JP2010133114A - Piling method accompanying soil improvement - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the horizontal displacement of a pile head and a bending moment arising at the pile head to improve the horizontal resistance of the pile. <P>SOLUTION: A drilled hole 4 for placing a pile 5 therein and a foundation consolidating part 4B for supporting the pile 5 are formed on the ground 3, using a drill bit 2. Fillers including removed soil removed upon drilling the drilled hole 4 are put back in the drilled hole 4, and the ground 3 near the head of the pile 5 is stirred as a hardener is injected onto the ground 3, and then the pile 5 is set in an underground position. It is preferable that the drilling bit 2 having an expandable drilling edge 6 capable of radial expansion be used when the drilled hole 4 and the foundation consolidating part 4B are formed, and that the expandable drilling edge 6 be pulled up without expanding it at a part 4A near the pile head that is the subject of soil improvement when the drilling bit 2 is pulled out. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for constructing a pile using ground improvement in combination. More specifically, the present invention relates to an improvement of a pile construction method using a pre-boring method.

  As a pre-boring method for piles with spiral blades, before excavating a vertical hole deep enough to reach the support layer and injecting cement milk for root consolidation into the lower end of the vertical hole, before the cement milk solidifies There is a method in which a pile provided with overhanging wings (spiral blades) is inserted while rotating.

In such a pile construction method, when soft ground exists near the head of the pile, the displacement of the pile increases with respect to the horizontal force acting during an earthquake, which may adversely affect the superstructure. Therefore, as a technology that can reduce such influence, a method of constructing a pile after ground improvement (see, for example, Patent Document 1), a method of excavating the surrounding ground after pile construction and refilling it with high quality soil, installation of piles A method (for example, refer to Patent Document 2) of enlarging the vicinity of a pile head when forming a hole has been proposed.
JP 2005-320692 A JP 2002-97636 A

  However, in the case of the method of constructing the pile after the ground improvement, there is a problem that the ground improved body is loosened.

  Moreover, in the case of the method of excavating the surrounding ground and refilling it with high-quality soil after the construction of the pile, in addition to being troublesome in the first place, there is a risk of damaging the pile during excavation.

  Also, in the case of the method of enlarging the vicinity of the pile head when forming the pile installation hole, the soil cannot be crushed finely with the excavation rod or the expansion bit, so there is a lump in the ground improvement body and a uniform hardened body cannot be formed There is a problem.

  Then, this invention aims at providing the construction method of the pile which used together the ground improvement which can improve the horizontal resistance of a pile, considering the various subject in a prior art.

  In order to solve this problem, the present inventor has made various studies. If the pile is installed on soft ground, the displacement of the pile head is particularly large when a horizontal force is applied due to an earthquake, and a large bending moment is generated in the pile itself. It is necessary to ensure high rigidity that can withstand such as increasing the thickness of the steel pipe of the pile (steel pipe concrete composite pile). However, if it does so, the weight of a pile will increase and cost will increase and it is uneconomical. Based on these points, the present inventor, who has repeatedly studied about reducing the horizontal displacement amount and generated bending moment of the pile, has obtained new knowledge that leads to the solution of such problems.

  The present invention is based on such knowledge, and the excavation hole for installing the pile and the solidified part that supports the pile are formed in the ground using the excavation bit, and the filler is backfilled in the excavation hole, and the hardened material This is a method for constructing a pile using ground improvement in which the ground near the head of the pile is agitated while injecting and then the pile is sunk.

  Usually, ground improvement during pile construction is performed on the ground in a state where nothing is disturbed (a state where excavation or the like is not performed). In this regard, in the present invention, after the excavation hole that has been excavated and once loosened is backfilled with a filler such as earth and sand to increase the solids, and then stirred while injecting the hardener Sink the pile. By doing this, it is possible to reliably improve the soft ground of the pile after installation, especially near the pile head, and to suppress the horizontal displacement and generated bending moment near the pile head when a horizontal force is applied. It becomes. For this reason, the bending rigidity required for the pile may be further reduced, and the cost can be reduced by designing more economically than in the past.

  Moreover, although the construction method concerning this invention is a pre-boring method which used ground improvement together, it does not re-excavate after ground improvement. For this reason, the improved ground (improved body) is not disturbed again. Therefore, it is not necessary to adjust the ground again after the pile is set.

  Furthermore, according to the construction method concerning this invention, there is no effort which excavates a surrounding ground after the sedimentation of a pile. For this reason, the pile after installation is not damaged.

  In addition, when forming a drilling hole and a root consolidation part, use a drilling bit having an enlarged drilling blade that can be expanded in the radial direction, and at the time of lifting the drilling bit, at least in the vicinity of the pile head that is the target of ground improvement It is preferable to pull up the enlarged excavating blade without enlarging it. Usually, it is desirable to perform ground improvement in a state in which soil solid matter remains as much as possible. In this regard, according to the present invention, the bit is raised without enlarging the portion to be ground improved, so that it is possible to leave the solid matter so as not to loosen the portion to be ground improved as much as possible.

  Furthermore, as a drilling rod for rotating the drilling bit, a rod having a screw formed around it is used, and when the drilling bit is pulled up, a part between the portion near the pile head and the solidification part that is the target of ground improvement It is also preferable to rotate the excavating rod in a direction to reduce the amount of soil discharged. In the intermediate part between the upper ground improvement target part and the lower root consolidation part, the amount of soil removal can be reduced by pulling up the excavation bit while rotating it in reverse, for example. In this case, the intermediate portion is in a state where the loosened soil is present, and thus there is an advantage that the penetration of the pile is improved.

  In the construction method described above, it is preferable to use a ground improvement bit having a ground improvement rod with co-rotation prevention wings and agitate the ground near the pile head while injecting a hardening material through the ground improvement rod. It is possible to form a high-quality improved body by backfilling the soil discharged during excavation and then finely crushing the soil between the rod with the co-rotation prevention wing and the bit.

  Moreover, it is also preferable to use what has a spiral blade | wing in the front-end | tip outer peripheral part as a pile. By rotating the stake, the lower end of the stake can be easily entered into the rooted portion using the spiral blade.

  Furthermore, it is preferable to make the diameter of the ground improvement body formed near the pile head by improving the ground smaller than the diameter of the root consolidation part. If it does in this way, the bad influence given to the improvement object of other piles adjacent at the time of pile construction can be decreased. In addition, excavation, ground improvement, and pile setting can be easily performed with the same heavy machinery, which is efficient.

  According to the present invention, it is possible to reduce the horizontal displacement of the pile head and the generated bending moment while taking into account various problems in the prior art, thereby improving the horizontal resistance of the pile.

  Hereinafter, the configuration of the present invention will be described in detail based on an example of an embodiment shown in the drawings.

  The embodiment of the construction method of the pile which used together the ground improvement concerning this invention in FIG. 1 is shown. The construction method of the pile 5 combined with the ground improvement according to the present invention is that the excavation hole 4 for installing the pile 5 and the consolidation part 4B for supporting the pile 5 are formed on the ground 3 using an excavation bit, and the filling is performed. The material (for example, the soil discharged during excavation of the excavation hole 4) is backfilled in the excavation hole 4, and the ground 3 near the pile head of the pile 5 is agitated using the ground improvement bit 21 while injecting the hardening material. Then, the pile 5 is sunk.

  In FIG. 1, reference numeral 1 denotes an excavation rod that is driven to rotate by an auger motor (not shown) and excavates an excavation hole 4 in which a pile 5 is set. A spiral blade 1a is attached to the peripheral surface of the excavation rod 1, and an enlarged excavation bit 2 is provided at the lower end. In this embodiment, when viewed from above the ground 3, the excavation rod 1 (and the ground improvement rod 20) rotates clockwise and is called “forward rotation”, and when it rotates counterclockwise, “reverse rotation”. (See FIG. 1). When the excavation rod 1 rotates forward, the excavation rod 1 advances in the direction of digging down the ground 3 due to the normal rotation of the spiral blade 1a. On the other hand, when the excavation rod 1 reverses, the excavation rod 1 advances in the direction of pulling up from the ground 3 due to the reverse rotation of the spiral blade 1a.

  The excavation rod 1 has a hollow structure and also serves as a pipe for passing a liquid or the like. When this excavation rod 1 excavates in advance, air, water, excavation liquid, etc. are ejected from the lower end nozzle. Further, a drilling blade 8 is provided at the lower end of the enlarged excavation bit 2 so as to be slightly smaller than the outer diameter of the spiral blade 1a (see FIG. 1).

  The enlarged excavation bit 2 is provided with, for example, a pair of enlarged excavation blades 6 that can be expanded by contact with the ground 3 with the reverse rotation of the excavation rod 1 (see FIG. 1). The expanded excavating blade 6 is in a state of being housed inside the outer diameter of the spiral blade 1a when the excavating rod 1 is rotated forward. On the other hand, in a state where the excavation rod 1 is reversed, the enlarged excavation blade 6 bites in contact with the wall surface of the ground 3 and expands due to its resistance, and protrudes further outward than the outer diameter of the spiral blade 1a. Become.

  Specific examples of the pile 5 include a concrete pile, a steel pipe concrete pile, a steel pipe pile, and the like. In addition, when making the spiral blade | wing 5a provided in the front-end | tip of the pile 5 into steel, the pile 5 is made into a steel pipe concrete pile and a steel pipe pile, or even in the case of a concrete pile, a bellows is wound with a steel pipe, and it welds and attaches to this A steel spiral blade 5a may be provided by a method or the like. In the case of a concrete pile, a concrete spiral blade may be integrally formed with the pile 5 using a mold.

  Here, a state in which the lower end portion of the excavation hole 4 is enlarged and excavated using the above-described enlarged excavation bit 2 is shown (see FIG. 1A and the like).

  First, the axial core of the expanded excavation bit 2 provided at the lower end of the excavation rod 1 is aligned with the core position of the pile 5. Next, the auger motor (not shown) is rotated to rotate the excavation rod 1 in the forward direction, and the ground 3 is dug down in a state where the enlarged excavation blade 6 is stored. Thereby, a small-diameter excavation hole 4a corresponding to the outer diameter of the spiral blade 1a is formed (see FIG. 1A).

  During excavation, water is supplied from a plant (not shown) installed on the ground to a pipe provided inside the excavation rod 1, and excavation is performed while discharging water from a nozzle located at the tip of the pipe. . Of course, air or the like may be used other than water. In addition, when an appropriate amount of bentonite drilling fluid is used when excavating sandy collapsible ground, not only excavation torque and settling torque of pile 5 can be reduced, but also the final amount of soil removal may be reduced. .

  After excavating the ground 3 to a predetermined depth by the excavation rod 1, the excavation rod 1 is reversed to expand the enlarged excavation blade 6, and the predetermined excavation hole 4 is pulled up to form an enlarged excavation hole 4 b at the lower end of the excavation hole 4. (See FIG. 1B). Further, while moving the excavating rod 1 up and down, for example, cement milk as a rooting liquid is supplied as an example of a hardened body material to an internal pipe of the excavating rod 1 from a batcher plant (not shown) installed on the ground. This cement milk is injected into the enlarged excavation hole 4b from the nozzle at the tip of the pipe to form a rooted portion 4B. The cement milk illustrated here is only an example of a slurry for cement hardening body for root hardening, and other cement powder may be used. The cement powder can be mixed with water used during excavation or the like and water contained in the ground 3 to form a slurry. Moreover, it is desirable to stir the cement milk by raising and lowering the enlarged excavation bit 2 for example about three times during the injection of the cement milk.

  In addition, before the excavation blade 8 reaches the target depth, the expansion excavation blade 6 may be expanded by switching the excavation rod 1 from normal rotation to reverse rotation. In this way, the ground 3 can be dug down and the enlarged excavation hole 4 b can be formed at the tip of the excavation hole 4.

  Thereafter, the expansion excavation bit 2 is pulled up to the middle of the excavation hole 4 while maintaining the rotation of the auger motor in the reverse rotation. As a result, a large-diameter excavation hole 4c continuous with the enlarged excavation hole 4b is formed in the excavation hole 4 (see FIG. 1C). In the present embodiment, the large-diameter excavation hole 4c is a portion (hereinafter referred to as 4A in the figure) from the above-described root consolidation portion 4B to the target portion for ground improvement (hereinafter also referred to as a ground improvement portion, indicated by reference numeral 4A in the figure). It is also referred to as an intermediate portion, which is indicated by reference numeral 4C in the drawing, so that the excavation hole 4 has a three-layer structure (see FIG. 1C, etc.).

  Among the excavation holes 4, the ground 3 is loosened at the intermediate portion 4 </ b> C. That is, since the enlarged excavation bit 2 is pulled up while being reversed in the present embodiment from the formation of the root consolidation portion 4B to the formation of the large-diameter excavation hole 4c, the exhaust by the spiral blade 1a is performed in the meantime. Soil action (effect of discharging excavated soil to the surface) is difficult to work. For this reason, in the intermediate part 4C, the soil of the ground 3 is loosened.

  Subsequently, when the large-diameter excavation hole 4c reaches the ground improvement part 4A, the reverse rotation of the expansion excavation bit 2 is stopped, and the expansion excavation bit 2 is pulled up in a state of normal rotation. The enlarged excavating blade 6 that has been expanded so far is in the storage state by changing the rotation direction in this way. Therefore, when the expanded excavation bit 2 in this state is pulled up to the ground surface, the small-diameter excavation hole 4a is not expanded but remains small (see FIG. 1C). However, since the enlarged excavation bit 2 is rotated forward during this time, the soil removal action by the spiral blade 1a works, and the soil in the ground improvement part 4A is discharged to the ground surface (see FIG. 1C).

  Subsequently, the soil is filled back into the excavation hole 4 (see FIG. 1D). As described above, the small-diameter excavation hole 4a corresponding to the ground improvement portion 4A in the excavation hole 4 has a small amount of soil due to the soil removal action by the spiral blade 1a. Therefore, in this embodiment, the small-diameter excavation hole 4a is backfilled with the soil, and the hardened material and the soil can be stirred more effectively (see FIG. 1D). There is also an advantage that the surrounding environment can be taken into consideration by backfilling the soil. In addition, although the example which backfills the soil discharged at the time of excavation is shown in this embodiment, you may make it backfill in the excavation hole 4 as a filler other than soil, earth and sand other than the soil discharged.

  Thereafter, the ground improvement rod 20 is used to stir the hardened material and the soil for the portion around the small-diameter excavation hole 4a (that is, the ground improvement portion 4A) (see FIGS. 1E and 1F). Here, the ground improvement rod 20 used in the present embodiment will be described as follows.

  The ground improvement rod 20 is a rod that is rotationally driven by, for example, an auger motor (not shown) and stirs a part of the excavation hole 4 (in the present embodiment, the ground improvement portion 4A). A ground improvement bit 21 is provided at the lower end of the ground improvement rod 20. The ground improvement rod 21 can supply a cement-type hardener from the tip of its internal piping. In addition, a co-rotation prevention blade 22 and a stirring blade 23 are provided on the upper stage of the ground improvement bit 21 (see FIGS. 1E and 1F).

  The co-rotation preventing wing 22 is a wing formed to have a length exceeding the diameter of the small-diameter excavation hole 4 a, and both ends thereof enter the ground 3, so that they do not co-rotate with the ground improvement bit 21. Although not shown in detail, the co-rotation preventing wing 22 is attached to the ground improvement rod 20 through a pipe or the like so as to be relatively rotatable. Further, the co-rotation preventing wing 22 and the ground improvement bit 21 are arranged at a somewhat narrow interval suitable for shearing and finely pulverizing the soil (see FIG. 1E), and form a high-quality improved body. It contributes to that.

  The stirring blade 23 is composed of a plurality of rod-like members disposed so as to be orthogonal to the ground improvement rod 20, for example (see FIG. 1 (E) and the like). The stirring blade 23 rotates together with the ground improvement rod 20 and stirs the finely crushed soil in the small-diameter excavation hole 4a.

  In the present embodiment, for example, such a ground improvement rod 20 is used, and the earth discharged with the small-diameter excavation hole 4a backfilled is agitated with the hardener. Specifically, the ground improvement rod 20 is rotated and pulled down in the small hole excavation hole 4a while injecting the cement hardening material, and the ground improvement bit 21 reaches the boundary between the ground improvement portion 4A and the intermediate portion 4C. Pull up by the way. Such a vertical movement may be repeated a plurality of times. As described above, the portion of the excavation hole 4 corresponding to the ground improvement portion 4A is finely crushed, and the hardener and the soil of the portion are uniformly mixed (see FIGS. 1E and 1F).

  Then, before cement milk hardens | cures, the pile 5 is sunk and construction is completed (refer FIG. 1 (G), (H)). In this embodiment, the pile 5 is set on an auger motor (not shown), the shaft core at the tip of the pile 5 is aligned with the pile core position, and the pile 5 is first rotated while the auger motor is rotated to rotate the pile 5 forward. It penetrates into the ground improvement part 4A and further penetrates into the intermediate part 4C (see FIG. 1G). As described above, since the intermediate portion 4C is in a disturbed state in the present embodiment, there is an advantage that the penetration of the pile 5 is particularly good in the intermediate portion 4C. Moreover, since the pile 5 of this embodiment is provided with the spiral blade | wing 5a from which the propulsive force is obtained at the front-end | tip, it is easy to penetrate also into the solidified part 4B in the enlarged excavation hole 4b by rotating suitably. (See FIG. 1 (H)). After the pile 5 has been laid down until the spiral blade 5a is positioned at the root consolidation portion 4B, the cement milk injected into the enlarged excavation hole 4b is hardened, so that the pile circumference of the pile 5 and the spiral blade 5a are enlarged. The pile 5 is fixed on the ground 3.

  As explained so far, the construction method of the pile 5 of the present embodiment uses ground improvement in combination with the pre-boring method, and re-excavation is not performed after the pile 5 is installed. In other words, in this embodiment, the pile construction is completed by sinking the pile 5 in the excavation hole 4 in which the hardener and the soil are partially stirred. For this reason, according to this construction method, the ground (that is, the improved body) in the ground improvement part 4A is not disturbed. Similarly, since there is no need to excavate the surrounding ground 3 after the pile 5 is installed, the pile 5 after the installation is not damaged.

  Moreover, in this embodiment, although the expansion excavation bit 2 provided with the expansion excavation blade 6 that can be expanded in the radial direction is used as a bit for excavation, when the expansion excavation bit 2 is pulled up, at least the ground improvement target In the portion (the ground improvement portion 4A), the enlarged excavating blade 6 is pulled up without being enlarged, so that the ground improvement portion 4A is not disturbed as much as possible, and a solid state of soil can be left (FIG. 1). (See (C) etc.). According to this, even after excavation, it is possible to maintain the ground 3 in a more desirable state when stirring the hardened material and the soil, and to form a high-quality improved body. In addition, in this embodiment, since the ground improvement rod 20 provided with the co-rotation preventing blade 22 and the stirring blade 23 is used for stirring, it is possible to form a high-quality improved body due to the effects of the co-rotation preventing blade 22 and the like. is there.

  As described above, according to the construction method of the present embodiment in which ground improvement is used in combination with the pre-boring method, ground force can be reliably improved especially in the vicinity of the pile head of the pile 5 after installation. The amount of horizontal displacement and generated bending moment near the pile head can be suppressed. For this reason, the bending rigidity required for the pile 5 may be small, and it becomes possible to aim at cost reduction by designing more economically than before. Moreover, since the generated moment in the pile head can be suppressed in this way, there is an effect that the reinforcing bars in the pile head or footing can be reduced. Incidentally, the bending moment or the like becomes a problem when a horizontal force is applied in the vicinity of the upper pile head and does not become a large problem in the vicinity of the intermediate portion 4C. Therefore, there is little influence on the horizontal displacement and the generated bending moment even when the soil in the portion (intermediate portion 4C) between the ground improvement portion 4A and the root consolidation portion 4B is loosened.

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the scope of the present invention. For example, in each of the above-described embodiments, the construction method using the excavation rod 1 in which the spiral blades (screws) 1a are formed is described. However, the excavation without the spiral blades 1a on the soft ground is contrary to this. It is also possible to use the rod 1. In the absence of the spiral blade 1a, the resistance during excavation increases or it becomes difficult to positively evacuate, but the soil does not loosen much. There is an advantage that more can be left.

  Further, in the above-described embodiment, when the excavating rod 1 is reversed, the enlarged excavating blade 6 is automatically expanded by contact with the ground 3. However, the excavating apparatus in which a hydraulic path is separately built in the excavating rod 1. The expansion excavation blade 6 can also be configured to be expanded by a hydraulic mechanism or the like. In such a case, it is possible to perform an extended excavation with the excavation rod 1 rotated forward. Further, if the enlarged excavating blade 6 can be expanded at any time using external power such as a hydraulic mechanism as described above, the above-described intermediate portion (a portion between the ground improvement portion 4A and the root consolidation portion 4B) 4C. It is possible to arbitrarily set how much soil is to be loosened.

  The present invention is suitable for application to pre-boring methods for ready-made piles such as concrete piles, steel pipe concrete piles, steel pipe piles, etc., particularly when soft ground exists near the pile heads.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing of the excavation hole which shows one Embodiment of this invention, (A) Forward excavation by an expansion excavation bit, (B) Expansion excavation by an expansion excavation bit, (C) Normal rotation raising of the expansion excavation bit in a ground improvement part , (D) Backfilling the soil in the excavation hole, (E) Ground improvement by ground improvement bit, (F) Lifting of ground improvement bit, (G) Pile setting, (H) Pile fixing Represents each.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Excavation rod, 1a ... Spiral blade (screw), 2 ... Expansion excavation bit (excavation bit), 3 ... Ground, 4 ... Excavation hole, 4A ... Ground improvement part (the part near the pile head which is the object of ground improvement ) 4B: Root consolidation part, 4C: Intermediate part (part between the part near the pile head and the consolidation part), 5 ... Pile, 5a ... Spiral blade, 6 ... Expanding excavation blade, 20 ... Ground improvement rod , 21 ... Ground improvement bit, 22 ... Co-rotation prevention wing

Claims (7)

  The excavation hole for installing the pile and the solidified part that supports the pile are formed on the ground using the excavation bit, the filler is backfilled in the excavation hole, and the ground near the pile head is injected while injecting the hardener. A method for constructing a pile that is used in combination with ground improvement, which is stirred and then laid down.   At the time of forming the excavation hole and root consolidation part, a drill bit having an enlarged excavation blade that can be expanded in the radial direction is used, and at the time of lifting the excavation bit, at least in the vicinity of the pile head that is the target of the ground improvement The construction method of the pile which used the ground improvement of Claim 1 together pulling up without expanding the said expansion excavation blade.   As the excavation rod for rotating the excavation bit, a rod having a screw formed around is used, and when the excavation bit is pulled up, the portion between the portion near the pile head to be ground improvement target and the root consolidation portion The pile construction method using ground improvement according to claim 2, wherein the excavation rod is rotated in a direction to reduce the amount of soil removal at a portion.   4. The ground near the pile head is agitated using a ground improvement bit having a ground improvement rod with a co-rotation preventing wing and injecting a hardening material through the ground improvement rod. Pile construction method using ground improvement as described in 1.   The construction method of the pile which used the ground improvement as described in any one of Claim 1 to 4 using what has a spiral blade | wing in a front-end | tip outer peripheral part as the said pile.   The diameter of the ground improvement body formed in the vicinity of the pile head by improving the ground is made smaller than the diameter of the root consolidation part, and the ground improvement according to any one of claims 1 to 5 is used in combination. Pile construction method.   The pile filling method using the ground improvement according to any one of claims 1 to 6, wherein the filler is soil discharged during excavation of the excavation hole.

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