JP7535019B2 - Ground improvement method - Google Patents

Description

The present invention relates to a ground improvement method that contributes to disaster prevention through a combination of ground vibration isolation and liquefaction prevention technology.

Conventionally, a method of preventing liquefaction of ground using large machinery has been used in which the pore water pressure in soil particles caused by earthquake motion is absorbed and dissipated using highly permeable sand piles or crushed stone piles. A method that utilizes this concept as a liquefaction countermeasure for detached housing areas, etc., is the Liquefaction Prevention Method (for example, Patent Document 1).

The crushed stone pillars made using the liquefaction prevention method have high water permeability, and during an earthquake, the water pressure generated in the ground can be dissipated in the gaps within the crushed stone pillars, preventing liquefaction in the ground. They are easy to work with and can efficiently compact the fill material, providing high bearing capacity. However, during construction, it was necessary to inject compressed water and compressed air from around the bottom spiral blade to keep the borehole wall stable.

In response to this, there is a drain pile embedding device for ground improvement (see, for example, Patent Document 2) that has a pipe casing in which multiple filling material discharge ports and compaction cam surfaces are alternately formed on a tapered cone bit, and a pipe rod in which a tapered cone surface that acts as an opening and closing valve for the filling material discharge port is correspondingly formed on the tapered cone bit, and with this embedding device, a drain pile made of filling material can be installed in a borehole without using compressed water or compressed air.

In the above-mentioned embedding device, during the excavation process, filler materials such as crushed stone, gravel, and gravel are fed from the filler material feeding hopper through the filler material receiving port of the pipe casing into the inside of the pipe casing. However, with materials with a large internal friction angle such as crushed stone, the filler material will become lumpy inside the hopper due to the unevenness of the crushed stone shape interlocking with each other and will not fall into the receiving port as is, and the crushed stone may not be fed smoothly.

In addition, the above-mentioned burial device has a helical blade on the outer surface of the pipe casing that functions as a screw auger, so when it is inserted into the ground or pulled out, a borehole with a larger diameter than the diameter of the pipe casing body is created, creating a cavity on the outer surface of the pipe casing and on the wall of the borehole. This causes the wall of the borehole to collapse before it is filled with crushed stone, loosening the original ground.

Furthermore, since there is a longitudinal opening inside the pipe casing from the bottom of the outer side to the top in the axial direction, through which a shooter for feeding crushed stone can be inserted, the pipe casing must be pulled out without rotation, and soil and sand adhere to the spiral blades on the outer periphery of the pipe casing and are discharged to the ground surface. Even if the outer periphery of the pipe casing is flat, clay from the clayey soil sticks to the outer surface when it is pulled out without rotation, which causes the original ground to become loose.

Patent No. 3669288 JP 2009-62762 A

The problem to be solved is to provide a ground improvement method that can drop-feed filler material into a casing pipe, and additionally to provide a ground improvement method that can consolidate soft ground by rotating the rod in the direction opposite to excavation , thereby providing vibration isolation and suppressing liquefaction.

The invention of claim 1 is a ground improvement method that uses a rod with a helical blade and a casing pipe that is fitted to the rod, inserts the rod and the casing pipe into the ground to a predetermined depth, and rotates the rod in the counter-excavation direction to form a consolidated pile in the ground using filler material in the casing pipe, wherein a tip-side helical blade and a base-side helical blade in the same helical direction are provided on the tip side of the rod, and a gap is provided in the longitudinal direction of the rod between the tip-side helical blade and the base-side helical blade, and with the tip-side helical blade protruding from the tip of the casing pipe, the rod is inserted to the predetermined depth while rotating together with the casing pipe in the counter-excavation direction.

The invention of claim 2 is characterized in that when the tip spiral blade is in soft ground, the rod is inserted together with the casing pipe while rotating in the anti-excavation direction, and when the tip spiral blade is in ground that is harder than the soft ground and cannot be inserted by rotation in the anti-excavation direction, the rod is inserted while rotating in the excavation direction.

The invention of claim 1 is characterized in that a rotary drive device is provided on the leader so that it can be raised and lowered, the rotary drive device rotates the rod and inserts it into the ground, and an extension casing pipe is used that has a rod insertion portion along the entire length of the side through which the rod can be inserted from the diameter direction, and the tip of this extension casing pipe is connected to the base end of the casing pipe.

According to the configuration of claim 1 , by filling the gaps with filler material to prevent excavated soil from entering the casing pipe, the rod is rotated together with the casing pipe in the counter-excavation direction while being inserted, whereby the casing pipe can be inserted to a predetermined depth while compacting the ground, and a columnar cylindrical space for introducing crushed stone can be secured inside the casing pipe.

According to the configuration of claim 2 , in ground where the rod and casing pipe cannot be inserted by rotating in the anti-excavation direction, the rod can be switched to rotating in the excavation direction, and the underground soil and sand can be loosened and stirred while excavating, and then the rotation can be returned to the anti-excavation direction to insert the rod and casing pipe into the ground.

Furthermore, according to the configuration of claim 1 , after the casing rod is inserted into the ground, the extension casing pipe is fitted onto the rod by inserting the rod into the rod insertion portion from the side, and the extension casing pipe is connected to the casing pipe inserted into the ground, and the integrated casing pipe and extension casing pipe can be inserted into the ground. In this way, a casing pipe and an extension casing pipe longer than the length of the leader can be inserted into the ground.

1 is an overall side view showing a first embodiment of the present invention; FIG. FIG. FIG. FIG. FIG. 2 is an enlarged cross-sectional view of a main part of the hopper device according to the first embodiment. FIG. 1 is a cross-sectional plan view of the rod and casing pipe. FIG. 13 is an explanatory cross-sectional view of the first embodiment at the start of excavation. FIG. 13 is a cross-sectional view of the tip bit when it reaches a specified excavation depth. FIG. 11 is a cross-sectional view illustrating the step of horizontally spreading the piled up filling material. Same as above, a cross-sectional explanatory diagram explaining the construction of the crushed stone consolidation section. FIG. 13 is a cross-sectional explanatory diagram illustrating the construction of a columnar crushed stone pile. Same as above, a cross-sectional explanatory diagram of the columnar crushed stone pile after construction has been completed. FIG. 1 is a flow chart showing the steps of constructing crushed stone piles. FIG. 5 is a cross-sectional explanatory diagram illustrating the construction of an expanded diameter portion of a crushed stone pile according to a second embodiment of the present invention. Same as above, a cross-sectional explanatory diagram of the columnar crushed stone pile after construction has been completed. FIG. 11 is a cross-sectional view of a switching means showing a third embodiment of the present invention. FIG. FIG. 11 is an overall side view showing a fourth embodiment of the present invention. FIG. 10 is a cross-sectional view of the tip side of a rod and a casing pipe showing a fifth embodiment of the present invention.

A preferred embodiment of the present invention will be described with reference to the attached drawings. Note that the embodiment described below does not limit the content of the present invention described in the claims. Furthermore, not all of the configurations described below are necessarily essential requirements of the present invention.

A first embodiment of the present invention will be described with reference to Figures 1 to 16. As shown in the figures, the ground improvement device 1 has an endless track 3 as a traveling means attached to the bottom of a self-propelled vehicle body 2 as the main body, and this endless track 3 is driven by a prime mover (not shown) mounted on the vehicle body 2. In addition, a leader 5 is provided at the front of the vehicle body 2 so that it can be raised and lowered, and this leader 5 can be raised and lowered by a lifting device (not shown) in the fore-and-aft direction.

A guide rail 6 is provided in front of the leader 5, and a rotary drive device 7 is provided on the guide rail 6 so that it can be raised and lowered, with an elevation drive device 8 for raising and lowering the rotary drive device 7. The rotary drive device 7 has an insertion portion 11 through which a rod 9 is inserted, and a rod lock 12 that can lock and unlock the rod 9. With the rod 9 locked by the rod lock 12, the rod lock 12 rotates to rotate the rod 9.

As shown in FIG. 2, a cam clutch 15 is provided at the lower end of the rod lock 12 as a rotation transmission means. This cam clutch 15 is a switching means that can be switched between a rotation mode in which the casing pipe 10 is rotated together with the rod 9 by the rotary drive device 7, and a non-rotation mode in which the rod 9 is rotated but the casing pipe 10 is not rotated.

The cam clutch 15 is fixed to the rod lock 12 and has a main body 16 that rotates integrally with the rod lock 12, and a plurality of connecting arms 17 that serve as connecting parts provided on the main body 16. The connecting arms 17 are roughly U-shaped, with the base end of the parallel upper piece 18U and the base end of the parallel lower piece 18S connected by a vertical piece 18T.

The tip end of the upper piece 18U of the connecting arm 17 is rotatably connected to the main body 16 by a pivot 19, and a connecting hole 21 into which the lower piece 18S of the connecting arm 17 can be inserted and removed is drilled at the base end (upper end) of the casing pipe 10. By a connecting drive means (not shown), the lower piece 18S is rotated between a connecting position where it is inserted into the connecting hole 21 as shown by the solid line in FIG. 2, and a disconnecting position where the lower pieces 18S, 18S are removed from the connecting holes 21, 21 so that both connecting arms 17, 17 open as shown by the dashed line in FIG. 2.

The main body 16 has a slit-shaped groove 22 that opens onto the outer periphery, the pivot 19 is provided in this groove 22, and the upper piece 18U is loosely inserted into the groove 22. In addition, in the connected position, the cam clutch 15 is in a transmission state in which the rotation of the rotary drive device 7 is transmitted to the casing pipe 10, and in the disconnected position, the cam clutch 15 is in a transmission-disconnected state in which the rotation of the rotary drive device 7 is not transmitted to the casing pipe 10.

The main body 16 is provided with a through hole 16T through which the rod 9 can rotate and move axially. The rod 9 is loosely inserted into the through hole 16T, and the casing pipe 10 is fitted around the rod 9.

As shown in FIG. 2, the lower end of the rod 9 is provided with a tip bit 31, which is a drilling bit having a sharp triangular pyramid shape toward the tip of the rod 9, and the base end of this tip bit 31 is formed larger than the rod 9.

A lower helical wing 32, which is a tip-side helical wing, is provided on the outside of the casing pipe 10 at the base end side of the bit 31, and an upper helical wing 34, which is a base-side helical wing, is provided on the rod 9 with a gap 33 in the length direction of the rod from the lower helical wing 32. The gap 33 is a portion between the helical wing 32, 34 where there is no helical wing. The lower helical wing 32 and the upper helical wing 34 have the same helical direction, and the lower helical wing 32 has a spiral of about two turns, while the upper helical wing 34 has a spiral of about one turn, which is less than the lower helical wing 32.

The outer diameter of the lower spiral blade 32 is formed to be the same as the outer diameter of the casing pipe 10.

In the rotation mode, the rod lock 12 is connected to the main body 16, and when the rod 9 moves axially together with the rotation drive device 7 by the lift drive device 8, the casing pipe 10 moves axially together with the rod 9. In the non-rotation mode, the upper end of the casing pipe 10 is pushed by the rod lock 12 via the main body 16, and the casing pipe 10 moves axially toward the tip side (downward in FIG. 1) together with the rod 9. In addition, when the rod 9 moves toward the base end side in the axial direction, the outer diameter of the lower spiral blade 32 is formed to be the same as the outer diameter of the casing pipe 10, so that in the non-rotation mode, when the rod 9 is pulled up toward the base end side in the axial direction, the lower spiral blade 32 engages with the tip of the casing pipe 10, and the casing pipe 10 moves toward the base end side in the axial direction.

The casing pipe 10 is provided with a plurality of crushed stone inlets 41 spaced apart along its length, and the crushed stone inlets 41 are filler inlets. In addition, the crushed stone inlet 41 at the base end of the casing pipe 10 is larger than the other crushed stone inlets 41, so that crushed stone 42 can be efficiently supplied from the large crushed stone inlet 41 at the base end during construction of the crushed stone consolidation section 102, which uses a relatively large amount of crushed stone 42.

A hopper device 51 is also provided to feed crushed stone 42 as a filling material into the crushed stone inlet 41 from the outside. As shown in FIG. 4, the hopper device 51 has a support body 52 as a support part, which has a support column 53 and a bottom surface 54 provided on the bottom surface on which the support columns 53 are erected, and a bottom insertion hole 55 is drilled in the bottom surface 54 through which the casing pipe 10 is loosely inserted. The bottom surface 54 is then placed directly or indirectly on the ground G at the excavation site for use.

The hopper device 51 includes a hopper body 56 having a side surface that tapers downward, and a circular insertion hole 57 is provided at the bottom of the hopper body 56, and the insertion hole 57 is formed to have a larger diameter than the bottom insertion hole 55. Furthermore, the outer periphery of the hopper body 56 is placed or fixed to the upper ends of the multiple support parts 53, and the hopper body 56 is supported by the support 52.

A roughly cylindrical rotating body 58 is provided on the bottom surface portion 54, and a through hole 59 is drilled in the center of this rotating body 58, through which the casing pipe 10 is inserted. The casing pipe 10 is loosely inserted into the through hole upper portion 59A of the through hole 59.

The lower through-hole 59B of the through-hole 59 is formed with a larger diameter than the upper through-hole, and a downward through-hole step surface 59C is provided between the upper through-hole 59A and the lower through-hole 59B. The ring-shaped upper surface 58J of the rotor 58 is disposed so as to close the insertion hole 57 of the hopper body 56, and the rotor 58 is rotatably disposed within the insertion hole 57 of the hopper body 56.

A lower surface rotation support member 60 is provided on the lower surface of the rotor 58, outside the lower through-hole 59B. This lower surface rotation support member 60 is a plate-shaped ring body 61 that holds multiple spheres 61A in a freely rotatable manner. The lower surface rotation support member 60 can be fixed to either the lower surface of the rotor 58 or the upper surface of the bottom portion 54.

A rotation transmission member 62 is provided inside the through hole lower portion 59B, and this rotation transmission member 62 holds multiple (four) spheres 63 in a rotatable state in a positioning state using a ring-shaped storage case 64. The spheres 63 abut against the outer periphery of the casing pipe 10, and also abut against the inner periphery of the through hole lower portion 59B of the rotor 58. The spheres 63 are made of rubber balls or the like.

The storage case 64 is a bearing that rotatably holds the plurality of spheres 63, and includes upper and lower ring parts 65, 66 that are arranged above and below the spheres 63, with the lower ring part 66 being integrally provided on the bottom part 54. As shown in FIG. 6, an outer peripheral side holder 67 and an inner peripheral side holder 68 that rotatably hold the spheres 63 are provided on the outer peripheral side and inner peripheral side of the storage case 64, respectively, corresponding to each sphere 63, and the top and bottom of these holders 67, 68 are fixed to the lower surface of the upper ring part 65 and the upper surface of the lower ring part 66.

In addition, a spherical opening 67A smaller than the diameter of the sphere 63 is provided on the inside of the outer circumference side holding body 67, and a spherical opening 68A smaller than the diameter of the sphere 63 is provided on the outside of the inner circumference side holding body 68. A plurality of balls 69 are rotatably held in each of the spherical openings 67A, 68A, and these plurality of balls 69 are arranged at equal intervals in the circumferential direction. The plurality of balls 69 provided in the spherical openings 67A, 68A hold the sphere 63 rotatably in the outer circumference side holding body 67 and the inner circumference side holding body 68 in a non-slip state. Note that the openings 67A, 68A are shown as being curved in a spherical shape, but they may also be tapered in the shape of a truncated cone.

In addition, an upper surface rotating support member 60A is disposed between the storage case 64 and the through hole step surface 59C, and this upper surface rotating support member 60A can be fixed to either the upper surface of the upper ring portion 65 or the through hole step surface 59C.

As shown in Figures 4 and 5, a number of plate-shaped agitating blades 70, 70... are vertically installed on the top surface 58J of the rotor 58, and the agitating blades 70, 70... are installed at an angle from the base end on the center side of the hopper body 56 to the tip. The rotor 58, the sphere 63, and the agitating blades 70 as the agitating part constitute an agitating means 71 that agitates the crushed stone 42 as the filling material.

As shown in FIG. 5, when the casing pipe 10 rotates counterclockwise, the sphere 63 in contact with the outer circumference of the casing pipe 10 rotates clockwise, and the rotor 58 in contact with this sphere 63 rotates clockwise, causing the multiple mixing blades 70, 70... to mix the crushed stone 42 in the hopper body 56, so that the crushed stone 42 falls from the crushed stone inlet 41 into the casing pipe 10 without solidifying in the hopper body 56.

When the casing pipe 10 is pushed downward, the rotation of the sphere 63 generates a force that lifts the rotor 58 upward. Therefore, a member (not shown) may be provided on the bottom surface 54 to engage with the rotor 58 to prevent the rotor 58 from floating up and to allow the rotor 58 to rotate in the engaged state, or a vertical central axis of rotation may be provided on the sphere 63, and the top and bottom of this central axis may be rotatably supported by the upper and lower ring portions 65, 66 so that the sphere 63 rotates around the vertical central axis of rotation and does not rotate around a horizontal axis.

As shown in FIG. 6 and other figures, a stripping member 75 for stripping mud is provided around the bottom insertion hole 55 on the underside of the bottom portion 54, and this stripping member 75 is formed in a ring shape from rubber or the like, and a sharp tip 77 is formed at the lower end of the inner circumferential surface 76. Therefore, when the casing pipe 10 is pulled out, as shown in FIG. 4, the inner circumferential surface 76 of the stripping member 75 is pressed against the outer surface of the casing pipe 10, and the sharp tip 77 can strip off dirt and sand adhering to the outer periphery of the casing pipe 10.

A hopper-shaped storage section 81 is provided on the vehicle body 2, and the crushed stone 42 is stored in this storage section 81. A belt conveyor 82 is provided at the bottom of the storage section 81 as a feeding device, and this belt conveyor 82 feeds the crushed stone 42 from the rear to the front. An input path 83 is provided in the storage section 81 at the end side of the belt conveyor 82, and this input path 83 is inclined so that the input port 84 at the tip side becomes lower, and this input port 84 is extended to the top of the hopper body 56. Walls are provided on both sides of the input path 83. The belt conveyor 82 and input path 83 form an input device 85 when the crushed stone 42 is input.

In addition, when groundwater infiltrates into the casing pipe 10, buoyancy acts on the crushed stone 42 introduced from the top of the casing pipe 10, causing a delay in the settling of the crushed stone 42. To solve this problem, as shown in FIG. 7, a water intake hole 91 is provided in the axial center of the rod 9 installed inside the casing pipe 10, which runs from the lower end to the upper end, and as shown in FIG. 2, the lower end 91S of the water intake hole 91 opens into the casing pipe 10 between the spiral blades 32 and 34. In addition, the water intake hole 91 is connected to a horizontally rotatable swivel joint 92 at the upper end of the rod 9, and a water intake port 93 is provided on the side of the swivel joint 92. One end of a suction hose 94, which is a pipe, is connected to the water intake port 93, and the other end of the suction hose 94 is connected to a vacuum pump (not shown) installed on the vehicle body 2 or on the ground, and the groundwater in the casing pipe 10 is sucked up by the vacuum pump. In addition, the sucked-up groundwater can be treated by returning it underground from the top of the installed crushed stone pile 103 or by discharging it into an aboveground drain.

Next, an example of construction using the ground improvement device 1 will be described with reference to Figures 8 to 13. The vehicle body 2 is moved to the construction position, the leader 5 is aligned with the construction position, and the axis of the rod 9 is aligned with the position of the drilling hole 101. The lower end of the casing pipe 10 is aligned with the underside of the bottom part 54 of the hopper device 51, the hopper device 51 is lifted a specified distance from the ground surface G by a lifting means (not shown), and the tip height of the tip bit 31 protruding from the tip of the casing pipe 10 is adjusted to the ground surface G, preparing for excavation.

Before starting drilling, the cam clutch 15 is set to rotation mode so that the casing pipe 10 rotates and moves axially together with the rod 9.

During excavation, the rod 9 and casing pipe 10 are rotated in the direction opposite to the excavation direction of the helical blades 32, 34 while repeatedly moving up and down, and the casing pipe 10 is inserted into the ground while compacting the original ground of the external volume of the casing pipe 10. If the ground is hard and it is not possible to insert the casing pipe 10 into the ground by rotating in the opposite direction to the excavation direction, the rotation is switched to the right, which is the excavation direction, and after loosening and mixing the ground, the excavated soil that has been loosened by repeatedly rotating up and down to the left is compacted and inserted into the ground. Note that in this example, the rotation of the helical blades 32, 34 in the opposite direction to the excavation direction is counterclockwise as viewed from above.

If the ground G is hard at the start of excavation and the rod 9 and casing pipe 10 cannot be inserted into the ground by rotating the helical blades 32, 34 in the counterclockwise direction, the rod 9 and casing pipe 10 are rotated in the excavation direction, the lifting drive device 8 pushes down the rod 9 and casing pipe 10, and the hopper device 51 is lowered together with the casing pipe 10, so that the bottom surface 54 of the support 52 of the hopper device 51 is grounded on the ground G as shown in FIG. 8. Note that if the ground G is soft and the rod 9 and casing pipe 10 can be pushed into the ground while rotating the helical blades 32, 34 together with the rod 9 in the counter-excavation direction as described below, the helical blades 32, 34 are rotated in the counter-excavation direction from the start of excavation to form the borehole 101.

When rotating the helical blades 32, 34 in the drilling direction to form a drilled hole 101, as shown in FIG. 8, crushed stone 42 is filled in the gap 33 between the lower helical blade 32 and the upper helical blade 34 inside the casing pipe 10, and the ground is excavated while rotating the rod 9 in the drilling direction to loosen the ground and form a drilled hole 101. When the lower helical blade 32 is rotated in the drilling direction in this way, the rotation of the lower helical blade 32 in the drilling direction moves the excavated soil upward and tries to enter the casing pipe 10, but the crushed stone 42 in the gap 33 acts as a lid for the lower end of the casing pipe 10, suppressing the intrusion of the excavated soil, thereby preventing the excavated soil from rising.

The results of the experiment showed that by setting the height of the gap 33 to about 10 cm in soft ground and about 30 cm in hard ground, it was possible to prevent excavated soil from rising into the casing pipe 10. As a result, it was found that it was necessary to set the gap 33 larger in soft ground than in soft ground.

In addition, since there is a risk of the crushed stone 42 being fed from above becoming clogged, the upper spiral blade 34 may have 1 to 1.5 turns. And in order to drop the crushed stone 42 into the gap 33 by rotating in the direction opposite to excavation, the upper spiral blade 34 needs to have at least 1 turn. With 1.5 turns, the crushed stone 42 from above is likely to become clogged. The lower spiral blade 32 for excavation has 2 turns.

As shown in FIG. 8, the hard ground of the ground G is excavated by rotating in the excavation direction to form a borehole 101, and when the lower spiral blade 32 reaches the soft ground, the rod 9, which rotates in conjunction with the casing pipe 10, is rotated in the opposite excavation direction while repeatedly moving up and down, and the original ground of the outer volume of the casing pipe 10 is consolidated and inserted into the ground. If the ground is hard during the process and the rod 9 and casing pipe 10 cannot be inserted, the spiral blades 32, 34 are switched to rotating in the excavation direction, and the underground soil is loosened and stirred while excavating, and then the rotation is returned to the opposite excavation direction, and the loosened underground soil is inserted into the ground by repeatedly moving the rod 9 and casing pipe 10 up and down while rotating in the opposite excavation direction. Note that until the tip bit 31 reaches the specified excavation depth, crushed stone 42 is filled only in the gap 33 in the casing pipe 10, and no additional crushed stone 42 is added.

When the specified excavation depth is reached as shown in FIG. 9, the rod 9 and casing pipe 10 are repeatedly moved up and down in the direction opposite to the excavation rotation, and the rod 9 and casing pipe 10 are loosened and stirred in the excavation rotation direction as necessary. The cam clutch 15 is switched to non-rotation mode, the rotation of the casing pipe 10 is stopped, and only the rod 9 is rotated counterclockwise. The upper spiral blade 34 in the casing pipe 10 discharges the excavated soil into the ground from the bottom end of the casing pipe 10, and a columnar cylindrical space is secured in the casing pipe 10 for introducing crushed stone. The diameter and length of the casing pipe 10 can also be changed depending on the performance required for the columnar crushed stone pile 103.

The upper spiral blade 34 in the casing pipe 10 discharges the excavated soil in the casing pipe 10 into the ground, and after securing a columnar cylindrical space in the casing pipe 10 for introducing crushed stone, crushed stone 42 is introduced into the hopper body 56, the cam clutch 15 is switched to the rotation mode, and the rod 9 and the casing pipe 10 are rotated in the opposite direction to the excavation direction (counterclockwise direction). Then, the multiple spheres 63, 63, 63, 63 in contact with the outer periphery of the casing pipe 10 rotate in the clockwise direction, and the rotor 58, whose through-hole lower part 59B is in contact with the outside of these spheres 63, 63, 63, 63, rotates in the clockwise direction, and the multiple agitating blades 70, 70, 70, 70 provided on the upper surface part 58J of the rotor 58 rotate. These rotating agitator blades 70, 70, 70, 70 guide the crushed stone 42 in the hopper body 56 to the center of the casing pipe 10, where it falls into the casing pipe 10 through the crushed stone inlet 41.

The crushed stone 42 supplied into the casing pipe 10 is deposited at the bottom of the borehole 101 by the upper helical blade 34 and the lower helical blade 32 rotating in the counter-drilling direction, as shown in FIG. 10. In the compaction of the crushed stone 42, the rotating rod 9 and the casing pipe 10 are driven in by moving the rod 9 rotating in the counter-drilling direction and the casing pipe 10 up and down against the crushed stone 42 deposited at the bottom of the borehole 101, driving the lower helical blade 32 and the tip bit 31 into the deposited crushed stone 42 with a set pressure, and the deposited crushed stone 42 is spread horizontally. After that, the tip bit 31 is temporarily pulled out of the deposited crushed stone 42, and more crushed stone 42 is poured into the gap that has been spread.

The thrusting is performed multiple times, and the piled crushed stone 42 is pushed horizontally and further crushed stone 42 is added into the expanded gap, and this rolling compaction is repeated until the set pressure force is supported. That is, by pushing the piled crushed stone 42 horizontally, as shown in FIG. 11, the top surface position of the piled crushed stone 42 is lower than before thrusting, and between the top surface position and the lower end of the casing pipe 10, there is soil in the ground, but there is no crushed stone 42 or the density of the crushed stone 42 is lower than the lower part, forming a portion where additional supply is possible (the expanded gap). As an additional supply operation in the rolling compaction of the crushed stone 42, the helical blades 32, 34 additionally supply crushed stone 42 to the portion where additional supply is possible, and the thrusting operation is performed, and the rolling compaction is repeated until the set pressure force is supported.

After confirming that the set pressure input (bearing force) is secured by measuring the reaction force applied to the rod 9 during thrust, the rod 9 is rotated left in the same position and crushed stone 42 is poured in. Since there is already crushed stone mass at the bottom that has been compacted and has sufficient bearing force, the crushed stone 42 begins to expand horizontally due to the left rotation pressure of the lower spiral blade 32. The crushed stone 42 that has expanded due to the intermittent pouring of crushed stone 42 and the rotation of the lower spiral blade 32 consolidates the original ground soil particles in the horizontal direction, and eventually the rotational torque of the motor that is the driving means of the rotary drive device 7 reaches the pushing resistance reaction force that satisfies the set rotational torque, and the crushed stone 42 is formed at the bottom of the borehole 101 by expanding the bottom, and the consolidated crushed stone 42 with a predetermined bearing force expands in the circumferential direction of the borehole 101. The consolidated crushed stone 42 expands in the circumferential direction of the borehole 101, forming a bulb-shaped consolidated crushed stone portion 102 (formation of consolidated crushed stone portion).

When the rotational torque reaches the set value, the rod 9 connected to the casing pipe 10 is raised to a specified height of about 10 cm, and the work of constructing the columnar crushed stone pile 103, which serves as a consolidated pile, begins.

After the above-mentioned compacted portion is formed, as shown in Figure 12, the rod 9 is inserted into the casing pipe 10, and the lower spiral blade 32 and the tip bit 31 protrude from the lower part of the casing pipe 10 with the rod 9 inside, and the rod 9, which has its axial positional relationship locked, repeats the crushed stone input and up-and-down repeated compaction with a preset compaction pressure input and the rotational torque, forming a columnar crushed stone pile 103 with external dimensions suitable for a weak ground environment up to the height of the ground G (Figure 13). At this time, the magnitude of the internal friction angle (e.g., 30 degrees or more) of the crushed stone 42 can be used to promote the compaction of the soil particles of the original ground. In addition, the crushed stone pile 103 is constructed by, for example, pulling up the casing pipe 10 and the rod 9 to a predetermined height of about 10 cm (pulling up to a predetermined height), discharging additional crushed stone 42 into the ground, and repeating up and down movements in the opposite direction to the excavation (adding crushed stone, up and down movements in the opposite direction to the excavation) to construct the crushed stone pile 103 to a predetermined height using the crushed stone 42 (construction of the crushed stone pile to a predetermined height), and then pulling up the casing pipe 10 and the rod 9 again to a predetermined height (pulling up to a predetermined height), discharging additional crushed stone 42 into the ground, and repeating up and down movements in the opposite direction to the excavation (adding crushed stone, up and down movements in the opposite direction to the excavation). In this way, the crushed stone 42 is discharged from the casing pipe 10 to the excavation hole 101 at each predetermined height, and the discharged crushed stone 42 is repeatedly consolidated, and the crushed stone pile 103 of the design height is constructed (construction of the crushed stone pile is completed).

In this way, a columnar space is formed by inserting the casing pipe 10 to a specified depth into the ground, and an appropriate amount of crushed stone 42 is poured into the lowest end of the borehole 101. In the process of compacting the crushed stone blocks with vertical load, the propagation of the pushing pressure due to the internal friction angle of the crushed stone 42 can be used to compact a wider area of the original ground. In addition, the crushed stone compaction process during construction of the crushed stone piles 103 promotes consolidation of the soil particles of the original ground through the inner wall of the borehole 101, and compacting the ground around the borehole 101 can improve the seismic isolation of the entire construction area.

In addition, using crushed stone 42 with a large internal friction angle is advantageous for compacting the ground, but if crushed stone 42 with an internal friction angle of 30 degrees or more is used, the crushed stone 42 will harden in the hopper body 56, making it impossible to drop and supply the crushed stone 42 from the crushed stone inlet 41. In addition, the crushed stone 42 supplied into the casing pipe 10 will harden in the casing pipe 10, rotate together with the rod 9 and the casing pipe 10 while still solidified, and will not be able to drop and supply into the borehole 101. In this case, if the rod 9 is rotated counterclockwise with the cam clutch 15 in the non-rotation mode so that the casing pipe 10 does not rotate, the upper spiral blade 34 will agitate the crushed stone 42 at the tip side of the casing pipe 10, and the crushed stone 42 will be able to be supplied into the borehole 101 from the tip of the casing pipe 10.

As described above, when the casing pipe 10 is pressed into the ground, earth pressure resistance occurs on the outer surface of the casing pipe 10. In the prior art, a method of inserting the casing pipe with a larger outer diameter than the lower end is used as a method of avoiding this. However, if the outer diameter of only the lower end is large, a cavity is generated between the inner wall of the drilling hole 101 and the outer surface of the casing pipe 10 due to the difference in size, and the original ground is loosened at the same time as the casing pipe 10 is inserted. In addition, when the casing pipe 10 is pulled out of clay soil, clay adheres to the outer surface of the casing pipe 10, so there is a possibility that a drilling hole space larger than the diameter of the casing pipe 10 is formed. It is difficult to restore the ground that has once been loosened by compacting it with a filling material, etc., and it can be said that this is unreasonable from the viewpoint of the original ground reinforcement. In contrast, in this embodiment, the casing pipe 10, which has the same outer diameter and a flat outer surface, and the lower spiral blade 32 are rotated simultaneously to press in and pull out while cutting friction, so that construction can be performed without loosening the original ground.

In addition, known liquefaction countermeasure methods include ground compaction, solidification (solidifying the entire ground), replacement (replacing soil), lowering the groundwater level (artificially lowering the groundwater level), pore water dissipation (absorbing water pressure with sand piles or crushed stone piles), and increasing shear resistance (resisting external forces). However, all of these are large-scale construction methods using large machinery, and it is practically impossible or difficult to use them as liquefaction countermeasures for detached residential ground. In contrast, in this embodiment, by adopting the above-mentioned construction method, ground compaction, replacement, soil particle pore water pressure dissipation, and shear resistance strengthening can be incorporated into the construction process, and a ground that is seismically isolated and liquefaction-resistant for the entire construction area can be constructed through a complex synergistic effect. This construction method allows the selection of construction machinery of a size according to the construction scale of the liquefaction prevention construction work, and the advantages of each type of construction are incorporated into the construction method, improving the suppression performance through the synergistic effect of seismic isolation and liquefaction, making it possible to miniaturize construction machinery.

In this way, in this embodiment , the system comprises a casing pipe 10 which is rotated and pressed into the ground to create a columnar space, a rotating rod 9 arranged within the casing pipe 10, the rod 9 which is rotated by a rotary drive unit 7 and inserted into the ground, the casing pipe 10 which is fitted around the rod 9 and inserted into the ground, a crushed stone inlet 41 provided on the outer periphery of the casing pipe 10, a hopper body 56 which is arranged on the ground and has an insertion hole 57 for the casing pipe 10 at its bottom, and a stirring means 71 provided in the hopper body 56 for stirring the crushed stone 42 which serves as the internal filler material. Therefore, by stirring the crushed stone 42 in the hopper body 56 with the stirring means 71, the crushed stone 42 can be smoothly dropped and supplied into the casing pipe 10 from the crushed stone inlet 41.

In this embodiment , the stirring means 71 comprises a rotating body 58 that rotates due to the rotation of the casing pipe 10, and a stirring blade 70 which serves as a stirring section provided on this rotating body 58, so that the rotation of the casing pipe 10 can be utilized to rotate the stirring blade 70 to stir the crushed stone 42.

In this embodiment , a tip bit 31 serving as a drilling bit is provided at the tip of the rod 9, and a lower helical wing 32 serving as a tip side helical wing and an upper helical wing 34 serving as a base side helical wing in the same spiral direction are provided at the tip side of the rod 9, and a gap 33 is provided in the longitudinal direction of the rod 9 between the lower helical wing 32 and the upper helical wing 34.Therefore, by filling the gap 33 with crushed stone 42 serving as a filling material and inserting the casing pipe 10 into the ground, the crushed stone 42 acts as a lid to prevent the excavated soil from entering the casing pipe 10.

In this way, in this embodiment , the rotary drive device 7 is equipped with a cam clutch 15 as a switching means that can switch between a rotation mode in which the casing pipe 10 rotates together with the rod 9, and a non-rotation mode in which the rod 9 rotates but the casing pipe 10 does not rotate.In the rotation mode, the rod 9 and the casing pipe 10 rotate together in the same rotational direction to be inserted or removed from the ground, and when the crushed stone 42, which serves as filling material, inserted into the casing pipe 10 has hardened, the mode can be switched to the non-rotation mode, and the rod 9 can be rotated while the casing pipe 10 is not rotating, thereby stirring and loosening the hardened crushed stone 42.

In this embodiment, corresponding to claim 1 , a rod 9 having helical wings 32, 34 and a casing pipe 10 fitted around the rod 9 are used, the rod 9 and the casing pipe 10 are inserted into the ground to a predetermined depth, and the rod 9 is rotated in the direction opposite to excavation to form a crushed stone pile 103 as a compaction pile in the ground with crushed stone 42 as a filling material in the casing pipe 10. In this ground improvement method, the rod 9 is provided at its tip with the lower helical wing 32 as a tip side helical wing and the upper helical wing 34 as a base side helical wing in the same helical direction, and a gap is formed between the lower helical wing 32 and the upper helical wing 34 along the length of the rod 9. A gap 33 is provided in the casing pipe 10, and with the lower spiral blade 32 protruding from the tip of the casing pipe 10, the rod 9 is inserted to the specified depth while rotating in the counter-excavation direction together with the casing pipe 10.By filling the gap 33 with crushed stone 42 as a filler material to prevent the excavated soil from entering the casing pipe 10, the rod 9 is inserted together with the casing pipe 10 while rotating in the counter-excavation direction, so that the casing pipe 10 can be inserted to the specified depth while compacting the ground, and a columnar cylindrical space for introducing crushed stone can be secured inside the casing pipe 10.

In this manner, in this embodiment, corresponding to claim 2 , in soft ground, the lower helical blade 32, which is the tip side helical blade, inserts the rod 9 together with the casing pipe 10 while rotating in the counter-excavation direction, and in ground where the lower helical blade 32 is harder than soft ground and cannot be inserted by rotation in the counter-excavation direction, the rod 9 is inserted while rotating in the excavation direction. Therefore, in ground where it is not possible to insert the rod 9 and casing pipe 10 by rotating in the counter-excavation direction, the rod 9 can be switched to rotating in the excavation direction, and the underground soil is loosened and stirred while excavating, and then the rotation is returned to the counter-excavation direction so that the rod 9 and casing pipe 10 can be inserted into the ground.

As the effects of the embodiment, the upper helical blade 34 has fewer turns of the spiral than the lower helical blade 32, so the lower helical blade 32, which has a larger number of turns, consolidates the ground and crushed stone 42 by rotating in the direction opposite to the excavation, and the upper helical blade 34 has a smaller number of turns of the spiral, so that the crushed stone 42 supplied from above is less likely to get clogged on the upper helical blade 34. In addition, since the outer diameter of the lower helical blade 32 is formed to be the same as the outer diameter of the casing pipe 10, when the rod 9 is pulled up toward the base end in the axial direction in the non-rotation mode, the lower helical blade 32 engages with the tip of the casing pipe 10, and the casing pipe 10 can move toward the base end in the axial direction. Furthermore, since the crushed stone inlet 41 on the base end side of the casing pipe 10 is larger than the other crushed stone inlets 41, the crushed stone 42 can be efficiently supplied during the construction of the crushed stone consolidation part 102, which uses a relatively large amount of crushed stone 42.

In addition, the mixing means 71 includes a plurality of spheres 63 that contact the outer peripheral surface of the casing pipe 10 and the inner peripheral surface of the rotor 58, so that the rotation of the casing pipe 10 is transmitted to the rotor 58 by the rotating spheres 63, and the crushed stone 42 in the hopper body 56 can be mixed by the plurality of mixing blades 70 provided on the rotor 58 without hardening. Furthermore, the surfaces of the spheres 63 are made of an elastic material such as rubber balls, so that the rotation of the casing pipe 10 made of a hard material such as metal can be smoothly transmitted. Also, as shown in FIG. 5, the agitator blade 70 rotates to the right as the rod 9 rotates in the direction opposite to excavation (left rotation), and since the outer end 70G of the agitator blade 70 is set at an angle to the direction of rotation during this right rotation, the tilted agitator blade 70 rotating to the right can guide the crushed stone 42 to the center inside the casing pipe 10, pushing the crushed stone 42 outward from the tip of the casing pipe 10, and the lower spiral blade 32 rotating in the direction opposite to excavation can compact the crushed stone 42 downward.

In addition, crushed stone 42 with a large internal friction angle of 30 degrees or more is used as the filling material, and the propagation of the pushing pressure due to the internal friction angle can be used to compact a wider area of the original ground. Furthermore, by using the stirring means 71, crushed stone 42 with a large internal friction angle can be used, and the unevenness of the crushed stone shape can be prevented from interlocking with the crushed stone 42 and forming clumps inside the hopper body 56.

Furthermore, this embodiment has the following characteristic configuration. A rod 9 is installed inside a casing pipe 10 that is rotated and pressed into the ground to create a columnar space, and a tip bit 31, which is an inverted cone bit that spreads the crushed stone 42 and the original ground, is attached to the lowest end of the rod 9. A lower spiral blade 32 for supplying crushed stone and compacting it is wound about two times on the top of this tip bit 31, and an upper spiral blade 34 for supplying crushed stone and wound about two times is further installed about 20 cm above the rod 9.

In addition, multiple crushed stone inlets 41 are provided at intervals in the axial direction of the casing pipe 10.

In addition, when the casing pipe 10, which has a flat outer surface and is pressed into the ground, is pulled out, friction cutting is performed by rotating the casing pipe 10 to reduce the earth pressure resistance on the outer surface of the casing pipe 10.

The upper end of the casing pipe 10, which houses the rod 9, is equipped with a cam clutch 15 that selects between simultaneous rotation of the casing pipe 10 and rod 9, and rotation of the rod 9 alone.

In addition, as a method of securing a cylindrical space for introducing crushed stone while compressing the original ground by the outer volume of the casing pipe 10, the lower spiral blade 32 and the tip bit 31 are protruded from the lower end of the casing pipe 10, and the rod 9 and casing pipe 10 are rotated left (rotating in the opposite direction to the excavation) in a repetitive up and down motion to compress the original ground while pressing the casing pipe 10 into the cylindrical space for introducing crushed stone into the ground.

The device is also equipped with a funnel-shaped hopper device 51 for feeding crushed stone, which is installed at the core of the pile on the ground G. The hopper body 56 is wide at the top and slightly wider at the bottom than the diameter of the casing pipe 10, and is shaped so that the casing pipe 10 can penetrate the hopper body 56 and be inserted into the ground. The device is also equipped with a crushed stone agitator 70 that uses the rotational force of the casing pipe 10 to rotate the crushed stone 42 from the crushed stone inlet 41 of the casing pipe 10, and guides the crushed stone 42 to the crushed stone inlet 41 of the casing pipe 10.

In addition, in the process of constructing crushed stone piles in the ground, the original ground is compacted by utilizing the large internal friction angle of the crushed stone 42 from the lowest end of the construction pile, and by using crushed stone 42 with a large internal friction angle and providing a hopper device 51, the crushed stone 42 can be smoothly dropped and supplied into the casing pipe 10.

In addition, the tip of the columnar crushed stone pile 103 constructed in the ground can be expanded to form a crushed stone compaction portion 102 that serves as a support pressure bulb.

The casing pipe 10 is inserted into the deep soft ground layer of the supporting layer to a pre-determined depth, and the cylindrical space inside the casing pipe 10 is filled with filler material such as sand, gravel or crushed stone 42 while being compacted. The volume of the material added increases the compaction density of the original soil particles, while at the same time creating a crushed stone compaction portion 102 in the soft ground, which acts as a support pressure bulb.

In addition, in a layered ground of differing ground strength, sand and/or crushed stone 42 can be inserted into the intermediate weak layer to increase the compaction degree of the original ground.

In addition, during the process of constructing the crushed stone pile and extracting the casing pipe 10, the outer periphery of the columnar crushed stone pile formed by rotating the casing pipe 10 and repeatedly moving it up and down can be compacted and friction on the outer periphery of the casing pipe 10 can be reduced.

In addition, we can provide a ground improvement device and a ground improvement method that incorporates all of the characteristics of well-known liquefaction prevention measures, such as ground compaction, pore water dissipation, and increased shear resistance, into the actual construction work and reconstructs it into a liquefaction prevention method. Furthermore, this method allows the selection of construction machinery of a size appropriate to the scale of the liquefaction prevention work.

In addition, when the casing pipe 10 is inserted into highly permeable ground, the water level inside the casing pipe 10 rises. This rise in water level creates buoyancy in the injected crushed stone 42, slowing down the settling speed, so in this embodiment, the crushed stone pile 103 can be constructed while draining water from inside the casing pipe 10.

Figures 15 and 16 show a second embodiment of the present invention, in which the same parts as those in the first embodiment are given the same reference numerals and their explanations are omitted. As shown in the figures, this example shows a construction example in a weak layer.

In this embodiment, soil particles from the original ground are driven horizontally and vertically into a deep soft ground layer of the supporting layer, increasing the soil particle density and constructing a crushed stone compaction section 102 with crushed stone 42 at a desired depth, and then a columnar crushed stone pile 103 is constructed on top of the crushed stone compaction section 102.

As in the first embodiment, the casing pipe 10 is inserted to the pre-determined set depth, and crushed stone is poured in. The rod 9 is rotated left while the crushed stone pouring and compaction are repeated intermittently to ensure vertical bearing capacity. When more crushed stone 42 is poured in under this condition, the crushed stone 42 begins to radially expand horizontally within the range of the rotational torque due to the rotation of the lower spiral blade 32, and a bulb-shaped crushed stone compaction portion 102 is constructed. A vertical load is applied to this crushed stone compaction portion 102, the bearing capacity is confirmed, and a columnar crushed stone pile 103 is constructed above.

Furthermore, in a layered ground with different ground strengths, when the rotating rod 9 and casing pipe 10 are used to drive and pour crushed stone into the intermediate weak layer 105 located in the middle, an expanded diameter section 103K of the crushed stone pile 103, which is larger in diameter than the others, is formed in the crushed stone pile 103 as shown in Figures 15 and 16. This expanded diameter section 103K of the crushed stone pile is formed because the intermediate weak layer 105 is weaker than the weak layers above and below it, and the original ground in the intermediate weak layer 105 can be consolidated.

As a method of consolidating and strengthening the weak layer 105 of the intermediate ground layer, the crushed stone 42 is inserted with a constant load and constant motor torque during the construction process of the columnar crushed stone pile 103, so that the amount of crushed stone input is suitable for the ground environment with different degrees of softness. In addition, the rotation of the lower spiral blade 32 in the opposite direction to the excavation pushes the crushed stone 42 into the weak layer, improving the soil particle density of the original ground, thereby improving the strength of the intermediate weak layer.

In this way, this embodiment achieves the same effects and advantages as the above-mentioned embodiment 1. Also, in this way, the crushed stone pile 103 can be formed with an enlarged diameter portion 103K in the crushed stone pile 103 above the crushed stone compaction portion 102.

Figures 17 and 18 show a third embodiment of the present invention. The same parts as those in the above embodiments are given the same reference numerals, and their explanation will be omitted. The figures show a modified cam clutch.

In this example, the cam clutch 15A has a connecting arm 17A, which is a connecting part, and is formed in a generally L-shape with a vertical piece 18T and a lower piece 18S. The vertical piece 18T is rotatably attached to the main body 16 by a pivot 19, and is rotated by a connecting part driving means (not shown) between a connected position where the lower piece 18S is inserted into the connecting hole 21 as shown by the solid line in FIG. 17, and a disconnected position where the lower piece 18S is removed from the connecting hole 21 as shown by the dashed line in FIG. 17 so that both connecting arms 17A, 17A are closed. The main body 16 has a slit-shaped groove 22 that opens on the outer periphery, the pivot 19 is provided in this groove 22, and the upper end side of the vertical piece 18T is loosely inserted into the groove 22.

Also, as shown in FIG. 17, in the non-rotation mode, when the rod 9 is pulled up toward the base end in the axial direction, the left side of the lower spiral wing 32 in the figure engages with the tip of the casing pipe 10, causing the casing pipe 10 to move toward the base end in the axial direction. Therefore, a stay 108 is provided as a support between the right side of the lower spiral wing 32 in the figure and the tip of the casing pipe 10, and the lower part of this stay 121 is fixed to the upper surface of the lower spiral wing 32, and the upper part abuts against the tip edge of the casing pipe 10.

In this way, this embodiment provides the same effects and advantages as the above embodiments.

Figure 19 shows the fourth embodiment of the present invention, in which the same parts as those in the above embodiments are given the same reference numerals and their explanations are omitted. As shown in the figure, this example shows an example in which an extension casing pipe 10A is connected to a casing pipe 10 used to start excavation.

Generally, a leader 5 is attached to the vehicle body 2, which is the main body of the ground improvement device 1. A rotary drive device 7 equipped with an electric or hydraulic drive motor is attached to the leader 5, and the length of the pile to be driven is determined by the up and down stroke of the drive motor, but long leaders cannot be attached to small ground improvement devices.

In this embodiment, as shown in FIG. 19, the casing pipe 10 is driven to the lower limit of the stroke of the leader 5 by the rotary drive device 7, which is a penetrating rod 9 longer than the leader 5, and the lifting drive device 8, which raises and lowers the rotary drive device 7. Then, the cam clutch 15 is switched to the non-rotation mode and the lock by the rod lock 12 is released, leaving the rod 9 and casing pipe 10 in the ground, and the rotary drive device 7 is moved upward.

The extension casing pipe 10A has a small diameter spigot 111 at its tip, which is inserted into the casing pipe 10 and connected to the casing pipe 10 by a connecting means 112 such as a flat screw that is screwed into the spigot 111 while inserted. The extension casing pipe 10A has a connecting hole 21 at its base end, just like the casing pipe 10.

The extension casing pipe 10A is provided with a rod insertion section 113 that is open over the entire length, including the insertion section 111. The rod insertion section 113 also serves as a crushed stone inlet.

After the casing pipe 10 is driven into the lower limit of the leader stroke by the rotation drive device 7 equipped with a through-type drive motor, which is a rod 9 longer than the length of the leader 5, the rod lock 12 is released and the cam clutch 15 is switched to non-rotation mode, and the rotation drive device 7 is moved upward by the lift drive device 8 as shown in Figure 19.

The extension casing pipe 10A is fitted to the ground rod 9 by inserting the ground rod 9 through the rod insertion section 113, and the spigot section 111 of the extension casing pipe 10A is inserted into the upper end of the casing pipe 10, and the two are connected by the connecting means 112. The cam clutch 15 is also connected to the upper end of the extension casing pipe 10A.

After connecting the extension casing pipe 10A of the same diameter as the driven casing pipe 10 in this way, it is rotated and pressed in to the set depth in the same way as the casing pipe 10. The extension casing pipe 10A has a rod insertion section 113 cut in the axial direction with a cut width that does not pass through the rod width in a C-shaped horizontal cross section. By connecting this extension casing pipe 10A, it becomes possible to install a crushed stone pile 103 that is longer than the stroke of the leader 5.

In existing ground improvement machines using other construction methods, the function of rotating horizontally left and right by raising and lowering a hydraulic or electric motor, as well as a constant motor torque, pressure input, and pull-out force can be shared with all machinery and equipment via the special plug, making it possible to build a foundation that suppresses liquefaction and has anti-seismic measures. For example, if a device has a through-type drive motor that penetrates and drives the rod 9 and is installed on the leader 5 so that it can be raised and lowered, it can be used with various machines by using a special plug that connects the through-type drive motor to the main body 16 of the cam clutch 15.

In this embodiment, in accordance with claim 1 , the rotary drive device 7 is provided on the leader 5 so that it can be raised and lowered, the rotary drive device 7 rotates the rod 9 to insert it into the ground, and an extension casing pipe 10A is used as a casing pipe having a rod insertion portion 113 through which the rod 9 can be inserted from the diameter direction along the entire length of the side surface. The tip of the extension casing pipe 10A is connected to the base end of the casing pipe 10, so that after the casing pipe 10 is inserted into the ground, the rod 9 is inserted into the rod insertion portion 113 from the side, and the extension casing pipe 10A is fitted to the rod 9, and the extension casing pipe 10A is connected to the casing pipe 10 inserted into the ground, so that the integrated casing pipe 10 and the extension casing pipe 10A can be inserted into the ground. In this way, the casing pipe 10 and the extension casing pipe 10A, which are longer than the length of the leader 5, can be inserted into the ground.

Figure 20 shows a fifth embodiment of the present invention, in which the same parts as those in the above-mentioned embodiments are given the same reference numerals, and their explanation will be omitted. The figure shows modified examples of the upper and lower spiral blades.

As shown in the figure, the upper helical blade 34 is formed so that the outer diameter at the bottom is a maximum diameter that is slightly smaller than the inner diameter of the casing pipe 10, and the outer diameter decreases toward the top. In other words, the radial dimension between the center of the rod 9 and the outer edge of the upper helical blade 34 decreases from the lower end to the upper end. Specifically, as shown in the planar cross-sectional view of Figure 20, the upper helical blade 34 is formed so that the outer peripheral edge 35S at the tip (lower end) has a radius that is close to the inner surface of the casing pipe 10, and the radius gradually decreases toward the outer peripheral edge 35 at the base end (upper end).

In this embodiment, the upper spiral blade 34 is formed so that its outer diameter decreases toward the top, making it difficult for crushed stone 42 and excavated soil to rise from below the upper spiral blade 34, and making it easier for crushed stone 42 to be sent downward from above.

The present invention is not limited to the present embodiment, and various modifications are possible within the scope of the present invention. For example, the tip bit is shown to be triangular pyramid shaped in the embodiment, but it may be a square pyramid or a pentagonal pyramid with four or more sides. In addition, the stirring means is shown to use the rotation of the casing pipe, but it may be a means using a power source such as an electric motor . Furthermore, the embodiment shows a stirring blade as a plate-shaped stirring part, but a stirring part of various shapes other than a plate-shaped one, such as a multiple rod-shaped stirring part, can be used.

1 Ground improvement device 5 Leader 7 Rotation drive device 8 Lifting drive device 9 Rod 10 Casing pipe
10A Extension casing pipe (casing pipe)
15,15A cam clutch (switching means)
31 Tip bit (drilling bit)
32 Lower spiral wing (tip side spiral wing)
33 Gap 34 Upper spiral wing (tip side spiral wing)
41 Crushed stone inlet 42 Crushed stone (filling material)
51 Hopper device (agitation means)
56 Hopper body 57 Insertion hole 70 Plate-shaped stirring blade (stirring portion)
71 Stirring means 101 Boring hole 102 Crushed stone compaction part 103 Crushed stone pile (compacted pile)
113 Rod insertion part

Claims (2)

A rod having a spiral blade and a casing pipe fitted to the rod are inserted into the ground to a predetermined depth, and the rod is rotated in the direction opposite to excavation to form a consolidation pile in the ground using the filling material in the casing pipe.
a tip-side helical wing and a base-side helical wing having the same helical direction are provided at the tip side of the rod, and a gap is provided between the tip-side helical wing and the base-side helical wing in the longitudinal direction of the rod,
A ground improvement method in which the rod is inserted to the predetermined depth while rotating the casing pipe together with the casing pipe in a direction opposite to excavation with the tip side spiral blade protruding from the tip of the casing pipe,
A rotary drive device is provided on the leader so as to be capable of ascending and descending, and the rod is rotated by the rotary drive device to be inserted into the ground;
A ground improvement method characterized by using an extension casing pipe having a rod insertion portion along the entire length of its side surface through which the rod can be inserted from the radial direction, and connecting the tip of this extension casing pipe to the base end of the casing pipe . A ground improvement method as described in claim 1, characterized in that when the tip spiral blade is in soft ground, the rod is inserted together with the casing pipe while rotating in the anti-excavation direction, and when the tip spiral blade is in ground that is harder than the soft ground and cannot be inserted by rotating in the anti-excavation direction, the rod is inserted while rotating in the excavation direction.

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