Rock bolt structure and ground reinforcement structure

Abstract

To provide a natural ground reinforcement structure allowing a rock bolt structural body to be securely fixed on the natural ground over a long length even where the natural ground has a lot of cracks.SOLUTION: A rock bolt structural body comprises: a steel pipe expansion type rock bolt 2 in which a front end is sealed and a screwed part having a water injection port is arranged at a rear end; a hollow rock bolt 3 for fixing a fixing material inside which an injected water guide space is provided along an axial direction; and a joint sleeve 4 which is communicated in the axial direction and in which a screw part is formed in a front part, wherein the screw part of the joint sleeve 4 and the screwed part of the steel pipe expansion type rock bolt 2 are screwed as well as a front part of the hollow rock bolt 3 and a rear part of the joint sleeve 4 are secured, and an annular seal member 42 liquid-tightly sealed from an outer part by pressing force in a screw-in direction of the screw part and the screwed part is arranged on the joint sleeve 4.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a rock bolt structure in which a hollow rock bolt is fixed by an anchoring material injected into a bored hole, and to a natural ground reinforcement structure including this rock bolt structure. [Background technology]

[0002] Conventionally, there is known a natural ground reinforcement structure in which a hollow rock bolt is fixed by an anchoring material injected into a borehole. For example, Patent Document 1 discloses a structure in which a hollow rock bolt with a drilling bit attached to its tip is rotated to drill a hole in the natural ground, and the hollow rock bolt is added to the hole to a specified depth, and after the hole is drilled, grout is injected between the hollow rock bolt and the wall surface of the borehole through the hollow part of the hollow rock bolt in the borehole, and the grout is solidified to fix the hollow rock bolt (see paragraphs

[0002] and

[0018] of Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-97260 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, when a hollow rock bolt is extended and cast deep into the ground, and an anchoring material is injected to fix the bolt in place, it is necessary to use an anchoring material with high fluidity in order to inject the anchoring material deep into the ground. However, in the case of ground with many cracks, the anchoring material flows out into the cracks due to its high fluidity, and runs away before it hardens, causing a problem that the anchoring material disappears between the hollow rock bolt and the wall of the borehole. On the other hand, if an anchoring material with low fluidity such as thickened mortar is used, it becomes impossible to inject the anchoring material deep into the borehole, which causes another problem that it becomes difficult to fix the hollow rock bolt located deep into the ground.

[0005] The present invention has been proposed in view of the above problems, and aims to provide a rock bolt structure that can be reliably fixed into the ground over a long length even in ground with many cracks, and a ground reinforcement structure equipped with this rock bolt structure. Note that, for convenience in explaining the present invention, the side that is positioned at the back of a drilled hole when the rock bolt is installed in the drilled hole may be referred to as the "front" or "front end", "front part", or "tip", and the side that is positioned at the mouth of the drilled hole may be referred to as the "rear", "rear end", "rear side", etc. [Means for solving the problem]

[0006] The rock bolt structure of the present invention comprises a steel pipe expansion type rock bolt whose front end is closed and which is provided with a threaded portion having a water inlet at its rear end, a hollow rock bolt for fixing a fixing material which is provided with a water injection introduction space inside along the axial direction, and a joint sleeve which communicates with the axial direction and has a threaded portion formed at its front portion, wherein the threaded portion of the joint sleeve and the threaded portion of the steel pipe expansion type rock bolt are threadedly connected to each other, the front portion of the hollow rock bolt and the rear portion of the joint sleeve are fixed together, and an annular sealant is provided on the joint sleeve which provides a liquid-tight seal from the outside by pressing the threaded portion and the threaded portion in the screwing direction. According to this, when a long rock bolt structure is driven and fixed deep into the natural ground, the steel pipe expansion type rock bolt can be fixed by frictional fixing in the expanded state at the back of the drilled hole, and there is no need to use a fixing material with high fluidity to inject deep into the natural ground or the back of the drilled hole. In other words, even when a long rock bolt structure is fixed into a natural ground with many cracks, there is no problem that the fixing material with high fluidity escapes from the crack before solidifying, and the rock bolt structure can be reliably fixed into the natural ground over a long length by both frictional fixing and fixing of the fixing material. In addition, since the steel pipe expansion type rock bolt can be fixed by frictional fixing in the expanded state at the back of the drilled hole, a fixing material with low fluidity such as thick mortar can be used, and the variety of fixing materials that can be used can be increased. Furthermore, when pressurized water is injected into the inside of the steel pipe expansion type rock bolt to expand it using the water injection introduction space of the hollow rock bolt and the water injection port of the steel pipe expansion type rock bolt, the liquid-tight seal of the annular sealing material of the joint sleeve reliably prevents the injected water from leaking from the gap between the threaded portion of the joint sleeve and the threaded portion of the steel pipe expansion type rock bolt, thereby increasing the reliability of pressurized water injection into the inside of the steel pipe expansion type rock bolt and expansion deformation of the steel pipe expansion type rock bolt.

[0007] The lock bolt structure of the present invention is characterized in that the threaded portion of the steel pipe expansion type lock bolt is a male threaded portion, the threaded portion of the joint sleeve is a female threaded portion, and the annular sealing material is provided at the base of the female threaded portion and is pressed by the rear end of the male threaded portion. The rock bolt structure of the present invention comprises a steel pipe expansion type rock bolt having a closed front end and a male threaded portion with a water inlet at its rear end, a hollow rock bolt for fixing a fixing material having a water inlet space inside along the axial direction, and a joint sleeve which communicates with the bolt in the axial direction and has a female threaded portion formed at its front portion, and the female threaded portion of the joint sleeve and the male threaded portion of the steel pipe expansion type rock bolt are screwed together, and the front portion of the hollow rock bolt and the rear portion of the joint sleeve are fixed together, and the female threaded portion and The present invention is characterized in that an annular sealant, which provides a liquid-tight seal from the outside by being pressed in the screwing direction of the male threaded portion, is installed at the base of the female threaded portion of the joint sleeve so as to be pressed by the rear end of the male threaded portion, a female threaded portion for screwing into a water injection pipe is provided immediately behind the annular sealant of the joint sleeve, and a front end face of the water injection pipe, which is screwed into the female threaded portion for screwing into the water injection pipe by a water injection pipe male threaded portion formed in a front part of the water injection pipe inserted into the water injection introduction space, is abutted so as to be pressed against the annular sealant. This allows the steel pipe expansion type lock bolt and the joint sleeve to be screw-connected with high strength and stability. Also, the annular seal at the base of the female thread of the joint sleeve is pressed by the rear end of the male thread of the steel pipe expansion type lock bolt, ensuring a liquid-tight seal of the annular seal. Also, since the annular seal is placed at the base of the female thread of the joint sleeve during transportation and delivery to the site, damage to the annular seal is prevented.

[0008] The lock bolt structure of the present invention is characterized in that the threaded portion of the steel pipe expansion type lock bolt is a female threaded portion, the threaded portion of the joint sleeve is a male threaded portion, and the annular sealing material is provided at the base of the male threaded portion and is pressed by the rear end of the female threaded portion. This allows the steel pipe expansion type lock bolt and the joint sleeve to be screw-connected with high strength and stability. Also, the annular seal material at the base of the male thread of the joint sleeve is pressed by the rear end of the female thread of the steel pipe expansion type lock bolt, ensuring a liquid-tight seal of the annular seal material. Furthermore, by arranging the annular seal material at the base of the male thread of the joint sleeve, it is possible to visually check for any detachment or displacement of the annular seal material during the work of connecting the steel pipe expansion type lock bolt and the hollow rock bolt, thereby increasing the reliability of the work.

[0009] The rock bolt structure of the present invention is characterized in that a connection portion to which the front portion of a water injection pipe can be freely connected and detached is provided behind the threaded portion of the joint sleeve, and a discharge hole through which an anchoring material can be injected between the hole wall of the drilled hole in the ground and the outer surface of the hollow rock bolt and the outer surface of the joint sleeve is formed in the peripheral wall rear of the connection portion of the joint sleeve or in the peripheral wall of the hollow rock bolt. The rock bolt structure of the present invention is further characterized in that a discharge hole through which an anchoring material can be injected between the wall of the hole in the natural ground and the outer surface of the hollow rock bolt and the outer surface of the joint sleeve is formed in the peripheral wall rear of the female thread portion of the joint sleeve for screwing into the water injection pipe, or in the peripheral wall of the hollow rock bolt. This makes it possible to introduce and connect the water injection pipe up to the rear side of the screwed part of the joint sleeve, and further increases the reliability of pressurized water injection into the inside of the steel pipe expansion type rock bolt by the water injection pipe and expansion deformation of the steel pipe expansion type rock bolt. Also, by forming a discharge hole through which the anchoring material can be injected between the hole wall and the outer surface of the drilled hole in the natural ground in the joint sleeve or in the hollow rock bolt located on the mouth side of the drilled hole, it is possible to prevent the anchoring material from escaping to the back side of the drilled hole. Also, when a discharge hole through which the anchoring material can be injected is formed in the peripheral wall of the joint sleeve, it becomes possible to more reliably fill the anchoring material up to just behind the steel pipe expansion type rock bolt.

[0010] The lock bolt structure of the present invention is characterized in that a separate annular sealant is attached to the joint sleeve, which provides a liquid-tight seal from the outside by pressing in the screw-in direction between the front part of the hollow lock bolt and the rear part of the joint sleeve. According to this, it is possible to liquid-tightly seal the gap between the steel pipe expansion type rock bolt and the joint sleeve with an annular sealant, and liquid-tightly seal the gap between the hollow rock bolt and the joint sleeve with another annular sealant, and the water injection introduction space of the hollow rock bolt itself can be used as a water injection channel for injecting pressurized water into the inside of the steel pipe expansion type rock bolt. Also, since pressurized water injection can be performed without using a water injection pipe, the work of inserting and removing the water injection pipe is eliminated, and the construction process can be made more efficient.

[0011] The lock bolt structure of the present invention is characterized in that all of the screw mechanisms that are screwed are left-handed screw mechanisms. According to this, by simply rotating the hollow rock bolt protruding from the drilling hole in the tightening direction of the left-handed thread, a liquid-tight seal for the annular sealant, etc. can be reliably achieved. In other words, when the base of the hollow rock bolt is a drilling rod, the left-handed rotation of the drilling machine is the normal rotation, so the hollow rock bolt is a left-handed thread, but if all the screwing mechanisms are left-handed mechanisms to match this, by rotating the hollow rock bolt in the tightening direction of the left-handed thread, the screwing between the steel pipe expansion type lock bolt and the joint sleeve is further tightened without loosening, and the annular sealant, etc. is pressed in the screwing direction, so that a highly liquid-tight sealing state can be easily achieved.

[0012] The rock bolt structure of the present invention is characterized in that the hollow rock bolt is a rope screw. This allows the hollow rock bolt to be smoothly inserted into the borehole, while also improving the adhesion of the fixing material to the hollow rock bolt, thereby increasing the fixing strength of the fixing material of the hollow rock bolt and rock bolt structure to the borehole wall.

[0013] The ground reinforcement structure of the present invention is a ground reinforcement structure equipped with the rock bolt structure of the present invention, characterized in that the steel pipe expansion type rock bolt, the joint sleeve, and the hollow rock bolt are arranged in that order from the back side of a drilled hole in the ground, the steel pipe expansion type rock bolt is frictionally fixed to the hole wall of the drilled hole in an expanded state, and a fixing material is filled and solidified between the hole wall of the drilled hole and the outer surface of the hollow rock bolt and the outer surface of the joint sleeve. With this, the rock bolt structure can be securely fixed into the ground over its long length and the ground can be reinforced by both the frictional fixation of the expanded steel pipe expansion type rock bolt at the back of the drilling hole and the fixation of the fixing material between the hole wall of the drilling hole and the outer surface of the hollow rock bolt and the outer surface of the joint sleeve at the mouth of the drilling hole.

[0014] The joint sleeve of the present invention is a joint sleeve that connects a steel pipe expansion type rock bolt having a closed front end and a threaded portion with a water inlet at its rear end, and a hollow rock bolt for fixing a fixing material, which has a water injection introduction space provided inside along the axial direction, and is characterized in that the threaded portion communicates with the steel pipe expansion type rock bolt, a threaded portion formed at the front portion can be threaded into the threaded portion of the steel pipe expansion type rock bolt, the front portion of the hollow rock bolt can be fixed to the rear portion, and an annular seal material is provided that provides a liquid-tight seal from the outside by pressing the threaded portion and the threaded portion in the screwing direction. According to this, when a rock bolt structure consisting of a steel pipe expansion type rock bolt, a hollow rock bolt, and a joint sleeve is driven into the ground deep and fixed, the steel pipe expansion type rock bolt can be fixed by frictional fixing in the expanded state at the back of the drilled hole by the joint sleeve, and there is no need to use a highly fluid fixing material to inject into the deep layer of the ground or the back of the drilled hole. In other words, even when a rock bolt structure is fixed over a long length in a ground with many cracks, there is no problem that the highly fluid fixing material escapes from the crack before solidifying, and the rock bolt structure can be reliably fixed into the ground over a long length by both frictional fixing and fixing of the fixing material. In addition, since the steel pipe expansion type rock bolt can be fixed by frictional fixing in the expanded state at the back of the drilled hole, a fixing material with low fluidity such as thick mortar can be used, and the variety of fixing materials that can be used can be increased. Furthermore, when pressurized water is injected into the inside of the steel pipe expansion type rock bolt to expand it using the water injection introduction space of the hollow rock bolt and the water injection port of the steel pipe expansion type rock bolt, the liquid-tight seal of the annular sealing material of the joint sleeve reliably prevents the injected water from leaking from the gap between the threaded portion of the joint sleeve and the threaded portion of the steel pipe expansion type rock bolt, thereby increasing the reliability of pressurized water injection into the inside of the steel pipe expansion type rock bolt and expansion deformation of the steel pipe expansion type rock bolt.

[0015] The water injection structure of the present invention is a water injection structure that is screwed onto a steel pipe expansion type rock bolt that has a closed front end and a threaded portion with a water injection port at its rear end, and is characterized in that it comprises a hollow rock bolt for fixing an anchoring material, a water injection pipe that is inserted axially into the inside of the hollow rock bolt, and a joint sleeve that communicates with the axial direction, has a threaded portion at its front that is threadedly attached to the threaded portion and has a front part of the hollow rock bolt fixed to its rear part, the front part of the water injection pipe is detachably connected to a connection portion provided inside the joint sleeve on the rear side of the threaded portion, a discharge hole through which an anchoring material can be injected between the hole wall of a drilled hole in the ground and the outer surface of the hollow rock bolt and the outer surface of the joint sleeve is formed in the peripheral wall of the joint sleeve rearward of the connection portion or in the peripheral wall of the hollow rock bolt, and an annular sealant that provides a liquid-tight seal from the outside by pressing the threaded portion and the threaded portion in the screw-in direction is installed on the joint sleeve. The water injection structure of the present invention is a water injection structure that is screwed onto a steel pipe expansion type rock bolt that is closed at its front end and provided with a male threaded portion having a water injection port at its rear end, and includes a hollow rock bolt for fixing an anchoring material, a water injection pipe that is inserted into the hollow rock bolt along the axial direction, and a joint sleeve that communicates with the anchoring material in the axial direction, has a female threaded portion formed at its front portion that is screwed onto the male threaded portion, and has a front portion of the hollow rock bolt fixed to its rear portion, and the male threaded portion of the water injection pipe formed at the front portion of the water injection pipe is detachably screwed into the female threaded portion for screwing the water injection pipe that is provided inside the joint sleeve on the rear side of the female threaded portion, and the wall of a hole in the natural ground and the outer surface of the hollow rock bolt and the joint sleeve are connected to each other. a discharge hole through which an anchoring agent can be injected between the outer surface of the hollow lock bolt and the female threaded portion of the joint sleeve is formed in a peripheral wall of the joint sleeve rearward of the female threaded portion for screwing into the water injection pipe, or in a peripheral wall of the hollow lock bolt, an annular sealant which provides a liquid-tight seal from the outside by pressing in the screwing direction of the female threaded portion and the male threaded portion is installed at the base of the female threaded portion of the joint sleeve so as to be pressed by the rear end of the male threaded portion, a female threaded portion for screwing into the water injection pipe is provided located immediately behind the annular sealant, and a front end face of the water injection pipe which is screwed into the female threaded portion for screwing into the water injection pipe by the male threaded portion of the water injection pipe is abutted against the annular sealant so as to be pressed. According to this, when a rock bolt structure consisting of a steel pipe expansion type rock bolt, a hollow rock bolt, and a joint sleeve is driven into the ground deep and fixed, the steel pipe expansion type rock bolt can be fixed by frictional fixing in the expanded state at the back of the drilled hole by the joint sleeve, and there is no need to use a highly fluid fixing material to inject into the deep layer of the ground or the back of the drilled hole. In other words, even when a rock bolt structure is fixed over a long length in a ground with many cracks, there is no problem that the highly fluid fixing material escapes from the crack before solidifying, and the rock bolt structure can be reliably fixed into the ground over a long length by both frictional fixing and fixing of the fixing material. In addition, since the steel pipe expansion type rock bolt can be fixed by frictional fixing in the expanded state at the back of the drilled hole, a fixing material with low fluidity such as thick mortar can be used, and the variety of fixing materials that can be used can be increased. In addition, when the steel pipe expansion type rock bolt is expanded by injecting pressurized water into the inside of the steel pipe expansion type rock bolt using the water injection introduction space of the hollow rock bolt and the water injection port of the steel pipe expansion type rock bolt, the liquid-tight seal of the annular seal material of the joint sleeve can reliably prevent the injected water from leaking from the gap between the screwed part of the joint sleeve and the screwed part of the steel pipe expansion type rock bolt, thereby increasing the reliability of pressurized water injection into the inside of the steel pipe expansion type rock bolt and expansion deformation of the steel pipe expansion type rock bolt. In addition, by forming a discharge hole through which the fixing material can be injected between the hole wall and the outer surface of the drilled hole in the natural ground in the joint sleeve or the hollow rock bolt located on the mouth side of the drilled hole, it is possible to suppress the escape of the fixing material to the back side of the drilled hole. In addition, by using a water injection structure in which the front part of the water injection pipe is connected to the joint sleeve, it is possible to facilitate the pressurized water injection work when expanding the steel pipe expansion type rock bolt.

[0016] The method for constructing a rock bolt structure of the present invention includes a first step of inserting a steel pipe expansion type rock bolt, which has a front end closed and a threaded portion with a water inlet at its rear end, into a drilled hole in natural ground in an unexpanded state, and a second step of threading the threaded portion of the joint sleeve into the threaded portion of the steel pipe expansion type rock bolt, which is connected in the axial direction, has a threaded portion formed at its front end, and has a water inlet space formed inside along the axial direction, and the threaded portion of the joint sleeve is used to thread the threaded portion of the steel pipe expansion type rock bolt and a ring installed in the joint sleeve. a second step of pressing the annular seal in the screwing direction to form a liquid-tight seal from the outside with the annular seal and moving the steel pipe expansion type rock bolt to the back of the borehole; a third step of injecting pressurized water into the inside of the steel pipe expansion type rock bolt using the water injection introduction space and the water injection port to expand the steel pipe expansion type rock bolt and frictionally fix it to the hole wall of the borehole; and a fourth step of injecting and solidifying an anchoring material between the outer surface of the hollow rock bolt and the outer surface of the joint sleeve and the hole wall of the borehole to fill them. According to this, when a rock bolt structure consisting of a steel pipe expansion type rock bolt, a hollow rock bolt, and a joint sleeve is driven into the ground deep and fixed, the steel pipe expansion type rock bolt can be fixed by frictional fixing in the expanded state at the back of the drilled hole by the joint sleeve, and there is no need to use a highly fluid fixing material to inject into the deep layer of the ground or the back of the drilled hole. In other words, even when a rock bolt structure is fixed over a long length in a ground with many cracks, there is no problem that the highly fluid fixing material escapes from the crack before solidifying, and the rock bolt structure can be reliably fixed into the ground over a long length by both frictional fixing and fixing of the fixing material. In addition, since the steel pipe expansion type rock bolt can be fixed by frictional fixing in the expanded state at the back of the drilled hole, a fixing material with low fluidity such as thick mortar can be used, and the variety of fixing materials that can be used can be increased. Furthermore, when pressurized water is injected into the inside of the steel pipe expansion type rock bolt to expand it using the water injection introduction space of the hollow rock bolt and the water injection port of the steel pipe expansion type rock bolt, the liquid-tight seal of the annular sealing material of the joint sleeve reliably prevents the injected water from leaking from the gap between the threaded portion of the joint sleeve and the threaded portion of the steel pipe expansion type rock bolt, thereby increasing the reliability of pressurized water injection into the inside of the steel pipe expansion type rock bolt and expansion deformation of the steel pipe expansion type rock bolt. Effect of the Invention

[0017] According to the present invention, a rock bolt structure can be reliably fixed into the ground over a long length even in ground with many cracks. [Brief description of the drawings]

[0018] [Figure 1] 1 is an exploded perspective view of a rock bolt structure and a water injection pipe according to a first embodiment of the present invention. FIG. [Diagram 2] FIG. 2 is a partial vertical cross-sectional view showing a water injection pipe connected to the rock bolt structure of the first embodiment. [Diagram 3] FIG. 2 is a sectional perspective view of a joint sleeve in the lock bolt structure of the first embodiment. [Figure 4] FIG. 2A is a front view of the rock bolt structure of the first embodiment with a water injection pipe connected thereto, and FIG. [Diagram 5] FIG. 2A is a front view of the lock bolt structure of the first embodiment in an expanded state, and FIG. [Figure 6] FIG. 1( a ) is a cross-sectional explanatory diagram illustrating the screwing of a water injection structure in which a hollow rock bolt and a water injection pipe are connected to a joint sleeve in the first embodiment, and a steel pipe expansion type rock bolt; FIG. 1( b ) is a cross-sectional explanatory diagram illustrating the pressurized water injection from the water injection structure in FIG. 1( a ) into the inside of the steel pipe expansion type rock bolt; and FIG. 1( c ) is a cross-sectional explanatory diagram of the rock bolt structure of the first embodiment in an expanded state with the water injection pipe removed. [Figure 7] 3(a) to 3(d) are process explanatory views illustrating the construction process of the rock bolt structure of the first embodiment. [Figure 8] FIG. 2 is an explanatory cross-sectional view of a tunnel into which the rock bolt structure of the first embodiment has been installed. [Figure 9] FIG. 6 is an exploded perspective view of a rock bolt structure and a water injection pipe according to a second embodiment of the present invention. [Figure 10] FIG. 11 is a sectional perspective view of a joint sleeve in a lock bolt structure according to a second embodiment. [Figure 11] 1(a) is a cross-sectional explanatory diagram illustrating the screwing of a water injection structure in which a hollow rock bolt and a water injection pipe are connected to a joint sleeve in the second embodiment, and a steel pipe expansion type rock bolt; (b) is a cross-sectional explanatory diagram illustrating the pressurized water injection from the water injection structure in FIG. 1(a) into the inside of the steel pipe expansion type rock bolt; and (c) is a cross-sectional explanatory diagram of the rock bolt structure of the second embodiment in an expanded state with the water injection pipe removed. [Figure 12] FIG. 11 is an exploded perspective view of a rock bolt structure and a water injection pipe according to a third embodiment of the present invention. [Figure 13] FIG. 11 is a sectional perspective view of a joint sleeve in a lock bolt structure according to a third embodiment. [Figure 14]FIG. 13( a ) is a cross-sectional explanatory diagram illustrating the screwing of a joint sleeve to which a hollow rock bolt is connected and a steel pipe expansion type rock bolt in the third embodiment, FIG. 13( b ) is a cross-sectional explanatory diagram illustrating pressurized water injection into the inside of a steel pipe expansion type rock bolt in the third embodiment, and FIG. 13( c ) is a cross-sectional explanatory diagram of the rock bolt structure of the third embodiment in an expanded state. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] [Rock bolt structure of the first embodiment] As shown in Figures 1 to 6, a rock bolt structure 1 of a first embodiment according to the present invention is composed of a steel pipe expansion type rock bolt 2 that expands when pressurized water is injected into it, a hollow rock bolt 3 for fixing an anchoring material, and a joint sleeve 4 that connects the steel pipe expansion type rock bolt 2 and the hollow rock bolt 3.

[0020] The steel pipe expansion type rock bolt 2 is formed by compressing and rolling a raw steel pipe from the outside over its entire length, forming a base 21 which is folded into a roughly C-shaped unexpanded state in cross section and then expanded into a roughly cylindrical state by injecting pressurized water into the inside (see Figure 5). A front end sleeve 22 and a rear end sleeve 23 which restrict the expansion of the base 21 are fitted onto the outer periphery and fixed to the front and rear ends of the base 21, respectively.

[0021] A welded portion 24 that closes the front end of the steel pipe expansion type rock bolt 2 is provided on the inner periphery near the front end of the front end sleeve 22. The welded portion 24 is build-up welded on the inner periphery of the front end sleeve 22 so as to close the internal space of the base body 21 of the steel pipe expansion type rock bolt 2 and to fix the base body 21 and the front end sleeve 22. In the illustrated example, welding is used to close the internal space of the base body 21 of the steel pipe expansion type rock bolt 2, but instead of the welded portion 24, it may be closed with a cap that can withstand pressurized water injection. In this case, the cap also serves well as a cap that is fixed with enough strength to be released by further increasing the water pressure after the steel pipe expansion type rock bolt 2 has been expanded by injecting water under pressure. This allows the cap to be released by injecting water under pressure with increased water pressure after the steel pipe expansion type rock bolt 2 has expanded, making it possible to drain water from inside the steel pipe expansion type rock bolt 2 regardless of the direction of the drilling hole 101 in the natural ground 100, even if the drilling hole 101 is not facing upward or diagonally upward, such as horizontally.

[0022] A hollow male threaded portion 25 corresponding to the screwed portion is disposed on the rear side of the rear end sleeve 23 and fixed to the rear end sleeve 23, so that the male threaded portion 25 is provided at the rear end of the steel pipe expansion type rock bolt 2. A hollow portion 251 of the male threaded portion 25 corresponding to the water inlet of the screwed portion communicates with the inside of the base body 21 of the steel pipe expansion type rock bolt 2, making it possible to inject pressurized water into the inside of the base body 21 of the steel pipe expansion type rock bolt 2 through the hollow portion 251. In addition, the male threaded portion 25 is configured to form a left-handed screw mechanism with a counterclockwise tightening direction.

[0023] The hollow rock bolt 3 fixed by the fixing material 10 is a rope screw type hollow rock bolt 3 with a rope male thread portion 32 formed on the peripheral wall 31, and the rope male thread portion 32 is configured to form a left-handed screw mechanism with a left-handed tightening direction. The hollow rock bolt 3 has a hollow portion 33 corresponding to a water injection introduction space along the axial direction inside, and a water injection pipe 5 can be inserted along the axial direction of the hollow rock bolt into the water injection introduction space formed by the hollow portion 33 in the first embodiment. Note that, if necessary, a discharge hole through which the fixing material 10 can be injected may be formed in the peripheral wall 31 of the hollow rock bolt 3 between the hole wall 102 of the drilled hole 101 in the natural ground 100 and the outer surface of the hollow rock bolt 3 or the outer surface of the joint sleeve 4.

[0024] The joint sleeve 4 is a generally cylindrical shape that is connected in the axial direction, and has a female thread 41 corresponding to the screwed portion formed at the front. The female thread 41 can be screwed into the male thread 25 corresponding to the screwed portion at the rear end of the steel pipe expansion type lock bolt 2, and forms a left-handed screw mechanism. The joint sleeve 4 is also provided with an annular seal 42 that provides a liquid-tight seal from the outside by pressing in the screwing direction between the screwed portion of the joint sleeve 4 and the screwed portion of the steel pipe expansion type lock bolt 2. In the first embodiment, the annular seal 42 is provided at the base of the female thread 41 of the joint sleeve 4 and is pressed by the rear end of the male thread 25 of the screwed steel pipe expansion type lock bolt 2. The annular sealing material 42 is pressed against the rear end face of the male threaded portion 25 of the steel pipe expansion type lock bolt 2 being screwed in, and this contact creates a liquid-tight seal, preventing water from leaking to the outside from the threaded portion between the male threaded portion 25 and the female threaded portion 41 when water is poured in under pressure.

[0025] A female rope threaded portion 43 that can be screwed into the male rope threaded portion 32 of the hollow lock bolt 3 is formed at the rear of the joint sleeve 4, and the female rope threaded portion 43 forms a left-handed screw mechanism. In this example, the male rope threaded portion 32 at the front or front end of the hollow lock bolt 3 is screwed into the female rope threaded portion 43 at the rear of the joint sleeve 4, thereby fixing the front or front end of the hollow lock bolt 3 to the rear of the joint sleeve 4.

[0026] A connection part to which the front part of the water injection pipe 5 can be detachably connected is provided behind the female thread part 41 corresponding to the screwed part of the joint sleeve 4, and in the first embodiment, a female thread part 44 corresponding to a connection part with a smaller diameter than the rope female thread part 43 is formed, and the female thread part 44 is provided immediately behind the annular seal material 42. A male thread part 51 is formed at the front part or front end part of the water injection pipe 5 used in the first embodiment, and the male thread part 51 part of the water injection pipe 5 inserted into the hollow part 33 of the hollow lock bolt 3 can be screwed into the female thread part 44. The front end face of the water injection pipe 5 screwed into the female thread part 44 abuts against the annular seal material 42 so as to be pressed against it, and the liquid-tight seal caused by this abutment prevents water from leaking to the outside from the screwed part between the male thread part 51 and the female thread part 44 during pressurized water injection. The male threaded portion 51 of the water injection pipe 5 and the female threaded portion 44 corresponding to the connection portion also constitute a left-handed thread mechanism, and all of the threaded mechanisms screwed into the lock bolt structure 1 are left-handed thread mechanisms.

[0027] A hole 45 without a thread groove is provided between the rope female thread portion 43 of the joint sleeve 4 and the female thread portion 44 corresponding to the connection portion, and the hole 45 is a cylindrical space with a smaller diameter than the rope female thread portion 43 and a larger diameter than the female thread portion 44. In addition, a discharge hole 47 is provided in the peripheral wall 46 behind the female thread portion 44 corresponding to the connection portion of the joint sleeve 4 so as to communicate the hole 45 with the outside of the joint sleeve 4. This discharge hole 47 is formed so that the fixing material 10 can be injected between the hole wall 102 of the drilled hole 101 in the natural ground 100 and the outer surface of the hollow rock bolt 3 or the outer surface of the joint sleeve 4.

[0028] Before the rock bolt structure 1 of the first embodiment is driven into the natural ground 100, it is preferable to configure a water injection structure in which the hollow rock bolt 3, joint sleeve 4, and water injection pipe 5 are integrated, without having the steel pipe expansion type rock bolt 2 (see Figs. 6(a), (b), and 7(b)). In this water injection structure, the front part of the hollow rock bolt 3 is fixed to the rear part of the joint sleeve 4 by screwing the rope male thread part 32 into the rope female thread part 43, and the male thread part 51 of the water injection pipe 5 inserted axially inside the hollow rock bolt 3 is detachably screwed and connected to the female thread part 44 corresponding to the connection part of the joint sleeve 4, and the front end face of the water injection pipe 5 abuts against the annular seal material 42 so as to be pressed against it.

[0029] When constructing a natural ground reinforcement structure by driving the rock bolt structure 1 of the first embodiment into the natural ground 100, for example as shown in Fig. 7, a steel pipe expansion type rock bolt 2 in a non-expanded state is inserted into a drilled hole 101 formed in the natural ground 100 in a required direction such as diagonally upward (see Fig. 7(a)). Then, using a water injection structure in which a hollow rock bolt 3, a joint sleeve 4, and a water injection pipe 5 are integrated, the female threaded portion 41 corresponding to the threaded portion of the joint sleeve 4 of this water injection structure is screwed into the male threaded portion 25 corresponding to the threaded portion of the steel pipe expansion type rock bolt 2, and the steel pipe expansion type rock bolt 2 is moved to the back of the drilled hole 101 (see Figs. 7(b), 6(a) and (b)).

[0030] At this time, by screwing the female threaded portion 41 of the joint sleeve 4 into the male threaded portion 25 of the steel pipe expansion type lock bolt 2, the annular sealant 42 of the joint sleeve 4 is pressed in the screwing direction against the rear end surface of the male threaded portion 25 of the steel pipe expansion type lock bolt 2, forming a liquid-tight seal so that water does not leak to the outside from the screwed portion between the male threaded portion 25 and the female threaded portion 41. In this sealed state, the water injection pipe 5, the hollow portion 251 equivalent to the water injection port of the male threaded portion 25, and the inside of the steel pipe expansion type lock bolt 2 are in communication.

[0031] Thereafter, water is injected under pressure from the water injection pipe 5 inserted into the water injection introduction space of the water injection structure, and water W is injected under pressure into the inside of the steel pipe expansion type rock bolt 2 through the hollow portion 251 corresponding to the water injection port of the male thread portion 25, thereby expanding the steel pipe expansion type rock bolt 2 in the radial direction, bringing the base body 21 into a substantially cylindrical expanded state and frictionally fixing the steel pipe expansion type rock bolt 2 to the hole wall 102 of the borehole 101. After the steel pipe expansion type rock bolt 2 is expanded and frictionally fixed, the male thread portion 51 of the water injection pipe 5 is unscrewed from the female thread portion 44 of the joint sleeve 4 to remove the water injection pipe 5, and the water injection pipe 5 is removed from the inside of the hollow rock bolt 3 (see Fig. 7(c), Fig. 6(b), (c), and Fig. 5). The removed water injection pipe 5 is reused.

[0032] Then, an anchoring material 10 such as mortar, urethane or silica resin is injected from the rear end of the hollow rock bolt 3, and the interior of the hollow rock bolt 3 is used as a flow path for the anchoring material 10 to be injected and filled between the outer surface of the hollow rock bolt 3, the outer surface of the joint sleeve 4 and the hole wall 102 of the borehole 101 through the discharge hole 47 of the joint sleeve 4 or a discharge hole near the tip of the hollow rock bolt 3, and the anchoring material 10 is allowed to harden to construct a natural ground reinforcement structure (see Figures 7(d) and 6(c)). A washer 103 and a nut 104 are attached to the rear end of the hollow rock bolt 3 before or after the anchoring material 10 is injected.

[0033] In the natural ground reinforcement structure constructed in this manner, a steel pipe expansion type rock bolt 2, a joint sleeve 4, and a hollow rock bolt 3 are arranged in this order from the back side of a borehole 101 in the natural ground 100, and the steel pipe expansion type rock bolt 2 at the back side of the borehole 101 is frictionally fixed to the hole wall 102 of the borehole 101 in an expanded state, while at the mouth side of the borehole 101, the hollow rock bolt 3 and the joint sleeve 4 are fixed by the fixing material 10 that has been filled and solidified between the hole wall 102 of the borehole 101 and the outer surface of the hollow rock bolt 3 and the outer surface of the joint sleeve 4.

[0034] 8 shows an example of a natural ground reinforcement structure constructed by driving multiple rock bolt structures 1 radially into the natural ground 100 of a tunnel T. In this example of a natural ground reinforcement structure, in each of the radially driven rock bolt structures 1, the expanded steel pipe expansion type rock bolts 2 are frictionally fixed to the wall of the borehole in their expanded state, and the hollow rock bolts 3 and joint sleeves 4 are fixed with solidified fixing materials 10.

[0035] According to the first embodiment, when the rock bolt structure 1 is driven and fixed over a long length deep into the natural ground 100, the steel pipe expansion type rock bolt 2 can be fixed in the deep part of the borehole 101 by frictional fixing in the expanded state, and there is no need to use a highly fluid fixing material to inject into the deep part of the natural ground 100, or into the deep part of the borehole 101. In other words, even when fixing a long length of the rock bolt structure into the natural ground 100 with many cracks, there is no problem that the highly fluid fixing material escapes from the cracks and disappears before solidifying, and the rock bolt structure 1 can be reliably fixed into the natural ground 100 over a long length by both frictional fixing and fixing of the fixing material. Furthermore, by both the frictional fixation of the expanded steel pipe expansion type rock bolt 2 at the back of the borehole 101 and the fixation of the fixing material 10 between the hole wall 102 of the borehole 101 and the outer surface of the hollow rock bolt 3 and the outer surface of the joint sleeve 4 at the mouth side of the borehole 101, the rock bolt structure 1 can be securely fixed to the ground 100 over its long length, thereby reinforcing the ground 100.

[0036] In addition, since the steel pipe expansion type rock bolt 2 can be fixed by frictional fixation in its expanded state at the back of the drilled hole 101 in the natural ground 100, it is possible to use a fixing material with low fluidity such as thickened mortar, thereby increasing the variety of fixing materials 10 that can be used. In addition, when pressurized water is injected into the inside of the steel pipe expansion type rock bolt 2 using the water injection introduction space of the hollow rock bolt 3 and the water injection port of the steel pipe expansion type rock bolt 2 to bring it into an expanded state, the liquid-tight sealing of the annular seal material 42 of the joint sleeve 4 reliably prevents the injected water from leaking from the gap between the screwed part of the joint sleeve 1 and the screwed part of the steel pipe expansion type rock bolt 2, thereby increasing the reliability of pressurized water injection into the inside of the steel pipe expansion type rock bolt 2 and expansion deformation of the steel pipe expansion type rock bolt 2.

[0037] Furthermore, by making the threaded portion of the steel pipe expansion type lock bolt 2 the male thread portion 25 and the threaded portion of the joint sleeve 4 the female thread portion 41, the steel pipe expansion type lock bolt 2 and the joint sleeve 4 can be screwed together with high strength and stability. Furthermore, the annular seal material 42 at the base of the female thread portion 41 of the joint sleeve 4 can be pressed by the rear end portion of the male thread portion 25 of the steel pipe expansion type lock bolt 2, thereby ensuring a liquid-tight seal of the annular seal material 42.

[0038] In addition, by providing a female threaded portion 44 corresponding to a connection portion to which the front portion of the water injection pipe 5 can be detachably connected on the rear side of the screwed portion of the joint sleeve 4, the water injection pipe 5 can be introduced and connected up to the rear side of the screwed portion of the joint sleeve 4, and the reliability of pressurized water injection into the inside of the steel pipe expansion type rock bolt 2 by the water injection pipe 5 and expansion deformation of the steel pipe expansion type rock bolt 2 can be further improved. In addition, by forming a discharge hole 47 or the like through which the fixing material 10 can be injected between the hole wall 102 and the outer surface of the drilled hole 101 in the natural ground 100 in the joint sleeve 4 or the hollow rock bolt 3 arranged on the mouth side of the drilled hole 101, it is possible to suppress the escape of the fixing material 10 to the back side of the drilled hole 101. In particular, when the discharge hole 47 through which the fixing material 10 can be injected is formed in the peripheral wall 46 of the joint sleeve 4, it becomes possible to more reliably fill the fixing material 10 up to just behind the steel pipe expansion type rock bolt 2.

[0039] Furthermore, by making all the screwing mechanisms in the rock bolt structure 1, including the screwing mechanism for the water injection pipe 5, left-handed thread mechanisms, it is possible to reliably achieve liquid-tight sealing of the annular sealant 42 simply by rotating the hollow rock bolt 3 sticking out from the base of the drilling hole in the tightening direction of the left-handed thread. That is, when the base of the hollow rock bolt 3 is a drilling rod, the left-handed rotation of the drilling machine is the normal rotation, resulting in a left-handed hollow rock bolt 3. However, if all the screwing mechanisms are left-handed thread mechanisms to match this, rotating the hollow rock bolt 3 in the tightening direction of the left-handed thread further tightens the screwing between the steel pipe expansion type rock bolt 2 and the joint sleeve 4 without loosening, and the annular sealant 42 is pressed in the screwing direction, so that a highly liquid-tight sealing state can be easily obtained.

[0040] Furthermore, by using a rope screw for the hollow rock bolt 3, the hollow rock bolt 3 can be smoothly inserted into the borehole 101, and the adhesion of the anchoring material 10 to the hollow rock bolt 3 can be improved, thereby increasing the fixing force of the anchoring material 10 of the hollow rock bolt 3 and the rock bolt structure 1 to the borehole wall 102. Furthermore, by using a water injection structure in which the front part of the water injection pipe 5 is connected to the joint sleeve 4, the pressurized water injection work when expanding the steel pipe expansion type rock bolt 3 can be facilitated.

[0041] [Rock bolt structure of the second embodiment] 9 to 11, a rock bolt structure 1a according to a second embodiment of the present invention is composed of a steel pipe expansion type rock bolt 2a that expands when pressurized water is injected into it, a hollow rock bolt 3 for fixing an anchoring material that is the same as in the first embodiment, and a joint sleeve 4a that connects the steel pipe expansion type rock bolt 2a and the hollow rock bolt 3. If necessary, a discharge hole through which the anchoring material 10 can be injected may be formed in the peripheral wall 31 of the hollow rock bolt 3, as in the modified example of the first embodiment.

[0042] The steel pipe expansion type rock bolt 2a is composed of the same base 21, front end sleeve 22, rear end sleeve 23, and welded portion 24 as in the first embodiment, and a hollow female threaded portion 26a corresponding to the screwed portion is arranged on the rear side of the rear end sleeve 23 and fixed to the rear end sleeve 23, and the female threaded portion 26a is provided at the rear end of the steel pipe expansion type rock bolt 2a. As in the modified example of the first embodiment, the front end of the steel pipe expansion type rock bolt 2a may be blocked with a cap that can withstand pressurized water injection instead of the welded portion 24. The water injection hole 261a of the female threaded portion 26a corresponding to the water injection port of the screwed portion communicates with the inside of the base 21 of the steel pipe expansion type rock bolt 2a, and it is possible to inject water under pressure into the inside of the base 21 of the steel pipe expansion type rock bolt 2 through the water injection hole 261a. The female threaded portion 26a is configured to form a left-handed screw mechanism with a counterclockwise tightening direction.

[0043] The joint sleeve 4a is generally cylindrical and communicates in the axial direction, and has a male threaded portion 48a corresponding to the screwing portion formed in the front portion, and the inside of the male threaded portion 48a is a hollow portion 481a communicating in the axial direction. The male threaded portion 48a can be screwed into the female threaded portion 26a corresponding to the screwed portion at the rear end of the steel pipe expansion type lock bolt 2a, and forms a left-handed screw mechanism.

[0044] The joint sleeve 4a is provided with an annular seal 42a that provides a liquid-tight seal from the outside by pressing in the screwing direction between the screwed portion of the joint sleeve 4a and the screwed portion of the steel pipe expansion type lock bolt 2a, and in the second embodiment, the annular seal 42a is fitted to the base of the male thread 48a of the joint sleeve 4a and is pressed by the rear end of the female thread 26a of the screwed steel pipe expansion type lock bolt 2a. The rear end of the female thread 26a of the screwed steel pipe expansion type lock bolt 2a abuts against the annular seal 42a so as to be pressed, and this liquid-tight seal prevents water from leaking to the outside from the screwed portion between the female thread 26a and the male thread 48a when water is poured under pressure.

[0045] The rear part of the joint sleeve 4a is formed with a rope female thread 43 that can be screwed with the rope male thread 32 of the hollow lock bolt 3, as in the joint sleeve 4 of the first embodiment. A female thread 44a that corresponds to a connecting part with a smaller diameter than the rope female thread 43 is formed on the rear side of the male thread 48a that corresponds to the screwing part of the joint sleeve 4a as a connecting part to which the front part of the water injection pipe 5 can be detachably connected, and the female thread 44a is located immediately behind the annular seal material 42a in the axial direction of the joint sleeve 4 and communicates with the hollow part 481a of the male thread 48a. The male thread 51 of the water injection pipe 5, similar to the first embodiment, is screwed into the female thread 44a. The male thread 51 of the water injection pipe 5 and the female thread 44a that corresponds to the connecting part also constitute a left-handed screw mechanism, and all screwing mechanisms screwed in the lock bolt structure 1a are left-handed screw mechanisms.

[0046] A hole portion 45 similar to that of the first embodiment is provided between the rope female thread portion 43 of the joint sleeve 4a and the female thread portion 44a corresponding to the connection portion, and a discharge hole 47 similar to that of the first embodiment is provided in the peripheral wall 46 rearward of the female thread portion 44a corresponding to the connection portion of the joint sleeve 4a so as to communicate the hole portion 45 with the outside of the joint sleeve 4.

[0047] Before the rock bolt structure 1a of the second embodiment is driven into the natural ground 100, it is preferable to configure a water injection structure in which the hollow rock bolt 3, joint sleeve 4a, and water injection pipe 5 are integrated, without having the steel pipe expansion type rock bolt 2a, as in the first embodiment (see Figs. 11(a) and (b) and 7). In this water injection structure, the front part of the hollow rock bolt 3 is fixed to the rear part of the joint sleeve 4a by screwing the rope male thread part 32 into the rope female thread part 43, and the male thread part 51 of the water injection pipe 5 inserted axially inside the hollow rock bolt 3 is detachably screwed and connected to the female thread part 44a corresponding to the connection part of the joint sleeve 4a.

[0048] When the rock bolt structure 1 of the second embodiment is driven into the ground 100 to construct a ground reinforcement structure, a steel pipe expansion type rock bolt 2 in a non-expanded state is inserted into a drilled hole 101 formed in the ground 100 in the required direction, such as diagonally upward, and a water injection structure in which a hollow rock bolt 3, a joint sleeve 4a, and a water injection pipe 5 are integrated is used, and the male threaded portion 48a corresponding to the threaded portion of the joint sleeve 4a of this water injection structure is screwed into the female threaded portion 26a corresponding to the threaded portion of the steel pipe expansion type rock bolt 2a, and the steel pipe expansion type rock bolt 2 is moved to the back of the drilled hole 101 (see Figures 7(b), 11(a) and (b)).

[0049] At this time, by screwing the male threaded portion 48a of the joint sleeve 4a into the female threaded portion 26a of the steel pipe expansion type lock bolt 2a, the annular sealant 42a of the joint sleeve 4a is pressed in the screwing direction against the rear end of the female threaded portion 26a of the steel pipe expansion type lock bolt 2a, and a liquid-tight seal is formed so that water does not leak from the screwed portion between the female threaded portion 26a and the male threaded portion 48a to the outside. In this sealed state, the water injection pipe 5, the hollow portion 481a of the male threaded portion 48a, the water injection hole 261a of the female threaded portion 26a, and the inside of the steel pipe expansion type lock bolt 2 are in communication.

[0050] Thereafter, as in the first embodiment, water W is pressurized and injected from the water injection pipe 5 inserted into the water injection introduction space of the water injection structure, and pressurized water is injected into the inside of the steel pipe expansion type rock bolt 2a through the water injection hole 261a of the female thread portion 26a, thereby expanding the steel pipe expansion type rock bolt 2a in the radial direction, bringing the base body 21 into a substantially cylindrical expanded state, and frictionally fixing the steel pipe expansion type rock bolt 2 to the hole wall 102 of the borehole 101. After the steel pipe expansion type rock bolt 2a is expanded and frictionally fixed, the male thread portion 51 of the water injection pipe 5 is unscrewed from the female thread portion 44a of the joint sleeve 4a to remove the water injection pipe 5, and the water injection pipe 5 is removed from the inside of the hollow rock bolt 3 (see Fig. 7(c), Fig. 11(b), (c)). The removed water injection pipe 5 is reused.

[0051] Then, as in the first embodiment, an anchoring material 10 such as mortar, urethane or silica resin is injected from the rear end of the hollow rock bolt 3, and the interior of the hollow rock bolt 3 is used as a flow path for the anchoring material 10 to be injected and filled between the outer surface of the hollow rock bolt 3, the outer surface of the joint sleeve 4a and the hole wall 102 of the borehole 101 through the discharge hole 47 of the joint sleeve 4a or the discharge hole near the tip of the hollow rock bolt 3, and the anchoring material 10 is allowed to solidify to construct a natural ground reinforcement structure (see Figures 7(d) and 11(c)).

[0052] According to the second embodiment, the threaded portion of the steel pipe expansion type lock bolt 2a is the female threaded portion 26a, and the threaded portion of the joint sleeve 4a is the male threaded portion 48a, so that the steel pipe expansion type lock bolt 2a and the joint sleeve 4a can be screwed together with high strength and stability. In addition, the annular seal material 42a at the base of the male threaded portion 48a of the joint sleeve 4a is pressed by the rear end of the female threaded portion 26a of the steel pipe expansion type lock bolt 2a, so that the liquid-tight seal of the annular seal material 42a can be reliably achieved. In addition, the corresponding effects can be obtained from the configuration corresponding to the first embodiment.

[0053] [Rock bolt structure of the third embodiment] As shown in Figures 12 to 14, a rock bolt structure 1b according to a third embodiment of the present invention is composed of the same steel pipe expansion type rock bolt 2 as in the first embodiment, a hollow rock bolt 3b for fixing an anchoring material, and a joint sleeve 4b connecting the steel pipe expansion type rock bolt 2 and the hollow rock bolt 3b. As in the modified example of the first embodiment, the front end of the steel pipe expansion type rock bolt 2 may be closed with a cap that can withstand pressurized water injection instead of the welded portion 24.

[0054] The hollow rock bolt 3b fixed with the fixing material 10 has the same basic configuration as the hollow rock bolt 3 of the first embodiment, and is composed of a peripheral wall 31, a rope male thread portion 32, and a hollow portion 33, but has a fixing material injection pipe 34b attached along the axial direction and is attached to the outside of the peripheral wall 31 with a string or wire or the like not shown.

[0055] The joint sleeve 4b is a generally cylindrical shape that is connected in the axial direction, and has a female thread 41b corresponding to the screwed portion formed at the front. The female thread 41b can be screwed into the male thread 25 corresponding to the screwed portion at the rear end of the steel pipe expansion type lock bolt 2, and forms a left-handed screw mechanism. The joint sleeve 4b is provided with an annular seal 42b that provides a liquid-tight seal from the outside by pressing in the screwing direction between the screwed portion of the joint sleeve 4b and the screwed portion of the steel pipe expansion type lock bolt 2. In the third embodiment, the annular seal 42b is provided at the base of the female thread 41b of the joint sleeve 4b, and is pressed by the rear end of the male thread 25 of the screwed steel pipe expansion type lock bolt 2. The rear end face of the male threaded portion 25 of the steel pipe expansion type lock bolt 2 being screwed in is pressed against the annular sealing material 42b, and this contact creates a liquid-tight seal, preventing water from leaking to the outside from the threaded portion between the male threaded portion 25 and the female threaded portion 41b when water is poured in under pressure.

[0056] As in the first embodiment, a rope female thread portion 43b that can be screwed into the rope male thread portion 32 of the hollow lock bolt 3b is formed at the rear of the joint sleeve 4b, and the rope female thread portion 43b forms a left-handed screw mechanism.

[0057] In addition, another annular seal 491b is attached to the joint sleeve 4b, which seals the front part of the hollow lock bolt 3b and the rear part 4b of the joint sleeve in a liquid-tight manner by pressing in the screwing direction of the screwing of the front part of the hollow lock bolt 3b and the rear part of the joint sleeve 4b. In the third embodiment, the annular seal 491b is installed inside the tip side of the female rope thread 43b of the joint sleeve 4b, and is pressed by the tip of the screwed hollow lock bolt 3b. The tip surface of the hollow lock bolt 3b abuts against the annular seal 491b so as to be pressed against it, and this abutment creates a liquid-tight seal, preventing water from leaking to the outside from the screwed part of the male rope thread 32 and the female rope thread 43b when water is poured under pressure. All screwing mechanisms screwed in the lock bolt structure 1b of the third embodiment are also left-handed screw mechanisms.

[0058] A hole 492b having a smaller diameter than both the outer diameter of the annular sealing material 42b and the outer diameter of the annular sealing material 491b is provided between the annular sealing material 42b and the annular sealing material 491b, and the annular sealing material 42b and the annular sealing material 491b are fixed in place and their movement is restricted by the periphery of the hole 492b.

[0059] Before the rock bolt structure 1 of the third embodiment is driven into the natural ground 100, it is preferable to configure a water injection structure in which a hollow rock bolt 3b to which an anchoring material injection pipe 34b is attached and a joint sleeve 4b are integrated, without the steel pipe expansion type rock bolt 2 (see Figs. 14(a) and (b)). In this water injection structure, the front part of the hollow rock bolt 3b is fixed to the rear part of the joint sleeve 4b by screwing the rope male thread part 32 into the rope female thread part 43b, and the tip face of the hollow rock bolt 3b is abutted against the annular seal material 491b of the joint sleeve 4b so as to be pressed against it. Furthermore, the tip opening of the anchoring material injection pipe 34b is located in the vicinity of the joint sleeve 4b but not reaching the joint sleeve 4b.

[0060] When constructing a natural ground reinforcement structure by driving the rock bolt structure 1b of the third embodiment into the natural ground 100, a steel pipe expansion type rock bolt 2 in a non-expanded state is inserted into a drilled hole 101 formed in the natural ground 100 in a required direction such as diagonally upward, as in the first embodiment. Then, using a water injection structure in which a hollow rock bolt 3b to which an anchoring material injection pipe 34b is attached and a joint sleeve 4b are integrated, the female threaded portion 41b corresponding to the threaded portion of the joint sleeve 4b of this water injection structure is screwed into the male threaded portion 25 corresponding to the threaded portion of the steel pipe expansion type rock bolt 2, and the steel pipe expansion type rock bolt 2 is moved to the back of the drilled hole 101 (see Fig. 7(b), Fig. 14(a) and (b)).

[0061] At this time, by screwing the female threaded portion 41b of the joint sleeve 4b into the male threaded portion 25 of the steel pipe expansion type lock bolt 2, the annular sealant 42b of the joint sleeve 4b is pressed in the screwing direction against the rear end surface of the male threaded portion 25 of the steel pipe expansion type lock bolt 2, and a liquid-tight seal is formed so that water does not leak to the outside from the screwed portion between the male threaded portion 25 and the female threaded portion 41b. In this sealed state, the hollow portion 33 of the hollow lock bolt 3b corresponding to the water injection introduction space, the hole portion 492b, the hollow portion 251 corresponding to the water injection port of the male threaded portion 25, and the inside of the steel pipe expansion type lock bolt 2 are in communication.

[0062] Thereafter, without using a water injection pipe, water W is injected under pressure directly from the hollow portion 33 of the water injection introduction space of the hollow rock bolt 3b of the water injection structure, and by injecting water under pressure into the inside of the steel pipe expansion type rock bolt 2 through the hollow portion 251 corresponding to the water injection port of the male thread portion 25, the steel pipe expansion type rock bolt 2 expands in the radial direction, bringing the base body 21 into a substantially cylindrical expanded state and frictionally fixing the steel pipe expansion type rock bolt 2 to the hole wall 102 of the borehole 101 (see Figures 14(b) and (c)). Note that in the third embodiment, the work of inserting and removing a water injection pipe is not required.

[0063] Then, an anchoring material 10 such as mortar, urethane or silica resin is injected from the anchoring material injection pipe 34b to fill the gap between the outer surface of the hollow rock bolt 3b and the outer surface of the joint sleeve 4b and the hole wall 102 of the borehole 101, and the anchoring material 10 is allowed to harden to construct a natural ground reinforcement structure (see Figs. 7(d) and 14(c)). A washer 103 and a nut 104 are attached to the rear end of the hollow rock bolt 3b before or after the anchoring material 10 is injected.

[0064] According to the third embodiment, it is possible to liquid-tightly seal the gap between the steel pipe expansion type rock bolt 2 and the joint sleeve 4b with the annular seal material 42b, and liquid-tightly seal the gap between the hollow rock bolt 3b and the joint sleeve 4b with another annular seal material 491b, and the water injection introduction space of the hollow rock bolt 3b itself can be used as a water injection channel for injecting water under pressure into the inside of the steel pipe expansion type rock bolt 2. In addition, since it is possible to inject water under pressure without using a water injection pipe, it is possible to eliminate the need to insert and remove the water injection pipe, and to make the construction process more efficient. In addition, it is possible to obtain the corresponding effects from the configuration corresponding to the first embodiment.

[0065] [Scope of the invention disclosed herein] The invention disclosed in this specification includes, in addition to each invention, embodiment, and example listed as the invention, those specified by changing partial contents of these to other contents disclosed in this specification, those specified by adding other contents disclosed in this specification to these contents, or those specified by deleting partial contents of these to the extent that partial action and effect can be obtained, and specifying them as a higher conceptualization. The invention disclosed in this specification also includes the following contents and further modified examples described below.

[0066] For example, it is preferable to use a rope thread-shaped hollow rock bolt 3 as the hollow rock bolt in the rock bolt structure of the present invention, but it is also possible to use any appropriate hollow rock bolt that has a water injection and introduction space provided inside along the axial direction and is fixed with an anchoring material.

[0067] In addition, the fixing structure between the front of the hollow lock bolt and the rear of the joint sleeve in this invention, and the structure of the detachable connection between the joint sleeve and the water injection pipe are preferably formed as a male-female threaded screw structure, but it is also possible to use other fixing structures or connection structures, such as a hook structure in which a hook-shaped protrusion on one side engages with a locking groove on the other side.

[0068] Furthermore, when constructing a ground reinforcement structure by driving the rock bolt structure of the present invention, which is constructed using a water injection pipe, into the ground, it is preferable to use a construction method that uses a water injection structure as in the first and second embodiments, but it is also possible to use a construction method that uses a structure in which a steel pipe expansion-type rock bolt in a non-expanded state is already attached to the tip of the water injection structure, or a construction method in which the rock bolt structure is inserted into a drilled hole in the ground and then a water injection pipe is connected to the joint sleeve of the rock bolt structure. [Industrial Applicability]

[0069] The present invention can be used when reinforcing ground using rock bolts. [Explanation of symbols]

[0070] 1, 1a, 1b... Rock bolt structure 2, 2a... Steel pipe expansion type rock bolt 21... Base body 22... Front end sleeve 23... Rear end sleeve 24... Welded portion 25... Male thread portion 251... Hollow portion 26a... Female thread portion 261a... Water injection hole 3, 3b... Hollow rock bolt 31... Circumferential wall 32... Rope male thread portion 33... Hollow portion 34b... Anchoring material injection pipe 4, 4a, 4b... Joint sleeve 41, 41b... Female thread portion 42, 42a, 42b... Annular seal material 43, 43b... Rope female thread portion 44, 44a... Female thread portion 45... Hole portion 46... Circumferential wall 47... Discharge hole 48a... Male thread portion 481a... Hollow portion 491b... Annular seal material 492b... Hole portion 5... Water injection pipe 51... Male thread portion 10... Anchoring material 100... Ground 101... Drilling hole 102... Hole wall 103... Washer 104... Nut T... Tunnel W... Water

Claims

1. A steel pipe expansion type rock bolt having a closed front end and a male threaded portion having a water inlet at a rear end; A hollow rock bolt for fixing an anchoring material, the hollow rock bolt having a water injection introduction space formed therein along the axial direction; a joint sleeve that communicates in the axial direction and has a female thread portion formed at a front portion thereof; The female threaded portion of the joint sleeve and the male threaded portion of the steel pipe expansion type lock bolt are screwed together, and the front portion of the hollow lock bolt and the rear portion of the joint sleeve are fixed together, An annular seal material that provides a liquid-tight seal from the outside by pressing in the screw-in direction of the female threaded portion and the male threaded portion is installed so as to be pressed by the rear end of the male threaded portion against the root of the female threaded portion of the joint sleeve, A female thread portion for screwing in a water injection pipe is provided immediately behind the annular seal of the joint sleeve, a water injection pipe male thread portion formed in a front portion of the water injection pipe to be inserted into the water injection introduction space and a front end face of the water injection pipe that is screwed into the water injection pipe female thread portion is abutted so as to be pressed against the annular sealing material.

2. A rock bolt structure as described in claim 1, characterized in that a discharge hole capable of injecting an anchoring material between the hole wall of the drilled hole in the ground and the outer surface of the hollow rock bolt and the outer surface of the joint sleeve is formed in the peripheral wall rear of the female threaded portion of the joint sleeve for screwing into the water injection pipe, or in the peripheral wall of the hollow rock bolt.

3. 3. The lock bolt structure according to claim 1, wherein all of the screw mechanisms are left-handed screw mechanisms.

4. 4. A rock bolt structure according to any one of claims 1 to 3, characterized in that the hollow rock bolt is a rope screw.

5. A ground reinforcement structure comprising a rock bolt structure comprising: a steel pipe expansion type rock bolt whose front end is closed and whose rear end is provided with a threaded portion having a water inlet; a hollow rock bolt for fixing a fixing material, the interior of which is provided with a water introduction space along the axial direction; and a joint sleeve which communicates with the axial direction and has a threaded portion formed at its front portion, the threaded portion of the joint sleeve and the threaded portion of the steel pipe expansion type rock bolt are threadedly connected, the front portion of the hollow rock bolt and the rear portion of the joint sleeve are fixed, and an annular sealing material is installed on the joint sleeve which provides a liquid-tight seal from the outside by pressing the threaded portion and the threaded portion in the screwing direction, The steel pipe expansion type rock bolt, the joint sleeve, and the hollow rock bolt are arranged in this order from the deepest side of the drilling hole in the natural ground, The steel pipe expansion type rock bolt is frictionally fixed to the wall of the borehole in an expanded state, A ground reinforcement structure, characterized in that an anchoring material is filled and solidified between the hole wall of the borehole and the outer surface of the hollow rock bolt and the outer surface of the joint sleeve.

6. A water injection structure that is screwed onto a steel pipe expansion type rock bolt having a male threaded portion with a water injection port at its rear end and a closed front end, A hollow rock bolt for fixing the fixing material; A water injection pipe is inserted into the hollow rock bolt along the axial direction; a joint sleeve that communicates with the lock bolt in the axial direction, has a female threaded portion formed in a front portion thereof that is screwed into the male threaded portion, and has a front portion of the hollow lock bolt fixed to a rear portion thereof; a water injection pipe male thread portion formed in a front portion of the water injection pipe is detachably screwed into a water injection pipe female thread portion provided inside the rear side of the female thread portion of the joint sleeve; A discharge hole capable of injecting an anchoring material between a wall of a drilled hole in the natural ground and an outer surface of the hollow rock bolt and an outer surface of the joint sleeve is formed in a peripheral wall of the joint sleeve rearward of the female thread portion for screwing in the water injection pipe or in a peripheral wall of the hollow rock bolt, An annular seal material that provides a liquid-tight seal from the outside by pressing in the screw-in direction of the female threaded portion and the male threaded portion is installed so as to be pressed by the rear end of the male threaded portion against the root of the female threaded portion of the joint sleeve, A female thread portion for screwing into the water injection pipe is provided immediately behind the annular seal member, a front end face of the water injection pipe, the front end face of which is screwed into the water injection pipe female threaded portion at the water injection pipe male threaded portion, being abutted against the annular seal material so as to be pressed against the annular seal material.

7. A first step is to insert a steel pipe expansion type rock bolt, the front end of which is closed and the rear end of which is provided with a threaded portion having a water inlet, into a drilled hole in the natural ground in an unexpanded state; a second step of using a joint sleeve in which a hollow rock bolt for fixing an anchoring material, which is connected in the axial direction, has a threaded portion formed in the front part, and has a water injection and introduction space formed inside along the axial direction, and the front part of the hollow rock bolt is fixed to the rear part, the threaded portion of the joint sleeve is threadedly attached to the threaded portion of the steel pipe expansion type rock bolt, an annular seal material installed in the joint sleeve is pressed in the threading direction to liquid-tightly seal the outside with the annular seal material, and the steel pipe expansion type rock bolt is moved to the back of the drilled hole; A third step of injecting pressurized water into the inside of the steel pipe expansion type rock bolt using the water injection introduction space and the water injection port to expand the steel pipe expansion type rock bolt and frictionally fix it to the hole wall of the borehole; A construction method for a rock bolt structure, comprising a fourth step of injecting and filling an anchoring material between the outer surface of the hollow rock bolt and the outer surface of the joint sleeve and the hole wall of the borehole, and solidifying the anchoring material.

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