JP2013159987A - Ground liquefaction prevention and consolidation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ground liquefaction prevention and consolidation method having both the functions of strong support on a ground and drainage.SOLUTION: Blocking rods 14 each of which is housed in a casing 10 and is equipped with a drilling bit 14c at its tip and the casings 10 are rotated and pressed into a ground 1 to form drilled holes. After the drilled holes are formed, the blocking rods 14 are pulled out from the casings 10, crushed stones 2 are charged into each of the casings 10, and the charged crushed stones 2 are rolled by a rolling rod 11 and pressed out from the casing to form a foot protection part 3A. A hoop-shaped belt 21 is inserted into the casing 10 and installed above the foot protection part 3A, the casing 10 is pulled out from the drilled hole, the crushed stones 2 are newly charged into a hollow part of the installed hoop-shaped belt 21, and the crushed stones in the hoop-shaped belt 21 are rolled by the rolling rod to form a crushed stone pillar 3.

Description

  The present invention relates to a soft ground strengthening method for strengthening the ground where a building stands, and in particular, a ground for realizing land strengthening of a detached house at a low cost and reducing liquefaction of the ground. It relates to the strengthening method.

  For relatively large-scale reinforced concrete buildings and steel buildings such as buildings and condominiums, a foundation pile structure that reaches a solid ground foundation layer deep in the ground of the erected land is buried, and the foundation pile structure is placed on the foundation pile structure. Built. As construction methods of foundation pile structures of these large-scale buildings, various foundation pile materials such as steel pipe piles and PHC piles are constructed by various embedment methods that embed the land into the ground by cutting or hammering or hydraulic pressure. .

  On the other hand, in the construction of detached houses and relatively small apartment houses, full-scale foundation pile construction as described above is often difficult due to cost problems. In the case of soft ground that is determined not to meet certain standards, the ground surface improvement work (soil replacement, etc.) is carried out, and then a simple reinforced concrete housing foundation is applied to build the house. It is normal.

  On the other hand, large-scale earthquakes and landslide disasters caused by heavy rains have frequently caused the collapse of house ground in places that were constructed on soft ground or slopes that were landfills of fields, rivers, or seas.

  When building a house on soft ground, it is clear that conventional ground reinforcement measures by surface improvement of land cannot cope with ground depression, uplift or liquefaction caused by earthquakes of a certain scale or larger. It has become.

  As reinforced soil wall construction methods for landslides caused by earthquakes or heavy rains on slopes, a number of anchor type reinforced soil walls, tail armure construction methods, geotextile reinforcement walls (see, for example, Patent Document 1), and the like are known.

  And when the land of a detached house is soft ground that does not meet the prescribed criteria, not only surface improvement work (such as soil replacement) of the land, but also low-cost reinforced soil pile construction is performed As an example of such a simple reinforced soil pile method, geotextile (high-textured) is obtained by mixing expansive material with cement-based (calcium or lime-based) water absorption into cutting soil, waste glass or demolition glass, etc. There is known a technique in which a water-permeable sheet made of molecular chemical fiber material) is tightly wound in a cylindrical shape and used as a reinforcing pile (for example, see Patent Document 2).

  In addition, a ground improvement pile is known in which an outer peripheral surface of a large-diameter gravel formed on a soft ground is covered with a material having a predetermined strength and durability such as a mesh sheet (for example, a patent document) 3).

JP 2010-90592 A JP-A-7-305334 JP-A-6-294136

  However, N value (value indicating the strength of the ground required in the standard penetration test, using a boring hole, the tip of the rod rod (steel rod) is 5.1 cm in diameter and 81 cm in length. A sample with a hollow cylindrical sampler was dropped freely from a height of 75 centimeters with a hammer weighing 63.5 kilograms and the number of impacts required for penetration per 30 centimeters of penetration depth was 4 or less. In the case of a soft ground, a highly rigid pile or reinforced pile construction method may be buckled by a deformation strain force applied to the ground by an earthquake. In particular, when the N value of the pile head is 4 or less, the risk of buckling is particularly high. Therefore, in the case of the ground of a detached house, it has a flexible structure for deformation strains up to a certain extent, and can withstand deformation strains exceeding a predetermined level without buckling while following the deformation of the ground. It must have a flexible structure.

  In addition, in the case of the ground of a detached house, in order to prevent or reduce the liquefaction of the ground due to earthquake motion, if the groundwater level rises and is pushed up into the ground, a drainage drain that allows water to pass through Must have function.

  In addition, hexavalent chromium contained in the cement-based solidifying agent has a risk of leaching into the land depending on the soil quality, and contaminates the ground soil.

  However, in the method for producing the reinforced soil pile and the reinforced soil pile described in Patent Document 2, the tubular geotextile filling member is made of ground excavated soil, glass waste material, demolition glass, etc. Due to the construction to expand the volume, the drainage is poor and it does not have a function as a drainage drain.

  Although the ground improvement pile described in Patent Document 3 has drainage properties, it is pressed by the building load after construction, and due to the construction method of gradually increasing the strength by repeatedly subsidence and compaction, it is considerable to stabilize It takes time, and considering the amount of settlement before that, it is not sufficient for ground strengthening.

  In view of the above, it is an object of the present invention to provide a ground reinforcement method using a pile having a deformability that is not easily buckled by following the deformation of the ground as well as supporting the ground firmly.

  And this pile makes it the subject to provide the ground reinforcement method which reduced the amount of settlement of a pile by improving the adhesiveness with the surrounding soil buried.

  Moreover, this pile has also the function of the drainage drain, and is making it the subject to provide the ground reinforcement method corresponding also to liquefaction.

  In order to solve the above-mentioned problems, a ground strengthening method according to the present invention is a ground strengthening method for strengthening the ground by embedding a crushed stone pillar in the ground, and is housed in a casing and has a bit for excavation at the tip. A first step of rotationally press-fitting the provided blocking rod and the casing into the ground to form a digging hole; and after the formation of the digging hole, the blocking rod is pulled out of the casing, and crushed stone is put into the casing. Inserting a rolling rod into the casing and inserting the rolling rod into the casing, and rolling out the crushed stone charged in the second step with the rolling rod to form a rooted portion. A third step of performing, a fourth step of inserting a cylindrical shear reinforcement band into the casing and installing it above the root-solidifying portion, and extracting and installing the casing from the digging hole A fifth step of newly introducing the crushed stone into the hollow part of the shear reinforcement band, and rolling the crushed stone in the shear reinforcement band with the rolling rod to form the crushed stone column. Provide a strengthening method.

  The shear reinforcement band is a hoop-shaped band. Further, the material of the shear reinforcement band is high density polyethylene.

  Further, the closing rod has a plate for closing the front end opening of the casing, and the bit is provided below the plate.

  The construction machine that drives the vertical movement of the casing, the closing rod, and the rolling rod has two types of drive shafts. The casing and the closing rod are attached to one drive shaft, and the rolling machine The pressure rod is attached to the other shaft. At this time, the said casing and the said obstruction | occlusion rod are connected through the connection part which can be isolate | separated.

  Further, the root hardening portion is characterized in that it is compacted so as to protrude in a spherical shape larger than the diameter of the digging hole.

  In addition, the method further includes a step of adding pickled gravel to form the head of the crushed stone pillar. In addition to this, the method includes a step of rolling the upper opening surface of the digging hole with a rolling plate after the addition of the pickled gravel.

  As described above, the present invention provides a ground strengthening method having a structure that is difficult to buckle by combining a crushed stone and a shear reinforcement band by forming a pile made of crushed stone columns.

  Then, by forming the crushed stone column while applying the rolling pressure by the rolling rod, the crushed stone presses the shear reinforcement band against the wall surface of the digging hole, so that the adhesion to the soil around the crushed stone column increases and the amount of settlement is reduced. Can be reduced.

  Moreover, since the crushed stone functions as a drain for drainage, the crushed stone column can reduce liquefaction of the ground.

The example of the construction method of the ground reinforcement method by this invention is shown with sectional drawing. The example of the construction method of the ground reinforcement method by this invention is shown with sectional drawing following FIG. The construction of the construction machine is shown in front view. (A) shows the configuration of the casing and the closing rod in a side sectional view, (b) shows the tip of the closing rod in a plan view, and (c) shows the configuration of the plate in a side sectional view. . Part (a) shows the configuration of the compaction plate in a side sectional view, and part (b) shows the configuration of the compaction plate in a plan view. A configuration of a hoop-like band as a shear reinforcement band is shown in a perspective view.

  Hereinafter, an embodiment of a ground strengthening method according to the present invention will be described in detail with reference to the drawings.

  FIG.1 and FIG.2 is explanatory drawing which shows the construction method of this invention in a cross section, forms a digging hole in the ground 1 using the construction machine 5 shown in FIG. 3, and shows the crushed stone 2 inserted in the formed digging hole. The crushed stone pillar 3 is formed by restraining with a shear reinforcement band. In this case, the crushed stone 2 is preferably the same size, and in this embodiment, either a crushed stone group having a size within a range of 20 mm to 40 mm or a crushed stone group having a size within a range of 60 mm to 100 mm is used. .

  First, the construction machine 5 will be described. As shown in FIG. 3, the construction machine 5 includes a drive unit 6 that moves up and down and a reader 7 having a height of about 10 m that guides the drive unit 6 in the vertical direction. I have. The drive unit 6 has two drive shafts 6A and 6B. The drive shaft 6A is attached with a casing 10 and a closing rod 14 which are cylindrical bodies having a cross-sectional diameter of 355 mm. A pressure rod 11 is attached.

  The drive unit 6 applies rotational force simultaneously to the drive shafts 6A and 6B while reciprocating up and down individually. And the drive part 6 changes the position of drive shaft 6A, 6B in the horizontal direction with the ground surface by moving drive shaft 6A, 6B on the predetermined | prescribed circular orbit on a horizontal surface.

  The closing rod 14 is arranged along the longitudinal direction inside the casing 10, and is connected to the casing 10 at the connecting portion 15. Then, the closing rod 14 is connected to the drive shaft 6A, and when the rotational movement and vertical movement of the drive shaft 6A are transmitted to the closing rod 14, they are also transmitted to the casing 10 via the connecting portion 15 and both of them are transmitted. To drive. The connecting portion 15 can freely connect and disconnect the closing rod 14 and the casing 10, and when disconnected, only the closing rod 14 is driven.

  The configuration of the casing 10 and the closing rod 14 will be described in detail with reference to FIG. 4A shows a side sectional view of the casing 10 and the closing rod 14, and the closing rod 14 is composed of a rod shaft 14a whose cross section is a square pipe port (100 mm × 100 mm) and a rod shaft accommodating portion 14b. The rod shaft 14a and the rod shaft accommodating portion 14b are connected in a nested structure so that they can be expanded and contracted. The rod shaft 14a of the closing rod 14 is provided with a drilling bit 14c having a conical shape at the tip, and a circular plate 24 on the top of the bit 14c. The retractable closing rod 14 is shown in FIG. ) Portion, the tip opening of the casing 10 is closed by the plate 24, and the state in which the bit 14c protrudes from the casing 10 can be held in a locked state by operating the stopper 19. The operation to the stopper 19 at this time is performed through the operation window 9 provided in the casing 10. Then, excavation is performed by rotationally press-fitting the casing 10 into the ground 1 with the bit 14 c protruding from the casing 10.

  The configuration of the bit 14 c and the plate 24 will be described. The bit 14 c is fixed to the closing rod 14 through the base portion 25. The plate 24 is composed of two separable semi-circular plates 24a and 24b. A concave portion is formed at each edge of the straight portions of the semi-circular plates 24a and 24b. When configured, the plate 24 can be attached to the closing rod 14 by fitting the base portion 25 of the bit 14c into the holes formed by these recesses.

  The semicircular plates 24a and 24b are each formed by sandwiching a semicircular rubber member 28 having an appropriate thickness between a pair of upper and lower iron plates 26 and 27 having a thickness of 6.0 mm. 24b has a diameter of 346 mm, and the peripheral edge of the rubber member 28 protrudes toward the inner peripheral wall of the casing 10 rather than the semicircular plates 24a and 24b. Thereby, when the plate 24 moves in the longitudinal direction together with the bit 14 c in the casing 10, it moves in contact with the inner wall of the casing 10 by the rubber member 28.

  A compressed air supply pipe 30 is attached to the side of the casing 10, and the compressed air supply pipe 30 is introduced through a valve 31 when the casing 10 is inserted into the ground 1 and then pulled out. Is ejected from the bottom outlet.

  Returning to the description of FIG. 1, the steps of the ground strengthening method using the construction machine 5 will be described. First, the drive shaft 6 </ b> A is horizontally moved by the drive unit 6, and the casing 10 and the closing rod 14 are set on the target point of the ground 1. At this time, the closing rod 14 is locked by the stopper 19 with the plate 24 closing the tip opening of the casing 10 and the bit 14c protruding from the casing 10. Further, the closing rod 14 and the casing 10 are in a state of being connected by a connecting portion 15.

  When the drive unit 6 moves downward while rotating the drive shaft 6A in this state, the casing 10 and the closing rod 14 are rotationally pressed into the ground 1 to perform a digging operation (part (a) in FIG. 1). . The soil cut by the rotation of the bit 14c in this excavation is pushed out in the direction around the casing 10 without moving into the casing 10 because the tip opening of the casing 10 is closed by the plate 24. The side of the rotating casing 10 is pressed against the surrounding soil. Thus, when the casing 10 is rotationally press-fitted into the ground 1 to form a digging hole, the excavated soil is not discharged to the ground surface, but the periphery of the casing 10 is compacted with this soil to form a consolidated state. Therefore, a digging hole having a strong wall surface is formed.

  Part (b) of FIG. 1 shows a state in which the lower end of the casing 10 reaches about 2.5 m from the ground surface, and the digging hole has been completed. In this state, when the connection between the casing 10 and the closing rod 14 at the connecting portion 15 is disconnected, and then the driving portion 6 moves the drive shaft 6A upward, only the closing rod 14 is pulled up above the digging hole. The casing 10 is left behind in the digging hole (part (c) in FIG. 1). And in the state which pulled out the obstruction | occlusion rod 14 from the casing 10, as shown by the arrow, the crushed stone 2 is thrown in ((d) part of FIG. 1). At this time, the semicircular plates 24 a and 24 b are separated and the plate 24 is removed from the closing rod 14.

  Then, the drive shaft 6B is horizontally moved by the drive unit 6, the rolling rod 11 is set on the pit where the casing 10 remains, and the drive shaft 6B is moved up and down while the crushed stone 2 is additionally charged. Then, the rolling rod 11 is reciprocated within the casing 10 (portion (e) in FIG. 1). As a result, the crushed stone 2 held at the lower end of the casing 10 and the crushed stone 2 added to the casing 10 are pushed out of the casing 10 and diffused into the ground 1 to form a root consolidation portion 3A, whereby the crushed stone pillar 3 is consolidated. Is called.

  As a result of the rolling pressure by the rolling rod 11, the root-solidified portion 3A is compacted until it protrudes into a spherical shape larger than the diameter of the shaft portion 3B of the crushed stone column 3 to be formed later. By forming such a solidified part 3 </ b> A, the crushed stone pillar 3 can ensure the tip support force against the load of the building constructed on the ground surface of the ground 1.

  When the root consolidation part 3A is formed, a cylindrical shear reinforcement band is inserted into the casing 10 and installed above the root consolidation part 3A (part (f) in FIG. 1). As the shear reinforcement band, a hoop-shaped band or a spiral-shaped band conventionally used for preventing buckling can be used in an Rc (reinforced concrete) column reinforcement or the like. In this embodiment, a hoop-like band 21 is used, and as shown in FIG. 6, hoops 21a are laminated to a height of 2 m at a pitch interval of 22 mm, for example, and are configured in a cylindrical shape. At this time, the hoop 21a is supported in the vertical direction by a plurality of support bodies 21b arranged in a circle.

  The hoop-shaped band 21 is made of high-density polyethylene with a high tensile strength used for civil engineering. Among them, Tensor (registered trademark), which is particularly excellent in tensile resistance and creep resistance, is optimal in the field of ground reinforcement. Therefore, further strengthening against buckling can be achieved.

  After inserting the hoop-like band 21 into the casing 10, the crushed stone 2 is filled in the hoop-like band 21 (part (g) in FIG. 1). And the drive shaft 6A is horizontally moved by the drive part 6, and the obstruction | occlusion rod 14 of the state from which the plate 24 is removed is set so that it may be located on a digging hole.

  Next, the drive shaft 6A is driven, and the closing rod 14 is inserted into the hoop-like band 21 (part (h) in FIG. 1), and is lowered until the bit 14c reaches below the hoop-like band 21 (FIG. 1). (I) part).

  Then, in a state where the closing rod 14 is in contact with the casing 10 at the connecting portion 15, both are connected by the connecting portion 15, and after the connection, the drive shaft 6 </ b> A is moved upward by the driving portion 6, 10 are pulled up from the burrow together (portion (j) in FIG. 2). At this time, the compressed air supply pipe 30 injects the compressed air introduced through the valve 31 from the lower end outlet.

  When the pulling up of the closing rod 14 and the casing 10 from the digging hole is completed, the stopper 19 is operated to release the locking state of the closing rod 14, and the rod shaft 14a is made free. Then, the semicircular plates 24a and 24b are combined, and at the time of this combination, the plate 24 is attached to the closing rod 14 by sandwiching the base portion 25 with the concave portion at the edge of the straight portion of the semicircular plates 24a and 24b (see FIG. (K) part). At this time, in order to prevent the rod shaft 14a of the closing rod 14 in a free state from dropping into the digging hole due to its own weight, the shielding plate 27 temporarily covers the opening of the digging hole.

  After the plate 24 is attached to the closing rod 14, the stopper 19 is operated again to close the tip opening of the casing 10 with the plate 24, and the bit 14c is returned to the state protruding from the casing 10 and locked (FIG. 2). (L) part).

  Subsequently, it becomes a step of forming the shaft portion 3B of the crushed stone pillar 3 as shown in FIG. 6, but first the drive shaft 6B is moved by water in the drive portion 6 to set the rolling rod 11 on the digging hole, The drive shaft 6B is moved up and down to reciprocate the rolling rod 11 within the borehole (part (m) in FIG. 2). At this time, the rolling rod 11 rolls the crushed stone 2 in the hoop-shaped band 21 at a pressure of 25 kN.

  Then, the rolling rod 11 is moved up and down while adding the crushed stone 2 to the hoop-like band 21 and the rolling operation is continued ((n) part in FIG. 2). By the rolling, the hoop-like band 21 is pushed and expanded in the direction of the peripheral wall of the digging hole as indicated by the triangular arrow in the crushed stone 2. On the other hand, the crushed stone 2 is restricted by the tension of the hoop-shaped band 21 due to the rolling force applied by the rolling rod 11, so that the internal friction angle of the shaft portion 3 </ b> B of the crushed stone column 3 is limited. It becomes large and has a large strength against the load of the building from above, and the amount of settlement can be reduced.

When the rolling of the crushed stone 2 into the hoop-shaped band 21 and the rolling by the vertical movement of the rolling rod 11 are finished, the pickled gravel 23 for forming the head 3C of the crushed stone column 3 is loaded from above as indicated by the arrow. Next, the upper opening of the hoop-like band 21 is covered with the rolling plate 20 and then rolled with a rolling rod 11 at a pressure of about 450 kN / m ³ (see FIG. 2 (o)). (P) part 2). As shown in FIG. 5, the rolling plate 20 is a disc having a trapezoidal cross-sectional shape with a thickness of 25 mm, an upper surface diameter of 316 mm, and a lower surface diameter of 250 mm, and includes an installation wire 26.

  By the rolling pressure through the rolling plate 20 by the rolling rod 11, the pickled gravel 23 bites into the gap between the crushed stones 2, and the installation wire 26 is grasped, the rolling plate 22 is taken out from the burrow, and the root consolidation portion The crushed stone pillar 3 which consists of 3A, the axial part 3B, and the head 3C is completed ((q) part of FIG. 2).

  In the crushed stone pillar 3, the diameter of the hoop-shaped band 21 is expanded to a maximum of about 360 mm by rolling the crushed stone 2 against a pit formed by inserting the casing 10 having a diameter of 355 mm into the ground 1. The hoop-like band 21 comes into close contact with the wall surface of the digging hole, and the frictional force increases. Moreover, in the hoop-shaped belt | band | zone 21, the adhesion degree with the wall surface of a digging hole increases also by the crushed stone 2 protruding from between each hoop 21a.

  Land where a building stands by arranging a plurality of crushed stone pillars 3 elongated in the vertical direction formed by the above construction method in the horizontal and vertical directions according to the softness of the ground 1 in the vertical and horizontal directions The ground can be strengthened. That is, the crushed stone pillar 3 is supported by the circumferential friction of the root consolidation part 3A when the load of the foundation and the building constructed on the ground 1 is transmitted, but the crushed stone 2 filled in the middle has a large shear strength, Since the crushed stone pillar 3 is restrained and reinforced from the outside by the hoop-like band 21, the crushed stone pillar 3 can be prevented from changing its shape. Therefore, by increasing the internal pressure and maintaining the shear strength, the ground 1 can be reliably supported against the load from above. Furthermore, since the hoop-like band 21 has a structure in which the hoops 21a are laminated, the hoop-like band 21 also has strength against horizontal force due to earthquake motion.

  In addition, as described above, the crushed stone pillar 3 has a large frictional force between the crushed stone pillar 3 and the ground 1 because a part of the crushed stone 2 protrudes from the gaps between the hoops 21a of the hoop-like band 21, and from this surface. Also, the settlement of the crushed stone pillar 3 is suppressed.

  And the crushed stone pillar 3 has the softness | flexibility which can follow the deformation | transformation of the ground 1 from the soft structure of the structure which restrains the individual crushed stone 2 by the hoop-shaped belt | band | zone 21, and the crushed stone pillar 3 Even if a strong force is applied to one of the three places, the force does not break in order to spread this force throughout, and it has excellent impact resistance. Therefore, when receiving the force of seismic motion, since it deforms integrally with the ground 1, it does not buckle and can support the load from above.

  For example, when the contents of the hoop-like belt 21 are formed by hardening with an expanding material or a solidifying material, the hoop-shaped belt 21 does not have a flexible structure and is destroyed depending on the strength of seismic motion. Sudden loss of support capacity can cause damage to the building.

  Similarly, when the pore water pressure rises due to seismic motion or the like, the crushed stone column 3 functions as a crushed stone drain and drains the pore water to the surface of the ground 1 so that the ground 1 is prevented from being liquefied.

  The present invention provides a ground strengthening method for strengthening the ground on which a building stands, and has industrial applicability.

DESCRIPTION OF SYMBOLS 1 Ground 2 Crushed stone 3 Crushed stone pillar 3A Rooting part 5 Construction machine 6 Drive part 6A, 6B Drive shaft 10 Casing 11 Rolling rod 14 Blocking rod 14c Bit 20 Rolling plate 21 Hoop-shaped band (shear reinforcement band)
23 Mezuke gravel

The present invention relates to a soft ground strengthening method for strengthening the ground where a building stands, and in particular, a ground for realizing land strengthening of a detached house at a low cost and reducing liquefaction of the ground. The present invention relates to a liquefaction prevention and strengthening method.

In view of the above, it is an object of the present invention to provide a ground liquefaction prevention and strengthening method using a pile having a deformability that is hard to buckle by following the deformation of the ground as well as firmly supporting the ground.

And this pile makes it the subject to provide the ground liquefaction prevention and the reinforcement | strengthening method which reduced the amount of subsidence of the pile by improving the adhesiveness with the surrounding soil buried.

Moreover, this pile has also the function of the drainage drain, and is making it a subject to provide the ground liquefaction prevention and reinforcement method corresponding to liquefaction .

In order to solve the above-mentioned problems, the ground liquefaction prevention and strengthening method according to the present invention is a ground strengthening method for strengthening the ground by embedding a crushed stone pillar in the ground, which is housed in a casing and excavated at the tip. A first step of rotationally press-fitting a closing rod provided with a bit for use and the casing into the ground to form a digging hole; and after the formation of the digging hole, pulling out the closing rod from the casing; a second step of turning on the crushed stone within, by inserting the compacting rod to said casing, extruding the crushed stone which supplied in the second step from the casing by compacting by the compacting rod, wherein A third step of forming a root-solidified portion by compacting so as to project in a spherical shape larger than the diameter of the shaft portion of the crushed stone pillar; and inserting a cylindrical shear reinforcement band into the casing to Up A fourth step of installing the crushed stone, pulling out the casing from the digging hole, newly introducing the crushed stone into the hollow portion of the installed shear reinforcing band, and using the crushed stone in the shear reinforcing band to the rolling rod And a fifth step of forming the crushed stone pillar by rolling.

As described above, the ground liquefaction prevention and strengthening method according to the present invention is capable of strengthening the tip support force at the root consolidation part by forming a pile of crushed stone columns having a root consolidation part. By improving the internal pressure by combining with the reinforcing band , the supporting force of the ground increases. Moreover, the crushed stone pillar is not easily buckled against ground fluctuation because of its soft structure .

Claims (9)

A ground strengthening method for strengthening the ground by burying crushed stone pillars in the ground,
A first step of forming a digging hole by rotationally press-fitting a closing rod, which is housed in a casing and provided with a bit for excavation at the tip, and the casing into the ground;
After the formation of the digging hole, a second step of pulling out the closing rod from the casing and putting crushed stone into the casing;
A third step of inserting a rolling rod into the casing and extruding the crushed stone introduced in the second step with the rolling rod to push out from the casing to form a solidified portion;
A fourth step of inserting a cylindrical shear reinforcement band into the casing and installing it above the rooting part;
The casing is pulled out from the digging hole, the crushed stone is newly introduced into the hollow portion of the installed shear reinforcement band, the crushed stone in the shear reinforcement band is rolled with the rolling rod, and the crushed stone column is A fifth step of forming;
A ground strengthening method comprising:   The ground reinforcing method according to claim 1, wherein the closing rod has a plate that closes a front end opening of the casing, and the bit is provided below the plate.   The ground reinforcing method according to claim 1, wherein the shear reinforcement band is a hoop-shaped band.   The ground reinforcement method according to claim 1, wherein the material of the shear reinforcement band is high-density polyethylene.   The construction machine for driving the casing, the closing rod and the rolling rod to move up and down has two driving shafts, and the casing and the closing rod are attached to one driving shaft, and the rolling rod The ground reinforcement method according to claim 1, wherein is attached to the other shaft.   The ground reinforcing method according to claim 5, wherein the casing and the closing rod are connected to each other through a detachable connecting portion.   The ground reinforcement method according to claim 1, wherein the root consolidation portion is compacted so as to project in a spherical shape larger than the diameter of the digging hole.   The ground strengthening method according to claim 1, further comprising a step of introducing pickled gravel to form the head of the crushed stone pillar.   The ground strengthening method according to claim 8, further comprising a step of rolling the upper opening surface of the digging hole with a rolling plate after feeding the pickled gravel.

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