JP2012167497A - Chemical injection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To evade deposition of excavated sediment in a rotation space part held in order to rotate a casing side engaging part in an opposite direction to a bit side engaging part and release an engaged state, and to smoothly detach and pull out a drilling casing from a tip bit, in a soil improvement method of improving soil by injecting a chemical by a double packer system.SOLUTION: Other than a plurality of jetting ports 15 made to pass through and opened from a valve chamber 19 to a tip of a bit body part 23, a tip bit 11 is provided with a washing port 20 passing through a peripheral wall part of a valve chamber 19 at a part more on the tip side than an enclosed position of a valve body 18 closely attached to a valve seat part 19b. The washing port 20 is opened toward a rotation space part 29 held on the rotation side in the opposite direction of a casing side engaging part 22, for allowing the casing side engaging part 22 to be rotated in the opposite direction of one direction X to a bit side engaging part 21 and detached, and is capable of discharging washing water to the rotation space part 29.

Description

  The present invention relates to a chemical solution injection device, and more particularly to a chemical solution injection device used in a ground improvement method in which a chemical solution is injected by a double packer method to improve the ground.

  For example, as a ground improvement method for improving soft ground or the like, a method of improving the ground by injecting a chemical solution into the improved target ground by a double packer method is known (for example, see Patent Document 1). The ground improvement method using the double packer method is, for example, rotating a hollow pipe-shaped drilling casing in one direction, drilling with a tip bit attached to the tip of the hollow drilling casing, and pushing the drilling casing to a predetermined position on the improved target ground Then, after inserting the injection outer tube into the installed drilling casing and connecting the tip of the outer pipe to the tip bit, the hole casing is removed from the tip bit, and the hole casing is pulled out from the improved ground. This is a known method for improving the ground by inserting an injection inner tube having a double packer into the injection outer tube left on the improved target ground and injecting a chemical into the improved target ground. In the ground improvement method using the double packer method, it is possible to improve the foundation by propelling the hole-drilling casing into the ground with a considerable length not only in the vertical direction but also in the lateral and oblique directions.

  In addition, so that the ground improvement method by the double packer system can be performed more efficiently, the drilling sediment and drilling water are prevented from leaking out at the mouth, which is the starting point of the drilling casing, or propelled to a predetermined position. Various improved techniques have been developed in order to facilitate the work of removing the drilled casing from the tip bit and the work of pulling it out (see, for example, Patent Document 2 and Patent Document 3).

Japanese Patent Publication No. 5-65651 Japanese Patent Publication No. 6-86727 Japanese Examined Patent Publication No. 7-103545

  On the other hand, in the step of propelling the hole casing into the ground, the tip bit attached to the tip portion can be held in a stable mounting state, and when the hole casing is pulled out after being propelled to a predetermined position. As a simple means for easily removing the hole casing from the tip bit, for example, a bit side engaging portion 51 and a casing side engaging portion as shown in FIGS. A detachable structure consisting of 52 is proposed. 8 (a) to 8 (c), the distal end bit 50 has a boundary portion between the distal end side bit main body 53 and a reduced inner diameter mounting inner cylindrical portion 54. In addition, the outer peripheral portion of the bit main body portion 53 is cut out, and the engagement engaging portion 51a having a wide width is formed by being bent in a hook shape from the portion on the bit leading end side of the engagement introducing portion 51a to one side in the circumferential direction. A bit side engaging portion 51 formed with a mating groove 51b is provided. Further, a drive shoe 56 as a joining member to the tip bit 50 is integrally attached to the tip portion of the hole casing 55 via a screw portion 57, and the tip of the mounting outer cylinder portion 58 of the drive shoe 56 is attached. A casing side engaging portion 52 is provided that protrudes from the edge portion and includes a base end portion 52a and an engaging protrusion 52b that is bent from the distal end portion of the base end portion 52a to one side in the circumferential direction. Yes.

  8A to 8C, the casing side engaging portion 52 is disposed inside the bit side engaging portion 51 via the engagement introducing portion 51a, and the tip bit 50 is attached. After the inner cylinder portion 54 is fitted inside the outer cylinder portion 58 of the drive shoe 56, the drive shoe 56 is rotated in the circumferential direction one side X with respect to the tip bit 50, and the engagement protrusion of the casing side engagement portion 52 is engaged. By engaging the portion 52b with the engaging groove 51b (see FIG. 8C) of the bit side engaging portion 51, the tip bit 50 is attached to the tip portion of the hole casing 55 with the drive shoe 56 interposed. It can be attached (see FIG. 8C). As a result, it is possible to excavate the ground by the tip bit 50 while rotating it in one direction toward the circumferential one side X, and to push the hole-drilling casing 55 into the ground to a predetermined position.

  When the hole casing 55 is pulled out with the tip bit 50 left in the ground after the hole casing 55 is propelled and installed to a predetermined position, the hole casing 55 and the drive shoe 56 are circumferentially pulled out. If it is rotated in the opposite direction opposite to the one side X, the engagement state of the engagement protrusion 51b of the casing side engagement part 52 with the engagement groove 51b of the bit side engagement part 51 is released. It is possible to remove the holed casing 55 and the drive shoe 56 from the tip bit 50 by moving the casing side locking portion 52 to the outside of the bit side engaging portion 51 through the introduction portion 51a.

  8A to 8C, the bit side engaging portion 51 and the casing side engaging portion 52 are spaced by 180 degrees in the circumferential direction of the tip bit 50 and the drive shoe 56. Two positions are provided at opposite positions. Thereby, the excavation of the ground by the tip bit 50 when propelling the hole casing 55 into the ground can be performed in a stable state.

  However, in the detachable structure shown in FIGS. 8A to 8C, the drive shoe 56 is rotated in the circumferential one side X with respect to the tip bit 50, and the engagement protrusion 52a of the casing side engagement portion 52 is moved to the bit side. In the process of propelling the hole casing 55 into the ground by rotation in the circumferential direction one side X in a state of being engaged with the engaging groove 51b of the engaging portion 51, the outer peripheral portion of the bit main body portion 53 is notched. In the bit side engaging portion 51 formed as described above, the casing side engaging portion 52 held on the rotation side in the direction opposite to the circumferential one side X of the casing side engaging portion 52 is changed to the bit side engaging portion 51. The rotating space portion 59 (see FIG. 8C) for releasing the engaged state by rotating in the opposite direction with respect to FIG. The earth and sand excavated in the When deposited on part 59, making it difficult to rotate the casing engagement portion 52 in the opposite direction is considered to become difficult to remove the drilling casing 55 from the distal end bit 50. For this reason, further improvement is desired.

  The present invention was excavated during the propulsion of the drilling casing into the rotating space portion held for rotating the casing side engaging portion in the opposite direction with respect to the bit side engaging portion to release the engaged state. An object of the present invention is to provide a chemical injection device that can effectively avoid sedimentation and can smoothly remove and remove the hole casing from the tip bit.

  The present invention relates to a drilling hole in which a tip bit provided with a nozzle for drilling water and a check valve is detachably attached to the tip part, which is used in a ground improvement method in which a chemical solution is injected by a double packer method to improve the ground. In the chemical injection device including a casing, the chemical injection device is configured to excavate and drill the hole casing to a predetermined position on the improved target ground by excavating with the tip bit while rotating the hole casing in one direction. After inserting the injection outer tube into the drilled casing and connecting the tip of the outer pipe to the tip bit, the drilled casing is removed from the tip bit by rotating the drilled casing in the reverse direction. Is pulled out from the improved target ground, and an injection inner pipe with a double packer is inserted into the outer injection pipe left on the improved target ground. It has a structure capable of improving the ground by injecting a chemical into the ground, and the tip bit has a valve chamber in a portion on the tip side of the sealing position of the valve body of the check valve The casing-side engaging portion of the bit-side engaging portion that can be removed by rotating the casing-side engaging portion in the opposite direction with respect to the bit-side engaging portion. The above object is achieved by providing a chemical injection device having a cleaning port that opens toward a rotating space portion held on the rotating side in the reverse direction.

  According to the chemical injection device of the present invention, the casing-side engagement portion is rotated in the opposite direction with respect to the bit-side engagement portion to disengage the engagement state. It is possible to effectively avoid sedimentation of excavated earth and sand during propulsion, and to smoothly remove the hole casing from the tip bit and pull it out.

The structure of the principal part of the chemical | medical solution injection device which concerns on preferable one Embodiment of this invention is demonstrated, (a) is a side view of a front-end | tip bit, (b) is a partially broken side view of a drilling casing and a drive shoe, (c). FIG. 4 is a side view of a state in which a tip bit is attached to the tips of the hole drill casing and the drive shoe. It is a partial fracture side view explaining the internal structure of a tip bit. It is sectional drawing which shows the structure which connects the front-end | tip part of an injection | pouring outer tube | pipe to a front-end | tip bit, and has shown in the state which abbreviate | omitted the drill casing and drive shoe. It is a partially broken side view of the state which inserted the injection | pouring outer tube | pipe inside the hole-drilling casing and connected the front-end | tip part to the front-end | tip bit. It is a side view which illustrates other forms of a drive shoe. (A) The side view which illustrates the other form of a front-end | tip bit, (b) is the expanded view which looked at the A section of (a) from the downward direction. (A)-(d) is explanatory drawing of the ground improvement construction method (penetration solidification processing construction method) using the chemical | medical solution injection | pouring apparatus which concerns on preferable one Embodiment of this invention. The structure of the main part of the conventional chemical injection device will be described. (A) is a side view of the tip bit, (b) is a partially broken side view of the drilling casing and drive shoe, and (c) is the drilling casing and drive shoe. FIG.

  The chemical solution injection device according to a preferred embodiment of the present invention is an infiltration by horizontal injection as shown in FIGS. 7A to 7D, for example, as a ground improvement method for improving the ground by injecting a chemical solution by a double packer method. It is used as a device for constructing the solidification method. The chemical injection device of the present embodiment is the permeation solidification processing method shown in FIGS. 7 (a) to 7 (d), with the hole casing 10 propelled and installed on the improved target ground 30 to a predetermined position, leaving the tip bit 11. When pulling out from the ground, it has a function of smoothly performing the operation of rotating the drilling casing 10 in the direction opposite to that during propulsion drilling and removing it from the tip bit 11.

  Here, the seepage solidification method shown in FIGS. 7 (a) to 7 (d) is, for example, injected from the work shaft 31 constructed by digging in the ground from the ground surface to the improved target ground 30 in the lateral direction. After the pipe 12 is installed, an infusion inner pipe 14 having a double packer 13 is inserted into the infusion outer pipe 12, and a chemical solution is injected from the inner injection pipe 14 into the improved target ground 30. Is a construction method for improving the ground, and is generally constructed by the following process.

  That is, in the permeation solidification processing method, for example, a known method is used to install a mouth pipe (not shown) with a predetermined position on the wall surface of the vertical shaft 31 facing the improved target ground 30 as a mouth portion, and then FIG. As shown in a), a known drilling machine 33 is set at a predetermined position of the shaft 31. Moreover, after adjusting the angle of the drilling hole of the steel hollow pipe-shaped drilling casing 10 having an outer diameter of about 120 mm, for example, with the tip bit 11 attached to the tip by the set drilling machine 33, the tip While excavating the ground 30 with the bit 11 and propelling it while rotating in one direction X and drilling in the lateral direction, the drilling casing 10 is propelled to a predetermined position of, for example, about 20 m.

  In such a horizontal drilling, the drilling casing 10 can be propelled into the ground while sequentially adding unit pipes having a length of, for example, about 1.5 m at the mouth portion in the same manner as a known method. In addition, pressurized water is supplied from the mouth portion into the hollow interior of the hole-drilling casing 10, and the ground 30 is moved by the tip bit 11 while discharging the supplied pressurized water from the nozzle 15 (see FIG. 2) of the tip bit 11. Excavate. The earth and sand or drilling water excavated by the tip bit 11 is sent to the mouth portion through a gap between the outer peripheral surface of the drilling casing 10 and the inner wall surface of the formed drilling hole 34, and a known method. In the same manner as described above, for example, it is excluded via a discharge valve or the like provided in the mouth tube.

  Once the hole casing 10 is propelled and installed to a predetermined position on the improved ground 30, a three-dimensional measuring device (gyro) is preferably inserted into the hole casing 10, and the position of the hole 34 by the hole casing 10 is three-dimensional. 7 (b), as shown in FIG. 7 (b), for example, a known sleeve packer 16 is attached to the outer peripheral surface at a predetermined pitch in the axial direction, for example, an outer diameter of about 40 to 60 mm, for example. A hollow pipe-like vinyl chloride pipe provided with is inserted into the bore casing 10 and the tip portion thereof is connected to the tip bit 11. After that, the hole casing 10 is removed from the tip bit 11, and the hole casing 10 is pulled out to the mouth side while the tip bit 11 and the injection outer tube 12 remain in the ground. Since the distal end portion of the injection outer tube 12 is connected to the distal end bit 11, the distal end bit 11 functions as an anchor, and the injection outer tube 12 is pulled out toward the mouth side as the holed casing 10 is pulled out. Can be effectively avoided.

  When the holed casing 10 is pulled out from the ground and removed, as shown in FIG. 7 (c), in order to prevent water leakage or back flow of the chemical solution, for example, after the mouth water treatment plate 35 is used, A sleeve packer 16 attached to the outer peripheral surface of the injection outer tube 12 in order to prevent the chemical solution from flowing out through the clearance between the tube 12 and the inner wall surface of the hole 34 after the hole casing 10 is pulled out. Inflates. In order to expand the sleeve packer 16, the injection inner tube 14 including the double packer 13 is inserted into the injection outer tube 12, and the double packer is formed in the portion of the injection outer tube 12 where the inlet to each sleeve packer 16 is formed. Set 13 Thereafter, a filler made of, for example, cement bentonite is injected into the sleeve packer 16 through the injection inner tube 14 and the double packer 13, and the sleeve packers 16 are expanded until they are in close contact with the inner wall surface of the hole 34. As a result, the clearance between the outer peripheral surface of the injection outer tube 12 and the inner wall surface of the drilling hole 34 is firmly removed, except for the space between the sleeve packers 16 adjacent in the axial direction of the injection outer tube 12. It becomes possible to occlude.

  When each sleeve packer 16 is inflated to close the clearance between the outer peripheral surface of the outer injection tube 12 and the inner wall surface of the hole 34, as shown in FIG. The space between adjacent sleeve packers 16 is used as a permeation path for the chemical solution, and the double packer 13 is set in a part of the outer injection pipe 12 where the inlets to these permeation paths are formed. Thereafter, the chemical solution for osmotic solidification, for example, through the injection inner tube 14 and the double packer 13 is improved, for example, through a permeation path between the sleeve packers 16 at a predetermined injection pressure and injection speed designed in advance. Infiltrate into the target ground 30. Such an infiltration and injection operation of the chemical solution can be performed while sequentially moving the position where the double packer 13 is set from the rear side of the hole 34 toward the mouth. As a result, a continuous solidification improved body 32 that is continuous along the hole 34 is sequentially formed on the improved target ground 30.

  After the chemical solution is infiltrated and injected into the improved target ground 30 to form the osmotic solidified improved body 32, a post-survey is performed after a predetermined curing period, and the improved strength of the ground by the osmotic solidified improved body 32 is confirmed.

  And the chemical | medical solution injection device of this embodiment is used in the above-mentioned osmosis solidification processing method, and the drilling casing 10 propelled and installed up to a predetermined position on the improved target ground 30 is left from the ground, leaving the tip bit 11. When pulling out, the hole casing 10 is rotated in the direction opposite to that at the time of drilling, and a function of smoothly removing it from the tip bit 11 is provided.

  That is, the chemical injection device of the present embodiment is provided with the drilling water nozzle 15 and the check valve 17 (see FIG. 2) used in the ground improvement method in which the chemical is injected by the double packer method to improve the ground. It is an apparatus for chemical | medical solution injection | pouring provided with the hole casing 10 which attached the front-end | tip bit 11 detachably to the front-end | tip part. As described above, the chemical injection device of the present embodiment excavates with the tip bit 11 while rotating the drilling casing 10 in one direction X, and pushes and installs the drilling casing 10 on the improved ground 30 to a predetermined position. After the injection outer tube 12 is inserted into the installed drilling casing 10 and its tip is connected to the tip bit 11, it is removed from the tip bit 11 by rotating the drilling casing 10 in the opposite direction. The hole casing 10 is pulled out from the improved target ground 30, and the injection inner pipe 14 including the double packer 13 is inserted into the injection outer pipe 12 left on the improved target ground 30 to inject the chemical solution into the improved target ground 30. The tip bit 11 is provided with a check valve 17 as shown in FIGS. 1 (a) to 1 (c) and FIG. The casing side engaging portion 22 is rotated in the direction opposite to the one direction X with respect to the bit side engaging portion 21 through the peripheral wall portion of the valve chamber 19 at the tip side of the sealing position of the body 18. Opening toward the rotation space portion 29 (see FIG. 1C) held on the rotation side in the reverse direction of the casing side engagement portion 22 in the bit side engagement portion 21. A cleaning port 20 is formed.

  According to the present embodiment, the chemical injection device enables the tip bit 11 attached to the tip portion to be held in a stable mounting state in the step of propelling the hole casing 10 into the ground, As shown in FIGS. 1A to 1C, as a simple structure that enables the hole casing 10 to be easily detached from the tip bit 11 when the hole casing 11 is pulled out after being pushed to the position. Such a detachable structure including the bit side engaging portion 21 and the casing side engaging portion 22 is provided.

  In the attachment / detachment structure shown in FIGS. 1A to 1C, the distal end bit 11 has a boundary portion between the distal end side bit main body portion 23 and the diameter-reduced mounting inner cylinder portion 24 subsequent thereto. The wide engagement introducing portion 21a is formed by cutting out the outer peripheral portion of the bit main body portion 23, and the engagement is formed by being bent in a hook shape from the bit leading end side portion of the engagement introducing portion 21a to one side in the circumferential direction. A bit side engaging portion 21 formed of the groove 21b is provided. In addition, a drive shoe 26 as a joining member to the tip bit 11 is integrally attached to a tip portion of the hole casing 10 via a screw portion 27, and a mounting outer cylinder portion 28 of the drive shoe 26 is attached. A casing-side engagement portion 22 is provided that protrudes from the distal end edge portion and includes a proximal end portion 22a and an engagement protrusion 22b that is bent from the distal end portion of the proximal end portion 22a to one side in the circumferential direction. It has been.

  The casing side engaging portion 22 is disposed inside the bit side engaging portion 21 via the engagement introducing portion 21a, and the mounting inner cylinder portion 24 of the tip bit 11 is replaced with the mounting outer cylinder portion 28 of the drive shoe 26. Then, the drive shoe 26 is rotated in the circumferential direction one side X with respect to the tip bit 11, and the engagement protrusion 22 b of the casing side engagement portion 22 is engaged with the engagement groove 21 b of the bit side engagement portion 21. The tip bit 11 can be attached to the tip portion of the hole casing 10 with the drive shoe 26 interposed (see FIG. 1C). Thus, the improved target ground 30 can be excavated by the tip bit 11 while rotating in one direction X to the circumferential one side X so that the hole casing 10 can be propelled into the ground to a predetermined position. It has become.

  In addition, when the hole casing 10 is pulled out with the tip bit 11 left in the ground after the hole casing 10 is propelled and installed to a predetermined position, the hole casing 10 is circumferentially moved together with the drive shoe 26 in the circumferential direction. If it is rotated in the opposite direction opposite to the one side X, the engagement state of the engagement protrusion 21b of the casing side engagement portion 22 with the engagement groove 21b of the bit side engagement portion 21 is released. The casing casing 22 and the drive shoe 26 can be removed from the tip bit 11 by moving the casing side engaging section 22 to the outside of the bit side engaging section 21 via the introduction section 21a.

  1A to 1C, the bit side engaging portion 21 and the casing side engaging portion 22 have an angular interval of 180 degrees in the circumferential direction of the tip bit 11 and the drive shoe 26. Two positions are provided at opposite positions. As a result, excavation of the ground by the tip bit 11 when propelling the hole casing 10 into the ground can be performed in a stable state.

  Further, in the present embodiment, the tip bit 11 is provided with a hole 15 for drilling water and a check valve 17 as shown in FIG. The check valve 17 includes a coil spring 25 disposed in the valve chamber 19 inside the tip bit 11 and a spherical valve body 18. The valve body 18 is connected to the inner peripheral edge portion of the communication port 19a that connects the valve chamber 19 and the hollow interior of the mounting inner cylinder portion 24 by a biasing force from the bit tip end toward the rear by the coil spring 25. For example, when the propulsion of the hole casing 10 is stopped and the supply of pressurized water through the hollow interior of the hole casing 10 is stopped, the pressure applied from the improved target ground 30 is reduced. It is possible to prevent water from flowing back into the hole casing 10 through the nozzle hole 15. Further, when the hole casing 10 is propelled while excavating the improved target ground 30 with the tip bit 11, the pressure of pressurized water supplied through the hole casing 10 resists the biasing force from the coil spring 25. By extruding the valve body 18 toward the tip of the bit, the communication port 19a is opened so that pressurized water can be discharged as drilling water from the nozzle 15 toward the improved ground 30 in front of the tip bit 11. It has become.

  In this embodiment, the tip bit 11 has a valve body 18 in close contact with the valve seat portion 19b in addition to the plurality of nozzle holes 15 penetrating and opening from the valve chamber 19 toward the tip cutting surface of the bit body portion 23. A cleaning port 20 is provided through the peripheral wall of the valve chamber 19 at a portion closer to the tip than the sealing position. The cleaning port 20 allows the casing-side engagement portion 22 to be removed by rotating the casing-side engagement portion 22 in the opposite direction with respect to the bit-side engagement portion 21. It opens toward the rotation space portion 29 (see FIG. 1C) held on the rotation side in the direction opposite to X. Accordingly, when the drilling casing 10 is propelled while excavating the improved target ground 30 with the tip bit 11, the pressurized water is discharged from the nozzle 15 toward the improved target ground 30 as drilled water. In addition, the cleaning water can be discharged from the cleaning port 20 to the rotary space 29 as cleaning water.

  Further, in the present embodiment, the inner side surface of the mounting inner cylinder portion 24 of the tip bit 11 has a substantially semicircular shape continuously in a ring shape over the entire circumference thereof as shown in FIG. A connection locking groove 36 having a cross-sectional shape is formed. On the other hand, as shown in FIG. 4, a connection adapter 37 is integrally joined to the distal end portion of the outer injection tube 12 inserted into the hollow inside of the hole casing 10. As shown in FIG. 3, for example, there are four plungers 38 each having a spherical potch 38 a that can advance and retreat in the radial direction by a radially outward biasing force by a spring at an angular interval of 90 degrees in the circumferential direction. Is provided. The head portion 37a provided with the plunger 38 of the connection adapter 37 is pushed into the hollow inside of the mounting inner cylinder portion 24 of the tip bit 11, thereby locking the spherical potch 38a of the plunger 38 in the connection locking groove 36. Thus, the distal end portion of the outer injection tube 12 can be easily connected to the distal end bit 11.

  Furthermore, in this embodiment, a guide rib 39 having a guide taper portion 39a formed at the rear portion extends in the axial direction of the drive shoe 26 on the inner surface of the portion of the drive shoe 26 where the screw portion 27 is provided. A plurality of them are provided at intervals in the circumferential direction. By providing the guide rib 39 on the inner surface of the drive shoe 26, the axial center of the outer injection pipe 12 and the connecting adapter 37 is guided so as to substantially coincide with the axial center of the inner cylinder portion 24 of the distal end bit 11. Thus, the operation of connecting the distal end portion of the outer injection tube 12 to the distal end bit 11 can be performed more smoothly.

  In the present embodiment, as shown in FIG. 5, the gap portion between the engagement protrusion 22 b of the casing side engagement portion 22 provided on the drive shoe 26 and the tip edge of the mounting outer cylinder portion 28 is outside. The covering plate 40 can also be attached. The covering plate 40 does not interfere with the operation of rotating the drive shoe 26 in the circumferential side X to engage the engaging protrusion 22b of the casing side engaging portion 22 with the engaging groove 21b of the bit side engaging portion 21. Thus, it is provided to extend to a position slightly higher than the outer peripheral surface of the engaging protrusion 22b. Engagement of the casing-side engagement portion 22 brought into an engagement state by covering the gap portion between the engagement protrusion 22b and the distal end edge portion of the mounting outer cylinder portion 28 so that the cover plate 40 is attached. It is possible to prevent the earth and sand from biting into the gap between the protrusion 22b and the engagement groove 21b of the bit side engagement portion 21 so that the hole casing 10 can be removed from the tip bit 11 more easily. It becomes possible to do.

  Further, in the present embodiment, as shown in FIGS. 6A and 6B, the engagement groove is disposed adjacent to the bit rear end side of the engagement groove 21b of the bit side engagement portion 21 of the front end bit 11. When the engaging protrusion 22b of the casing side engaging portion 22 is engaged with 21b, the bit side that is engaged with the interval portion between the engaging protrusion 22b and the distal end edge portion of the mounting outer cylinder portion 28 The length L of the protrusion 41 can be kept as short as possible within a range that does not hinder the function of the engagement groove 21b. Further, the front end corner of the bit side protrusion 41 on the engagement groove 21b side can be chamfered as a chamfer 41a, preferably in a curved shape. These also make it possible to more easily perform the operation of removing the hole casing 10 from the tip bit 11.

  And according to the chemical | medical solution injection device of this embodiment provided with the above-mentioned structure, the casing side engaging part 22 is rotated in the direction opposite to the one direction X with respect to the bit side engaging part 21, and an engagement state is cancelled | released. Therefore, it is possible to effectively prevent the excavated earth and sand from being accumulated during the propulsion of the drilling casing 10 and to smoothly remove the drilling casing 10 from the tip bit 11 and pull it out. It becomes possible to do so.

  That is, according to the present embodiment, the tip bit 11 is in close contact with the valve seat portion 19b in addition to the plurality of nozzle holes 15 penetrating and opening from the valve chamber 19 toward the tip cutting surface of the bit body portion 23. A cleaning port 20 is provided through the peripheral wall portion of the valve chamber 19 at a portion closer to the distal end than the sealing position of the valve body 18. The cleaning port 20 is a part of the casing side engaging portion 22 in the bit side engaging portion 21 that allows the casing side engaging portion 22 to be removed by rotating in the reverse direction with respect to the bit side engaging portion 21. It opens toward the rotation space portion 29 (see FIG. 1C) held on the rotation side in the direction opposite to the direction X. Accordingly, when the drilling casing 10 is propelled while excavating the improved target ground 30 with the tip bit 11, the pressurized water is discharged from the nozzle 15 toward the improved target ground 30 as drilled water. Since the cleaning water can be discharged from the cleaning port 20 to the rotating space portion 29, it is possible to effectively prevent sediment from being accumulated in the rotating space portion 29, and to smoothly remove the drilling casing 10 from the tip bit 11. Can be removed.

  The present invention is not limited to the above-described embodiment, and various modifications can be made. For example, the casing-side engagement portion and the bit-side engagement portion are not limited to those having the configuration as in the above embodiment, and are rotated in the direction opposite to the rotation direction in one direction during propulsion. Thus, the present invention can be applied to other various casing side engaging parts and bit side engaging parts that enable the hole casing to be removed from the tip bit. In addition, the present invention can be applied to various other ground improvement methods for improving the ground by injecting a chemical solution by a double packer method other than the infiltration solidification processing method by horizontal injection, and also in an oblique direction or a vertical direction other than the horizontal direction. It can also be applied to a ground improvement method for improving the ground by propelling a drilling casing.

DESCRIPTION OF SYMBOLS 10 Drilling casing 11 Tip bit 12 Injection outer pipe 13 Double packer 14 Injection inner pipe 15 Injection hole 16 Sleeve packer 17 Check valve 18 Valve body 19 Valve chamber 19a Communication port 19b Valve seat part 20 Washing port 21 Bit side engagement part 21a Engagement introduction part 21b Engagement groove 22 Casing side engagement part 22a Base end part 22b Engagement projection part 23 Bit body part 24 Installation inner cylinder part 25 Coil spring 26 Drive shoe 27 Screw part 28 Installation outer cylinder part 29 Rotating space part 30 Improvement target ground 32 Permeation solidification improved body 34 Drilling hole X Direction of rotation to the circumferential shape side (direction of rotation in one direction)

Claims (1)

Chemical solution equipped with a hole casing that is removably attached to the tip portion of a tip bit provided with a nozzle for drilling water and a check valve, which is used in the ground improvement method to improve the ground by injecting the chemical solution with the double packer method In the injection device,
The chemical injection device is configured to excavate with the tip bit while rotating the drill casing in one direction and to push the drill casing to a predetermined position on the improved target ground, and to install the drill casing inside the drill casing. After inserting the injection outer pipe and connecting the tip portion thereof to the tip bit, the hole casing is removed from the tip bit by rotating in the reverse direction, and the hole casing is pulled out from the improved ground. Inside the injection outer tube left on the improved target ground, it is equipped with a configuration capable of performing ground improvement by inserting an injection inner tube with a double packer and injecting a chemical into the improved target ground,
In addition, the tip bit penetrates the peripheral wall portion of the valve chamber on the tip side from the sealing position of the valve body of the check valve, and the casing side engaging portion is connected to the bit side engaging portion. The cleaning port that opens toward the rotating space portion held on the rotating side in the reverse direction of the casing side engaging portion in the bit side engaging portion that enables the bit side engaging portion to be removed by rotating in the reverse direction. The chemical injection device that is formed.

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