JP4952911B2 - Ground improvement method - Google Patents

Description

  The present invention relates to a ground improvement method, and more particularly, to a ground improvement method performed by applying a static compaction pile method that statically compacts to create an enlarged diameter pile.

  Conventionally, this type of static compaction pile method has been performed in the procedure shown in FIG. In the figure, reference numeral 1 denotes a double tube comprising an outer tube 2 and an inner tube 3 inserted into the outer tube 2, a drill bit 4 at the tip of the outer tube 2, and an upper end of the inner tube 3. A hopper 5 for receiving gravel M such as sand and crushed stone is attached. The outer tube 2 is supported by a rotating mechanism 7 in a lifting unit 6 that can be lifted and lowered along a leader of a construction machine (not shown), while the inner tube 3 is a vertical mechanism (hydraulic jack) 8 in the lifting unit 6. The outer tube 2 is supported so as to be movable relative to the outer tube 2.

  When carrying out the static compaction pile construction method, the double pipe 1 is set at the placement position on the ground G with the front end of the outer pipe 2 and the front end of the inner pipe 3 aligned, and then from the hopper 5 A predetermined amount of gravel M is put into the tube 3. First, as shown in FIG. 5 (a), the outer pipe 2 is rotated to penetrate the double pipe 1 to a predetermined depth in the ground G (to the deepest position of the enlarged-pile creation target layer G1). As shown in FIG. 2B, the double pipe 1 is pulled out by a predetermined distance while rotating (reversing) the outer pipe 2, and during this drawing, the gravel M in the inner pipe 3 is discharged into the ground G and gravel column. P1 is formed.

  Next, as shown in FIG. 4C, the inner pipe 3 is pushed down by the vertical mechanism 8 so that the tip of the inner pipe 3 protrudes from the outer pipe 2, and the gravel column P1 is solidified to form an enlarged diameter column P2. Subsequently, while rotating the outer tube 2 again, the outer tube 2 is moved downward until the tip is aligned with the inner tube 3 as shown in FIG. Next, as shown in FIG. 5E, the double pipe 1 is pulled out by a predetermined distance to form a new gravel column P1, and thereafter, the steps (c) to (e) are repeated, As shown in f), the expanded-diameter pile P in which the expanded-diameter column P2 is continuous is formed in the expanded-diameter pile formation target layer G1. After that, with the inner pipe 3 protruding from the outer pipe 2, the double pipe 1 is pulled out from the ground G, and the drain pile D is created in the formation (upper layer) G2 on the enlarged-pile creation target layer G1. The ground improvement for one place is completed. The same static compaction pile construction method is also disclosed in Patent Document 1, for example.

Japanese Patent Publication No. 6-99901

  By the way, in the conventional static compaction pile method described above, when the inner pipe 3 is pushed down by the vertical mechanism in the elevating unit 6 to form the enlarged column P2, the elevating unit 6 is fixed to the leader of the construction machine. It is necessary to take reaction force. For this reason, conventionally, a dedicated attachment / detachment mechanism is provided between the lifting unit 6 and the reader, and the lifting unit 6 is fixed to the reader when the enlarged diameter column P2 is formed. However, the desorption mechanism has a problem that the structure is complicated and expensive, and the cost burden on the construction machine is large. Further, depending on the shape of the reader, the attachment / detachment mechanism cannot be installed, and the reader may need to be changed.

  Further, the step of pushing down the inner tube 3 to create the enlarged column P2 (FIG. 5C) and the step of drawing the double tube 1 by a predetermined distance to form a new gravel column P1 (FIG. 5E). ), A step of moving the outer tube 2 down to a position where the inner tube 3 and the tip are aligned (FIG. 5D), that is, a step of returning the outer tube before discharging the gravel, is required. There was a problem that the extension of the construction was inevitable and the construction time was extended accordingly.

In addition, when the inner pipe 3 is pulled out with the inner pipe 3 protruding from the outer pipe 2, the outer pipe returning process before discharging the gravel as described above is performed in order to form the enlarged-diameter pile P2 having a desired diameter. This is because the necessary drawing length and pressing length become longer and the construction time is greatly extended. More specifically, the outer diameter of the outer tube 2 is φ ₁ , the outer diameter of the inner tube 3 is φ ₂ , the drawing length when the tips of the outer tube 2 and the inner tube 3 are aligned is L ₁ , and the inner tube 3 alone. Assuming that the drawing length of L ₂ is L ₂ , there is a relationship between the following formulas (1) and (2). When drawing only with the inner tube 3, the diameter ratio (φ ₁ / φ ₂ ) is 2 It must be pulled out and pushed down for a long time.
[φ ₁ ² × π / 4] × L ₁ = [φ ₂ ² × π / 4] × L ₂ (1)
L ₂ = [φ ₁ / φ ₂ ] ² × L ₁ (2)

  The present invention has been made in view of the above-described conventional problems, and the object of the present invention is to eliminate the need for a detaching mechanism for causing the reader to take a reaction force and to strike the outer tube before discharging the gravel. An object of the present invention is to provide a ground improvement method that eliminates the need for a return step and greatly contributes to cost reduction of construction equipment and cycle time.

In order to solve the above-mentioned problem, the present invention supports a double pipe composed of an outer pipe and an inner pipe inserted into the outer pipe on a lifting unit that can be lifted and lowered along a leader of a construction machine , While rotating forward by the rotation mechanism in the lifting unit, the double pipe penetrates to the ground to a predetermined depth with the tips of the outer pipe and the inner pipe aligned, and then the outer pipe of the double pipe With the tip aligned with the inner pipe, the outer pipe is reversed and pulled out by a predetermined distance. During this drawing, the gravel in the inner pipe is discharged into the ground, and then the outer pipe of the double pipe With the tips of the inner pipe and the inner pipe aligned , the outer pipe is pushed down while being reversed to solidify the discharged gravel to form an expanded column, and thereafter the outer pipe and the inner pipe of the double pipe in a state of aligning the tip of the, repeated withdrawal and depression of while reversing the outer tube, ground A diameter-expanded pile forming step in which the diameter-expanded column is continuously formed, and an outer pipe and an inner pipe constituting the double pipe are relatively moved by an up-and-down mechanism in the lifting unit, and the inner pipe Projecting a predetermined length from the outer pipe and pulling out the double pipe while maintaining this state, a drain pile having the same diameter as the outer diameter of the inner pipe is formed on the upper layer and / or lower layer of the layer to be expanded pile construction And a drain pile creation process to be created.

In the expanded pile construction process of the ground improvement method performed in this way, the double pipe consisting of the outer pipe and the inner pipe is pushed down integrally, so there is no need to take a reaction force on the leader, and the lifting unit is installed on the construction machine. A detaching mechanism for detaching from the reader is not required. Further, since the double pipe is pushed down and pulled out integrally, the step of returning the outer pipe before discharging the gravel becomes unnecessary.
Further, in the drain pile building process, the outer pipe and the inner pipe constituting the double pipe are relatively moved by the vertical mechanism in the lifting unit so that the inner pipe protrudes from the outer pipe by a predetermined length. pull out the double pipe while maintaining, by construct a top layer and / or the lower layer to the drain pile of enlarged diameter pile reclamation target layer, an outer diameter of the inner tube, the smaller diameter of the same diameter as the outer diameter of the inner tube Drain piles can be created and gravel consumption can be reduced.
Further, in the present invention, the outer tube is rotated forward by the rotation mechanism in the lifting unit and penetrated to a predetermined depth in the ground with the outer tube and the inner tube of the double tube aligned with the distal ends. The outer tube is reversed when the tube is pushed down. By pressing down the double pipe while reversing the outer pipe in this way, the compaction effect on the gravel is enhanced.

  In the present invention, the above-described double pipe can be pushed down through the lifting unit by operating a winch mounted on the construction machine. In this case, the winch force can be easily and efficiently transmitted to the double pipe by connecting the winch wire to the lifting unit via the reader.

  Furthermore, in the present invention, when the tip of the outer tube and the inner tube of the double tube are aligned, a predetermined distance is drawn, and during this drawing, when the gravel in the inner tube is discharged into the ground, By compressing air in the upper space of the inner tube and ejecting compressed air downward from the injection nozzle attached to the inner wall of the tip of the inner tube, the combined use of the pressure in the tube and the air ejection from the ejection nozzle The gravel in the inner pipe is smoothly discharged into the ground.

  According to the ground improvement method according to the present invention, it is not necessary to apply a reaction force to the leader, so that an expensive detaching mechanism for detaching the lifting unit from the leader of the construction machine becomes unnecessary, and the cost of the construction equipment is accordingly reduced. Reduction can be achieved. Further, since the outer tube returning process before gravel discharge is not required, the cycle time is shortened and the construction period can be shortened.

  The best mode for carrying out the present invention will be described below with reference to the accompanying drawings.

  1 and 2 show an embodiment of a static compaction pile construction method as a ground improvement construction method according to the present invention. Note that the double pipe 1 and the elevating unit 6 composed of the outer pipe 2 and the inner pipe 3 used here are not changed at all from the conventional one. Therefore, the reference numerals shown in FIG. It will be omitted. In FIG. 1, reference numeral 10 denotes a construction machine, which includes a base machine 11 capable of self-propelling and a leader 12 capable of moving up and down. The elevating unit 6 is movably mounted on the leader 12. The elevating unit 6 extends from the main winch 13 mounted on the base machine 11 by bypassing the pulley 14 at the top of the leader 12. A suspension wire 15 is connected. In the state where the reader 12 is erected vertically with respect to the ground G as shown in the figure, the elevating unit 6 is suspended and supported on the top of the reader 12 via the suspension wire 15 and the main winch 13 is rotated. Accordingly, it moves up and down along the reader 12. Further, a guide member 16 for guiding the double pipe 1 is provided at the lower part of the leader 12, and the double pipe 1 is also attached to the ground G in a state where the leader 12 is erected vertically with respect to the ground G. On the other hand, it stands upright.

  As described above, the elevating unit 6 includes a rotating mechanism 7 that supports the upper end portion of the outer tube 2 that constitutes the double tube 1, and a vertical mechanism (hydraulic jack) that supports the inner tube 3 to be movable relative to the outer tube 2. 8 (FIG. 2). A hopper 5 provided at the upper end of the inner tube 3 extends upward from the lifting unit 6, and gravel M is put into the hopper 5 from a lifting bucket 17 attached to the reader 12. The upper end of the inner pipe 3 is closed, and an opening / closing valve 18 is attached to the communication port with the hopper 5 as shown in FIG. A pressure air nozzle 19 for sending compressed air into the pipe is provided at the upper end portion of the inner pipe 3, and an air source (not shown) mounted on the base machine 11 is connected to the pressure air nozzle 19 by piping. Has been. The on-off valve 18 is configured to close or open by performing in-pipe pressure air / exhaust through the pressure air nozzle 19. On the other hand, a jet nozzle 20 that jets compressed air downward is attached to the inner wall of the tip of the inner tube 3. An air pipe 22 extending along a pipe wall from a pipe joint 21 provided at the upper end of the inner pipe 3 is connected to the ejection nozzle 20, and the pipe joint 21 is mounted on the base machine 11. Air source is connected by piping. An annular seal 23 that seals between the inner tube 3 and the outer tube 2 is fixed to the outer periphery of the distal end portion.

  In the present embodiment, the lifting unit 6 is connected to a pressing wire 25 extending from a pressing winch 24 mounted on the base machine 11. The wire 25 is wound around a top pulley 26 disposed on the top of the reader 12 and a lower pulley 27 disposed on the lower portion of the reader 12, and a tip portion of the wire 25 bypasses the lower pulley 27 and is drawn out to the lifting unit 6. ing. As a result, when the push-down winch 24 is rotated in the wire winding direction, the elevating unit 6 moves down along the leader 12, and the outer tube 2 and the inner tube 3 constituting the double tube 1 are pushed together. Can be lowered.

Hereinafter, the construction procedure by the ground improvement method will be specifically described with reference to FIG.
In carrying out the static compaction pile method, the double pipe 1 is set at the placement position on the ground G with the tip of the outer pipe 2 and the tip of the inner pipe 3 aligned, and then through the hopper 5 A predetermined amount of gravel M is put into the inner tube 3. First, as shown in FIG. 3 (A), the outer tube 2 is rotated forward to penetrate the double tube 1 to a predetermined depth in the ground G (up to the deepest position of the enlarged-pile creation target layer G1). Next, compressed air is sent from the air source to the pressurized air nozzle 19 to pressure the upper space of the inner pipe 3, and compressed air is sent from the same air source to the air pipe 22 to eject air from the ejection nozzle 20. While maintaining the pressure and the air jet, the outer tube 2 is reversed as shown in FIG. This pulling is performed by operating the main winch 13; however, since the outer tube 2 is pulled out while being reversed, the pulling resistance is kept small, and as a result, the double tube 1 can be pulled out smoothly. Then, the gravel M in the inner pipe 3 is discharged into the ground G by pulling out the double pipe 1, and the gravel column P <b> 1 is formed in the trace of the double pipe 1. In this case, the gravel M in the inner pipe 3 is smoothly discharged into the ground G by the combined use of the pressure inside the pipe and the air ejection from the ejection nozzle 20. In addition, the enlarged diameter pile production | generation object layer G1 consists of a liquefied layer here.

  Next, the pressure in the pipe from the pressure nozzle 19 and the air jet from the jet nozzle 20 are stopped, and the push-in winch 24 is rotated in the wire winding direction while reversing the outer pipe 2, as shown in FIG. As shown, the outer tube 2 and the inner tube 3 constituting the double tube 1 are pushed down together via the lifting unit 6. By this pressing down, the gravel column P1 is solidified, and an enlarged column P2 having a desired diameter is formed. In this case, since the outer tube 2 and the inner tube 3 constituting the double tube 1 are pushed down integrally, there is no need to apply a reaction force to the reader 12, so that the elevating unit 6 is connected to the leader of the construction machine 10 as in the prior art. Therefore, a special desorption mechanism for desorbing to 12 is not required. At this time, since the outer tube 2 is reversed, a tightening force acts on the gravel column P1, and an enlarged column P2 having a desired diameter is effectively formed. Next, the pressure inside the pipe and the air jet from the jet nozzle 20 are restarted, and the double pipe 1 is pulled out by a predetermined distance while the outer pipe 2 is reversed as shown in FIG. By this drawing, a new gravel column P1 is formed on the enlarged diameter column P2, and thereafter, the steps (C) and (D) are repeated while replenishing the gravel M in the inner tube 3. As shown in (E), the expanded pile P in which the expanded column P2 is continuous is formed in the liquefied layer (expanded pile formation target layer) G1.

  Since the double pipe 1 is pulled out and pushed down with the tips of the outer pipe 2 and the inner pipe 3 aligned in this way, the drawing length / pushing length required to create the diameter-expanding column P2 having a desired diameter is reduced. It won't be long. In addition, since the double pipe 1 is pushed down and pulled out integrally, the outer pipe returning step (FIG. 5D) before discharging the gravel is not required, and the cycle time is shortened accordingly.

  FIG. 4 shows the depth change (operation change) of the outer tube 2 in a series of steps including the steps (A) to (D). In the same figure, the same change in the conventional method is shown with a broken line, and due to the change in the outer pipe depth, in this method, the construction time is shorter than the conventional method by reducing the time of one cycle of drawing-pressing. It is clear that is significantly shortened. In addition, in the same figure, although the construction time difference at the time of the end of the fifth (No. 5) cycle is added, this construction time difference becomes larger as the length of the required expanded diameter pile P becomes longer. It is clear.

  Thereafter, as shown in FIG. 3 (E), the inner tube 3 is protruded from the outer tube 2 by a predetermined distance by the operation of the vertical mechanism 8 in the lifting unit 6, and the double tube 1 is rotated while the outer tube 2 is rotated in the reverse direction. Pull out from ground G. By this drawing, the drain column D is formed in the formation (upper layer) G2 on the liquefied layer G1, but the diameter of the drain column D becomes the same as the outer diameter of the inner tube 3, so that the amount of gravel M used can be reduced. Can be planned. In this case, the vertical mechanism 8 to be used merely moves the outer tube 2 and the inner tube 3 relative to each other, so that the hydraulic mechanism is smaller than the vertical mechanism 8 (FIG. 5) in the conventional method used for pushing down the inner tube. The jack can be used, and the cost of the equipment is reduced in this respect as well.

  Here, when the lower layer G3 (FIG. 3) of the liquefied layer G1 is a viscous soil, a drain pile may be formed on the lower layer G3 for the purpose of consolidation. By operating the mechanism 8, the inner tube 3 protrudes from the outer tube 2 by a predetermined distance, and the double tube 1 is pulled out from the ground G while the outer tube 2 is rotated in the reverse direction.

  The type of gravel M used here is arbitrary, as well as general-purpose materials such as sand, crushed stone, and gravel, as well as construction-generated soil, coal ash, incinerated ash, volcanic ash, granulated glass, molten slag, plastic Recycled materials or mixed materials thereof can be used. Moreover, what mixed the cement-type solidification material, the polymeric solidification material, the soil improvement material, etc. with the above-mentioned various materials as needed can be used.

It is a side view which shows the whole structure of the equipment which performs the static compaction pile construction method as the ground improvement construction method which concerns on this invention. It is a front view which shows the installation structure of the double pipe which performs this static compaction pile construction method. It is sectional drawing which shows typically the construction procedure in this static compaction pile construction method. It is a cycle diagram which shows the depth change of the outer pipe | tube between the series of processes in this static compaction pile construction method, and the change of the sand removal length in an inner pipe compared with the conventional construction method. It is sectional drawing which shows typically the construction procedure in the static compaction pile construction method as the conventional ground improvement construction method.

DESCRIPTION OF SYMBOLS 1 Double pipe, 2 Outer pipe, 3 Inner pipe 5 Hopper, 6 Lifting unit 7 Lifting mechanism rotating mechanism 8 Lifting unit vertical mechanism 10 Construction machine, 11 Base machine, 12 Reader 13 Main rod winch, 15 Suspension wire 19 pressure nozzle, 20 ejection nozzle 24 push-down winch, 25 push-down wire G ground G1 diameter-expanded pile formation target layer, G2 above, G3 lower layer M gravel P1 gravel pillar P2 diameter-expanded pillar P diameter-expanded pile D drain pile

Claims (3)

A double pipe consisting of an outer pipe and an inner pipe inserted into the outer pipe is supported by a lifting unit that can be raised and lowered along a leader of a construction machine, and the outer pipe is rotated forward by a rotation mechanism in the lifting unit. While penetrating into the ground to a predetermined depth with the tips of the outer tube and inner tube of the double tube aligned, then, with the tips of the outer tube and inner tube of the double tube aligned , Withdrawing the outer tube by a predetermined distance while reversing , during this drawing, the gravel in the inner tube is discharged into the ground, and then the tips of the outer tube and the inner tube of the double tube are aligned. to construct a diameter column by hardening butt pressing Gaité the ejected gravel while reversing the outer tube, since, in a state of aligning the tip of the outer tube and the inner tube of the double tube, the outer Repeat withdrawal and depression of while reversing the tube, forming a diameter piles the diameter columns are continuous in the ground And the enlarged diameter pile reclamation step of,
The outer tube and the inner tube constituting the double tube are moved relative to each other by the vertical mechanism in the lifting unit so that the inner tube protrudes from the outer tube by a predetermined length, and the double tube is pulled out while maintaining this state. And a drain pile creation step of creating a drain pile having the same diameter as the outer diameter of the inner pipe in the upper layer and / or the lower layer of the layer to be expanded-pile creation target. 2. The ground improvement method according to claim 1, wherein the double pipe is pushed down through the lifting unit by operating a winch mounted on a construction machine. When the outer pipe and the inner pipe of the double pipe are aligned at the tip end, the pipe is pulled out by a predetermined distance, and during this drawing, when discharging the gravel in the inner pipe into the ground,
The ground improvement according to claim 1 or 2 , wherein compressed air is jetted downward from a jet nozzle attached to an inner wall of a tip end portion of the inner pipe while the upper space of the inner pipe is pressurized. Construction method.

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