JP5427285B1 - Ground strengthening system and ground strengthening method - Google Patents

Abstract

The present invention provides a ground reinforcement system having a function of a drainage drain together with strong support to the ground.
A crushed stone is formed by compacting a crushed stone, and a diameter of the crushed stone is larger than the diameter of the digging hole and has a shape that protrudes in a spherical shape, and a cylindrical water passage made of a polymer material. In a borehole 7 formed in the ground 1, a pile 3 comprising a columnar portion 3 </ b> A formed constrained by a sheet 4 and a steel pipe 3 </ b> C arranged in a vertical direction in alignment with the central axis of the columnar portion 3 </ b> A Provided. The pile 3 receives the compressive force in the vertical direction from the load from above the ground 1 and the tip support force of the root-solidifying part 3B from below, While maintaining the strength by increasing the internal pressure by suppressing with force, it has the flexibility to follow the deformation from the side of the ground 1 from its flexible structure. And the pile 3 drains out of the ground 1 promptly when rainwater or groundwater pressure rises as a crushed stone drain.
[Selection] Figure 1

Description

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

  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 a construction method of the foundation pile structure of these large-scale buildings, various foundation pile materials such as steel pipes and PHC piles are constructed by various embedding methods for embedding the land into the ground by cutting or hitting 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.

  In addition, the collapse of house ground due to large earthquakes and landslides caused by heavy rains in recent years has frequently occurred on soft ground and sloped land that were originally landfills of rice 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.

  Therefore, the casing is built while discharging the earth and sand to the liquefied formation, and then a foundation pile having an inner diameter smaller than the casing inner diameter is driven to the depth of the support ground so as to coincide with the center of the casing. A method is known in which a crushed stone is filled and then a casing is extracted, and then crushed stone is continuously laid on the ground surface above the foundation pile (see, for example, Patent Document 1). This conventional technology supports the building by the foundation pile, and when the groundwater level rises and is pushed up into the ground by the earthquake motion, it tries to drain the water through the crushed stones arranged around the foundation pile. Is.

  In addition, the filling material in which the expansive material is mixed with cement-based (calcium or lime-based) water absorption into cutting soil, waste glass or demolition glass, etc. is cylindrical with geotextile (water-permeable sheet composed of polymer chemical fiber material) There is also known a technique in which a stake is tightly wound around a stake (for example, see Patent Document 2).

Japanese Patent Laid-Open No. 10-25732 JP-A-7-305334

  However, in the case of Patent Document 1, if the foundation pile has a high rigidity, in the case of soft ground having an N value of 4 or less, there is a high possibility that it will buckle due to the deformation strain force applied to the ground by an earthquake. . In particular, when the ground intermediate layer has an N value of 4 or less, the risk of buckling is particularly high. And in terms of liquefaction countermeasures, there is also a problem that soil enters between crushed stones arranged around the foundation piles over the years and cannot function as a drain passage.

  On the other hand, in the case of Patent Document 2, since the reinforcing pile made of cylindrical geotextile and filling member has a flexible structure, it is less likely to buckle due to the deformation strain caused by the earthquake than the rigid foundation pile. Become. However, in terms of liquefaction countermeasures, the geotextile filling member is composed of ground excavated soil, glass waste, or demolished glass, etc., so that the volume is expanded with the expansion material, so the drainage is poor. Does not function as a drain.

  In view of the above, the present invention provides a ground strengthening method and a ground strengthening system that can firmly support a building on the ground, have a deformability capable of following the deformation of the ground, and also have a function of a drainage drain. The issue is to provide.

In order to solve the above-mentioned problems, the present invention is a ground strengthening system for strengthening a ground on which a building is constructed, and a dug hole formed in the ground and a crushed stone are compacted below the dug hole. A root-solidified portion having a shape that is formed and has a shape that protrudes spherically larger than the diameter of the digging hole, and is made of a polymer material, and is installed in the digging hole on the root-solidifying portion, A cylindrical water-permeable sheet having a diameter substantially equal to the diameter of the digging hole, a columnar part formed by compacting crushed stone filled in the hollow part of the water-permeable sheet, and a central axis of the columnar part A steel pipe arranged vertically, and the steel pipe is press-fitted into a base portion of the columnar portion formed on the root-fixed portion, so that a tip portion of the steel pipe is formed on the upper portion of the base portion. To keep the upright posture in the columnar part of the steel pipe by biting into the crushed stone Having an end edge, a ground enhancement system, characterized in that.

  And the said water flow sheet | seat is comprised with a geogrid raw material, It is characterized by the above-mentioned. Further, a permeation layer is provided between the columnar part and the foundation of the building.

  The ground strengthening method according to the present invention is a method for strengthening the ground on which a building is constructed, and (a) a step of forming a digging hole in the ground with a casing in which a tip opening is closed with a closing rod; (B) After the formation of the digging hole, the step of pulling up the closing rod while leaving the casing and throwing crushed stone into the casing; (c) the rolling rod that inserts the crushed stone into the casing; A step of compacting the crushed stone by extruding from the casing and rolling to form a root-solidifying portion having a shape in which the diameter is larger than the diameter of the digging hole, and (d) a cylindrical shape made of a polymer material Inserting the water flow sheet into the casing and installing the water flow sheet above the root consolidation part; and (e) a central axis of the water flow sheet remaining in the hole by lifting the casing from the hole. In Inserting the steel pipe having a diameter smaller than the diameter of the water-permeable sheet, and (f) inserting the crushed stone between the steel pipe and the water-permeable sheet and compacting to form a columnar portion. It is a ground strengthening method characterized by comprising.

  In the step (e), before inserting the steel pipe into the water-permeable sheet, crushed stone is introduced into the hollow portion of the water-permeable sheet, and the crushed stone is compacted by the compaction operation of the compaction rod. Forming a base portion of the columnar portion, and installing the steel pipe above the base portion.

  Furthermore, in the step (e), the charging of the crushed stone is performed in a plurality of times, and each time the charging is performed, the rolling rod descends while performing normal rotation and reverse rotation to roll the crushed stone. To do.

  In the step (f), the steel pipe has an upper tip connected to the rolling rod via a press-fitting jig, and the steel pipe rolls the crushed stone by lowering the rolling rod. Features.

  Further, in the step (f), the crushed stone is introduced into the space between the steel pipe and the water-permeable sheet in a plurality of times, and the rolling rod is lowered while performing normal rotation and reverse rotation each time it is input. Then, the steel pipe rolls the surrounding crushed stone.

  And it is characterized by further including the process of throwing the pickled gravel into the head of the columnar part.

  In the ground strengthening system and ground strengthening method according to the present invention, when a load of a building or the like from the ground surface is transmitted, the load is supported by the circumferential friction between the ground and the solidified portion. The columnar crushed stone has a high shear strength, and the crushed stone tends to protrude laterally under the compressive force from both the load from the top and the root support force from the bottom of the root. It is suppressed by the tensile strength of the water sheet, and as a result, the internal pressure of the columnar portion is increased and the supporting force of the ground is improved. Moreover, the support force at this time can be further enhanced by providing the steel pipe at the core of the columnar portion made of crushed stone.

  In addition, due to the flexible structure of the combination of crushed stone and water-permeable sheet, when subjected to the force of seismic motion, it deforms integrally with the ground, so it does not buckle and can maintain support for loads from above . And even when the groundwater pressure rises due to seismic motion or the like, the crushed stone in the columnar portion functions as a drain and drains the groundwater to the surface of the ground, so that liquefaction of the ground is prevented.

  Therefore, the ground strengthening system and the ground strengthening method according to the present invention can cope with any of the load from the ground surface, the impact from the side due to the seismic motion, and the rise of the groundwater pressure, and therefore the ground can be strengthened surely.

It is explanatory drawing explaining the ground reinforcement system which concerns on this invention. It is explanatory drawing explaining the process of the ground reinforcement method which concerns on this invention. It is explanatory drawing explaining the process of the ground reinforcement method which concerns on this invention following FIG. It is explanatory drawing explaining the construction machine which constructs the ground reinforcement method which concerns on this invention. It is explanatory drawing explaining the obstruction | occlusion rod part of a construction machine, (a) part is a side cross section, (b) is a plane cross-sectional view, (c) part has shown the side view of the plate, respectively. It is a top view which shows a rolling rod from the downward direction. It is explanatory drawing explaining a steel pipe with a side view.

  The structure of the ground reinforcement system according to the present invention is shown in FIG. The ground 1 supports a building (not shown) and its foundation 2, and in order to strengthen the supporting force of the ground 1, the piles 3 are horizontally spaced apart from each other in the horizontal and vertical directions. A plurality of bodies are embedded at intervals corresponding to the softness of the ground 1. And there is a gap of about 0.5 m between the surface of the ground 1 and the pile 3, and the buried portion of the foundation 2 and the permeation layer 8 are provided in this gap.

  As shown in FIG. 1 with a broken line in some of the piles 3, the piles 3 are columnar portions formed by restraining crushed stones 6 with a water-permeable sheet 4 having a mesh made of polymer fiber material. 3A, a root-solidifying part 3B having a shape of pressing the same crushed stone 6 below the columnar part 3A and projecting into a spherical shape larger than the diameter of the columnar part 3A, and a center of the columnar part 3A in a vertical direction Steel pipe 3C. The particle size of the crushed stone 6 is appropriately selected in the range of 20 mm to 100 mm according to the mesh size of the water-permeable sheet 4.

  The water-permeable sheet 4 is composed of high-strength polymer fibers used for civil engineering, and as the material, for example, geotextile is used. Geotextiles include geotextiles in a narrow sense, geogrids, geonets, and the like. Further, geotextiles in a narrow sense include woven fabrics (geo-wovens), non-woven fabrics (geonon-wovens), and knitted fabrics (geo-nits). Among these types of geotextiles, in the field of ground reinforcement, a geogrid that is particularly excellent in tensile resistance and creep resistance is most preferable.

The solidified portion 3B of the pile 3 is formed by rolling and compacting the crushed stone 6 with a pressure of about 500 kn / m ² , for example, and has a shape that protrudes in a spherical shape larger than the diameter of the columnar portion 3A. Thus, the tip support force of the pile 3 is increased.

  In the columnar portion 3A, the crushed stone 6 positioned below the steel pipe 3C and the crushed stone 6 surrounding the steel pipe 3C are constrained by the water-permeable sheet 4 in a state of being compacted by rolling. Although crushed stone has the property of being flexible to shear, it is further enhanced by compaction.

  When the load of the building constructed on the ground 1 and the foundation 2 is transmitted, the pile 3 having the above structure supports the load by the circumferential friction between the ground 1 and the columnar portion 3A and the root-solidified portion 3B. It will be. At this time, the inside-packed crushed stone 6 compacted in the water-permeable sheet 4 has a large shear resistance, and the crushed stone 6 is vertically moved from the load from above and the tip supporting force of the root-solidified portion 3B from below. When it receives a compressive force, it tries to project sideways. However, in order to suppress the shape change by suppressing the tensile strength of the water passing sheet 4 as the crushed stone 6 tries to project sideways, the columnar portion 3A increases the internal pressure according to the load from above and below. become. Thereby, the pile 3 has a big intensity | strength with respect to the load of the building on the ground 1, and can support a building and a foundation work.

  In this way, the pile 3 is deformed integrally with the ground 1 when subjected to the force of seismic motion, so that the pile 3 is not broken and can maintain support for the load from above. However, for example, in the case where the content member of the water-permeable sheet 4 is configured by being hardened with an expansion material or a solidifying material, it does not have a flexible structure, and it is destroyed depending on the strength of the seismic motion and against the load of the building There is a risk that the supporting force of the ground 1 will be lost at once, causing the building to collapse or landslide.

  In addition, when the groundwater pressure rises due to seismic motion or the like, the columnar portion 3A becomes a crushed drain with respect to the flow of groundwater and drains the ground 1 from the ground surface to prevent liquefaction of the ground 1. Is done. Then, the crushed stone 6 becomes rainwater flowing from the top to the bottom from the infiltration layer 8 and can prevent the soil around the pile 3 from entering the crushed stone 6 over a long period of time. There is no decline.

  Next, the ground reinforcement method achieved by forming said pile 3 in the ground 1 is demonstrated.

  2 and 3 are explanatory views showing the construction method of the present invention in cross-section, and the construction machine 5 is used to form the excavation hole 7 in the ground 1 and the excavation hole 7 to form the pile 3 (see FIG. 3). (P) part). In the present embodiment, a case is described in which a pile 3 having a length of 2.5 m is formed with the top end at a position 50 cm below the surface of the ground 1, and each length of the columnar portion 3 </ b> A of the pile 3 and the steel pipe 3 </ b> C. The height dimension is 2 m and 1.5 m, respectively, and the height dimension of the root hardening portion 3B is 50 cm. And the crushed stone 6 is good to use the thing of the same size, and in this Example, according to the dimension of the mesh | network of the water-permeable sheet 4, the size of the crushed stone in the range of 20 mm thru | or 40 mm, or 60 mm thru | or 100 mm Any group of crushed stones within the range is used.

  First, the construction machine 5 will be described. As shown in FIG. 4, the construction machine 5 includes a drive unit 8 that moves up and down and a reader 17 that has a height of about 10 m that guides the drive unit 8 in the vertical direction. I have. The drive unit 8 has two drive shafts 8A and 8B. A casing 10 and a closing rod 14 which are cylindrical bodies having a diameter of 355 mm are attached to the drive shaft 8A. A pressure rod 11 is attached.

  The drive unit 8 reciprocates up and down individually with respect to the drive shafts 8A and 8B and simultaneously applies forward and reverse rotational forces. And the drive part 8 can change the position of the drive shafts 8A and 8B in the horizontal direction with respect to the surface of the ground 1 by moving the drive shafts 8A and 8B on a predetermined orbit on the horizontal plane.

  The closing rod 14 is arranged along the longitudinal direction inside the casing 10, and is connected to the casing 10 by the connecting portion 15. Then, the closing rod 14 is connected to the drive shaft 8A, and when the rotational motion and vertical movement of the drive shaft 8A are transmitted to the closing rod 14, they are also transmitted to the casing 10 via the connecting portion 15 and both of them. 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, and the rod shaft 14a extends from the rod shaft accommodating portion 14b. The plate 24 closes the front end opening of the casing 10 in the protruding state. As described above, the extended state of the closing rod 14 can be locked and held by the operation of the stopper 19, and this operation can be performed through the operation window 9 provided in the casing 10. Then, excavation for forming the digging hole 7 in the ground 1 is performed by rotationally press-fitting the casing 10 into the ground 1 with the closing rod 14 extended and the bit 14 c protruding from the casing 10.

  The configuration of the bit 14 c and the plate 24 will be described with reference to FIGS. 4B and 4C. The bit 14 c is fixed to the closing rod 14 through the base 25. The plate 24 is composed of two separable semi-circular plates 24a and 24b, and concave portions are formed at the edge portions of the straight portions of the semi-circular discs 24a and 24b, respectively. Then, 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 plate 24a is configured by sandwiching a semicircular rubber member 28a having an appropriate thickness between a pair of upper and lower iron plates 26 having a thickness of 6.0 mm. Similarly, the semicircular plate 24b includes a rubber member 28a and a rubber member 28a. A rubber member 28b having the same thickness is sandwiched between a pair of upper and lower iron plates 27 having a thickness of 6.0 mm. The diameter of the plate 24 combined with the semicircular plates 24a and 24b is 346 mm, and the peripheral portions of the rubber members 28a and 28b are provided with a dimensional difference so as to protrude toward the inner peripheral wall of the casing 10 rather than the iron plates 26 and 27. . A gap dimension of 5 mm is provided between the peripheral edge portions of the rubber members 28 a and 28 b and the inner peripheral wall of the casing 10.

  In addition, a flexible pipe 30 is arranged in the vertical direction in the hollow of the rod shaft 14a and the rod shaft accommodating portion 14b, and compressed air introduced through a valve 31 from an air compressor (not shown) is downward from the compressed air supply pipe 32. It is supposed to be injected into.

  As shown in FIG. 6, the rolling rod 11 is provided with three tip blades 11 a at equal intervals on the periphery of the end face of the tip portion.

  Returning to the description of FIG. 2, the steps of the ground strengthening method using the construction machine 5 will be described. First, the drive unit 8 horizontally moves the drive shaft 8 </ b> A to set the casing 10 and the closing rod 14 above the target point where the digging hole 7 of the ground 1 is formed. 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 8 moves downward while rotating the drive shaft 8A with high torque in this state, the casing 10 and the closing rod 14 are rotationally press-fitted into the ground 1 to perform a digging operation ((A in FIG. 2). ) Part). At this time, it is pressed against the surrounding soil by the side portion of the casing 10 that is pushed out and rotated in the direction around the casing 10. In this way, instead of discharging the soil generated by excavation to the ground surface, the soil is compacted around the casing 10 to form a compacted hole 7 having a strong wall surface. In this digging step, it is important to ensure the excavation of the casing 10 from the ground surface accurately while maintaining the vertical state of the casing 10 in order to ensure the quality of the completed pile 3.

  The part (B) of FIG. 2 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 by the connecting portion 15 is disconnected, and then the driving portion 8 moves the drive shaft 8A upward, only the closing rod 14 is lifted above the digging hole 7. The casing 10 is left behind in the digging hole 7 (part (C) in FIG. 2). At this time, when pulling up the closing rod 14 from the inside of the casing 10, it is necessary to prevent a situation in which a vacuum state is generated inside the digging hole 7 due to rapid pulling and the wall of the digging hole 7 collapses. When the closing rod 14 is pulled up, it is pulled up while sending compressed air from the compressed air feed pipe 32.

  In the state where the closing rod 14 is pulled out from the casing 10, the crushed stone 6 is thrown in as shown by the arrow ((D) part in FIG. 2). The input amount of the crushed stone 6 at this time is an amount by which the crushed stone 6 is piled up from the lower end of the casing 10 to about 30 cm. At this time, the semicircular plates 24a and 24b are separated, the plate 24 is detached from the closing rod 14, and the stopper 19 is operated to release the locking state of the closing rod 14 so that the rod shaft 14a is free. And

  Then, the drive shaft 8B is moved horizontally by the drive unit 8, the rolling rod 11 is set above the digging hole 7 where the casing 10 remains, and the drive shaft 8B is moved up and down while the crushed stone 6 is additionally charged. Then, the rolling rod 11 is reciprocated in the casing 10 (portion (E) in FIG. 2). As a result, the rolling rod 11 pushes the tip blade 11a out of the casing 10 while biting into the crushed stone 6 accumulated at the lower end of the casing 10 and the additional crushed stone 6, and the crushed stone 6 diffuses into the ground 1 and piles. 3 roots 3B are formed.

  As a result of the rolling pressure by the rolling rod 11 as described above, the root-solidified portion 3B is compacted until it protrudes in a spherical shape larger than the diameter of the columnar portion 3A of the pile 3 to be formed later. By forming the root consolidation part 3 </ b> B, the pile 3 holds the tip support force against the load of the building constructed on the ground surface of the ground 1.

  When the root-solidifying portion 3B is formed, although not shown in the figure, after removing the soil adhering to the inner surface of the casing 10 with a keren rod, the cylindrical water-permeable sheet 4 made of geogrid is inserted into the casing 10 Installed above the root-solidifying part 3B (part (F) in FIG. 2). The diameter of the water flow sheet 4 is substantially matched to a degree slightly smaller than the inner diameter of the casing 10.

  And the sandbag bag 34 is set in the lower end opening of the water flow sheet 4, and a predetermined amount of crushed stone 6 is filled in the sandbag bag 34, and the blocking rod 14 in a state where the plate 24 is removed is inserted into the digging hole 7. The drive shaft 8A is horizontally moved by the drive unit 8 so as to be positioned above (portion (G) in FIG. 2).

  Next, the drive unit 8 inserts the closing rod 14 into the water sheet 4 and drives the drive shaft 8A so that the bit 14c descends until reaching the crushed stone 6 in the sandbag 34, and the connecting unit 15 is connected to the casing 10. The casing 10 and the closing rod 14 are connected by the connecting portion 15 (the portion (H) in FIG. 2). At this time, since the locking rod 14 is unlocked and the rod shaft 14a is in a free state, the pressing force downward from the drive shaft 8A is not transmitted to the crushed stone 6 in the sandbag 34, and the dead weight of the rod shaft 14a. Only added.

  After the closing rod 14 and the casing 10 are connected by the connecting portion 15, the drive shaft 8 </ b> A is moved upward by the driving portion 8, and both the closing rod 14 and the casing 10 are pulled up from the digging hole 7 ((I in FIG. 3 ) Part).

  When the lifting is completed, the opening of the digging hole 7 is temporarily covered with the shielding plate 36, and the semicircular plate 24a and the semicircular plate 24b are combined to form a concave portion at the edge of the straight portion of the semicircular plates 24a and 24b. Then, the plate 24 is attached to the closing rod 14 by sandwiching the base portion 25 ((J) portion in FIG. 3). After the plate 24 is attached, the drive unit 8 lowers the drive shaft 8 </ b> A until the closing rod 14 and the casing 10 reach the shielding plate 36. As a result, when the plate 24 is stored in the casing 10 and only the bit 14c is lowered from the casing 10 to a state as shown in FIG. 2A and FIG. The stopper 19 is operated to lock the closing rod 14 and return to the initial state.

  Then, the columnar portion 3A of the pile 3 is formed. First, the driving shaft 8B is horizontally moved by the driving portion 8 to set the rolling rod 11 above the digging hole 7, and the crushed stone input hopper 20 is dug. Set to cover 7 openings. The crushed stone charging hopper 20 has a funnel shape, and introduces the crushed stone 6 charged from above into the hollow portion of the water sheet 4. The amount of crushed stone 6 input at this time is an amount that is deposited in the water flow sheet 4 to form the columnar portion 3A of about 10 cm. The crushed stone 6 is uniformly deposited in the sheet 4.

  After throwing the crushed stone 6, the drive unit 8 drives the drive shaft 8B, and the rolling rod 11 descends while performing normal rotation and reverse rotation to apply a load of 70 kn to the crushed stone 6 to roll the crushed stone 6. At this time, the rolling rod 11 passes through the center of the crushed stone charging hopper 20 and moves in the water-permeable sheet 4 with a stroke of 15 cm. Then, the drive unit 8 pulls up the rolling rod 11 and again throws in the crushed stone 6 in an amount by which the columnar portion 3A is formed by about 10 cm by the crushed stone feeding hopper 20, and then the rolling rod 11 rotates forward and backward. Descending with a stroke of 15 cm while performing the above, a load of 70 kn is applied to the crushed stone 6 and rolled ((K) part in FIG. 3).

  By repeating this operation, when the columnar portion 3A is formed to a height of 70 cm, the portion becomes the base portion 35 of the columnar portion 3A, and the steel pipe coincides with the central axis of the hollow portion of the water-permeable sheet 4 on the base portion 35. 3C is set in the vertical state. The steel pipe 3C has a length of 1.5 m and a diameter of 10 cm, and its lower end is closed. As shown in FIG. 7, a pair of tip blades 33 are provided on the outer wall of the lower end so as to face each other.

  The steel pipe 3 </ b> C is connected to the rolling rod 11 by a steel pipe press-fitting jig 21, receives a pressure input of 70 kn from the rolling rod 11 by driving of the drive shaft 8 </ b> B by the driving unit 8, and has a tip blade 33 on the upper portion of the base portion 35. Grip in and hold upright. At this time, the level of the upper end portion of the steel pipe 3C is adjusted so as to coincide with the plane of the top end of the pile 3 ((L) portion in FIG. 3). The steel pipe press-fitting jig 21 is used for setting the steel pipe 3C in an upright state.

  After setting the steel pipe 3C by the rolling rod 11, the crushed stone 6 in an amount to form a columnar portion 3A of 10 cm is loaded from the crushed stone hopper 20 from 10,000, and the operation of compacting the charged crushed stone 6 is restarted each time. In this case, the rolling operation is performed by filling the crushed stone 6 between the steel pipe 3C and the water flow sheet 4 and lowering the rolling rod 11 with a stroke of 15 cm while performing normal rotation and reverse rotation by driving the drive shaft 8B. Then, the rotational force and a load of 70 kn are transmitted to the steel pipe 3C. As a result, the crushed stone 6 around the steel pipe 3C is compacted by rolling (part (M) in FIG. 3).

  When the columnar portion 3A is formed up to the top end of the pile 3 by repeating the charging of the crushed stone 6 and rolling, the crushed stone hopper 20 is removed from the digging hole 7, the appropriate amount of crushed stone 6 is loaded, and the pile 3 is loaded by the rolling rod 11. The top end of the slab is rolled with a pressure of 70 kn, and the pile 3 is again pressed into the ground 1 (portion (N) in FIG. 3). After rolling, the pickled gravel 23 is thrown into the head of the pile 3 from above as shown by the arrow, and is squeezed by a not-shown trunk (so-called octopus) ((O) portion in FIG. 3). Is completed (part (P) in FIG. 3).

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

DESCRIPTION OF SYMBOLS 1 Ground 2 Foundation 3 Pile 3A Column-shaped part 3B Rooting part 3C Steel pipe 4 Water flow sheet 5 Construction machine 6 Crushed stone 7 Digging hole 8 Penetration layer 10 Casing 11 Rolling rod 14 Blocking rod 23 Pickled gravel 35 Foundation part

Claims (9)

A ground strengthening system that strengthens the ground on which a building is built,
A burrow formed in the ground;
A root-solidifying part formed by compacting crushed stone below the digging hole and having a shape in which the diameter of the digging hole is larger than the diameter of the digging hole,
A cylindrical water-permeable sheet having a diameter substantially equal to the diameter of the digging hole, made of a polymer material, installed in the digging hole and on the root-sealing portion,
A columnar portion formed by compacting a crushed stone filled in the hollow portion of the water flow sheet;
A steel pipe arranged in a vertical direction in line with the central axis of the columnar part;
Have
The steel pipe is press-fitted into the base part of the columnar part formed on the root consolidation part, so that its tip part bites into the crushed stone at the upper part of the base part and takes an upright posture in the columnar part of the steel pipe. A ground reinforcement system having a tip blade for holding .   The ground reinforcement system according to claim 1, wherein the water flow sheet is made of a geogrid material.   The ground reinforcement system according to claim 1, wherein a permeation layer is provided between the columnar part and the foundation of the building. A method of strengthening the ground on which a building is built,
(A) forming a hole in the ground with a casing whose end opening is closed with a closing rod;
(B) After the formation of the digging hole, the step of pulling up the closing rod leaving the casing and throwing crushed stone into the casing;
(C) A root having a shape in which the crushed stone is pushed out from the casing with a rolling rod inserted into the casing and pressed to compact the crushed stone so that its diameter is larger than the diameter of the digging hole. Forming a hardened portion; and
(D) inserting a cylindrical water-permeable sheet made of a polymer material into the casing and installing it above the rooting part;
(E) a step of pulling up the casing from the digging hole and inserting a steel pipe having a diameter smaller than the diameter of the permeable sheet so as to coincide with the central axis of the permeable sheet remaining in the digging hole;
(F) inserting the crushed stone between the steel pipe and the water flow sheet and compacting to form a columnar part;
Ground strengthening method equipped with.   In the step (e), before inserting the steel pipe into the water-permeable sheet, crushed stone is introduced into the hollow portion of the water-permeable sheet, and the crushed stone is compacted by the rolling operation of the rolling rod. The ground reinforcement method according to claim 4, wherein a foundation part of a columnar part is formed and the steel pipe is installed on an upper part of the foundation part.   In the step (e), the crushed stone is thrown into a plurality of times, and each time the crushed stone is fed, the rolling rod descends while performing normal rotation and reverse rotation to roll the crushed stone. Item 6. The ground strengthening method according to Item 5.   In the step (f), the steel pipe has an upper tip connected to the rolling rod via a press-fitting jig, and the steel pipe rolls the crushed stone by lowering the rolling rod. The ground strengthening method according to claim 5.   In the step (f), the crushed stone is thrown in between the steel pipe and the water flow sheet in a plurality of times, and the rolling rod is lowered while performing normal rotation and reverse rotation each time it is charged. The ground reinforcement method according to claim 7, wherein the steel pipe rolls the crushed stone around.   The ground reinforcement method according to claim 4, further comprising a step of throwing pickled gravel into the head of the columnar part.

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