JP2005273331A5 - - Google Patents

Description

Liquefaction prevention method for ground directly under existing structures

  In the present invention, various buildings and civil engineering structures such as airport runways, large tanks in factories, etc. are already installed on the ground that may be liquefied, such as sand ground (also simply referred to as target ground). In this case, the present invention relates to a technique for taking measures against liquefaction by infiltrating the ground improvement material into the target ground.

  When various buildings and civil engineering structures such as airport runways and factory large tanks are already installed on the target ground that may be liquefied, such as sand ground, there is concern about ground subsidence due to ground liquefaction Is done.

  Therefore, a technique for taking measures against liquefaction on the target ground has been conventionally proposed. For example, a hole is formed so as to reach the target ground from the ground surface around an existing structure, and a hole formed thereby is used. Then, a method of taking measures to prevent liquefaction such as injecting a ground improvement agent has been proposed (for example, see Patent Document 1).

  In this case, in order to make a drilling so as to reach the target ground from the ground surface around the existing structure, it is necessary to perform a curved drilling at least from the ground surface to the improvement target depth, and the improvement range is In the case where it is wide in the horizontal direction, it is necessary to drill holes linearly together with curved holes.

  The following direction-controlled drilling methods are known for enabling such drilling. That is, in this direction control drilling method, a taper bit having a flat pressure-receiving surface inclined with respect to the axial direction is attached to the tip of a bendable drilling shaft, and when drilling in a curved manner, the drilling is performed. By applying only the propulsive force to the hole shaft, the drilling shaft is propelled into the ground while changing the propulsion direction by the force applied to the pressure receiving surface of the tapered bit at the tip. On the other hand, when drilling linearly, both rotational force and propulsive force are applied to the drilling shaft, and the direction of the force applied to the pressure-receiving surface is canceled out by a change around the rotation axis, so that linear drilling is performed. Is possible.

  The present applicant has been diligently researching such direction-controlled drilling, and by drilling drilling water along the axial direction of the drilling shaft from the pressure-receiving surface of the tapered bit at the time of drilling, the ground is relaxed. It has been confirmed that smoother drilling is possible.

  However, in the conventional method, since the injection port is provided at the axial center of the pressure receiving surface, the ground in front of the bit can be effectively relaxed during straight drilling, but drilling water is supplied in the curve propulsion direction of the bit during curved drilling. Since it was not possible to inject and sufficient relaxation was not possible, smooth and steep curve promotion was difficult.

Due to this problem, the drilling start position has to be far from the existing structure, and there has been a problem that a wider construction space is required.
JP-A-8-120661

  Therefore, the main problem of the present invention is that the ground can be sufficiently relaxed by the drilling water in the curved drilling so that the curve can be pushed smoothly and sharply, thereby reducing the construction space. Alternatively, even a narrow construction space can be handled.

The present invention that has solved the above problems is as follows.
<Invention of Claim 1>
A bendable drilling shaft, a tapered bit provided at the tip of the drilling shaft and having a pressure-receiving surface inclined with respect to the axial direction, and a rotation propulsion means for rotating and propelling the drilling shaft, The rotational propulsion means is configured to apply only a propulsive force to the drilling shaft, and to propel the drilling shaft into the ground while changing the propulsion direction by the force applied to the pressure receiving surface of the tapered bit at the tip. Using a drilling device,
A method of infiltrating and injecting a ground improvement agent into a target ground that may be liquefied existing directly under an existing structure to prevent liquefaction;
The drilling shaft is moved from the ground surface around the existing structure to the ground while spraying drilling water toward the front of the tapered bit and in a direction inclined toward the curve propulsion direction with respect to the axial direction. While forming an insertion hole to reach the target ground, the tube is inserted into the insertion hole formed sequentially,
If the tubular body is inserted so as to reach the target ground, the drilling shaft is collected leaving the tubular body, and then has a plurality of external packers on the outer surface portion spaced apart in the axial direction and adjacent to each other. After inserting the injection outer tube having an injection port between the outer packers to be inserted into the tube body, the tube body is pulled out from the insertion hole leaving the injection outer tube, and then the target ground using the injection outer tube A ground liquefaction countermeasure method directly under an existing structure characterized by injecting a ground conditioner into the ground.

(Function and effect)
FIG. 1 shows the characteristics of the drilling method according to the present invention. As indicated by the symbol w in the figure, in the present invention, toward the front ground of the tapered bit 6 and toward the direction D2 inclined toward the curve propulsion direction with respect to the axial direction D1 of the drilling shaft 5. While injecting the drilling water w1, the drilling shaft 5 is propelled into the ground along the axial direction D1. Therefore, as shown in FIG. 5A, the drilling shaft 5 is propelled without rotating, and the drilling shaft 5 is curved into the ground while changing the propulsion direction by the force applied to the pressure receiving surface 60 of the tapered bit 6. Even when propelled, the drilling water can be sprayed toward the propulsion destination of the tapered bit 6 to reliably relax the ground of the propulsion destination. Furthermore, when the form of drilling water is adopted, the ground on the curve propulsion direction side with respect to the axial direction D1 can be intensively relaxed. Therefore, as a result of the taper bit 6 becoming easier to escape to the loose ground side, the direction can be changed more smoothly and reliably.

  On the other hand, in the conventional form in which the drilling water is jetted from the axial center portion of the pressure receiving surface 60, the drilling water cannot be jetted in the curve driving direction of the bit as indicated by reference numeral w2, and a smooth curve is obtained. Promotion is impossible.

  On the other hand, when propelled while rotating the drilling shaft 5, the direction of the force applied to the pressure receiving surface 60 is canceled by the change around the rotation axis D1, as shown in FIG. While being possible, the injection direction of the drilling water is inclined with respect to the propulsion direction (axial center direction D1), but the injection direction of the drilling water is also denoted by reference numeral w3 as the drilling shaft 5 and the taper bit 6 rotate. Therefore, as a result, the drilling water can be sprayed over a wide range in front of the taper bit 6, and smooth linear propulsion is possible.

  In the present invention, “injecting the drilling water toward the front ground of the tapered bit 6 and in the direction D2 inclined toward the curve propulsion direction side with respect to the axial direction D1 of the drilling shaft 5” As shown in FIG. 2, the axial direction D1 is the x-axis, the plane including the x-axis and the tip position of the pressure-receiving surface 60 is the xy plane, and the inclination angle with respect to the x-axis in the xy plane is θ1. When the inclination angle around the x-axis with respect to the y-axis is θ2, drilling water is directed toward a direction satisfying both the conditions of 0 ° <θ1 <90 ° and −90 ° <θ2 <90 ° and a direction parallel thereto. Means to spray.

  Thus, according to the present invention, since the curve can be propelled at a steep angle more smoothly and surely than in the past, when improving the target ground, from the existing structure to the drilling start position. The distance can be shortened, the construction space can be narrowed, or even a narrow construction space can be handled.

  Further, in the present invention, after inserting an injection outer tube having a plurality of external packers on the outer surface portion at an interval in the axial direction and having an injection port between adjacent external packers, the injection outer tube The pipe body is withdrawn from the insertion hole, and then the ground improvement agent is infiltrated and injected into the target ground using the outer injection pipe. By using such an injection outer tube, the ground improvement material can be infiltrated and injected into the target ground in a limited manner, and liquefaction measures can be efficiently taken.

<Invention of Claim 2>
Adjacent external packers in the injection outer tube left in the insertion hole are bulged to adhere to the inner wall surface of the insertion hole, and a plurality of internal packers are provided in the outer surface portion at intervals in the axial direction in the injection outer tube. And inserting an injection inner tube having a discharge port between adjacent internal packers and expanding the adjacent internal packers into close contact with the inner surface of the injection outer tube, and then inserting the adjacent external packer into the insertion hole In a state where the area surrounded by the wall surface and the outer surface of the outer injection tube is a space, the inner tube, the discharge port of the inner injection tube, the inner surface of the injection outer tube, the inlet of the outer injection tube, and the space through the space in this order The liquefaction countermeasure method for the ground directly under an existing structure according to claim 1, wherein a ground improver is infiltrated and injected into the ground.

(Function and effect)
When this ground improvement method is adopted, the area surrounded by the adjacent packer, the wall surface of the insertion hole, and the outer surface of the injection outer pipe is a space where no filler exists, so the ground improvement agent injected through the injection port is between the adjacent packers. It is injected into the ground in a state filled with a relatively wide space. Therefore, since it penetrates into the target ground from the entire insertion hole wall facing the space, it is possible to penetrate without causing splitting even at a high injection rate. As a result, it is possible to inject a large amount of chemical liquid from one injection zone, and the chemical liquid that has penetrated into the ground is infiltrated far into the ground.

  As described above, according to the present invention, the ground can be sufficiently relaxed by the drilling water in the curved hole drilling, and the curve can be promoted smoothly and at a sharp angle, thereby reducing the construction space. The advantage that it becomes possible to cope with even a narrow construction space.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
<Pipe installation device>
FIG. 3 shows a construction state of the pipe erection device example 1, and this pipe erection device 1 includes a bendable outer pipe (corresponding to the pipe body of the present invention) 2 built in the ground, A ring bit 3 that is coaxially attached to the tip of the outer tube 2, passes through the outer tube 2 and the through hole of the ring bit 3, and extends forward from the ring bit 3, and is bent from the outer tube 2. A hard but bendable inner tube 5 (corresponding to the drilling shaft of the present invention), a tapered bit 6 attached to the tip of the inner tube 5, the inner tube 5 and the outer tube 2, and the inner tube 5 And a rotary propulsion device 7 that rotates and propels the motor.

(Configuration of rotating propulsion device)
For example, as shown in the figure, the rotation propulsion device 7 includes a leader 7L that is tiltably supported by a base machine 7B, and a hydraulic motor that is attached to the leader 7L so as to be vertically movable by hydraulic pressure. The rotary drive source 7M can be mainly configured. The inner tube 5 is coaxially connected to the rotation shaft of the rotational drive source 7M during propulsion, and the outer tube 2 is passed through the outer side of the inner tube 5, but is not connected to the rotational drive source 7M and is simply a reader. It is only supported along 7L.

(Configuration of outer tube)
The outer tube 2 is formed by connecting a plurality of unit outer tubes 20 in series according to the insertion depth, for example. As shown in FIG. 4, the unit outer tube 20 is a joint device in which a resin tube portion 21 occupying substantially the entire longitudinal direction is formed of a resin such as polyethylene, and one end portion of the resin tube portion has a female screw portion 22 a. What attached 22 and the joint apparatus 23 which has the external thread part 23a at the other end part can be used. However, in the present embodiment, as the leading outer tube 2, a tube with a ring bit holder 26 attached to the tip as shown in FIG. 5 is used. These joint devices 22 and 23 are made of a highly rigid material such as steel. As a specific example of the resin pipe portion, for example, Hishi pipe HPPE (high performance polyethylene) manufactured by Mitsubishi Plastics, Inc. can be suitably used.

For example, as shown in FIG. 4, the fitting structure between the joint device and the resin pipe portion has a male screw portion 24 a on the outer peripheral surface at the pipe attachment side end of the joint devices 22 and 23, and the resin pipe portion 21. The inner tube portion 24 having an outer diameter equal to or slightly smaller than the inner diameter, and the female screw portion 25a opposite to the male screw portion 24a of the inner tube portion 24 on the inner peripheral surface, and the outer diameter of the resin tube portion 21 A double structure portion DB comprising an outer tube portion 25 having the same or slightly larger inner diameter is provided, and an end portion 21S of the resin tube portion 21 is connected to a male screw portion 24a on the outer peripheral surface of the inner tube portion 24 and a female portion on the inner peripheral surface of the outer tube portion 25. It is preferable that the joint devices 22 and 23 are attached to the resin pipe portion 21 by being sandwiched in a gap with the screw portion 25a. In this case, a female screw part that is screwed with the male screw part 24a on the outer peripheral surface of the inner pipe part of the joint device 22, 23 is formed on the inner surface of the end part 21S of the resin pipe part, or the end part of the resin pipe part Although it is desirable to form on the outer surface of 21S a male threaded portion that is threadedly engaged with the female threaded portion 25a on the inner peripheral surface of the outer tube portion of the joint device, the material of the resin tube portion 21 is the joint device 22, even if not formed. If the male and female screw portions 24a and 25a are softer to some extent, the screw threads of these screw portions 24a and 25a bite into the resin tube portion 21 during clamping and fixing, so that they can be fixed without problems.

In particular, the coupling devices 22 and 23 are preferably formed so that the tip of the inner tube portion 24 protrudes from the tip of the outer tube portion 25 as shown in the figure. With such a configuration, even if the resin pipe portion 21 is bent, the end portion 21S clamping portion is not bent at all, so that the clamping and fixing between the inner tube portion 24 and the outer tube portion 25 of the joint devices 22 and 23 is difficult to be removed.

The unit outer pipe 20 is formed, for example, by forming the outer pipe portion 25 of the joint device slightly larger and separately, and after connecting the resin pipe portion 21 to the outer periphery of the inner pipe portion 24, on the outside of the resin pipe portion. After sliding the outer tube portion 25 arranged in advance or after that, the end portion 21S of the resin tube portion is positioned in the gap between the outer tube portion 25 and the inner tube portion 24, and then the outer tube portion 25 is compressed from the periphery. The resin tube portion end 21S is fixed in the gap between the outer tube portion 25 and the inner tube portion 24, and the thread of the female screw portion 25a on the inner peripheral surface of the outer tube portion 25 is bitten into the outer surface of the resin tube or screwed. Furthermore, the outer tube portion 25 can be manufactured by fixing it to the main body of the joint device 23 by welding W or the like.

  In this example, the ring bit 3 is coaxially connected to the tip of the outer tube 2, that is, the tip of the most advanced unit outer tube 20 via a ring bit holder 26 as shown in FIG. It can be attached to only freely. The ring bit holder 26 has an overall tubular shape as shown in an exploded state in FIG. 6, and has a clamping and fixing double structure DB similar to the above-described joint device at the end of the unit outer pipe at the base end. A ring-shaped holder clutch 27 having the same outer diameter is fixed coaxially by welding W or the like at the tip, and has an inner diameter enlarged portion 26D whose inner diameter is partially enlarged on the proximal end side of the holder clutch 27 It is. On the other hand, as shown in FIGS. 10 to 12 in addition to FIG. 5, the ring bit 3 is composed of a small-diameter tube shaft portion 30 and a distal-end large-diameter portion 31 on the proximal end side. A ring-shaped bit clutch 32 that engages with 27 is fixed by welding or the like, and an outer diameter enlarged portion 33 is provided at the proximal end portion of the small-diameter pipe shaft portion 30.

  In this example, the ring bit 3 is rotated by the bit holder 26 by accommodating the outer diameter enlarged portion 33 at the proximal end of the small diameter pipe shaft portion 30 of the ring bit 3 in the inner diameter enlarged portion 26D of the bit holder 26. It is supported freely, and is connected to the bit holder 26 in the front-rear direction with a play corresponding to the height of a step portion of a clutch, which will be described later. The holder clutch 27 and the bit clutch 32 have substantially similar shapes having a plurality of step portions 27A, 32A,... In the circumferential direction as shown in FIGS. 5 and the ring bit 3 are attached so that the formation surfaces of the stepped portions 27A, 32A,... Face each other as shown in FIG. Touched. In particular, the step portions 27A of the holder clutch 27 and the bit clutch 32 are mutually connected to the step portions 32A of the bit clutch 32 when the bit clutch 32 side is rotated in the drilling rotation direction. It is configured to rotate while moving back and forth by the height of the step portion without being caught by the step portion 27A, and when it is rotated in the direction opposite to the drilling rotation direction, it is caught and does not rotate any further.

  On the other hand, in the ring bit 3, the outer diameter of the distal end large-diameter portion 31 is slightly larger than the outer diameter of the outer tube 2, and as shown in FIGS. Are provided with a plurality of bits 3a, 3a... And grooves 30D, 30D... In the circumferential direction from the base end to the middle in the longitudinal direction (not reaching the tip) along the axial direction on the inner peripheral surface. A plurality (six in the illustrated example) are formed. The function of the grooves 30D, 30D... Will be described later.

(Configuration of inner pipe)
On the other hand, the inner tube 5 of the present apparatus example can be formed by connecting a plurality of unit inner tubes 50 in series according to the insertion depth, for example. As shown in FIG. 13, the unit inner pipe 50 is formed of a material that is not easily bent (higher rigidity) than the outer pipe 2 but can be bent, such as a steel pipe, and has a female screw portion 51 at one end as a connecting means. And the other end portion formed with the male screw portion 52 can be used. However, as shown in FIG. 5, if the leading portion 50F protruding forward from the ring bit 3 in the inner tube 5 is easily bent, the accuracy at the time of linear propulsion to be described later becomes low. It is desirable to make the rigidity higher than the part and make it difficult to bend. In particular, if the boundary between the leading portion 50F and the base end side portion is located exactly in the vicinity of the front end portion of the ring bit 3, a leading dedicated unit tube made of a material having higher rigidity is prepared as a unit tube for the leading portion 50F. This is preferable because it can be completed.
By the way, when the rigidity of the outer tube 2 is included, the following equation (1) is obtained.
Inner pipe leading part> Inner pipe proximal end part> Outer pipe (1)
As described above, unless the outer tube 2 is bent more easily than the inner tube 5, smooth and sharp curve promotion becomes very difficult, and the leading portion 50 </ b> F protruding from the ring bit 3 in the inner tube 5 is the base end. If it is not difficult to bend more than the side part, the straightness during propulsion will be low.

In this example, the portion corresponding to the ring bit 3 in the inner tube 5 is constituted by a substantially cylindrical bit device 55 having an engaging portion. As shown in FIG. 14 and FIG. 15 in addition to FIG. 5, the bit device 55 has an outer diameter that can be fitted inside the ring bit 3, and means for connecting the unit inner pipe at the distal end and the proximal end. Are provided with a female screw portion 55A and a male screw portion 55B, respectively, and a plurality of ridges 55C, 55C,... Along the longitudinal direction are provided on the outer peripheral surface of the ring bit 3 corresponding to the grooves 30D, 30D,. 3 in the illustrated example). Each ridge 55C of the bit device 55, when obtained by advancing the inner tube 5 is inserted respectively to the front end limit of the corresponding the ring bit grooves 30D, more because not inserted, giving the advancing force on the inner tube 5 The inner pipe 5 advances while pulling the ring bit 3 and the outer pipe 2 connected thereto. Then the inner tube 5 by when rotating the engagement of circumferential ridge portions 55C and the groove 30D each other in this state, the rotational force of the inner tube 5 is transmitted to the ring bit 3, whereby the ring bit 3 outer tube 2 It is designed to be rotated with respect to. On the other hand, when retracting the inner tube 5 relative to the outer tube 2, convex portions 55C when is adapted disengaged from the ring bit 3 the inner surface of the groove 30D, is further retracted bit device 55 of the bit device 55 is a ring The bit holder 26 is separated from the rear and is retracted into the rear outer tube 2. In order to facilitate insertion of the convex portion 55C, it is less than the groove that number, preferably to about half in particular.

On the other hand, in this example, a tapered bit 6 having a pressure receiving surface 60 inclined with respect to the axial direction is attached to the tip of the inner tube 5 via a bit reducer 56 (which also constitutes the inner tube 5). As shown in FIG. 16 in addition to FIG. 5, the bit reducer 56 has a male screw portion 56A as a connecting means at the base end portion, and is screwed and connected to the distal female screw portion 51 of the inner tube 5 by this male screw portion 56A. Is done. An engaging groove 56 </ b> B is provided at the tip of the bit reducer 56 to connect the tapered bit 6. The inner space 56C serves as a passage for circulating the drilled water.

For example, as shown in FIGS. 17 to 21 in addition to FIG. 5, the tapered bit 6 has a substantially cylindrical shape and has a pressure receiving surface 60 formed of a flat surface inclined with respect to the axial direction on the head. . The outer diameter of the tapered bit 6 is slightly larger diameter than the ring bit 3, and is suitably used to form a plurality of convex portions 61, 61 along the axial direction ... in the circumferential direction in a proximal outer peripheral surface. Such tapered bit 6, the structure can be manufactured at low cost by utilizing the casting or the like for simple, even kill buried in the ground, as will be described later, is not such as facilities Engineering cost soars markedly.

In particular, in this example, as shown in FIG. 20 , an engagement hole 62 for engaging the bit reducer 56 is formed in the proximal end surface of the tapered bit 6 along the axial direction. An engaging convex portion 62 p is projected from the inner peripheral surface of the base end portion of the joint hole 62. By inserting and engaging the bit reducer 56 in the engagement hole 62 so that the engagement protrusion 62p passes along the engagement groove 56B of the bit reducer 56, the tapered bit 6 is formed at the tip of the inner tube 5. Is attached.

  An injection port 63 facing the direction parallel to the inclination direction of the pressure receiving surface 60 is formed at the center in the width direction at the tip of the non-pressure receiving surface of the taper bit 6. The inside of the engagement hole 62 is communicated. In particular, in the illustrated example, a flat inclined surface 65 is also formed on the opposite surface, and an injection port 63 is provided on the inclined surface 65. The injection direction of the injection port 63 is such that the axial direction D1 is the x axis, the plane including the x axis and the tip position of the pressure receiving surface 60 is the xy plane, and the inclination with respect to the x axis in the xy plane is When the angle is θ1 and the inclination angle around the x-axis with respect to the y-axis is θ2, both the conditions of θ1 = pressure-receiving surface inclination angle and θ2 = 0 ° are satisfied. θ1 is preferably about ± 5 ° with respect to the inclination angle of the pressure-receiving surface, and θ2 is preferably 0 °.

<Liquefaction countermeasures for ground where there is a risk of liquefaction directly under existing structures>
Next, the liquefaction countermeasure method according to the present invention using the above-described apparatus example will be described. First, as shown in FIG. 22, a guide tube 100 having a length at least about the same as the length of the inner tube leading portion 50F is inserted into the insertion portion of the ground G around the existing structure CS. Then, although not shown, the inner pipe leading portion 50F is connected to the rotation drive shaft of the rotary propulsion device 7, and the inner pipe leading portion 50F is inserted only by rotational propulsion or propulsion. This propulsion is performed by lowering the rotational drive source of the rotary propulsion device 7. Further, at this time, it is desirable to propel it while supplying drilling water such as muddy water to the tip through the inner pipe 5 and the flow path 64 of the tapered bit 6. Although the installation of the guide tube 100 can be omitted, since the propulsion direction is easily shifted because the propulsion is initially performed only by the inner tube 5, it is preferable to use the guide tube 100 as in the illustrated example. .

  Next, although not shown, the tip of the bit device 55 protruding from the tip of the ring bit 3 in a state where the unit inner tube 50 having the bit device 55 attached to the tip is inserted into the outer tube 2 to which the ring bit 3 is attached, It is added to the proximal end of the inner pipe leading portion 50F propelled first (see FIG. 5). Thereafter, the base end portion of the unit inner pipe 50 that has been added is connected to the rotational drive source.

  Thereafter, both the inner pipe 5 and the outer pipe 2 are further propelled into the ground as shown in FIG. At this time, in this example, the direction control can be performed at the time of propulsion.

More specifically, when performing linear propulsion, as shown in FIG. 25, the rotary propulsion device 7 applies rotational force and propulsive force to the inner tube 5, and the inner tube 5 is drilled by the tapered bit 6 at the tip of the inner tube 5 while drilling. 5 is propelled linearly into the ground. In this case, the tip of the taper bit 6 has the pressure receiving surface 60, but advances while rotating around the axis, so that the influence of the pressure receiving by the pressure receiving surface 60 is canceled and the hole can be drilled linearly. . Further, although the direction of spraying the drilling water from the tip of the taper bit 6 is inclined with respect to the propulsion direction (axial center direction D1), the shaft hole is rotated around the axial center along with the rotation of the drilling shaft 5 and the taper bit 6. As a result, the drilling water can be sprayed over a wide range in front of the taper bit 6, and smooth linear propulsion becomes possible.

Further, during this linear propulsion, the rotational force and propulsive force of the inner tube 5 are applied to the ring bit 3 by meshing between the convex portion 55C of the bit device 55 constituting the inner tube 5 and the groove portion 30D of the ring bit (FIG. 5). reference). As described above, the ring bit 3 is the step portions 32A of the outer tube 2 tip and is rotatably supported on the bit clutch 32 and the holder clutch 27 by the bit holder 26 ..., 27A ... mutually drilling bit clutch 32A side When rotating in the rotation direction, the ring bit 3 is allowed to rotate without being caught, and the outer tube 2 is subjected to the binding force of the surrounding ground, so the outer tube 2 is not rotated and only the ring bit 3 rotates. . Since the ring bit 3 is connected to the front end of the outer tube 2 in the front-rear direction, the outer tube 2 is pulled by the inner tube 5 so as to be pulled by the propulsive force applied to the ring bit 3.

On the other hand, when the curve is propelled, as shown in FIG. 26, the rotation of the inner tube 5 is stopped in a state where the tip of the pressure receiving surface 60 of the tapered bit 6 is located on the side to be bent with respect to the rotation axis. In this state, only the propulsive force is applied to the inner tube 5 by the rotary propulsion device 7 . At this time, the propulsion direction of the taper bit 6 is gradually changed by the force applied to the pressure receiving surface 60 of the taper bit 6, and the inner tube 5 can be propelled into the ground in a curved manner. Further, since the drilling water is sprayed toward the propulsion destination of the taper bit 6, the ground of the propulsion destination can be surely relaxed, and as a result, the taper bit 6 can easily escape to the loose ground side. Thus, the direction of drilling can be changed more smoothly and reliably and at a steeper angle.

Further, when this curve is propelled, the propulsive force of the inner tube 5 is given to the ring bit 3 by the meshing of the protrusion 55C of the bit device 55 constituting the inner tube 5 and the groove 30D on the inner peripheral surface of the ring bit. Since the ring bit 3 is connected to the front end of the outer tube 2 in the front-rear direction, the outer tube 2 is propelled in a curved manner by the inner tube 5 being pulled by the thrust applied to the ring bit 3. . In addition, although this curve propulsion can be propelled in a three-dimensional curve and is bent in the vertical plane direction in the illustrated example, it can also be bent in the horizontal plane direction.

  Further, in the direction control, it is necessary to know the position of the tip of the inner tube 5, the posture, the trajectory, and the like. For this reason, a gyroscope or a goniometer is built in the distal end portion of the inner tube 5 (for example, the inner tube leading portion 50F) to measure the posture or trajectory, or an electromagnetic wave transmitter is installed in the distal end portion of the inner tube 5 to Receiving electromagnetic waves to measure the position of the tip of the inner tube, or measuring the position of the tip of the inner tube 5 by measuring the elastic wave generated by excavation of the tip bit 6 of the inner tube 5 Can do.

Thus, as shown in FIG. 23, the inner pipe 5 is made to progress in an arc from the ground surface around the existing structure CS to the improvement target layer, and thereafter the improvement target layer is advanced along the horizontal direction to obtain the existing structure. While forming the insertion hole H that reaches the target ground directly under the object CS, the outer tube 2 is inserted into the insertion hole H that is sequentially formed, so that the outer tube 2 is inserted to reach directly under the existing structure CS. it can.

Then, in a desired route (which may be a straight route or a tortuous route such as an S-shape), at least the target ground immediately below the existing structure CS from the ground surface around the existing structure CS If the outer tube 2 is propelled to a predetermined depth that reaches, the taper bit 6 is removed from the inner tube tip as shown in FIG. Specifically, first, the inner tube 5 is retracted with respect to the outer tube 2, and the protruding strips 61, 61... At the base end of the taper bit 6 are inserted between the bits 3a, 3a on the front surface of the ring bit 3. Thereafter, in this state, when a rotational force in the direction opposite to that at the time of drilling is applied to the inner tube 5, a rotational force in the direction opposite to that at the time of drilling is also applied to the taper bit 6. 61, 61... Are caught by the bit 3a of the ring bit, and the rotational force in the direction opposite to that at the time of drilling is also transmitted to the ring bit 3. At this time, the step 32A of the bit clutch 32 of the ring bit 3 is Since it is caught by the stepped portion 27A of the holder clutch 27 at the tip of the outer tube 2 that is constrained not to rotate by the surrounding ground, the taper bit 6 can hardly rotate in the opposite direction. When the inner pipe 5 is pulled out while rotating in the opposite direction to the drilling state without the taper bit 6 rotating, the engagement convex portion 62p of the taper bit 6 is engaged with the bit reducer 56 at the distal end of the inner pipe 5. It can be pulled out along the groove 56B . By releasing the engagement, the tapered bit 6 can be detached from the tip of the inner tube 5.

  When the taper bit 6 is removed, the taper bit 6 is left in the ground in front of the outer tube 2 and the outer tube 2 is inserted into the ground as it is (in other words, the outer tube 2 is directly under the existing structure CS. The inner tube 5 is pulled out from the outer tube 2 by the rotary propulsion device 7 in a state where the taper bit 6 is detained at the removal position in front of the ground. Thus, as shown in FIG. 27, the outer pipe 2 can be built in the ground so as to reach at least the target ground from the ground surface around the existing structure CS. In this case, the tapered bit 6 may be buried in the ground as it is, or a shaft may be dug in advance or in the vicinity of the bit removal position, and the removed tapered bit 6 may be recovered.

  Thus, the outer pipe 2 built in the ground is used for infiltration injection of the ground improvement agent, such as a casing pipe for inserting the injection pipe of the ground improvement agent in the present invention. That is, when the outer pipe 2 is built up to the ground as shown in FIG. 27, the injection pipe 200 is inserted into the outer pipe 2, and then the outer pipe 2 is left as shown in FIG. After extracting 2, the ground improver is injected into the target ground through the injection pipe 200.

  As this injection method, the one proposed in Japanese Patent Application Laid-Open No. 2000-80640 by the present applicant is suitable. An injection state when this is applied is shown in FIG. That is, the injection outer tube 201 having a plurality of external packers 206, 206... On the outer surface portion with an interval in the axial direction and the injection ports 207, 207. After inserting into the target ground through the outer tube 2 built in the ground in this way, the outer tube 2 is pulled out from the insertion hole H leaving the injection outer tube 201.

Thereby, the injection outer tube 201 is built in the insertion hole H. Thereafter, the adjacent external packers 206 and 206 in the outer injection tube 201 are swelled and brought into close contact with the wall surface of the insertion hole H. In order to swell the external packers 206, 206, the inside is filled with a swell fluid such as water or air, preferably a caking material such as cement or cement bentonite. On the other hand, the injection inner tube 201 has a plurality of internal packers 216 and 216 on the outer surface thereof spaced apart in the axial direction, and a discharge port 217 between the adjacent inner packers 216 and 216. The tube 210 is inserted, and the adjacent internal packers 216 and 216 are bulged and brought into close contact with the inner surface of the injection outer tube 201. The bulging fluid similar to the external packer can be used for the bulging of the internal packers 216 and 216. At this time, a region surrounded by the adjacent external packers 206, 206, the wall surface of the insertion hole H, and the outer surface of the injection outer tube 201 is a space that is not filled with anything.

Thereafter, the ground improver is infiltrated through the inner pipe 210, the discharge port 217 of the inner pipe 210, the outer pipe 200, the inlet 207 of the outer pipe 201 , and the space between adjacent packers in this order. inject. Sites L and L indicated by a two-dot chain line in the figure are penetration sites of the ground improvement agent. Thus, it is possible to improve the target ground by infiltrating and injecting the ground improving agent into the ground that may be liquefied directly under the existing structure CS and solidifying the ground. As the ground improvement agent, it is preferable from the viewpoint of osmotic injection to use a water glass type chemical solution, particularly a silica sol type chemical solution. The gel time in the soil is preferably about 1 to 10 hours. The injection rate can be up to about 40 liters / minute.

In order to simplify the construction and improve the efficiency when injecting the ground improver, the injection outer tube 201 is used as the outer hole outer tube 2, and this injection outer tube 201 is directly connected to the inner tube for drilling when the insertion hole H is formed. 5 can also be pulled in. However, in this case, since the packer 206 protrudes from the outer surface of the outer tube 201 to be pulled in, it is difficult to pull it in by the inner tube 5. Therefore, in this case, as shown in FIG. 30, a plurality of injection ports 227 are provided at intervals in the longitudinal direction, and the injection outer tube 220 that is not overhanging on the outer peripheral surface (that is, flush) is inserted into the above-described drilling hole. It is desirable to pull in by the tube 5. In this case, each injection port 227 is closed with a sleeve SL so that it can be opened and closed. At the time of injection, the sleeve SL is deformed by the injection pressure (this state is indicated by a two-dot chain line), and the ground improving agent G is not injected. It is desirable that the sleeve SL be restored to close the injection port 227 when injected into the ground outside the tube 220 and the injection of the ground improving agent G is stopped.

  Further, even when the outer tube 2 having no injection port is inserted, a hole forming means such as a drilling device (not shown) is inserted therein to form an injection port, which can be used as an outer injection tube. it can.

<Others>
(A) In the above example, other known connection structures can be applied as the connection means between the unit outer tube 20 and the unit inner tube 50 in addition to the screw connection as in the above example.
(B) In the above example, not only the tapered bit 6 in the illustrated example but also a bent shaft-shaped taper bit and an arc-shaped taper bit form a pressure-receiving surface whose peripheral surface is inclined with respect to the axial direction. So available.
(C) In the above example, the ridges 55C, 55C... May be provided directly at predetermined positions on the outer surface of the unit inner tube 50 corresponding to the ring bit 3 without using the bit device 55.
(D) In the above example, the ring bit can be omitted if the diameter of the tapered bit is equal to or greater than the outer diameter of the outer tube.
(E) In the above example, as a means for detachably attaching the taper bit 6, a known detachable connection structure can be adopted in addition to the screw connection.

  The present invention is applied when various buildings and civil engineering structures such as airport runways and factory large tanks are already installed on the sand ground.

It is an outline explanatory view of the present invention. It is an outline explanatory view of the present invention. It is a construction state schematic diagram of a pipe erection device. It is a partially broken view of a unit outer tube. It is a principal part schematic diagram. It is an exploded state broken view of a ring bit holder. It is the front view and side view of a holder clutch. It is the side view and front view of a bit clutch. It is a side view which shows the meshing state of a clutch. It is a broken view of a ring bit and a holder part. It is a front view of a ring bit. It is a principal part longitudinal cross-sectional view of a ring bit. It is a longitudinal cross-sectional view of a unit inner pipe. It is a fracture view of a bit device. It is a front view of a bit device. It is a fracture view of a bit reducer. It is a front view of a taper bit. It is a top view of a taper bit. It is a bottom surface (back surface of a pressure receiving surface) of a taper bit. It is a right view of a taper bit. It is a longitudinal cross-sectional view of a taper bit. It is a construction procedure diagram. It is a construction procedure diagram. It is a construction procedure diagram. It is explanatory drawing of direction control. It is explanatory drawing of direction control. It is a construction guideline for ground improvement. It is a construction guideline for ground improvement. It is a principal part expanded longitudinal sectional view which shows the example of injection | pouring of a ground improvement agent. It is a principal part expanded vertical sectional view which shows the example of injection | pouring of another ground improvement agent.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Erecting device, 2 ... Outer pipe | tube, 3 ... Ring bit, 5 ... Inner pipe | tube (drilling shaft), 6 ... Taper bit, 7 ... Rotation propulsion apparatus, 63 ... Injection port.