JP4341029B2 - Pile foundation method - Google Patents

Description

  The present invention relates to a pile foundation method for constructing a pile foundation of a structure, and more particularly to a pile foundation method for constructing a composite pile in which a soil cement column and a steel pipe are integrated.

Conventionally, as a pile foundation construction method for constructing a synthetic pile in which a soil cement column and a steel pipe are integrated, there has been one described in Patent Document 1 or Patent Document 2, for example. Among them, the construction method described in Patent Document 1 is a method in which a soil cement pillar is formed by mechanically excavating and stirring the ground while injecting a cement-based solidified material from the tip of the excavating rod, and then, A steel pipe (steel pipe pile) with a diameter is built. On the other hand, the construction method described in Patent Document 2 is an improved body (soil cement pillar) by excavating and stirring the ground by a so-called high-pressure jet stirring method while injecting cement-based solidified material from the tip of the excavation rod at high pressure. Then, a hole is drilled in the improved body and a micropile is placed in the hole.
JP 200221072 A JP 2001-81770 A

  However, according to the pile foundation method described in the above-mentioned Patent Document 1, before the soil cement pillar that has been initially built is solidified, a steel pipe must be built therein, so that a quick replacement of the construction machine is necessary. As a result, there was a problem that the construction efficiency was unavoidable and construction in a narrow place became difficult. On the other hand, according to the pile foundation method described in Patent Document 2, since the amount of mud is increased by mass injection of cement-based solidified material, a large amount of cost is required for the waste mud treatment, and the material loss of cement-based solidified material is also reduced. There has been a problem that the increase in cost burden is inevitable.

  In addition, in the pile foundation method that performs mechanical excavation and agitation, excavation and agitation is often performed through the mouth pipe for the purpose of protecting the hole wall and preventing misalignment, but this mouth pipe anchors the steel pipe in the soil cement column. There was also a problem that the construction would be cumbersome after that.

  The present invention has been made in view of the above-described conventional problems, and the first problem is that it eliminates the need for quick replacement of construction machines and enables a significant reduction in the amount of mud. Therefore, it is to provide a pile foundation method that greatly contributes to improvement of construction efficiency and workability and cost reduction. Moreover, the place made into the 2nd subject is providing the pile foundation construction method which contributes to the further improvement by making the removal unnecessary even when using a mouth pipe in addition to the said 1st subject.

  According to a first aspect of the present invention for solving the first problem, a soil cement column is formed by mechanically excavating and stirring the ground while injecting cement-based solidified material from the tip of the excavating rod, After the cement column is solidified, a hole is drilled in the soil cement column, and a micropile is placed in the hole.

  In the first aspect of the invention, since the soil cement pillar that has been initially formed is solidified, a micropile is formed by drilling holes in the pillar, so that after the appropriate number of soil cement pillars are continuously formed, A micropile can be placed on the cement pillar, so that quick replacement of construction machines is not necessary. Further, since the soil cement pillar is formed by excavating and stirring mechanically, the amount of mud is remarkably reduced.

  According to a second invention for solving the second problem, after a mouth pipe is driven into the ground surface, the ground is machined while injecting a cement-based solidified material from the tip of the mouth pipe with a drilling rod through the mouth pipe. After excavating and stirring in accordance with the formula, a soil cement column is formed in a region deeper than the depth of implantation of the mouth tube, and after the soil cement column is solidified, a hole is drilled in the soil cement column, A micropile is placed, and then the pile head is constructed by joining the mouth tube and the core material of the micropile with concrete cast in the mouth tube.

  In the second invention, in addition to the action of the first invention, the mouth pipe used for excavation and stirring by the excavating rod and the core material of the micropile are joined with concrete to form a pile head. It can be used effectively.

  According to the first invention, since it is not necessary to quickly replace the construction machine, efficient construction can be performed, and furthermore, construction can be performed without difficulty in a narrow place, and the workability is improved. In addition, since the soil cement pillar is formed by excavating and stirring mechanically, the amount of mud is remarkably reduced and the cost burden is reduced.

  Moreover, according to 2nd invention, in addition to the effect of 1st invention mentioned above, since the operation | work which removes a mouth pipe becomes unnecessary, the further improvement of construction efficiency can be achieved. Further, since the mouth tube and the core material of the micropile are joined by concrete to form a pile head, the footing that is indispensable for the construction of the structure can be omitted, and the utility value is further increased.

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

  FIG. 1 shows one embodiment of a pile foundation construction method according to the present invention. In carrying out this pile foundation construction method, as shown in FIG. 1A, first, the mouth pipe 10 is driven into the surface (ground surface) of the ground 1 and then the excavation rod (hollow rod) is passed through the mouth pipe 10. 11 is rotated and lowered into the ground 1. The excavation rod 11 has an excavation stirring blade 12 and a discharge port 13 at the tip thereof, and the cement-based solidified material discharged from the discharge port 13 is supplied into the hollow interior of the excavation rod 11. It has become. Further, the movement of the excavation rod 11 is controlled by a rotation and lifting unit (not shown) of the construction machine, and the ground 1 is gradually excavated and stirred by the rotation and descent.

  In the present embodiment, the excavation and stirring by the excavation rod 11 is performed by stopping the injection of the solidified material from the discharge port 13 until the excavation and stirring blade 12 reaches substantially the driving depth D1 of the mouth tube 10. In a region deeper than that, excavation and stirring by the excavation rod 11 is performed while injecting the solidified material from the discharge port 13. Thereby, in the region deeper than the driving depth D1 of the mouth pipe 10, the earth and sand (soil) excavated by the excavation stirring blade 11 and the cement-based solidified material injected from the discharge port 13 are agitated and mixed, and the excavation rod 11 is mixed. These mixed layers, that is, a so-called soil cement mixed layer 2 is formed on the excavation trace.

  Then, when the formation of the soil cement mixed layer 2 reaches the planned depth D2, the injection of the solidified material from the discharge port 13 is stopped, and this is pulled out from the ground 1 while continuing the rotation of the excavating rod 11, and the soil cement is left as it is. The mixed layer 2 is solidified. As a result, as shown in FIG. 1B, a soil cement column 14 having a length that reaches the driving depth D1 of the mouth tube 10 from the planned depth D2 is formed in the ground 1. Next, as shown in FIG. 1 (B), a hole 16 is drilled in the soil cement pillar 14 using, for example, an earth auger 15. The hole 16 is drilled to the vicinity of the bottom surface of the soil cement column 14, and after the excavation is completed, the earth auger 15 is pulled out from the soil cement column 14. In addition, when excavating and stirring the ground 1 with the excavating rod 11, after the excavating and stirring up to the planned depth D2 while stopping the injection of the solidified material, the excavating rod 11 is rotated and raised while injecting the solidified material. In this case, the same soil cement pillar 14 is formed.

  Next, as shown in FIG. 1 (C), a micropile 17 is placed in the pit 16 after the drilling. The micropile 17 includes a steel pipe (core material) 18 having a small diameter of about 200 to 300 mm and a fixing layer 19 around the micropile 17. The steel pipe 18 is attached to the soil cement column 14 via the fixing layer 19. It is firmly established. Here, as the steel pipe 18, a steel pipe with a node having a large number of nodes 20 in the axial direction is used. Further, the steel pipe 18 is provided with a plurality of check valves 21 for discharging the solidified material equally arranged in the axial direction and the circumferential direction.

  For example, as shown in FIG. 2, the micropile 17 is placed by inserting a steel pipe 18 into the hole 16 and then inserting an injector (single packer) 22 into the steel pipe 18. The injector 22 includes a bulging body 23 that bulges out by air pressure, hydraulic pressure such as fresh water or antifreeze, and a discharge nozzle 24. The bulging body 23 includes a hose 25 that extends from a fluid pressure source on the ground. The discharge nozzle 24 is connected to a supply pipe 26 extending from a ground grout supply source. When placing the micropile 17, first, the injector 22 is inserted into the deepest position of the steel pipe 18, the bulging body 23 is expanded at the deepest position to fix the position of the injector 22, and then the supply pipe is connected thereto. 26, a cement-based solidified material grout (solidified material grout) 3 is fed under pressure. Then, this solidifying material grout 3 is discharged from the discharge nozzle 24 and fills the space inside and outside the front end opening of the steel pipe 18, thereby increasing the internal pressure on the front end side in the steel pipe 18 and opening the check valve 21. The hardened material grout 3 is ejected from the check valve 21 to the periphery and filled in the gap between the steel pipe 18 and the inner wall of the hole 16. Thereafter, the above operation is repeated while raising the injector 22 by a predetermined distance (the arrangement pitch of the check valves 21), whereby the hardened material grout 3 is filled in the entire gap between the steel pipe 18 and the inner wall of the bore hole 16. Is done.

  Then, after the filling of the hardener grout 3 is completed, the injector 22 is pulled out from the steel pipe 18 and cured for a predetermined time. Then, as shown in FIG. 1C, the hardener grout 3 hardens to become a fixing layer 19, and the steel pipe 18 is firmly joined to the soil cement column 14 by the fixing layer 19. As a result, the synthetic pile 27 in which the micropile 17 and the soil cement column 14 are integrated to exert a large supporting force is constructed. Particularly in the present embodiment, since a steel pipe with a node is used as the steel pipe 18, the frictional resistance between the steel pipe 18 and the fixing layer 19 is remarkably increased, and the micropile 17 itself also exhibits a large supporting force.

  Thereafter, as shown in FIG. 1D, the earth and sand inside the mouth pipe 10 is discharged, the steel pipe 18 constituting the micropile 17 is cut in the mouth pipe 10, and the upper end of the steel pipe 18 is placed at the mouth. An appropriate length is projected into the tube 10. Next, a support plate 28 is consolidated using a stiffener 28 a at the end of the cut steel pipe 18, and then concrete 29 is placed inside the mouth pipe 10. Then, the concrete pipe 29 joins the mouth pipe 10 and the steel pipe (core material) 18 of the micropile 17, thereby constructing a pile head 30 integrated with the synthetic pile 27. Since the pile head 30 functions as a footing that supports the structure, the structure can be directly supported by the pile head 30. In constructing the pile head 30, reinforcing bars may be embedded in the concrete 29 or anchors may be embedded. Further, the bearing plate 28 may be omitted depending on circumstances.

  Here, in the above embodiment, the drilling of the pothole 16 with respect to the soil cement column 14 and the placement of the micropile 17 into the pothole 16 are performed in separate steps. It can be carried out. FIG. 3 shows one embodiment in that case, and a drilling rod 32 having a cutting diameter expansion bit 31 at the tip is inserted into the steel pipe 18 having the check valve 21. The steel pipe 18 and the drilling rod 32 are integrally supported by a construction machine (drilling machine) (not shown), and the steel cement 18 is used as the soil cement column 14 while rotating the drilling rod 32 using the steel pipe 18 as a casing. Drilling is performed to form the pit hole 16, and at the same time, the steel pipe 18 is penetrated to a predetermined depth. Then, the drilling rod 32 is pulled out from the steel pipe 18, and then, in the same manner as shown in FIG. 2, the injector 22 is inserted into the steel pipe 18, and the hardened material grout 3 is injected in the same procedure. Finish the pile 17 placement. In this case, since the drilling of the pit hole 16 and the placement of the micropile 17 are performed continuously, it is not necessary to replace the construction machine, and improvement in construction efficiency can be achieved.

  In this pile foundation construction method, when drilling the pit 16 in the soil cement column 14 with the earth auger 15 (FIG. 1 (B)) or the cutting diameter expanding bit 31 (FIG. 3), the excavated soil is inspected, It is desirable to check the quality of the soil cement column 14, which will significantly increase the reliability of the foundation pile method.

It is sectional drawing which shows typically the construction procedure in one embodiment of the pile foundation construction method which concerns on this invention. It is sectional drawing which shows typically one embodiment of the micropile placement in this pile foundation construction method. It is sectional drawing which shows typically other embodiment of the micropile placement in this pile foundation construction method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ground 10 Mouth pipe 11 Excavation rod 12 Excavation stirring blade 13 Discharge port 14 Soil cement pillar 15 Earth auger 16 Borehole 17 Micropile 18 Steel pipe (heart material)
19 Fixing layer 20 Section 21 Check valve 22 Injection machine 27 Composite pile 29 Concrete 30 Pile head 31 Cutting diameter expansion bit 32 Drilling rod

Claims (2)

After the mouth pipe is driven into the ground surface, the ground is mechanically excavated and stirred while injecting cement-based solidified material from the tip of the drill pipe through the mouth pipe, and is deeper than the depth of the mouth pipe. After the soil cement column is solidified and the soil cement column is solidified, a hole is drilled in the soil cement column, and a micropile is placed in the hole, and then the mouth tube and the micro A pile foundation method characterized in that a pile head is constructed by joining pile cores with concrete cast in the mouth pipe. The pile foundation method according to claim 1, wherein a steel pipe with a knot is used as the core material of the micropile.

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