conventionally used in such a place, a large stress is generated in the rock bolt, which may cause brittle fracture of the rock bolt. Therefore, Patent Document 1 discloses a rock bolt that can cope with a wide range of ground characteristics. The rock bolt of Patent Document 1 achieves both the burden of loads caused by the overburden pressure and the allowance of large displacements of the tunnel.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The rock bolt described in Patent Document 1 achieves both load bearing capacity and tolerance of ground displacement. The magnitude of the load supporting the ground where the rock bolt is generated depends on the degree of deformation that occurs in the rock bolt. Therefore, in order to achieve a desired magnitude of load generated by the rock bolt, it is desirable to achieve a desired displacement in the rock bolt.

[0006] The present invention provides a support structure, a rock bolt, and a method for providing a support structure that can produce a desired displacement. [Means for solving the problem]

[0007] One embodiment of the present invention is a support structure provided in the ground. The support structure comprises: an anchoring material filled into a hole formed in the ground; a rod-shaped member that extends in a predetermined direction and is positioned in the hole, and moves relative to the anchoring material or extends in accordance with the deformation of the ground; a sleeve member having a larger outer diameter than the rod-shaped member, fixed to the base end of the rod-shaped member, and including a portion to which the anchoring material is attached, and generating a first resistance force against the deformation of the ground; a ring member having an inner diameter larger than the outer diameter of the rod-shaped member and a through hole through which the rod-shaped member is inserted, and positioned at a predetermined distance from the sleeve member toward the opening side of the hole in the ground, and maintaining a relative position with respect to the deformation of the ground and the anchoring material; and a cylindrical member positioned between the sleeve member and the ring member, including a base end surface facing the sleeve member. As the sleeve member moves toward the opening of the ground hole in response to the deformation of the ground, the sleeve member presses against the base end surface of the cylindrical member, causing the cylindrical member to be crushed and generating a second resistance force different from the first resistance force.

[0008] This support structure has a cylindrical member positioned between a sleeve member and a ring member. The second resistance force is generated when the cylindrical member is crushed by the sleeve member, and therefore the second resistance force is affected by the properties of the cylindrical member. This cylindrical member is provided as a component of the support structure. In this way, when constructing multiple support structures, the variation in the properties of the cylindrical member for each support structure can be suppressed compared to the variation in the properties of the anchoring material installed on-site for each support structure. As a result, the variation in the second resistance force generated for each support structure is also suppressed, and therefore the variation in the displacement of the rock bolt in response to the second resistance force is also suppressed. As a result, the desired displacement can be generated in the rock bolt.

[0009] In the above support structure, the amount of displacement of the cylindrical member along the axial direction until it reaches its maximum compressive strength may be greater than the amount of displacement of the anchoring material along the axial direction until it reaches its maximum compressive strength. Furthermore, the porosity of the cylindrical member may be greater than that of the anchoring material. Moreover, the density of the cylindrical member may be less than that of the anchoring material. With these configurations, the desired displacement can be reliably generated.

[0010] Another embodiment of the present invention is a rock bolt for a ground support structure provided with a ground hole into which an anchoring material is filled. The rock bolt comprises a rod-shaped member that is a rod body extending in a predetermined direction and positioned in the ground hole, and moves relative to the anchoring material as the ground deforms, or extends as the ground deforms; a sleeve member having a larger outer diameter than the rod-shaped member, fixed to the base end of the rod-shaped member and including a portion to which the anchoring material is attached, and generating a first resistance force against the deformation of the ground; a ring member having an inner diameter larger than the outer diameter of the rod body and a through hole through which the rod body is inserted, positioned at a predetermined distance from the sleeve member toward the opening side of the ground hole, and maintaining a relative position with respect to the anchoring material with respect to the deformation of the ground; and a cylindrical member positioned between the sleeve member and the ring member and including a base end face facing the sleeve member. As the sleeve member moves toward the opening of the borehole in the ground due to the deformation of the ground, the sleeve member presses against the base end face of the cylindrical member, causing the cylindrical member to be crushed and generating a second resistance force different from the first resistance force. With this rock bolt, a desired displacement can be produced.

[0011] A further embodiment of the present invention is a method for providing a support structure for a ground hole into which an anchoring material is filled. The method for providing a support structure includes the steps of preparing a rock bolt, which comprises a rod-shaped member that extends in a predetermined direction and is placed in the ground hole, and moves relative to the anchoring material in accordance with the deformation of the ground, or extends in accordance with the deformation of the ground; a sleeve member that has a larger outer diameter than the rod-shaped member, is fixed to the base end of the rod-shaped member and includes a portion to which the anchoring material is attached, and generates a first resistance force against the deformation of the ground; a ring member that has an inner diameter larger than the outer diameter of the rod-shaped member and has a through hole through which the rod-shaped member is inserted, and is positioned at a predetermined distance from the sleeve member toward the opening side of the ground hole to maintain the relative position with respect to the deformation of the ground and the anchoring material; and a cylindrical member that is placed between the sleeve member and the ring member and includes a base end face facing the sleeve member; and after filling the ground hole with anchoring material, the steps of placing the rock bolt in the ground hole. According to this method, a support structure capable of generating a desired displacement can be provided. [Effects of the Invention]

[0012] The present invention provides a support structure, a rock bolt, and a method for providing a support structure that can generate a desired displacement. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a cross-sectional view showing the support structure of an embodiment. [Figure 2] Figure 2(a) is a magnified view of the main parts of the rock bolt shown in Figure 1. Figure 2(b) is a view of the precast members included in the rock bolt shown in Figure 1. Figure 2(c) is a disassembled view of the rock bolt shown in Figure 2(a). [Figure 3] Figure 3(a) shows the main steps of the method for installing a support structure. Figure 3(b) shows another step in the method for installing a support structure that follows the steps shown in Figure 3(a). Figure 3(c) shows yet another step in the method for installing a support structure that follows the steps shown in Figure 3(b). [Figure 4] Figure 4(a) shows the support structure in the second state. Figure 4(b) shows the support structure in the third state. Figure 4(c) shows the support structure in the fourth state. [Figure 5] Figure 5 shows the relationship between displacement and support force. [Modes for carrying out the invention]

[0014] Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the attached drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant explanations are omitted.

[0015] The support structure 1 shown in Figure 1 is used in mountain tunnel construction methods such as the New Austrian Tunneling Method (NATM). The support structure 1 is composed of rock bolts 2. The rock bolts 2 are arranged radially to the ground 101 surrounding the tunnel 102. Each rock bolt 2 is anchored to the ground 101 by an anchoring material 3. Therefore, the rock bolts 2 can be considered to be integrated with the ground 101 surrounding the tunnel 102. For example, the tip side (ground side) of the rock bolt 2 may be integrated with a relatively hard ground area where the effects of excavation are negligible. The area where the ground 101 and the rock bolts 2 are integrated forms an arch-shaped support area that supports the tunnel 102.

[0016] The support structure 1 of this embodiment will be described in detail below. For the sake of explanation, in the following description, the side of the rock bolt 2 that is located on the opening side of the borehole 104 (ground hole) will be referred to as the "base end". The side of the rock bolt 2 that is located on the back side of the borehole 104 will be referred to as the "tip end". In Figures 1, 2(a), and 2(c), the rock bolt 2 is illustrated with the right side of the paper as the base end and the left side as the tip end.

[0017] Support structure 1 comprises rock bolts 2 and anchoring members 3. Support structure 1 supports the ground 101 by rock bolts 2 embedded in anchoring members 3 of boreholes 104 made in the ground 101.

[0018] The lock bolt 2 is mostly embedded in the anchoring material 3, with a portion of its base end protruding from the borehole 104. The lock bolt 2 has as its main components an anchoring unit 4, a movable shaft portion 5, a ring member 6, a precast member 7 (cylindrical member), a sleeve member 8, and a screw anchoring member 9. These components are arranged inside the borehole 104 along a direction D1 from the back of the borehole 104 toward the opening 104a of the borehole 104, in the order of screw anchoring member 9, sleeve member 8, precast member 7, ring member 6, and movable shaft portion 5, and are connected to each other. The anchoring unit 4 is then attached to the end of the movable shaft portion 5 that protrudes from the borehole 104.

[0019] For example, when the ground 101 attempts to deform in the direction D1 (rightward in the drawing), a force along the direction D1 acts on the fixing unit 4. As a result, a tensile force corresponding to this force also acts on the movable shaft portion 5, the sleeve member 8, and the screw fixing member 9 connected to the fixing unit 4. At this time, each component resists this tensile force depending on the adhesive force with the fixing material 3 and the tensile strength of each component. As a result, the deformation of the ground 101 is suppressed. That is, the ground 101 is supported.

[0020] Here, when the force acting on the movable shaft portion 5, the sleeve member 8, and the screw fixing member 9 becomes large and exceeds the allowable strength of the component, breakage occurs, and the rock bolt 2 loses its supporting function. More specifically, the supporting function is lost when the stress caused by the acting force exceeds the allowable stress of the component.

[0021] This stress corresponds to the relative displacement between the ground 101 and each component. For example, when the rock bolt 2 undergoes the same deformation as the displacement of the ground 101, the stress acting on the rock bolt 2 is very small (or zero). However, in this case, since the rock bolt 2 does not resist the deformation of the ground 101, it cannot be said that the rock bolt 2 is substantially performing its supporting function.

[0022] When the rock bolt 2 does not deform at all with respect to the deformation of the ground 101, the stress acting on the rock bolt 2 increases according to the displacement of the ground 101. In this case, it can be said that the rock bolt 2 is performing its supporting function, but breakage occurs when the stress acting on the rock bolt 2 exceeds the allowable value.

[0023] That is, the rock bolt 2 moves or deforms according to the deformation of the ground 101 in order to exhibit a supporting function that prevents the deformation of the ground 101 while ensuring that the generated stress does not exceed the allowable value. The rock bolt 2 can achieve such an effect by the components described in detail below.

[0024] <Fixing Unit> The anchoring unit 4 is mounted on the movable shaft portion 5 at the opening 104a of the borehole 104 and maintains its relative position to the ground 101. The anchoring unit 4 has a washer 41 and a nut 42. The washer 41 is a disc or rectangular plate. The area of ​​the washer 41 is larger than the opening area of ​​the opening 104a. A through hole is provided in the center of the washer 41, and the movable shaft portion 5 is inserted through this through hole. The nut 42 is attached to the movable shaft portion 5. The nut 42 generates a force that presses the washer 41 toward the ground 101.

[0025] <Movable shaft> The movable shaft portion 5 is positioned on the opening 104a side of the sleeve member 8. The movable shaft portion 5 has a rod-shaped member 51 and a sheath 52.

[0026] The rod-shaped member 51 is a single rod. The rod-shaped member 51 is integrated with the sleeve member 8 and the screw fixing member 9 to constitute the bolt module 2M. The rod-shaped member 51 includes a rod-shaped base neck portion 511, a rod-shaped body portion 512, and a rod-shaped tip neck portion 513. The rod-shaped base neck portion 511 is one end of the rod-shaped member 51. The rod-shaped tip neck portion 513 is the other end of the rod-shaped member 51.

[0027] The rod-shaped base neck portion 511 includes a male threaded portion 511a that protrudes from the drilled hole 104. The nut 42 of the fixing unit 4 is attached to this male threaded portion 511a.

[0028] The rod-shaped main body 512 is positioned in the borehole 104. The rod-shaped main body 512 is a rod extending along direction D1. The outer circumferential surface of the rod-shaped main body 512 is provided with helically formed projections. A relatively rigid, high-tensile deformed steel bar is used as the rod-shaped main body 512. The rod-shaped main body 512 may have an outer diameter of 20 millimeters or more and 30 millimeters or less, and a length of 3 meters or more and 6 meters or less. For example, the ratio of the outer diameter of the rod-shaped main body 512 to the outer diameter of the sleeve base 80 in the sleeve member 8 described later is 1 / 1.15 to 1 / 1.5, and as an example, it may be about 1 / 1.3. Note that the above outer diameter and length dimensions are examples and are not limited to these dimensions, and appropriate dimensions may be selected according to the support structure 1. Furthermore, the rod-shaped main body 512 may be made of twisted steel, a high-strength lightweight bolt rolled to reproduce the surface shape of a twisted bolt, or a deformed steel bar including a threaded steel bar.

[0029] As shown in Figure 2(c), the rod-shaped tip neck portion 513 includes a male threaded portion 513a and a cylindrical portion 513b. A male thread is provided on the outer circumferential surface of the male threaded portion 513a. The male threaded portion 513a is connected to the sleeve member 8. The cylindrical portion 513b is formed between the male threaded portion 513a and the rod-shaped main body portion 512. The outer diameter of the cylindrical portion 513b is smaller than the outer diameter of the rod-shaped main body portion 512. Therefore, a rod-shaped stepped portion 514 may be formed at the boundary between the cylindrical portion 513b and the rod-shaped main body portion 512. This rod-shaped stepped portion 514 may stand perpendicular to the outer circumferential surface of the cylindrical portion 513b, or it may be an inclined surface extending diagonally to the outer circumferential surface of the cylindrical portion 513b. The outer circumferential surface of the cylindrical portion 513b may also be a smooth cylindrical surface. The ring member 6 and the precast member 7 are arranged on this cylindrical portion 513b. For example, the length of the cylindrical portion 513b may be the same as the sum of the thickness of the ring member 6 and the length of the precast member 7.

[0030] As shown again in Figure 1, the sheath 52 has a through hole through which the rod-shaped member 51 is inserted. The shape of the sheath 52 is cylindrical. Ribs (recesses) may be provided on the outer surface of the sheath 52 as needed. The outer diameter of the sheath 52 is larger than the outer diameter of the rod-shaped member 51, and its inner diameter is also larger than the outer diameter of the rod-shaped member 51. For example, the inner surface of the sheath 52 and the outer surface of the rod-shaped member 51 may be spaced apart from each other. When the rod-shaped member 51 is placed in the sheath 52, a part of the rod-shaped member 51 is covered by the sheath 52. This covered part does not come into contact with the anchoring material 3. The part of the rod-shaped member 51 that the anchoring material 3 does not anchor is called the non-anchored region R52. This non-anchored region R52 is easily movable relative to the anchoring material 3. This movement includes a mode in which the entire rod-shaped member 51 moves toward the opening 104a relative to the ground 101, and a mode in which the length of the non-anchored region R52 increases (stretches).

[0031] Furthermore, the outer surface of the sheath 52 may be smooth. For example, the outer surface of the sheath 52 does not need to have any uneven structures such as ribs. In this case, the edge between the sheath 52 and the fixing material 3 becomes easier to break, so the sheath 52 becomes easier to move relative to the fixing material 3.

[0032] With this configuration, the rod-shaped member 51 and the anchoring material 3 are disconnected, allowing the rod-shaped member 51 to be reliably slid (moved) or extended. Therefore, large deformations of the ground 101 can be tolerated.

[0033] The length L52 of the sheath 52 is shorter than the length L51 of the rod-shaped member 51. The rod-shaped base neck portion 511 and the rod-shaped tip neck portion 513 of the rod-shaped member 51 are not covered by the sheath 52. The sheath 52 covers the portion of the rod-shaped member 51 that is positioned within the borehole 104. More specifically, the sheath 52 covers the rod-shaped main body portion 512. In this case, the length L52 of the sheath 52 is, for example, about 1.0 meter to 6.0 meters. The sheath 52 covers about 1 / 1.18 of the total length of the rod-shaped member 51. In this embodiment, the ratio of the length L52 of the sheath 52 to the total length of the rod-shaped member 51 is about 1 / 1.2, but it may preferably be 3 / 4 or at least 1 / 2.

[0034] A sealing member 53 may be provided at the tip 521 of the sheath 52. This sealing member 53 prevents the fixing material 3 from penetrating into the inside of the sheath 52. For example, the sealing member 53 may be a rod-shaped member 51 with sealing tape for pipe connection wrapped around it. This sealing member 53 does not hinder the relative movement of the rod-shaped member 51 and the sheath 52. In other words, the rod-shaped member 51 and the sheath 52 are not fixed to each other by the sealing member 53.

[0035] The sheath base end 522 contacts, for example, the anchoring unit 4. Note that the movable shaft portion 5 is intended for relative movement between the rod-shaped member 51 and the sheath 52, so the sheath base end 522 is not fixed to the anchoring unit 4. For example, even if the sheath base end 522 is in contact with the anchoring unit 4 in the initial state, a gap may be created between the sheath base end 522 and the anchoring unit 4 as the anchoring unit 4 moves.

[0036] With this sheath 52, a non-anchored region R52 is formed on the rod-shaped member 51, so that if the sleeve member 8 slips, the rod-shaped member 51 slides smoothly inside the sheath 52 and can follow large deformations of the ground 101 without impairing its function. In addition, since the rock bolt specified in the design can be used for the rod-shaped member 51, the enlargement of the outer diameter of the rock bolt 2 can be suppressed. As a result, there is no need to enlarge the inner diameter of the borehole 104 in the ground 101, so the constructability of the support structure 1 is improved. Moreover, since the rod-shaped member 51 can be a general-purpose product, it is economically advantageous.

[0037] <Ring component> As shown in Figures 2(a) and 2(c), the ring member 6 is positioned between the precast member 7 and the sheath 52. The ring member 6 obstructs the movement of the sleeve member 8. The rod-shaped tip neck portion 513 of the rod-shaped member 51 protrudes from the sheath tip 521 and is fixed to the sleeve member 8. The ring member 6 is positioned in the portion (rod-shaped tip neck portion 513) that protrudes from the sheath 52 and is fixed to the sleeve member 8.

[0038] The ring member 6 has a cylindrical shape and includes a ring base end face 61, a ring tip face 62, and a ring through hole 63. The ring base end face 61 abuts against the rod-shaped stepped portion 514. The ring tip face 62 abuts against the precast member 7. The ring through hole 63 penetrates from the ring base end face 61 to the ring tip face 62. The rod-shaped tip neck portion 513 of the movable shaft portion 5 is inserted through the ring through hole 63. The inner circumferential surface of the ring through hole 63 is not fixed to the outer circumferential surface of the rod-shaped tip neck portion 513. Therefore, when the bolt module 2M moves toward the opening 104a, the ring member 6 does not move with the bolt module 2M and can maintain its position.

[0039] The ring member 6 has a constant outer diameter along its axial direction. The outer diameter of the ring member 6 is larger than the outer diameter of the sleeve member 8. The inner diameter of the ring through-hole 63 is larger than the outer diameter of the rod-shaped member 51. Preferably, the inner diameter of the ring through-hole 63 is slightly larger than the outer diameter of the rod-shaped tip neck portion 513. On the other hand, it is preferable that the inner diameter of the ring through-hole 63 is smaller than the outer diameter of the sleeve member 8. The ring member 6 may have a slight taper along its axial direction, rather than a constant outer diameter, as long as it can maintain its relative position to the anchoring material 3 with respect to the deformation of the ground 101. Also, it does not have to be a perfect cylindrical shape; its outer circumference may be formed in a polygonal shape such as an octagon.

[0040] <Precast components> The precast member 7 is positioned between the ring member 6 and the sleeve member 8. When the sleeve member 8 moves toward the opening 104a, the precast member 7 is crushed by the sleeve member 8. The precast member 7 generates a supporting force (second resistance force) as the sleeve member 8 moves while crushing the precast member 7. In other words, the precast member 7 controls the supporting force to a desired value. Furthermore, the amount of displacement over which the supporting force can be exerted can be set according to the length of the precast member 7. Therefore, the length of the precast member 7 depends on the displacement to be controlled. This length of the precast member 7 can also be defined as the distance from the sleeve member 8 to the ring member 6. For example, the length of the precast member 7 may be 100 millimeters. The precast member 7 allows the intended supporting force to be generated over the intended length. The relationship between the precast member 7 and the supporting force will be explained in detail in the operation description section below.

[0041] The precast member 7 is cylindrical in shape. For example, the diameter of the precast member 7 is 40 millimeters. The outer diameter of the precast member 7 may be the same as the outer diameter of the ring member 6. The outer diameter of the precast member 7 may be larger than the outer diameter of the sleeve member 8. The precast member 7 has a precast base end face 71, a precast front end face 72, and a precast through hole 73. The precast member 7 may also be polygonal in shape, as long as it can generate a supporting force (second resistance force) when the sleeve member 8 moves while crushing the precast member 7.

[0042] The precast base end face 71 faces the ring member 6. More specifically, the precast base end face 71 faces the ring tip face 62. In the initial state (S10), the precast base end face 71 may be in contact with the ring tip face 62. The precast tip face 72 faces the sleeve member 8.

[0043] The precast member 7 may be a single, cylindrical member. Alternatively, as shown in Figure 2(b), the precast member 7 may have a so-called split configuration. The precast member 7 is composed of two precast pieces 7A and 7B. The precast pieces 7A and 7B have the same shape as each other. Therefore, the precast pieces 7A and 7B for the precast member 7 can be easily manufactured using a single mold. The precast pieces 7A and 7B each have a pair of contact surfaces 74 and 75. One contact surface 74 is provided with a convex portion 741. The other contact surface 75 is provided with a groove 751. The convex portion 741 of one precast piece 7A is fitted into the groove 751 of the other precast piece 7B. As a result, a cylindrical precast member 7 can be obtained.

[0044] A cylindrical portion 513b is inserted into the precast through-hole 73. The diameter of the precast through-hole 73 is approximately 24 millimeters, for example. The cylindrical portion 513b is not fixed to the inner circumferential surface of the precast through-hole 73. Therefore, when the bolt module 2M moves toward the opening 104a, the precast member 7 does not move with the bolt module 2M and can maintain its position.

[0045] The material constituting the precast member 7 is a foam. For example, the material constituting the precast member 7 may be a foamed urethane-based resin material. In other words, the precast member 7 contains air bubbles. The porosity of the precast member 7 is greater than that of the anchoring material 3. In other words, the density of the precast member 7 is less than that of the anchoring material 3. Furthermore, the amount of deformation required for the precast member 7 depends on the magnitude of the support force to be generated. For example, it is desirable that the displacement of the precast member 7 until it reaches the maximum compressive strength in a uniaxial compressive strength test is greater than the displacement of the anchoring material 3 until it reaches the maximum compressive strength.

[0046] When a precast member 7 made of foam is crushed, the length of the precast member 7 is reduced because the gaps, such as air bubbles, contained in the foam are crushed. Therefore, even if the precast member 7 is crushed, it is unlikely that the internal stress of the precast member 7 will increase or that it will expand outwards. For example, if a material that expands outwards when crushed is used, a restraining force may act on the sleeve member 8 if the filling rate of the anchoring material 3 is excessive. In other words, it may not be possible to control the displacement as intended. Therefore, a material that expands outwards when crushed is undesirable as a material for the precast member 7 because it may hinder the movement of the sleeve member 8. Mortar is an example of a material that expands outwards when crushed. Conversely, as mentioned above, foamed materials such as urethane are examples of materials that do not expand outwards when crushed and also have a certain degree of strength.

[0047] <Sleeve component> When the ground 101 deforms, the sleeve member 8 moves along direction D1 while crushing the precast member 7 that is located between the sleeve member 8 and the ring member 6.

[0048] The sleeve member 8 is provided at the back of the borehole 104, between the movable shaft 5 and the screw fixing member 9. The sleeve member 8 has a substantially cylindrical shape and includes a sleeve base portion 80, a base end tapered portion 81, a tip end tapered portion 82, and a sleeve through hole 84. The sleeve base portion 80 has a constant outer diameter along the axial direction. The sleeve base portion 80 has a cylindrical shape and an outer peripheral surface (adhesion surface) extending in the axial direction. Multiple ridges, which are knots, are provided on this outer peripheral surface, and the fixing material 3 is attached to it in the initial state (S10). Therefore, in the initial state (S10), the movement of the sleeve base portion 80 and the movement of the fixing material 3 coincide. In other words, when the sleeve base portion 80 is fixed to the fixing material 3, the sleeve member 8 does not slip relative to the fixing material 3. On the other hand, as the deformation of the ground 101 progresses, the adhesion between the sleeve base portion 80 and the fixing material 3 is broken. Therefore, in this state, the movement of the sleeve base 80 and the movement of the fixing material 3 do not coincide, and slippage occurs between the sleeve base 80 and the fixing material 3.

[0049] The tapered portion 81 at the base end and the tapered portion 82 at the tip end have an outer diameter that changes along the axial direction. The tapered portion 81 at the base end is located on the side of the opening 104a and includes the base end of the sleeve member 8. Therefore, the tapered portion 81 at the base end is connected to the movable shaft portion 5. The tapered portion 82 at the tip end is located on the inner side of the borehole 104 and includes the tip of the sleeve member 8. Therefore, the tapered portion 82 at the tip end is connected to the screw fixing member 9. The outer diameter of the sleeve base portion 80 is larger than the outer diameter of the screw fixing member 9. In each of the tapered portions 81 at the base end and the tapered portion 82 at the tip end, the maximum outer diameter is equal to the outer diameter of the sleeve base portion 80.

[0050] The length L80 of the sleeve base portion 80 along the axial direction may be, for example, 0.01 to 0.25 (0.01 ≤ (L80 / L2) ≤ 0.25) relative to the total length (length L2) of the lock bolt 2. Preferably, the length L80 may be 0.025 to 0.1 (0.025 ≤ (L80 / L2) ≤ 0.1) relative to the length L2.

[0051] The sleeve through-hole 84 extends from the base-side tapered portion 81 to the tip-side tapered portion 82. A female threaded portion 841 is formed on the inner circumferential surface of the sleeve through-hole 84.

[0052] The male threaded portion 513a provided on the rod-shaped tip neck portion 513 of the movable shaft portion 5 is screwed into the opening on the base end tapered portion 81 side. By adjusting the length of the rod-shaped tip neck portion 513 that is screwed into the sleeve member 8, the distance from the sleeve member 8 to the rod-shaped stepped portion 514 can be adjusted. For example, the ring member 6 is inserted into the rod-shaped tip neck portion 513, and then the precast member 7 is inserted. Then the sleeve member 8 is attached to the male threaded portion 513a of the rod-shaped tip neck portion 513 that protrudes from the precast member 7. When the sleeve member 8 is rotated, the sleeve member 8 approaches the rod-shaped stepped portion 514. As a result, the ring member 6 comes into contact with the rod-shaped stepped portion 514, the precast member 7 comes into contact with the ring member 6, and the sleeve member 8 comes into contact with the precast member 7. With this configuration, the displacement that generates the supporting force (second resistance force) by the precast member 7 can be easily defined.

[0053] The male threaded portion 513a provided on the screw fixing member 9 is screwed into the opening on the tapered tip side 82. As will be described later, the male threaded portion 513a protruding from the tapered tip side 82 exerts a fixing force with the fixing material 3. Since the fixing force depends on the length of the protruding male threaded portion 513a, the fixing force exerted by the screw fixing member 9 can be adjusted by adjusting the length to which it is screwed into the sleeve member 8.

[0054] <Screw fixing member> The screw anchoring member 9 is positioned at the innermost part of the drilled hole 104 in the lock bolt 2. The screw anchoring member 9 has a cylindrical shape and is connected to the sleeve member 8. The axis of the screw anchoring member 9 overlaps with the axis of the sleeve member 8. The screw anchoring member 9 has a male thread on its outer surface. This male thread provides anchoring force with respect to the anchoring material 3.

[0055] The length L9 of the screw fixing member 9 is 5 centimeters or more and 30 centimeters or less, and is 20 centimeters as an example. In other words, the length L9 of the screw fixing member 9 may be approximately the same as the length L8 of the sleeve member 8. Also, the length L9 of the screw fixing member 9 is shorter than the length L51 of the rod-shaped member 51. For example, the length L9 of the screw fixing member 9 may be about 1 / 11 of the length L51 of the rod-shaped member 51. Furthermore, for example, the length L9 of the screw fixing member may be 0.008 or more and 0.10 or less (0.008 ≤ (L9 / L2) ≤ 0.10) relative to the total length (length L2) of the lock bolt 2. Preferably, it may be 0.017 or more and 0.05 or less (0.017 ≤ (L9 / L2) ≤ 0.05).

[0056] The outer diameter of the screw fixing member 9 is between 2 centimeters and 4 centimeters, and for example, it is 2.4 centimeters. In other words, the outer diameter of the screw fixing member 9 is smaller than the outer diameter of the sleeve member 8. For example, the outer diameter of the screw fixing member 9 is 1 / 1.15 to 1 / 1.5 of the outer diameter of the sleeve member 8, and for example, it may be about 1 / 1.3. Also, the outer diameter of the screw fixing member 9 may be approximately the same as the outer diameter of the rod-shaped member 51 in the movable shaft portion 5.

[0057] <Construction method for support structures> Next, we will explain how to construct support structure 1.

[0058] First, prepare the lock bolt 2 (S10: see Figure 2(a)). The manufacturing of the lock bolt 2 can be carried out in any process. For example, prepare a deformed steel bar. Next, provide a rod-shaped base neck portion 511 at one end of the deformed steel bar and a rod-shaped tip neck portion 513 at the other end. As a result, obtain a rod-shaped member 51. Next, insert the rod-shaped member 51 into the sheath 52. Next, provide a seal member 53 at the base end 522 of the sheath. Next, attach the ring member 6 to the rod-shaped tip neck portion 513 and then attach the precast member 7. Next, attach the sleeve member 8 to the male threaded portion 513a of the rod-shaped tip neck portion 513. Then, attach the threaded fixing member 9 to the sleeve member 8. Finally, attach the fixing unit 4 to the rod-shaped base neck portion 511.

[0059] Next, a tunnel 102 is constructed in the ground 101. Then, a concrete wall 103 is constructed on the excavation surface of the tunnel 102. Next, multiple boreholes 104 extending from the concrete wall 103 to the ground 101 are made using a rock drill or the like (S11: see Figure 3(a)). Next, an anchoring material 3 such as mortar is prepared, and the anchoring material is filled into the boreholes 104 using a pump or the like (S12: see Figure 3(b)). Then, rock bolts 2 are embedded in the anchoring material 3 (S21: see Figure 3(c)). Through these steps, a support structure 1 can be obtained.

[0060] <Relationship between the condition of the rock bolt and the supporting force of the rock bolt> The relationship between the state of the rock bolts 2 in accordance with the displacement of the ground 101 and the support force (supporting work pressure) of the rock bolts 2 will be explained below with reference to Figures 3, 4, and 5. Figures 3 and 4 are schematic diagrams showing the state of the rock bolts 2 in accordance with the displacement of the ground. Figure 5 is a schematic graph showing the relationship between the displacement of the rock bolts 2 and the support force. In Figure 5, the horizontal axis shows the displacement of the ground 101, and the vertical axis shows the support force exerted by the rock bolts 2. The support force can also be said to be the reaction force to the force acting on the rock bolts 2, so the vertical axis can also be viewed as the force acting on the rock bolts 2.

[0061] In Figure 5, graph G5A shows the characteristics of the lock bolt 2 of the embodiment. Graph G5B shows the characteristics of the lock bolt according to the comparative example.

[0062] Section (c) of Figure 3 shows the initial state (S21) of the rock bolt 2. In the initial state (S21), the displacement of the ground 101 is zero, and the support force of the rock bolt 2 is also zero.

[0063] Part 4(a) of Figure 4 shows the second state (S22), in which the ground 101 has been displaced by a length V22 from the initial state (S21). In part 4(a) of Figure 4, the dashed line K21 represents the surface 101c of the ground 101 in the initial state (S21). In the second state (S22), the rock bolt 2 has its screw anchoring member 9, sleeve member 8, and sheath 52 anchored to the anchoring material 3. On the other hand, the rod-shaped main body 512 is not anchored to the anchoring material 3.

[0064] In the second state (S22), the anchoring unit 4 moves in direction D1 as the ground 101 is displaced. As a result, the screw anchoring member 9 becomes an anchor in the rock bolt 2. Therefore, there is no movement of the bolt module 2M, which includes the screw anchoring member 9 and the sleeve member 8. On the other hand, the displacement of the ground 101 (V22) causes elongation (T22) in the rod-shaped main body 512. The greater the displacement of the ground 101 (V22), the greater the force acting on the rod-shaped main body 512, and it resists this force. As a result, the reaction force (supporting force) generated by the rod-shaped main body 512 also increases (see the initial resistance section G5a in graph G5A). The supporting force of the rod-shaped main body 512 can be shown by Hooke's law, which is based on the elastic modulus (Young's modulus) of the rod-shaped main body 512 and the cross-sectional area of ​​the rod-shaped main body 512. In this state, a force corresponding to the displacement of the ground 101 acts on the rock bolt 2, but the stress is reduced by the elongation (T22) of the rod-shaped main body 512.

[0065] Here, when the screw anchoring member 9 is anchored to the anchoring material 3, the rod-shaped main body 512 deforms as if being pulled (T22) in accordance with the deformation (V22) of the ground 101. Therefore, the deformation (V22) of the ground 101 is permitted in accordance with the elongation (T22) of the rod-shaped main body 512. This elongation (T22) of the rod-shaped main body 512 relieves the stress acting on the rod-shaped main body 512 in accordance with the deformation (V22) of the ground 101. As a result, the rock bolt 2 does not lose its support function. In other words, the rock bolt 2 can continue to support the ground 101. Furthermore, the rod-shaped main body 512 can reliably slide against the anchoring material 3 due to the non-anchored region R52 formed by the sheath 52. As a result, the screw anchoring member 9 becomes a fixed point (anchor) to the ground 101. Therefore, the rod-shaped main body 512 can reliably extend (T22) in accordance with the deformation (V22) of the ground 101.

[0066] Then, we assume that the adhesion of the screw fixing member 9 breaks near point P2 in graph G5A. The fixing force of the screw fixing member 9 depends on the shape of the male threads formed on its outer surface. Therefore, the fixing force of the sleeve member 8, which does not have male threads formed on it, is lower than the fixing force of the screw fixing member 9. Thus, it is reasonable to assume that when the adhesion of the screw fixing member 9 breaks, the fixing of the sleeve member 8 has already broken.

[0067] Part 4(b) of Figure 4 shows the third state (S23) in which the ground 101 has been further displaced by a length V23. In part 4(b) of Figure 4, the dashed line K22 indicates the surface 101c of the ground 101 in the second state (S22). In the third state (S23), as described above, the anchoring in the screw anchoring member 9 and the sleeve member 8 is broken, and only the precast member 7, the ring member 6 and the sheath 52 are anchored to the anchoring material 3. In the third state (S23), the anchoring unit 4 moves in direction D1 in accordance with the displacement of the ground 101.

[0068] As a result, the bolt module 2M, including the screw anchoring member 9, sleeve member 8, and rod-shaped main body 512, slides toward the opening 104a in accordance with the displacement (V23) of the ground 101. In other words, the bolt module 2M moves relative to the anchoring material 3. In part 4(b), these movements are represented as the movement (T23) of the anchoring unit 4. That is, from the second state (S22) to the third state (S23), the screw anchoring member 9, sleeve member 8, and rod-shaped main body 512 move uniformly toward direction D1 without any substantial elongation. During this movement (T23), the rock bolt 2 exerts a supporting force (second resistance force) in a different manner (displacement control section G5b) than the supporting force (first resistance force) in the initial resistance section G5a from the transition from the initial state (S21) to the second state (S22).

[0069] As described above, the sleeve member 8 moves in the direction of the opening 104a of the borehole 104 while crushing or pushing aside the precast member 7. In other words, the sleeve member 8 moves along direction D1 while being hindered by the precast member 7 that is located between the sleeve member 8 and the ring member 6. Therefore, the support force can be controlled by the projected area of ​​the base end tapered portion 81 (see Figure 3) onto a virtual plane perpendicular to the axial direction, the angle of the base end tapered portion 81, and the material properties of the precast member 7. The relationship between displacement and support force during the transition from the second state (S22) to the third state (S23) is shown in the displacement control section G5b in graph G5A. The slope of the displacement control section G5b is smaller than the slope in the initial resistance section G5a.

[0070] Here, as a comparative example, we will examine the behavior of a rock bolt without the precast member 7. The rock bolt of the comparative example differs from the rock bolt 2 of the embodiment only in that it does not have the precast member 7. In the rock bolt of the comparative example, the cylindrical portion of the neck at the base end is covered by the anchoring material instead of the precast member. Consequently, when transitioning from the second state (S22) to the third state (S23), in the rock bolt of the comparative example, the sleeve member moves in the direction of the opening 104a of the borehole 104 while crushing the anchoring material.

[0071] In this case, the properties of the anchoring material between the sleeve member and the ring member are of particular interest. If the anchoring material is mortar, even if a specific construction procedure is followed, variations will occur in the final properties of the anchoring material. These variations may be caused, for example, by the influence of the ground 101 in which the borehole 104 is made.

[0072] For example, the mortar filling may be insufficient. When the mortar filling is insufficient, it does not excessively hinder the movement of the sleeve member 8. Therefore, deformation of the ground 101 is acceptable. However, when crushing mortar that is not sufficiently filled, a sufficient reaction force cannot be obtained. Therefore, the support force may be smaller than expected.

[0073] For example, the mortar may be filled too tightly. When the mortar is filled too tightly, the movement of the sleeve member 8 is excessively hindered. In other words, a large force is applied to crush the mortar, and the reaction force generated in proportion to that force is also large. Therefore, the support force may be larger than the expected magnitude. That is, the desired support force can be secured. However, the fracture strength (F3) is reached before the desired allowable displacement (T22+T23+T24) is reached, so the desired allowable displacement cannot be secured.

[0074] Thus, the member between the sleeve member 8 and the ring member 6 has a significant impact on the support force and allowable displacement. Therefore, it is important to ensure that the properties of the member between the sleeve member 8 and the ring member 6 are consistent. Ensuring consistent properties means that when multiple support structures 1 are constructed, the variation in the properties of the member between the sleeve member 8 and the ring member 6 is small for each support structure 1.

[0075] For example, if mortar is used as the fixing material 3, it may be possible to suppress variations in the properties of the mortar between the sleeve member 8 and the ring member 6 by appropriately controlling the amount of mortar filled. However, it is generally difficult to reliably control the amount of mortar filled.

[0076] The mortar's strength is too high (25-30 N / mm²). 2 ) and movement of the sleeve member 8 (from the second state S22 to the third state S23) becomes difficult. Therefore, it is conceivable to use a special low-strength mortar with inherently low strength. However, in this case, although movement of the sleeve member 8 is permitted, there was a possibility that the desired support force could not be achieved.

[0077] Therefore, the rock bolt 2 of this embodiment includes a precast member 7 located between the sleeve member 8 and the ring member 6. In other words, the rock bolt 2 of this embodiment installs a precast member 7, separate from the anchoring material 3 (mortar), between the sleeve member 8 and the ring member 6. Since the precast member 7 is manufactured in a factory or the like, the variation in its properties is smaller than the variation in the properties of the anchoring material 3 formed in the drilled hole 104. Consequently, even when multiple support structures 1 are constructed, the characteristics shown in the displacement control section G5b of graph G5A can be reliably achieved.

[0078] From another perspective, in the rock bolt 2 according to this embodiment, the sleeve member 8 moves in the direction of the opening 104a of the borehole 104 as the ground 101 deforms. Therefore, the stress acting on the rock bolt 2 as the ground 101 deforms is relieved by the movement of the rock bolt 2. This suppresses the generation of stress that would cause the rock bolt 2 to lose its function as a support structure, and allows for greater deformation of the ground 101. Furthermore, a non-anchored region R52 is formed in the portion of the rod-shaped main body 512 covered by the sheath 52, and in this non-anchored region R52, the rod-shaped main body 512 is not anchored to the anchoring material 3, so no resistance force is generated between it and the anchoring material 3. As a result, the rod-shaped main body 512 can be reliably slid relative to the anchoring material 3 without hindering the movement of the sleeve member 8. Therefore, the rock bolt 2 can further tolerate deformation of the ground 101 without losing its function as a support structure. Consequently, it can reliably follow even large deformations of the ground 101.

[0079] Section (c) of Figure 4 shows the fourth state (S24), in which the ground 101 has been further displaced by a length V24. In section (c) of Figure 4, the dashed line K23 indicates the surface 101c of the ground 101 in the third state (S23). In the fourth state (S24), the sleeve member 8 presses against the ring member 6 via the crushed precast member 7. In the fourth state (S24), as the anchoring unit 4 moves in direction D1 due to the displacement of the ground 101, the ring member 6 prevents the movement of the sleeve member 8. Therefore, the sleeve member 8 and the ring member 6 act as anchors. Consequently, it can be assumed that there is virtually no movement of the bolt module 2M including the sleeve member 8 along direction D1. As a result, the force caused by the displacement of the ground 101 again causes elongation (E2) in the rod-shaped main body 512. In other words, the greater the displacement of the ground 101 (V24), the greater the force acting on the rod-shaped main body 512, and in order to counteract this force, the reaction force (supporting force) exerted by the rod-shaped main body 512 also becomes larger (see the final resistance section G5c in graph G5A).

[0080] Furthermore, the support force when transitioning from the third state (S23) to the fourth state (S24) may take into account the resistance force of the ring member 6. In the above explanation, it was assumed that the sleeve member 8 and the ring member 6 do not move in response to the displacement of the ground 101. However, depending on the shape of the ring member 6 and the material properties of the anchoring material 3, the ring member 6 may also move toward the opening 104a in response to the displacement of the ground 101. In that case, the resistance force may be the resultant force of the force generated when the ring member 6 moves against the resistance force of the anchoring material 3 and the force in the rod-shaped main body 512 described above. When the support force reaches force (F3), the rock bolt 2 is considered to lose its support function.

[0081] As a result, the rock bolt 2 according to the embodiment can provide support up to a force (F3) in the displacement (T22 + T23 + T24) of the ground 101.

[0082] <Effects and Effects> The rock bolts 2 are for the support structure 1 of the ground 101, which has boreholes 104 into which anchoring material 3 is filled. The rock bolt 2 is a rod-shaped member 51 that extends in a predetermined direction and is positioned in the borehole 104, and moves relative to the anchoring material 3 as the ground 101 deforms, or extends as the ground 101 deforms; a sleeve member 8 that has a larger outer diameter than the rod-shaped member 51, is fixed to the base end of the rod-shaped member 51 and includes a sleeve base portion 80 to which the anchoring material 3 is attached, and generates a first resistance force against the deformation of the ground 101; a ring member 6 that has an inner diameter larger than the outer diameter of the rod-shaped member 51 and has a ring through-hole 63 through which the rod-shaped member 51 is inserted, is positioned at a predetermined distance from the sleeve member 8 toward the opening side of the borehole 104, and maintains its relative position to the anchoring material 3 with respect to the deformation of the ground 101; and a precast member 7 that is positioned between the sleeve member 8 and the ring member 6 and includes a base end surface facing the sleeve member 8. As the sleeve member 8 moves toward the opening of the borehole 104 in accordance with the deformation of the ground 101, the sleeve member 8 presses against the precast member 7, causing the precast member 7 to be crushed and generating a second resistance force different from the first resistance force.

[0083] The support structure 1 of the embodiment comprises a fixing material 3 that is filled into a borehole 104 formed in the ground 101, and the aforementioned rock bolt 2 that is placed in the borehole 104.

[0084] The method for providing the support structure 1 of the embodiment includes the step S10 of preparing the rock bolts 2 described above, and the step S21 of filling the drilled holes 104 with anchoring material 3 and then placing the rock bolts 2 in the drilled holes 104.

[0085] The rock bolt 2, support structure 1, and method of providing the support structure 1 described above include a precast member 7 positioned between a sleeve member 8 and a ring member 6. The second resistance force is generated when the precast member 7 is crushed by the sleeve member 8, and therefore the second resistance force is affected by the properties of the precast member 7. This precast member 7 is provided as a component of the support structure 1. In this way, when constructing multiple support structures 1, the variation in the properties of the precast member 7 for each support structure 1 can be suppressed compared to the variation in the properties of the anchoring material 3 installed on-site for each support structure 1. As a result, the variation in the second resistance force generated for each support structure 1 is also suppressed, and therefore the variation in the displacement of the rock bolt 2 in response to the second resistance force is also suppressed. As a result, the desired displacement can be generated in the rock bolt 2, and the quality of the displacement control section G5b of the rock bolt 2 can be improved.

[0086] Furthermore, by incorporating precast members 7, it becomes unnecessary to consider the ease of movement of the sleeve members 8 when selecting the material for the anchoring material 3. In other words, the amount of anchoring material 3 filled will never be insufficient. As a result, the support structure 1 can absorb the set displacement while appropriately securing the load when in the displacement control section G5b. Since the support force exerted by the support structure 1 is no longer dependent on the amount of anchoring material 3 filled, variations in the displacement of the rock bolts 2 are also suppressed. Consequently, the quality of construction at the site is improved.

[0087] Furthermore, since the precast member 7 does not expand outwards when it collapses, even if the amount of anchoring material 3 is excessive, the increase in restraint from the surroundings can be suppressed. As a result, appropriate displacement can be controlled while ensuring the load.

[0088] Furthermore, by incorporating the precast member 7, it is possible to create the desired displacement without using a special material (low-strength mortar) as the anchoring material 3. In other words, it is possible to use rock bolt filling mortar, which is commonly used as the anchoring material 3. By using commonly used mortar, workability is improved and the cost of the anchoring material 3 can be reduced.

[0089] Although embodiments of the present invention have been described above, it may be implemented in various forms without being limited to the above embodiments. [Explanation of symbols]

[0090] 1...Support structure, 2...Rock bolt, 3...Anchorage material, 6...Ring member, 7...Precast member (cylindrical member), 8...Sleeve member, 51...Rod-shaped member, 101...Natural ground, 104...Drilling (hole in the ground).

Claims

1. A support structure installed in the natural ground, A fixing material to be filled into a hole in the ground formed in the aforementioned ground, A rod-shaped member that extends in a predetermined direction and is positioned in the ground hole, moves relative to the anchoring material in accordance with the deformation of the ground, or extends in accordance with the deformation of the ground, A sleeve member having a larger outer diameter than the rod-shaped member, fixed to the base end of the rod-shaped member and including a portion to which the anchoring material is attached, and generating a first resistance force against the deformation of the ground, A ring member having an inner diameter larger than the outer diameter of the rod-shaped member and a through hole through which the rod-shaped member is inserted, positioned at a predetermined distance from the sleeve member toward the opening of the ground hole, and maintaining its relative position to the anchoring material with respect to the deformation of the ground, The system comprises a cylindrical member disposed between the sleeve member and the ring member, and including a base end face facing the sleeve member, A support structure wherein, when the sleeve member moves toward the opening of the ground hole in accordance with the deformation of the ground, the sleeve member presses against the base end surface of the cylindrical member, thereby crushing the cylindrical member and generating a second resistance force different from the first resistance force.

2. The support structure according to claim 1, wherein the amount of displacement of the cylindrical member along the axial direction until it reaches the maximum compressive strength of the cylindrical member along the axial direction is greater than the amount of displacement of the anchoring material along the axial direction until it reaches the maximum compressive strength of the anchoring material along the axial direction.

3. The support structure according to claim 1, wherein the void ratio of the cylindrical member is greater than the void ratio of the anchoring material.

4. The support structure according to claim 1, wherein the density of the cylindrical member is less than the density of the anchoring material.

5. A rock bolt for a ground support structure, in which a ground hole is provided into which a fixing material is filled, A rod-shaped member that extends in a predetermined direction and is positioned in the ground hole, moves relative to the anchoring material in accordance with the deformation of the ground, or extends in accordance with the deformation of the ground, A sleeve member having a larger outer diameter than the rod-shaped member, fixed to the base end of the rod-shaped member and including a portion to which the anchoring material is attached, and generating a first resistance force against the deformation of the ground, A ring member having an inner diameter larger than the outer diameter of the rod-shaped member and a through hole through which the rod-shaped member is inserted, positioned at a predetermined distance from the sleeve member toward the opening of the ground hole, and maintaining its relative position to the anchoring material with respect to the deformation of the ground, The system comprises a cylindrical member disposed between the sleeve member and the ring member, and including a base end face facing the sleeve member, A rock bolt in which, as the sleeve member moves toward the opening of the hole in the ground in accordance with the deformation of the ground, the sleeve member presses against the base end surface of the cylindrical member, thereby crushing the cylindrical member and generating a second resistance force different from the first resistance force.

6. A method for providing a support structure for ground in which holes are provided in the ground into which anchoring material is filled, A step to prepare a rock bolt comprising: a rod-shaped member that is positioned in the ground hole and extends in a predetermined direction, moves relative to the anchoring material in accordance with the deformation of the ground, or extends in accordance with the deformation of the ground; a sleeve member that has a larger outer diameter than the rod-shaped member, is fixed to the base end of the rod-shaped member and includes a portion to which the anchoring material is attached, and generates a first resistance force against the deformation of the ground; a ring member that has an inner diameter larger than the outer diameter of the rod-shaped member and has a through hole through which the rod-shaped member is inserted, is positioned at a predetermined distance from the sleeve member toward the opening side of the ground hole, and maintains a relative position with respect to the deformation of the ground with respect to the anchoring material; and a cylindrical member that is positioned between the sleeve member and the ring member and includes a base end surface facing the sleeve member. A method for providing a support structure, comprising the steps of filling the ground hole with the anchoring material and then placing the rock bolt in the ground hole.

Images