JP5931601B2 - Connection structure of inner pipes constituting double pipes - Google Patents

Description

  The present invention relates to a connection structure of inner pipes constituting a double pipe used when a ground improvement body is created in the ground.

  There are various ground improvement methods for soft ground and ground that does not have the desired strength. One method is to use a device consisting of a casing, an inner rod that slides inside the casing, and a stirring blade (stirring bit) attached to the tip of the casing, and a clearance (flow path) between the casing and the inner rod. Crush the ground with water pressure while jetting compressed air and water, then spread the stirring blade and rotate the rod, and improve the cement milk as the main component while stirring the ground ground with the stirring blade A ground improvement method for creating a ground improvement body (ground improvement pile) having a desired diameter by spraying and stirring a reaction material or the like that promotes hardening of the material or the improvement material is generally used.

  For example, a method of creating a ground improvement pile directly under an existing building B using a diameter expanding excavator will be described with reference to FIGS.

  As shown in FIG. 7, it is not easy to improve the ground directly under the existing building B with high accuracy, particularly when the existing building B has a large plan scale. Therefore, as shown in FIG. 7, the excavator M equipped with the swivel is used, and the casing C and the rod R are moved forward to the improved ground layer immediately below the existing building B while sequentially connecting the casing and the rod. In the process of moving forward, pressure water is sprayed onto the ground via the flow path between the casing C and the rod R to loosen the ground. Further, as shown in FIG. 8, the rod R is projected from the tip of the casing C (direction S1), and the stirring blades W, W provided rotatably at the tip of the rod R are spread and rotated (direction S2). ), Providing the improvement material forward through the flow path between the rod R and the casing C (S3 direction), spraying the improvement material forward (S4 direction) and stirring together with the ground, A ground improvement body P that extends horizontally directly below is created. It should be noted that by creating a plurality of horizontal ground improvement bodies P so as to be in contact with each other, or so as to be provided at a fixed interval, the desired soft ground directly below the existing building B regardless of the plane scale. Etc. can be reinforced with improved ground.

  In the improvement method shown in FIG. 8, the rod R is slid relative to the casing C to advance, and the ground and the improvement material are agitated by the stirring blade W while the improvement material is injected into the ground in the process of this advancement. In this method, the ground improvement body P is gradually created forward while mixing.

  By the way, as described above, Patent Documents 1 and 2 disclose techniques that can be applied when sequentially extending the length of a double pipe made of a casing or a rod.

  Patent Document 1 discloses a curved hole drilling device capable of drilling a curved hole. An outer tube formed with the same curvature as the curved hole, a hole drilling means disposed at the front end of the outer tube, and a front end A linear drilling shaft that is attached to the drilling means and can rotate around the axis in the outer tube. The front end is connected to the rear end of the drilling shaft in a bent state, and rotates around the axis in the outer tube. A linear extension shaft is provided, and by engaging the rear end gear provided at the rear end portion of the drilling shaft and the front end gear provided at the front end portion of the extension shaft, The hole drilling means is configured to rotate. That is, the connecting means disclosed herein is a gear.

  On the other hand, Patent Document 2 discloses a flexible boring rod composed of an intermediate rod, a male rod, and a female rod. The intermediate rod and the male rod are connected via a joint and are connected to be bent in two directions orthogonal to each other by a pin. In addition, the intermediate rod and the female rod are connected via a joint, and are connected so as to be bent in two directions orthogonal to each other by a pin. That is, the connection means disclosed here is a pin.

  Thus, when trying to connect the outer pipes that constitute the double pipe with the gears and pins disclosed in Patent Documents 1 and 2, the inner pipes, or between the outer pipes and the inner pipes via a fixing screw. In many cases, the length of the inner pipe and the outer pipe are different in the process of repeating the connection, and the curvatures of the outer pipe and the inner pipe are different. Therefore, when the inner tube is bent while being bent along the bend of the outer tube, the inner tube may jump out. In such a case, if the inner pipes are forcibly connected with screws, pins, gears, etc., the connecting work itself becomes extremely difficult, and the inner pipe itself may be damaged.

  Also, when improving the ground while rotating at least one of the pipes that make up the double pipe, when connecting the pipes with screws, it is necessary to rotate both the outer and inner pipes. However, when performing ground improvement, a repeated bending load acts as the connection rotates, and the bending strength decreases due to this repeated bending load, resulting in the pressure resistance of the inner pipe. There is a concern that the property may be reduced.

JP 2006-28751 A JP 2001-40986 A

  The present invention has been made in view of the problems described above, and relates to a connection structure for an inner pipe that constitutes a double pipe used when creating a ground improvement body in the ground, and is easily connected and flexible. It is an object of the present invention to provide a connection structure for an inner pipe that constitutes a highly durable double pipe that can reduce the repeated bending load and the like acting by the connection structure.

  In order to achieve the above object, the connection structure of the inner pipe constituting the double pipe according to the present invention includes a first flow path between the inner pipe and the outer pipe constituting the double pipe, and a second inside the inner pipe. In a double pipe in which a fluid flows through a flow path, a plurality of inner pipes are connected to extend the length of the inner pipe, and the inner pipe is connected to each other. Of the tubes, one inner tube has an accommodation groove extending from the opening to the groove bottom at its end, and the other inner tube has an insert accommodated in the accommodation groove at its end. The groove has a thread on the opening side of its end, and the insert has, in order from the distal end side when inserted into the receiving groove, a place where an O-ring is attached and a place with a thread, and the insert is accommodated. It is inserted into the groove, both threaded parts are screwed together, and the part having the threaded part of the insert is fed forward from the threaded part of the receiving groove. At this stage, the O-ring and the receiving groove are in contact with each other to form a seal structure, and a gap is formed between the tip of the insert and the groove bottom of the receiving groove. The relative movement of the inner pipe is guaranteed.

  The connection structure of the inner pipe of the present invention relates to the connection structure of the inner pipes constituting the double pipe, and the inner pipes are connected to each other so as to be movable relative to each other rather than a rigid connection such as a pin, a screw or a gear. In other words, it is a connection structure that is connected with play, which makes it easy to connect the inner pipes and eliminates repeated bending loads acting on the inner pipes. A double pipe having a pipe can be formed.

  The double pipe is composed of an outer pipe and an inner pipe, and is mainly used when creating a ground improvement body as described above. For this reason, the outer pipe and the inner pipe are sequentially connected together to improve the ground. It reaches the layer and is used to create a ground improvement body of a predetermined length. For example, the outer tube can be composed of a casing, and the inner tube can be composed of a hollow rod that can slide within the casing.

  The fluid flows through the first flow path between the inner pipe and the outer pipe constituting the double pipe and the second flow path inside the inner pipe. For example, pressure water flows through the first flow path, and the casing This pressure water is discharged from the tip, and the ground can be crushed and cut. On the other hand, a high-pressure improvement material circulates in the second flow path, and this improvement material is discharged from the tip of the inner tube and the ground improvement body having a desired diameter while being stirred and mixed with the ground by a stirring blade rotating at the tip of the casing. Can be created.

  As a configuration of the inner pipes that are sequentially connected, an accommodation groove extending from the opening to the groove bottom is provided at one end of the two ends, and an insert is provided at the other end. That is, when connecting two inner pipes, one end of one inner pipe and the other end of the other inner pipe are connected, and at this time, the other end of the other inner pipe is connected. The insertion body of the part becomes a male member, and the accommodation groove at one end of one inner tube becomes the female member.

  The inner tube itself has a hollow (through hole), but at one end portion, for example, an accommodation groove having a different inner diameter from the through hole is provided.

  Therefore, the “groove bottom” of the housing groove is the end position of the housing groove located inside the inner tube by a predetermined length from the opening at the end of the inner tube. (Through hole) communicates.

  And the threading is formed in the opening side which faces the exterior among accommodation grooves.

  On the other hand, the insert formed at the other end inserted into the receiving groove is formed with a place where an O-ring is attached and a place with threading in order from the tip side when inserted into the receiving groove. Yes.

  When the insert of the other inner tube is inserted into the housing groove of one of the two inner tubes, the “location where the O-ring is attached” is first inserted into the housing groove, and then “ The "location having" is inserted into the receiving groove, and the threading of this "location having threading" and the threading of the receiving groove are screwed together.

  By screwing both threaded parts and sending the “location with threading” of the insert forward from the threading of the receiving groove, the “location where the O-ring is attached” and the “location with threading” of the insert are In either case, the thread is sent to the “groove bottom” side of the housing groove. That is, in order to form such a state, the length from the “thread cutting” of the housing groove to the groove bottom is longer than the total length of “the place where the O-ring is attached” and “the part having the threading” of the insert. The receiving groove and the insert are formed so as to be.

  The O-ring and the receiving groove come into contact with each other to form a seal structure at a stage where the threaded portion of the insert is fed forward of the receiving groove. Further, based on the above length relationship between the receiving groove and the insert, a gap is formed between the tip of the insert and the groove bottom of the receiving groove, and the relative movement of both inner pipes is guaranteed by this gap.

  In this way, when the “location having threading” of the insert passes through the threading of the receiving groove, both cannot be detached, and the “location where the O-ring is attached” of the insert and the wall of the receiving groove The seal structure is formed by contact, and the insert is slidably received in the receiving groove. Further, the pressure resistance of the connection portion is ensured by the “location where the O-ring is attached”.

  Since the inner pipes are not rigidly connected to each other in this way, repeated bending load does not act on the connection place between the inner pipes when creating a ground improvement body while rotating the double pipe, etc. The problem of lowering the bending strength at the inner pipe connection location due to this repeated bending load is eliminated.

  Furthermore, since there is play at the connection location between the inner pipes, this play acts as a buffering part against pulling or pushing after the inner pipe connection, and excessive external force (compression force, tensile force) acts on the connection location. Nor.

  Also, when the inner tube is bent along the bend of the outer tube, even if the curvatures of both the inner tube and the outer tube are different, the inner tubes can be easily connected to each other and the inner tubes are forcibly connected. Problems such as damage can not occur.

  Here, as another embodiment of the connection structure, the one inner pipe is fitted into one end of a hollow connection pipe, and extends from the opening to the groove bottom at the other end of the connection pipe. The form in which the accommodation groove | channel is formed can be mentioned.

  The connection structure of the present embodiment uses a hollow connection pipe for connecting the inner pipes, the end of the inner pipe is connected to one end of the connection pipe, and the configuration described above at the other end of the connection pipe The receiving groove is provided.

  In this form, there is a form in which the end of the inner pipe is fitted and connected to one end of the connection pipe, a form in which both are screwed together and connected.

  By using a ground improvement body forming device having a double pipe having the inner pipe connection structure as a component, for example, a ground improvement body can be easily and accurately created directly under an existing building. It becomes possible.

  In addition to the case where ground improvement body (ground improvement pile) is created in the improved ground for the purpose of liquefaction measures, seismic reinforcement measures, settlement measures, etc. This can also be applied to the case where the anchor fixing portion in the earth anchor method is constructed with a ground improvement body. In particular, in the ground improvement for each purpose described above, the apparatus of the present invention is suitable for construction where improvement work is difficult, such as performing ground improvement directly under an existing building having a large planar scale as shown in FIG.

  Here, as an embodiment of the apparatus configuration of the ground improvement body generating apparatus described above, a casing that constitutes the outer pipe of the double pipe, and a sliding inside of the casing that can be freely moved in and out of the front end of the casing, are rotatable. A hollow rod constituting the inner tube of the double tube, and a slide that is slidable within the hollow of the rod and that has a flow path therein, the tip of which protrudes forward from the tip of the rod. A piston with two agitating blades rotatably mounted, a pipe fixed to the piston in the hollow of the rod and in fluid communication with the flow path of the piston, and a swivel for moving the casing and rod forward Provided in the flow path between the excavator and the casing and the rod for crushing and cutting the ground, and provided in the hollow of the rod with pressure water and high pressure improvement material for extruding the piston Compressor that provides pressure air for forming, tank that contains water and provided in the hollow of the flow path and rod, and contains improved materials such as cement milk, hardening accelerator, retarder, and provided to the inner pipe The form comprised from a tank etc. can be mentioned.

  As can be understood from the above description, according to the connection structure of the inner pipes constituting the double pipe of the present invention, the inner pipes are connected to each other so that the inner pipes cannot be detached and are relatively movable. Therefore, a flexible connection structure can reduce the repeated bending load acting on the connection location, and a highly durable inner tube connection structure can be formed.

It is a longitudinal cross-sectional view of a part of the double pipe. It is a schematic diagram which shows the state before the connection of an inner pipe. It is a schematic diagram of Embodiment 1 of the connection structure of an inner pipe. It is a schematic diagram of Embodiment 2 of the connection structure of an inner pipe. (A) is the schematic diagram which showed the ground improvement body formation apparatus, Comprising: It is the figure which showed the state in which the stirring blade and rod of the closed attitude | position were accommodated in the casing, (b) FIG. 5 is a view showing a state in which a stirring blade is formed in an extended posture in which the piston protrudes from the rod and is opened, and the improving material is discharged from the outer peripheral surface of the rod while the stirring blade rotates. It is the flowchart explaining the ground improvement body construction method to which the apparatus shown in FIG. 5 was applied in order of (a), (b), (c). It is a mimetic diagram explaining one embodiment of a ground improvement method just under an existing building. It is the schematic diagram which showed the state which is discharging the improvement material, rotating a stirring blade using a ground improvement body formation apparatus.

  Hereinafter, with reference to the drawings, the inner pipe connection structure of the present invention, a double pipe including the same, a ground improvement forming device provided at the tip of the double pipe, and a ground improvement body using the device A method will be described.

(Double pipe)
FIG. 1 is a longitudinal sectional view of a part of a double tube. As shown in the figure, the double pipe is composed of, for example, an outer pipe 20 made of a casing and an inner pipe 10 made of a hollow rod arranged inside thereof, and fluid flows between the inner pipe and the outer pipe. (X1 direction) The 1st flow path 30 and the 2nd flow path 40 through which a fluid distribute | circulates inside the inner pipe 10 (X2 direction) are formed. For example, pressure water flows through the first channel 30 as fluid, and the pressure water is discharged from the front end of the casing to crush and cut the ground. Further, a high-pressure improving material flows as a fluid in the second flow path 40, and the improving material is discharged from the tip of the inner tube 10 and the like, and is stirred and mixed with the ground by a stirring blade (not shown) that rotates at the casing tip. However, the ground improvement body of a desired diameter is created.

  The inner tube 10 is formed with an insert 10A at one of its two ends, and a receiving groove 10B into which the insert 10A of the separate inner tube 10 is inserted at the other end. Then, a separate insert 10A of the inner tube 10 is inserted into the receiving groove 10B of the inner tube 10 to form the inner tube connection structure 100.

(Embodiment 1 of inner pipe connection structure)
The structure of the inner pipe connection structure 100 will be described with reference to FIGS. Here, FIG. 2 is a schematic diagram showing a state before connection of the inner pipe, and FIG. 3 is a schematic diagram of Embodiment 1 of the connection structure of the inner pipe.

  The insertion body 10A at the end of one of the two inner pipes 10 and 10 to be connected is attached with an O-ring in order from the distal end side when inserted into the housing groove 10B of the separate inner pipe 10. 1 and 2 having threading, and the total length of these two locations is t1.

  At the location 1 where the O-ring is attached, the O-ring 3 is fitted in the O-ring attachment groove.

  On the other hand, an accommodation groove 10B extending from the opening 4 to the groove bottom 6 is formed at the end of one inner tube 10 into which the insert 10A of the other inner tube 10 is inserted. Is provided with a threading 5 on the opening side of its end, and the length from the inner end of the threading 5 to the groove bottom 6 is t2, and this length t2 is longer than the length t1 of the insert 10A. Is set.

  As shown in FIG. 2, the insert 10A of the other inner tube 10 is inserted into the receiving groove 10B of the one inner tube 10 (Y direction in the figure), and both threads are screwed together during this insertion process. By sending the part 2 having the threading of 10A forward of the threading 5 of the receiving groove 10B, the part 1 where the O-ring of the insertion body 10A is attached and the part 2 having the threading are both threaded 5 of the receiving groove 10B. As shown in FIG. 3, the inner pipe connection structure 100 is formed. In addition, about the number of the thread of the part 2 which has the threading 5 or threading, about three is preferable. This is because with one or two threads, there is a risk of pulling out, and conversely, when there are five or more threads, labor is required for connection.

  As shown in the figure, since the length t2 from the inner end of the threading 5 to the groove bottom 6 in the accommodation groove 10B is set longer than the length t1 of the insert 10A, the connection structure 100 is formed. At this time, a gap G (length Δt) is formed between the two, and the inner pipes 10 and 10 can be relatively moved by this gap G. Furthermore, in this connection structure 100, both the inner pipes 10 and 10 are not fixed, and are mutually rotatable. Therefore, in the connection structure 100, an excessive bending load does not act. Therefore, when the inner tube 10 is bent along the bend of the outer tube 20, the inner tubes 10 and 10 can be easily connected to each other even if the curvatures of the inner tube 10 and the outer tube 20 are different. The problem of damage to the connection structure that may occur when the inner tubes are forced to be bent and connected is not caused.

  Further, since there is play G in the connection structure 100, when a tensile force or pushing force acts on the connection structure 100, this play G acts as a buffer portion and an excessive compressive force or tensile force acts on the connection structure 100. In addition, the above-described excessive bending load does not act, and a highly durable connection structure is obtained.

  Furthermore, in the connection structure 100, the sealing performance is guaranteed between the O-ring 3 and the housing groove 10B, and the pressure resistance in the connection structure 100 is also guaranteed by the location 1 where the O-ring is attached.

(Embodiment 2 of inner pipe connection structure)
FIG. 4 is a schematic diagram of Embodiment 2 of the inner pipe connection structure. The connection structure 100A shown in the figure is formed by fitting the end portion 10B ′ of one inner tube 10 into the connection tube 50 and inserting a separate insert 10A of the inner tube 10 into the other end of the connection tube 50. Connection structure.

  That is, an accommodation groove 10B extending from the opening 4 to the groove bottom 6 is formed at the other end of the connecting pipe 50, and the accommodation groove 10B is provided with a thread 5 on the opening side of the end portion.

  Similar to the connection structure 100, this connection structure 100A also has a gap G having a length Δt that becomes play, and the inner tubes 10, 10 are connected to each other so as to be rotatable and slidable. The connection is easy, and an excessive bending load or the like does not act, resulting in a highly durable connection structure.

  Next, a method of forming a ground improvement body while extending the double pipe to the ground improvement area while sequentially forming the inner pipe connection structure 100 described above, and a ground improvement device formed at the tip of the double pipe An embodiment of the present invention will be outlined.

(Ground improvement body creation device and ground improvement body creation method)
FIG. 5a is a schematic view showing the ground improvement body generating apparatus, and is a view showing a state in which the stirring blade and the rod in a closed posture are accommodated in the casing, and FIG. It is the figure which showed the state in which the stirring blade of the attitude | position which the piston protruded and opened from the rod was formed, and the improvement material was discharged from the outer peripheral surface of the rod, rotating this stirring blade.

  The ground improvement body forming apparatus shown in the figure includes a casing that is an outer tube 20, a hollow rod that is an inner tube 10 that can slide in and out of the casing and can be rotated from the tip of the casing, and a hollow inside of the rod. A piston 10 'that is slidable and has a flow passage 10 "inside, and the tip of the piston 10' can be extended forward from the tip of the rod, and is rotatably attached to the tip of the piston 10 '. The at least two stirring blades 16, 16 are generally constituted.

  More specifically, the excavator (not shown) provided with a swivel or the like for advancing the casing 20 and the rod 10, and crushing and cutting the ground provided to the flow path 30 between the casing 20 and the rod 10, And a compressor that provides pressure water for extruding the piston 10 ′ provided to the hollow 40 of the rod 10 and pressure air for generating a high-pressure improving material (cement milk, etc.), and contains the water. The entire apparatus is composed of a tank provided in the hollow 40 of the path and the rod 10, a tank for containing an improved material such as cement milk, a hardening accelerator, a retarder and the like and provided to the inner pipe.

  An engagement groove 11 is provided on the wall surface of the hollow 40 of the rod 10, and the outer periphery of the piston 10 'is urged toward the hollow wall surface of the rod 10 by a spring which is a biasing means (not shown). A key 12 is provided. As shown in FIG. 5b, when the casing 20 accommodating the rod 10 reaches the improved ground layer, the rod 10 slides from the tip of the casing 20 by the length of the ground improvement body to be formed (Z1 direction). ). There is a gap between the hollow 40 of the rod 10 and the flow path 10 ″. When pressurized fluid is provided in this gap (X2 ′ direction), the pressurized fluid causes the rear end of the piston 10 ′ to have a fluid pressure Q. Push forward and slide the piston 10 'forward with respect to the rod 10 (Z2 direction) When the piston 10' slides a predetermined length, it is urged by the engagement groove 11 on the hollow inner wall of the rod 10 and the outer periphery of the piston. The engagement key 12 biased by the means is opposed at the engagement position, and the engagement key 12 enters the engagement groove 11 to engage with each other. When the piston 10 ′ is engaged, the tips of the stirring blades 16, 16 are fixed to the piston 10 ′ with a fixing pin so as to be rotatable and closed at the tip of the piston 10 ′. In response to this reaction force, Rotated in the direction of the wing 16, 16 is orthogonal to the axial direction of the rod 10 about their respective rotation axis (Z3 direction in FIG. 5b), stirring blades 16 and 16 of the open position is formed.

  Returning to FIG. 5 a, the discharge hole 15 through which the improving material flows is provided in the thick part of the rod 10, and this discharge hole 15 faces the external ground at the discharge port on the outer peripheral surface of the rod 10 and the hollow of the rod 10. It faces the hollow 40 at the inlet provided on the wall surface. On the other hand, the piston 10 ′ is provided with a flow passage 10 ″ therein and a through hole 14 penetrating the outer peripheral surface. As shown in FIG. 5b, the piston 10 ′ is pushed forward by the pressurized fluid, In a state where the rod 10 and the piston 10 'are engaged at the engagement position, the through hole 14 of the piston 10' is positioned at the inlet of the rod 10. That is, in this state, the piston 10 ' The flow path 10 "and the discharge hole 15 of the rod 10 are in fluid communication. When a high-pressure improving material is provided from the rear in a state where the flow path 10 ″ of the piston 10 ′ and the discharge hole 15 of the rod 10 are in fluid communication (in the direction X2 in FIG. 5b), the rod 10 passes through the through hole 14 of the piston 10 ′. The high pressure improving material is discharged from the discharge port to the outer side of the rod 10 through the discharge hole 15. (T direction in FIG. 5b) As can be seen from FIG. The discharge position and the discharge direction of the high-pressure improvement material discharged into the ground with respect to 16, 16 are on the casing 20 side of the stirring blade 16 and are parallel or substantially parallel to the stirring blade 16 The discharge position of the high-pressure improving material is closer to the casing 20 than the stirring blade 16, and the discharge direction is parallel or substantially parallel to the stirring blade 16 in the open posture. The stirring blade 16 When the ground improvement body is formed while being pulled back to the side 20, since the improvement material is provided on the pull back side of the rod 10 and the stirring blade 16, the ground and the improvement material are sufficiently stirred by the rotating stirring blade 16. Will be mixed.

  Next, with reference to FIG. 6, the ground improvement body construction method to which the apparatus shown to FIG. 5a, b is applied is outlined. In addition, FIG. 6a-FIG. 6c are the flowcharts explaining the ground improvement body construction method in the order.

  FIG. 6a shows a ground improvement body generating apparatus including a crawler type rotary percussion drill (excavator 60). First, as shown in FIG. 6a, using the excavator 60, the rod 10 is arranged in the casing 20, and both are advanced to the ground layer to be improved. The casing 20 and the rod 10 are made to reach the ground layer to be improved while pressure water is sprayed onto the ground through the flow path (X1 direction) to crush and cut. In this step, the two stirring blades 16 and 16 are closed in the axial direction of the rod 10 in the casing 20.

  Next, the excavator 60 is removed, an extension rod for sliding the rod 10 by a predetermined length from the tip of the casing 20 is attached to the excavator 60, and the casing 20 is further attached to the excavator 60, as shown in FIG. 6b. Then, the rod 10 is projected from the tip of the casing 20 by the length of the ground improvement body. When the rod 10 protrudes from the casing 20 by a predetermined length, as shown in FIG. 5b, a pressure fluid is supplied into the rod 10 to push the piston forward, and the rod 10 and the piston are engaged at both engagement positions. The stirring blades 16 and 16 in the closed posture are rotated to form an open posture (Z3 direction). Further, a high-pressure improvement material is provided from the rear, and the high-pressure improvement material is discharged from the discharge port of the rod 10 to the outer side of the rod 10 through the piston flow path and the through hole (T direction). ).

  The rod 10 is rotated as shown in FIG. 6c while discharging the high-pressure improvement material into the ground, the stirring blades 16 and 16 are rotated by rotation of the rod 10 (Z4 direction), and the ground and the improvement material are stirred and mixed. The ground improvement body P is created while retracting the rod 10 toward the casing 20 (X3 direction). In FIG. 6c, the ground improvement body P ′ is a ground improvement body formed by the retreat of the rod 10 after the illustration, and in addition to the ground improvement body P that has already been formed, the ground improvement body P ′ further includes By the creation, creation of the ground improvement body having a predetermined cross-sectional area and a predetermined length is completed.

  The construction flow shown in FIGS. 6a to 6c is repeated, or a plurality of devices are applied at the same time, and the double pipe is extended while sequentially forming the inner pipe connection structure 100, and a plurality of horizontal ground improvement bodies are formed. By making it so that it is in contact with it, or so as to be installed at a fixed interval, it becomes possible to accurately improve and reinforce the desired soft ground directly below it, regardless of the plane scale of the existing building. .

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and there are design changes and the like without departing from the gist of the present invention. They are also included in the present invention.

DESCRIPTION OF SYMBOLS 1 ... Location where O-ring is attached, 2 ... Location with threading, 3 ... O-ring, 4 ... Opening, 5 ... Threading, 6 ... Groove bottom, 10 ... Inner tube (rod), 10A ... Insert, 10B ... Housing groove, 20 ... outer pipe (casing), 30 ... first flow path (flow path), 40 ... second flow path (hollow), 50 ... connection pipe, 100, 100A ... connection structure, G ... gap ( play)

Claims (2)

In the double pipe in which the fluid flows through the first flow path between the inner pipe and the outer pipe constituting the double pipe and the second flow path inside the inner pipe, a plurality of inner pipes are connected and the length Is a connecting structure of the inner pipe,
Of the two inner pipes connected to each other, one inner pipe has a receiving groove extending from the opening to the groove bottom at the end, and the other inner pipe is inserted into the receiving groove at the end. Has a body,
The receiving groove has a thread on the opening side of its end,
The insert has, in order from the distal end side when inserted into the receiving groove, a location where an O-ring is attached, a location with threading,
The insert is inserted into the receiving groove, the two threaded parts are screwed together, and the part having the threaded part of the insert is sent forward of the threaded part of the receiving groove. A double pipe in which the groove contacts to form a seal structure, and a gap is formed between the tip of the insert and the groove bottom of the receiving groove, and this gap guarantees the relative movement of both inner pipes. The inner pipe connection structure. The one inner pipe is fitted into one end of a hollow connecting pipe,
The connecting structure of the inner pipe which comprises the double pipe of Claim 1 in which the accommodation groove | channel extended from the said opening to a groove bottom is formed in the other edge part of the said connecting pipe.

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