Non-widening AGF construction method

Abstract

This system allows workers to easily and reliably remove terminal pipes without having to perform dangerous work close to the tunnel face, and also ensures reliable ground reinforcement along the entire length of the area where long reinforcing pipes are installed. [Solution] The AGF method without widening comprises the steps of: placing a terminal pipe 5, which has a locking portion 52 at its rear end that can be locked to a centralizer 17, inside an external intermediate pipe in a guide cell 1; pulling the front pipe 2 by drilling with a drilling bit provided at the tip and locking the locking portion 52 to the centralizer 17 to pull out the terminal pipe 5 from the external intermediate pipe and drive it into the ground 100; bringing a pilot bit 14 that retracts inside the external intermediate pipe into contact with the tip of the terminal pipe 5, removing the pilot bit 14 and the terminal pipe 5 from the external intermediate pipe, and removing the terminal pipe 5 from the borehole 101; and inflating a packer 183 near the mouth of the borehole 101 and injecting a consolidating material 19 into the borehole 101 including the area where the terminal pipe 5 was removed.

Description

[Technical Field]

[0001] The present invention relates to a non-widening AGF construction method for reinforcing the natural ground ahead of the tunnel face without widening the tunnel cross section. [Background Art]

[0002] Conventionally, as a long-term advanced pre-supporting method for reinforcing the natural ground ahead of the tunnel face during tunnel excavation, a non-widening AGF construction method that does not widen the tunnel cross section is known. In the non-widening AGF construction method, a long reinforcing pipe of about 12 m, which is formed by connecting a plurality of reinforcing pipes in series obliquely forward from the tunnel face, is driven. As the tunnel face is excavated as the tunnel advances, the terminal pipe, which is the end portion of the long reinforcing pipe, is exposed into the tunnel space, so it becomes necessary to cut off the terminal pipe. However, since vibration generated when cutting off the terminal pipe is one of the factors that loosen the natural ground ahead, construction methods that do not cut off the terminal pipe, such as those disclosed in Patent Documents 1 and 2, have also been proposed.

[0003] In the construction method of Patent Document 1, the terminal pipe is pulled out from the accommodating intermediate pipe to drive the long reinforcing pipe into the natural ground, a packer disposed near the tip of the accommodating intermediate pipe is expanded to inject a consolidating material into the front side of the packer, after the consolidating material is discharged into the surrounding natural ground, the terminal pipe exposed as the tunnel advances is put back into the accommodating intermediate pipe.

[0004] In the construction method of Patent Document 2, after a plurality of reinforcing pipes are sequentially connected, the terminal pipe is connected to the rear end of the forward reinforcing pipe by a socket type or bayonet type to drive the long reinforcing pipe into the natural ground, an operator manually engages a pipe pulling jig with the terminal pipe, pulls out the terminal pipe using the rotational impact force of a drifter, and injects a consolidating material into the natural ground through the plurality of reinforcing pipes remaining in the natural ground. [Prior Art Documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Unexamined Patent Publication No. 2023-57421 [Patent Document 2] Japanese Patent No. 6357063 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] By the way, in the construction method described in Patent Document 1, when inserting the exposed terminal pipe back into the intermediate storage pipe during tunnel excavation, workers must work from a high-altitude worker position, approaching the tunnel face to perform the insertion and removal work, making it difficult to avoid dangerous work near the tunnel face. Furthermore, since the terminal pipe is housed in the intermediate storage pipe, it is not possible to fill the inside of the intermediate storage pipe with a consolidating agent, and depending on the ground conditions, there is a concern that sufficient consolidating agent may not reach the ground behind the packer near the tip of the intermediate storage pipe. Moreover, since it is necessary to push the packer into a location considerably deep from the rear end of the terminal pipe, which has a smaller inner diameter than the intermediate storage pipe, and set the injection pipe to reach beyond that point before injecting the consolidating agent, skilled workers are required for the injection of the consolidating agent.

[0007] Furthermore, in the construction method described in Patent Document 2, when removing the terminal pipe, the worker must approach the face of the tunnel while on a high-altitude work platform and engage the pipe extraction jig with the terminal pipe. This makes it difficult to avoid dangerous work near the tunnel face, similar to the construction method described in Patent Document 1. In addition, if the reinforcing pipe or terminal pipe ahead is deformed during casting, it may not be possible to remove the terminal pipe smoothly using the rotational impact mechanism of the drifter, raising concerns that a large rotational impact force may be applied, loosening the ground.

[0008] The present invention is proposed in view of the above problems, and aims to provide a non-widening AGF method that allows workers to easily and reliably remove terminal pipes without having to perform dangerous work in the immediate vicinity of the tunnel face, and that can reliably reinforce the ground over the entire length of the area corresponding to the area where long reinforcing pipes are driven. [Means for solving the problem]

[0009] The present invention relates to a non-widening AGF construction method for driving a long reinforcing pipe, which is composed of a leading pipe, an intermediate pipe, and a terminal pipe arranged in series, into the ground, and is characterized by comprising: a first step of placing the terminal pipe, which has a locking portion at its rear end that can be locked to the centralizer of the guide cell, inside the externally inserted intermediate pipe and placing it in the guide cell, pulling the leading pipe by drilling with a drilling bit provided at the tip and locking the locking portion to the centralizer, thereby pulling out the terminal pipe and driving the long reinforcing pipe into the ground; a second step of retracting the pilot bit that constitutes the drilling bit, bringing the pilot bit into contact with the tip of the terminal pipe inside the externally inserted intermediate pipe, removing the pilot bit and the terminal pipe from the externally inserted intermediate pipe, and removing the terminal pipe from the drilled hole; and a third step of inflating a packer near the mouth of the drilled hole and injecting a solidifying material into the inside of the drilled hole, including the area from which the terminal pipe was removed. According to this method, by pulling the leading pipe and locking the terminal pipe's locking portion to the centralizer, the terminal pipe can be easily pulled out from the external intermediate pipe and driven into the borehole. Furthermore, by bringing a pilot bit that retracts inside the external intermediate pipe into contact with the tip of the terminal pipe, and then removing the pilot bit and terminal pipe from the external intermediate pipe, the terminal pipe can be easily and reliably removed from the ground by mechanical means without the worker having to perform dangerous work close to the drill face. In addition, by inflating a packer near the borehole opening and injecting a consolidating material into the borehole, including the area where the terminal pipe was removed, the ground can be reliably reinforced along the entire length of the area corresponding to the area where the long reinforcing pipe is driven.

[0010] The non-widening AGF construction method of the present invention is characterized in that, in the first step, the locking portion is locked to the centralizer without being constrained to the circumferential rotational position of the terminal pipe. According to this, the locking part can be secured to the centralizer without having to pay attention to the circumferential position of the terminal pipe, thus simplifying the construction work.

[0011] The non-widening AGF construction method of the present invention is characterized in that a threaded portion is formed on the outer circumferential surface of the rear end of the externally inserted intermediate pipe, which can be screwed into another partial reinforcing pipe. According to this method, when it is necessary to further reinforce the ground around the borehole opening, it is possible to screw another reinforcing pipe, such as one that is scheduled to be cut off, into the threaded portion of the external intermediate pipe as a separate terminal pipe. This allows for the selective removal of the terminal pipe from the external intermediate pipe and the subsequent removal from the borehole, as well as the process of screwing another terminal pipe, such as one that is scheduled to be cut off, into the external intermediate pipe, thereby increasing the flexibility of the construction process. [Effects of the Invention]

[0012] According to the non-widening AGF method of the present invention, terminal pipes can be easily and reliably removed without workers having to perform dangerous work in the immediate vicinity of the tunnel face, and ground reinforcement can be reliably carried out over the entire length of the area corresponding to the area where the long reinforcing pipes are driven. [Brief explanation of the drawing]

[0013] [Figure 1] (a) is a front view showing the leading pipe of the long reinforcing pipe used in the non-widening AGF method of the embodiment of the present invention, (b) is a front view showing the front intermediate pipe of the long reinforcing pipe, (c) is a front view showing the extrapolated intermediate pipe which is the rear intermediate pipe of the long reinforcing pipe, and (d) is a front view showing the terminal pipe of the long reinforcing pipe. [Figure 2] (a) to (d) are diagrams illustrating the process of installing long reinforcing pipes in the non-widening AGF construction method of the embodiment. [Figure 3] A magnified view of a portion corresponding to Figure 2(c). [Figure 4] (a) to (c) are explanatory diagrams illustrating the locking mechanism between the terminal pipe and the centralizer. [Figure 5] (a) and (b) are perspective diagrams illustrating a first modified example of the locking portion of the terminal pipe. [Figure 6] A perspective view illustrating a second modified example of the locking portion of the terminal pipe. [Figure 7] (a) and (b) are diagrams illustrating the process of extracting terminal pipes in the non-widening AGF construction method of the embodiment. [Figure 8] (a) to (c) are process explanatory diagrams illustrating the step of extracting the terminal pipe from the externally inserted intermediate pipe. [Figure 9] (a) to (c) are process explanatory diagrams illustrating the step of injecting a consolidation material in the non-widening AGF construction method according to the embodiment. [Figure 10] A perspective view showing an injection unit for a consolidation material. [Figure 11] A cross-sectional explanatory diagram of a tunnel where the non-widening AGF construction method of the present embodiment is applied. MODE FOR CARRYING OUT THE INVENTION

[0014] [Non-widening AGF Construction Method of Embodiment] The non-widening AGF construction method according to an embodiment of the present invention is a non-widening AGF construction method in which a long reinforcing pipe configured by serially arranging a leading pipe, an intermediate pipe and a terminal pipe is driven into natural ground, and is constructed using the long reinforcing pipe 1 shown in FIG. 1 and FIG. 2. The long reinforcing pipe 1 is composed of a plurality of partial reinforcing pipes, and comprises: a leading pipe 2 to which a ring bit 16 that constitutes a drill bit together with a pilot bit 14 is attached; a first intermediate pipe 3 connected to the rear side of the leading pipe 2; a second intermediate pipe 4 connected to the rear side of the first intermediate pipe 3; and a terminal pipe 5 inserted into the second intermediate pipe 4. The second intermediate pipe 4 corresponds to an externally inserted intermediate pipe into which the terminal pipe 5 is inserted, and is disposed closer to the mouth of a drilled hole 101 in the natural ground 100 than the first intermediate pipe 3.

[0015] The leading pipe 2 is formed in a substantially cylindrical shape, and has a base portion 21 formed with substantially the same outer diameter and inner diameter, and a male screw portion 22 formed on the rear side of the base portion 21. In the base portion 21 constituting the peripheral wall of the leading pipe 2, discharge holes 23 which are through holes for discharging the consolidation material to the natural ground around the leading pipe 2 are formed in a scattered manner. In the example shown in FIG. 1, the ring bit 16 is attached to the tip end of the base portion 21 of the leading pipe 2 via a casing shoe 15.

[0016] The first intermediate pipe 3 is formed in a substantially cylindrical shape and has a base portion 31 formed with substantially the same outer and inner diameters, a female threaded portion 32 formed on the inside of the tip of the base portion 31, and a male threaded portion 33 formed on the rear side of the base portion 31. The base portion 31, which constitutes the peripheral wall of the first intermediate pipe 3, has discharge holes 34, which are through holes for discharging the solidifying material into the ground surrounding the first intermediate pipe 3, scattered therein. The female threaded portion 32 of the first intermediate pipe 3 is screwed into the male threaded portion 22 of the leading pipe 2, so that the first intermediate pipe 3 and the leading pipe 2 are screwed together and connected by a screw connection.

[0017] The second intermediate pipe 4, which corresponds to the extrapolated intermediate pipe, is formed in a substantially cylindrical shape and has a base portion 41 formed with substantially the same outer and inner diameters, a female threaded portion 42 formed on the inside of the tip of the base portion 41, and a male threaded portion 43 formed on the rear side of the base portion 41. The base portion 41 that constitutes the peripheral wall of the second intermediate pipe 4 has discharge holes 44, which are through holes for discharging the solidifying material into the ground surrounding the second intermediate pipe 4, scattered therein. The female threaded portion 42 of the second intermediate pipe 4 is screwed into the male threaded portion 33 of the first intermediate pipe 3, so that the second intermediate pipe 4 and the first intermediate pipe 3 are screwed together and connected by a screw connection.

[0018] Furthermore, the male threaded portion 43, which corresponds to the threaded portion formed on the outer circumferential surface of the rear end of the second intermediate pipe 4, is designed to be screwed into another partial reinforcing pipe. For example, if it is necessary to further reinforce the ground 100 around the mouth of the borehole 101, it is possible to screw another partial reinforcing pipe, such as one that is scheduled to be cut off, into the male threaded portion 43 of the second intermediate pipe 4 as another terminal pipe. In addition, the second intermediate pipe 4, which corresponds to the external intermediate pipe, can also be configured without the male threaded portion 43, for example, by providing a base 41 all the way to the rear end.

[0019] The terminal tube 5 is formed in a substantially cylindrical shape and has a base portion 51 formed with substantially the same outer and inner diameters. At the rear end of the base portion 51, in other words, at the rear end of the terminal tube 5, a locking portion 52 is provided that can be locked to the centralizer 17 of the guide cell 11. In this embodiment, the locking portion 52 is composed of projections 521 that protrude outward in the radial direction of the terminal tube 5, and a plurality of projections 521 are provided spaced apart at predetermined intervals in the circumferential direction of the terminal tube 5. In the illustrated example, a pair of projections 521-521, formed by attaching an L-shaped bracket to the rear end of the base portion 51, are provided at positions spaced 180 degrees apart in the circumferential direction of the terminal tube 5, so that even if the terminal tube 5 rotates in the circumferential direction, one of the projections 521 will be locked to the centralizer 17, and the locking portion 52 will be locked to the centralizer 17 without being constrained by the circumferential rotation position of the terminal tube 5 (see Figure 4).

[0020] As a modification, the locking portion 52 provided at the rear end of the terminal pipe 5 may be a single projection 521a formed by attaching an L-shaped bracket to the rear end of the base portion 51, as shown in Figure 5, and the terminal pipe 5 may be rotated circumferentially as needed to lock the projection 521a to the centralizer 17. Alternatively, as shown in Figure 6, a flanged ring material may be provided at the rear end of the base portion 51, or the rear end of the base portion 51 may be bent into a flange shape to provide a flange portion 521b as the locking portion 52 at the rear end of the base portion 51, so that the flange portion 521b can be locked to the centralizer 17 without being constrained by the circumferential rotation position of the terminal pipe 5.

[0021] The base portion 51 that constitutes the peripheral wall of the terminal pipe 5 does not have a discharge hole for a through hole that discharges the consolidating material into the surrounding ground. The outer diameter of the base portion 51 of the terminal pipe 5 is slightly smaller than the inner diameter of the base portion 41 and the inner diameter of the male thread portion 43 of the second intermediate pipe 4, which corresponds to the externally inserted intermediate pipe, so that the base portion 51 of the terminal pipe 5 can be inserted into the second intermediate pipe 4. In addition, at least the inner diameter of the base portion 51 of the terminal pipe 5, and in this embodiment, the outer diameter as well, is smaller than the maximum outer diameter of the pilot bit 14, so that the pilot bit 14, which is positioned deeper in the bore than the terminal pipe 5, does not penetrate into the interior of the terminal pipe 5, and a predetermined portion of the pilot bit 14 contacts the tip of the terminal pipe 5 (see Figure 8). Note that the thickness of the base portion 51 of the terminal pipe 5 in the illustrated example is thinner than the thickness of the base portion 41 of the second intermediate pipe 4, which corresponds to the externally inserted intermediate pipe.

[0022] When constructing the non-widening AGF method of the embodiment using the long reinforcing pipe 1, the drilling rod 13 is extended by connecting and extending the leading pipe 2, the first intermediate pipe 3, and the second intermediate pipe 4 using a double-pipe drilling and driving method, and the terminal pipe 5 is pulled out from the second intermediate pipe 4.

[0023] Specifically, the leading pipe 2 is placed on a guide cell 11 having a semicircular mounting section for the drilling device, and the drilling rod 13 connected to the drifter 12 on the guide cell 11 and the pilot bit 14 provided at the tip of the drilling rod 13 are inserted into the leading pipe 2. A ring bit 16 is attached to the leading pipe 2 via a casing shoe 15, and the pilot bit 14 is engaged with the ring bit 16 to form a drilling bit, enabling the driving force of the drifter 12 to be transmitted to the pilot bit 14 and the ring bit 16 (see Figures 2, 3, 8, and 11).

[0024] Then, the driving force of the drifter 12 is transmitted to the pilot bit 14 and the ring bit 16 via the drilling rod 13, and the leading pipe 2 is pulled and driven into the ground 100 while forming a bore 101 at a predetermined angle toward the ground 100 ahead, using the support structure F closest to the face 102 of the tunnel T as a guide (see Figures 2(a), (b), and 11).

[0025] After driving most of the leading pipe 2 into the ground 100, the first intermediate pipe 3 is placed on the guide cell 11, and the tip of the first intermediate pipe 3 and the rear end of the leading pipe 2 are connected by a screw connection. The drilling rod 13, which is extended by connecting the components via a screw connection through a shank sleeve, is inserted into the leading pipe 2 and the first intermediate pipe 3. In this state, the driving force of the drifter 12 is transmitted to the pilot bit 14 and the ring bit 16 via the drilling rod 13 to drill, and the leading pipe 2 and the connected first intermediate pipe 3 are pulled and driven into the ground 100 (see Figure 2(b)).

[0026] After driving the leading pipe 2 and the first intermediate pipe 3 until most of the first intermediate pipe 3 is embedded in the ground 100, the second intermediate pipe 4, with the terminal pipe 5 inserted inside, is placed on the guide cell 11 such that the rear end of the second intermediate pipe 4, which is provided with a locking portion 52, is exposed from the rear end of the second intermediate pipe 4. In other words, the second intermediate pipe 4, with most of the terminal pipe 5 housed inside, is placed on the guide cell 11. The tip of the second intermediate pipe 4 and the rear end of the first intermediate pipe 3 are connected by a screw connection, and the drilling rod 13, which has been extended by connecting the components by a screw connection via a shank sleeve, is inserted into the leading pipe 2, the first intermediate pipe 3, the second intermediate pipe 4, and the terminal pipe 5 inserted inside the second intermediate pipe 4 (see Figures 2(c) and 3).

[0027] After the second intermediate pipe 4 is embedded in the ground 100 and the locking portion 52 of the terminal pipe 5 is caught and locked on the rear surface of the centralizer 17, or after the leading pipe 2, the first intermediate pipe 3, and the second intermediate pipe 4 are driven in to a position close to the centralizer 17, the drifter 12 is temporarily moved back on the guide cell 11, and the drilling rod 13 is extended by connecting and extending the components with screw connections via shank sleeves.

[0028] Then, the driving force of the drifter 12 is transmitted to the pilot bit 14 and ring bit 16 via the extended drilling rod 13 to continue drilling, and as the leading pipe 2, the first intermediate pipe 3, and the second intermediate pipe 4 are pulled and driven into the ground 100, the locking part 52 of the end pipe 5 is locked to the centralizer 17, and the end pipe 5 is pulled out from the second intermediate pipe 4, and the long reinforcing pipe 1, which is formed by the end pipe 5, in other words the leading pipe 2, intermediate pipes 3 and 4 and the end pipe 5 arranged in series, is driven into the ground 100 (see Figure 2(d)). When the long reinforcing pipe 1 is driven, any slime generated during drilling that remains inside the long reinforcing pipe 1 is discharged with flushing water.

[0029] Subsequently, as shown in Figure 7(a), the drilling rod 13 is rotated in reverse to release the engagement between the pilot bit 14 and the ring bit 16, causing the drifter 12 to retract and the drilling rod 13, with the pilot bit 14 at its tip, to retract. A predetermined portion of the retracting pilot bit 14 comes into contact with the tip of the terminal pipe 5 inside the second intermediate pipe 4, which corresponds to the extrapolated intermediate pipe, and the pilot bit 14, drilling rod 13, and terminal pipe 5 are removed from the second intermediate pipe 4, and the pilot bit 14, drilling rod 13, and terminal pipe 5 are removed from the hole 101 (see Figures 8 and 7(b)).

[0030] When the leading pipe 2, the first intermediate pipe 3, and the second intermediate pipe 4 are driven into the ground 100 in a series configuration, as shown in Figure 7(b), the area around the mouth of the borehole 101 becomes hollow due to the removal of the terminal pipe 5. In the hollow borehole 101, an injection unit 18 is installed near the mouth to inject a chemical solution of a urethane-based injection material, for example, as a consolidating agent 19 (see Figures 9 and 10).

[0031] The injection unit 18 includes a hole collapse prevention body 181 with a through hole for inserting an injection hose, a cylindrical part 182 in which a permeable material such as cloth is wrapped around a mesh cylindrical member so that the chemical solution can seep out, a packer 183 which is filled with the chemical solution and can expand, and multiple injection hoses 184 of different lengths (four in the illustrated example). Of the tip openings of the multiple injection hoses 184, the tip opening of one injection hose 184 is provided inside the packer 183 or inside the cylindrical part 182. The tip openings of the remaining multiple injection hoses 184 are provided inside the reinforcing pipe 1a, which is composed of a leading pipe 2, a first intermediate pipe 3, and a second intermediate pipe 4, and are arranged at different positions spaced apart in the drilling direction of the borehole 101.

[0032] Then, by injecting the solidifying agent solution, the packer 183 is expanded near the opening of the borehole 101, forming a partition wall near the opening of the borehole 101 with the expanded packer 183, and the solidifying agent 19 is injected into the borehole 101, including the area where the front end pipe 5 of the expanded packer 183 has been removed.

[0033] The consolidating material 19 is filled into the interior of the reinforcing pipe 1a, which is composed of the leading pipe 2, the first intermediate pipe 3, and the second intermediate pipe 4. It then seeps out into the surrounding ground 100 from the discharge holes 23 of the leading pipe 2, the first intermediate pipe 3, and the second intermediate pipe 4, hardens, and forms a solidified region. As a result, a solidified region is formed around the borehole 101, including the terminal portion around the mouth of the borehole 101 where the leading pipe 2, the first intermediate pipe 3, and the second intermediate pipe 4 are driven. Therefore, when excavating the tunnel cross-section using the non-widening AGF method, it is possible to excavate through the ground reinforced by the solidified region, thereby ensuring safety against collapse.

[0034] According to the non-widening AGF method of this embodiment, by pulling the leading pipe 2 and locking the locking portion 52 of the terminal pipe 5 to the centralizer 17, the terminal pipe 5 can be pulled out from the second intermediate pipe 4, which corresponds to the externally inserted intermediate pipe, and the terminal pipe 5 can be easily driven into the borehole 101. Furthermore, by bringing the pilot bit 14, which retracts inside the second intermediate pipe 4, into contact with the tip of the terminal pipe 5, and then removing the pilot bit 14 and the terminal pipe 5 from the second intermediate pipe 4, the terminal pipe 5 can be removed from the borehole 101, allowing the terminal pipe 5 to be easily and reliably removed from the ground 100 by mechanical means without the worker having to perform dangerous work close to the face of the borehole. In addition, by inflating the packer 183 near the mouth of the borehole 101 and injecting the consolidating material 19 into the borehole 101, including the area from which the terminal pipe 5 was removed, the ground can be reliably reinforced along the entire length of the area corresponding to the area where the long reinforcing pipe is driven.

[0035] Furthermore, when using a locking portion 52 that is not constrained by the circumferential rotational position of the terminal pipe 5 but is locked to the centralizer 17, the locking portion 52 can be locked to the centralizer without having to consider the circumferential position of the terminal pipe 5, thereby simplifying the construction work.

[0036] Furthermore, if a threaded portion is formed on the outer surface of the rear end of the second intermediate pipe 4, which corresponds to an external intermediate pipe, so that it can be screwed with another partial reinforcing pipe, then if it is necessary to further reinforce the ground 100 around the mouth of the borehole 101, it is possible to screw another partial reinforcing pipe, such as one that is scheduled to be cut off, into the threaded portion of the second intermediate pipe 4 as another terminal pipe. This allows for the selective performance of the process of removing the terminal pipe 5 from the external intermediate pipe and removing it from the borehole 101, and the process of screwing another terminal pipe, such as one that is scheduled to be cut off, into the external intermediate pipe, thereby increasing the flexibility of the construction process.

[0037] [Scope of the invention disclosed herein] The inventions disclosed herein include, in addition to the inventions and embodiments listed herein, the inventions disclosed herein also include, to the extent applicable, those that modify the partial content of these inventions to include other content disclosed herein, or those that add other content disclosed herein to these inventions, or those that delete the partial content to the extent that partial effects are obtained and define them as broader concepts. Furthermore, the inventions disclosed herein also include the following and modifications.

[0038] For example, the locking portion 52 provided at the rear end of the terminal pipe 5 can be any type of locking portion that can engage with the centralizer 17 of the guide cell 11, in addition to the pair of equal projections 521, single projection 521a, and flange portion 521b described above. Furthermore, the number of partial reinforcing pipes that constitute the long reinforcing pipe, including the leading pipe and the terminal pipe, can be any number, and an appropriate intermediate pipe into which the terminal pipe is inserted can be an external intermediate pipe.

[0039] Furthermore, in the embodiment described above, the leading pipe 2 and the first intermediate pipe 3, and the first intermediate pipe 3 and the second intermediate pipe 4 are connected by screw connections. However, the leading pipe 2, the first intermediate pipe 3, and the second intermediate pipe 4 that constitute the long reinforcing pipe 1 may also be connected by a one-touch insert joint system that is connected by the pushing force of the drifter 12, rather than by screw connections. [Industrial applicability]

[0040] This invention can be used as a non-widening AGF method for tunnel excavation work. [Explanation of Symbols]

[0041] 1…Long reinforcing pipe 1a…Reinforcing pipe 2…First pipe 21…Base 22…Male threaded section 23…Discharge hole 3…First intermediate pipe 31…Base 32…Female threaded section 33…Male threaded section 34…Discharge hole 4…Second intermediate pipe 41…Base 42…Female threaded section 43…Male threaded section 44…Discharge hole 5…End pipe 51…Base 52…Locking section 521, 521a…Protrusion 521b…Flange section 11…Guide cell 12…Drifter 13…Drilling rod 14…Pilot bit 15…Casing shoe 16…Ring bit 17…Centralizer 18…Injection unit 181…Hole collapse prevention body 182…Cylinder section 183…Packer 184…Injection hose 19…Consolidating material 100…Ground 101…Drilling 102...Tunnel face T...Tunnel F...Support structure

Claims

1. This is a non-widening AGF method in which a long reinforcing pipe, consisting of a leading pipe, an intermediate pipe, and a terminal pipe arranged in series, is driven into the ground. The first step involves inserting a terminal pipe, which has a locking portion at its rear end that can be locked to the centralizer of the guide cell, into the external intermediate pipe and placing it in the guide cell, pulling the leading pipe by drilling with a drilling bit provided at the tip and locking the locking portion to the centralizer, thereby pulling the terminal pipe out from the external intermediate pipe and driving a long reinforcing pipe into the ground, A second step involves retracting the pilot bit that constitutes the drilling bit, bringing the pilot bit into contact with the tip of the terminal pipe inside the external intermediate pipe, removing the pilot bit and the terminal pipe from the external intermediate pipe, and removing the terminal pipe from the drilling hole. A non-widening AGF method, characterized by comprising a third step of expanding a packer near the mouth of the borehole and injecting a consolidating material into the borehole, including the area where the terminal pipe was removed.

2. The non-widening AGF method according to claim 1, characterized in that, in the first step, the locking portion is locked to the centralizer without being constrained to the circumferential rotational position of the terminal pipe.

3. The non-widening AGF method according to claim 1 or 2, characterized in that a threaded portion is formed on the outer circumferential surface of the rear end of the externally inserted intermediate pipe, which can be screwed into another partial reinforcing pipe.

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