JP3880002B2 - Construction method of tip-reinforced cast-in-place concrete pile, injection bag and steel frame - Google Patents

Description

  The present invention relates to a method for constructing a tip-reinforced cast-in-place concrete pile provided with an injection bag at the tip and inflated at the bottom of the pile, an injection bag, and a steel frame.

  The present applicant has already proposed a tip preload cast-in-place pile method in which an injection bag is provided at the tip and inflated at the bottom of the pile (Patent Document 1). This tip preload cast-in-place pile method is a method that improves the support ground properties and suppresses the settlement of the pile, and improves the pile tip design support force by compressing and strengthening the pile tip ground with high pressure. .

FIG. 14 is a view for explaining the proposed tip preload cast-in-place pile method, and FIG. 15 is a view for explaining a steel frame.
In FIG. 14, a steel frame 3 is attached to a tip of a reinforcing bar 2 disposed in a pile hole 1 for constructing a cast-in-place pile with a fixture such as a number wire. An infusion bag 4 in which the edges of the two upper and lower base fabrics are sewn so as to surround the steel frame 3 is attached. A blue sheet and a non-woven fabric surrounding it are provided. This reinforcing bar 2 is built in the excavated pile hole 1, and the steel frame is crushed at the bottom of the pile to spread the injection bag over the entire pile bottom. The steel frame 3 has a braided structure with a ring-shaped side at the upper and lower ends and a plurality of vertical sides connecting the ring-shaped sides, and a cross-shaped side connected to the lower-end ring-shaped side. A protective side 5 is provided so that the frame bent at this portion does not break the injection bag.

  As shown in FIG. 15, when the steel frame 3 is crushed, the vertical side is bent at a bending point P, the point Q of the steel frame is displaced to the position q, and the bending point P is at the position of the outer point p. The infusion bag is bulged out, and at this time, the protective side 5 prevents the frame from sticking into the bag and breaking.

FIG. 16 is a diagram for explaining a method for constructing cast-in-place piles.
FIG. 16A shows a state in which the excavation of the pile hole has been completed, and the pile bottom is fragile with a lot of slime. Insert a steel frame at the tip of this pile hole, a reinforcing bar rod installed with a tip preload unit consisting of an injection bag (Fig. 16 (b)), press the injection bag against the pile bottom and crush the steel frame, After spreading the injection bag on the bottom of the pile (FIG. 16C), the reinforcing bag is lifted to a predetermined position while leaving the injection bag on the bottom of the pile (FIG. 16D). Next, after placing and hardening concrete, cement milk is pressurized and injected from the injection hose through the pile body (Fig. 16 (e)) to inflate the injection bag, and the pile tip ground is compressed and compressed. Strengthen. At this time, the slime is discharged through the slime discharge hose disposed through the back surface of the bag and having a plurality of holes.
JP 2003-171930 A

  In the conventional tip preload cast-in-place pile method, it is not possible to cope with a pile with a large diameter, a pile such as a BH method in which a large amount of slime is accumulated, and a pile with a lot of excavation. In the case of an expanded pile, the steel frame cannot follow the expanded diameter of the bottom plate of the expanded pile, and when the pile length is dug, the reinforcing bag is pulled up to a predetermined position. This is because there is a problem that a load is applied to the crane carrying the steel rod and lifting the reinforcing bar rod. Moreover, in the case of a construction method in which a large amount of slime is left at the tip of a pile such as a BH pile, in order to push away a large amount of slime at the time of preloading the tip, a large expansion allowance is required for the injection bag. Furthermore, the amount of slime is large, and the slime discharge function that can follow it is necessary.

The present invention is intended to solve the above-mentioned problem, and can be applied to a construction method in which a large amount of slime is accumulated, an expanded-diameter pile, a pile having a large amount of extra excavation, etc. The purpose is to make sure that the pile tip ground can be strengthened.
The present invention relates to an injection bag that is installed at the bottom of a steel frame attached to the tip of a reinforcing bar rod and pressurizes and compresses a pile tip ground by injection of an injection material. And a tubular member attached to the opening of the contra-inverted bag body, and an injection tube attached through the tubular member, between the folded inner part and outer part. The injection material is injected from the injection tube through the tubular member.
Further, the present invention is characterized in that the contra-rotating bag body has a diameter slightly larger than the pile diameter and can prevent the slime and the concrete from entering the back side of the pile bottom.
Further, the present invention is characterized in that the contra-rotating bag body is folded and extends in the longitudinal direction by injection of an injection material.
Further, the present invention is characterized in that the infusion bag is made of a thick woven fabric and covered with a bag of non-woven fabric or the like.
Further, the present invention comprises a contra-inversion bag body in which one half of a hollow tubular body having both ends open is folded back inside the other half, and a tubular member is attached in the opening of the counter-inversion bag body. An injection tube is attached through the member, and an injection bag in which an injection material is injected from the injection tube through the tubular member between the folded inner part and outer part is attached to the bottom of the frame, and the steel is disposed at the tip of the reinforcing bar rod The steel frame is a braided structure of a plurality of ring-shaped frame sides and a plurality of vertical frame sides that connect the ring-shaped frame sides in the vertical direction, omitting the cross-shaped arm on the bottom surface of the frame, The tubular member of the infusion bag can be inserted from the lower center part.
Further, the present invention comprises a contra-inversion bag body in which one half of a hollow tubular body having both ends open is folded back inside the other half, and a tubular member is attached in the opening of the counter-inversion bag body. The injection tube is attached through the member, and the tubular member of the injection bag in which the injection material is injected from the injection tube through the tubular member between the folded inner portion and the outer portion is inserted and attached from the lower central portion. A step of attaching a frame to the end of a reinforcing rod and installing it in a drilling hole, a step of injecting an injection material from one injection hose into the injection bag, and venting from the other injection hose arranged on the opposite side of the injection hose, The method includes a step of pressurizing and compressing the ground by injecting the injection material from the injection hoses on both sides to inflate the injection bag.

Since the contra-rotating bag body of the present invention has a diameter larger than the pile diameter when inflated by the injection of the injection material, the slime and concrete can be prevented from turning around to the back side.
Moreover, this invention can extend the vertical direction by injection | pouring of an injection material, and can enlarge a bulge allowance by folding the contra-fold bag body.
In addition, the present invention makes the injection bag strong as a thick woven fabric, eliminating the need for a blue sheet (cover sheet) conventionally used to cover the bag and extending the injection bag in the longitudinal direction during construction. It can only be covered with a bag so that it will not be damaged.
In addition, when using an infusion bag made of a contra-rotating bag, the present invention forms a steel frame with a ring-shaped frame side on the bottom side by adopting a braided structure of a ring-shaped frame side and a vertical frame side. The tubular member of the infusion bag can be placed in the opening to be made.
Moreover, this invention can inject | pour an injection material equally to an injection bag by inject | pouring injection material from multiple injection | pouring hose places.

Embodiments of the present invention will be described below.
FIG. 1 is a view for explaining the structure of a steel frame of this embodiment used in a method for constructing a tip-reinforced cast-in-place pile.
The steel frame 3 is attached to the tip of the reinforcing bar to be placed in the pile hole where the cast-in-place pile is to be constructed, and an injection bag (not shown) is installed at the bottom of the steel frame 3, and the reinforcing bar is built into the pile hole and Crush the frame and spread the injection bag over the entire pile bottom, press the injection material such as cement milk into the injection bag from the ground using the pipe passed through the pile after concrete injection and hardening, The infusion bag is inflated and the pile tip ground is pressurized and reinforced.

  The steel frame 3 has a braided structure of ring-shaped sides at the upper and lower ends and a plurality of vertical sides. The vertical side of the steel frame 3 has a center point P as a bending point. A bag extension arm 10 is provided. When the steel frame 3 is crushed, the Q point at the bottom of the frame is displaced to the q position, and the bending point P is displaced to the outer p point. At this time, the injection bag expansion arm 10 is further out of the p position. Even if it is a diameter-expanded pile extending in the direction, it is possible to expand the injection bag over the entire bottom surface. In addition, if the height of the steel frame is increased and the length from the bending point P to the point Q is lengthened instead of providing the injection bag extension arm, the point q to the point p becomes longer when the frame is crushed. It is possible to spread the injection bag over the entire bottom of the expanded pile.

FIG. 2 is a view for explaining another example of the steel frame of the present embodiment.
Since the conventional steel frame is bound to the reinforcing bar, it cannot be removed even if it is crushed at the bottom of the pile. However, it is necessary to lift the reinforcing bar rod after crushing the steel frame and expanding the injection bag in the case of piles with expanded diameter or overexcavation. At this time, the collapsed steel frame is caught on the side wall of the pile hole. Inconvenience arises. In order to eliminate this, in this embodiment, it is set as the structure which detaches | leaves from a rebar rod when a steel frame is crushed.

  The bending point P is formed on the vertical side of the steel frame 3 as in the case of FIG. 1, and a hook side 11 is provided at the same position as the vertical side, and the tip thereof is the main reinforcing bar of the reinforcing bar rod. 6 is hooked to the rebar 7 that binds it. Then, the steel frame is crushed at the bottom of the pile, the Q point of the frame bottom is in the position of q, and the tip of the hook side 11 is disengaged from the rebar 6 in the process of displacing the bending point P to the p point. Overhang and spread the injection bag over the entire pile. Since the hook side 11 is detached from the rebar, when the rebar is lifted, the steel frame and the expanded bag remain on the bottom of the pile. Can be lifted.

  In the above example, the hook side is hooked on the band reinforcing bar, but the latch type that hooks the rotating hook biased clockwise in the clockwise direction counterclockwise with a larger spring force and hooks on the band reinforcing bar. The unit may be attached to a steel frame, and a mechanism may be used in which when the steel frame is crushed, the counterclockwise spring force disappears and the hook is released by the clockwise spring force.

  In addition, when there is a large amount of slime, it is difficult to expand the injection bag unless the strength of the steel frame is increased. Therefore, in the case of the example in FIGS. 1 and 2, the number of the vertical sides of the steel frame having a braided structure is 8 or more in the past, and the thickness of each side of the steel frame is 3 mm. Thicker and wider 15mm to allow expansion of the infusion bag against slime.

FIG. 3 is a diagram for explaining a method for constructing a cast-in-place pile when there is a lot of overexcavation or a large amount of slime. In this example, a type in which the steel frame is detached is used.
FIG. 3A shows a state in which the excavation of the pile hole has been completed, and there is a mud cake on the hole wall, and there is a lot of slime on the bottom of the pile and it is fragile. Insert a steel frame with a steel frame at the tip of this pile hole, a reinforcing bar rod with a tip preload unit consisting of an injection bag (Fig. 3 (b)), press the injection bag against the pile bottom and crush the steel frame, After the injection bag is spread on the pile bottom (FIG. 3C), the steel frame and the injection bag that have been detached are left on the pile bottom, and the reinforcing bar is lifted to a predetermined position (FIG. 3D). Next, after placing and hardening the pile body concrete, cement milk is pressurized and injected from an injection hose passing through the pile body to inflate the bag, and the pile tip ground is pressurized and reinforced. At this time, the slime is discharged through the slime discharge hose disposed through the back surface of the bag and having a plurality of holes.

FIG. 4 is a diagram for explaining a method for constructing a cast-in-place pile in the case of an expanded-diameter pile. In this example, the steel frame is separated.
FIG. 4A shows a state in which the excavation of the pile hole has been completed. There is a mud cake on the hole wall, and there is a lot of slime on the bottom of the pile, which is fragile. Reinforcing bar with steel frame and injection bag installed at the tip of this pile hole is inserted (Fig. 4 (b)), the injection bag is pressed against the pile bottom, the steel frame is crushed, and the injection bag is expanded. After spreading to the bottom of the pile (FIG. 4 (c)), the steel frame and the injection bag that have been detached are left on the bottom of the pile, and the reinforcing bar is lifted to a predetermined position (FIG. 4 (d)). Next, after placing and hardening the pile body concrete, cement milk is pressurized and injected from an injection hose passing through the pile body to inflate the bag, and the pile tip ground is pressurized and reinforced (FIG. 4 ( e)). At this time, the slime is discharged through a slime discharge hose disposed through the back of the bag and having a plurality of holes.

FIG. 5 is a view for explaining the infusion bag of the present embodiment. FIGS. 5A and 5B show a small-diameter reversal type, and FIGS. 5C and 5D show a large-diameter reversal type.
The infusion bag of the present embodiment has a seamless structure made of a contra-rotating bag, and in the case of FIGS. 5 (a) and 5 (b), it is made of a polyester fabric or the like made up of a small diameter portion 20a and a large diameter portion 20 (b). It is a structure in which the small-diameter portion 20a of the hollow tubular body 20 (FIG. 5 (a)) open at both ends is folded back into the large-diameter portion 20b (FIG. 5 (b)), and between the small-diameter portion 20a and the large-diameter portion 20b ( An injection material such as cement milk is put in the shaded area in the figure. The infusion bag may be nylon or the like other than polyester, and a thickened yarn is used. If the bag is woven with a thicker thread, the seam becomes rough, and cement milk may leak from there, so a fine sheet is applied inside the bag to prevent leakage. Since this structure is a seamless structure with no seams other than the opening, there is no possibility of the injection material leaking and the pressure resistance is improved.

  In the case of FIGS. 5 (c) and 5 (d), one opening 21a of the large-diameter hollow tubular body 21 (FIG. 5 (c)) having a double-end opening made of a woven fabric made of polyester or the like is folded back into the tubular body. The structure is pulled up to the opening 21b (FIG. 5D), and an injection material such as cement milk is put between the folded inner part and outer part (shaded area in the figure). As in the case of FIGS. 5A and 5B, since the seamless structure has no seams other than the openings, there is no possibility of the injection material leaking and the pressure resistance is improved.

FIG. 6 is a cross-sectional view three-dimensionally showing an example of an infusion bag having a contra-rotating bag structure.
The contra-rotating bag 30 is folded and thinned, and a plastic tube 31 is attached to the opening and reinforced with a steel band, and the tube member 31 made of a plastic tube or a steel tube is inserted into the bag through the injection tube 33. It is structured to inject cement milk.

  This injection bag is expanded when the cement milk is injected under pressure, so that the folded part will extend to the lower side (longitudinal direction) of the figure. In addition, the pile bottom can be sufficiently compressed and strengthened even when there is a lot of slime and excessive digging. In addition, the material of the injection bag is made of a strong material such as a polyester fabric, and by making it seamless, the blue sheet that has been used to cover the bag can be eliminated. However, it is desirable to cover with a bag such as a nonwoven fabric so that the injection bag does not extend in the vertical direction in the process of inserting the reinforcing bar rod into the pile hole.

  As shown in FIG. 6, since the infusion bag having a contra-rotating bag structure is provided with a tubular member such as a plastic tube from the center of the bag upward, a cross is formed on the bottom of the frame like a conventional steel frame. If the arm is shaped, it will interfere with the bag installation. Therefore, the cross-shaped arms on the bottom surface of the steel frame are omitted, and a braided structure with ring-shaped sides at the upper and lower ends and a plurality of vertical sides connecting them prevents the installation from being hindered. can do.

7 and 8 are diagrams for explaining the advantages of the contra-rotating bag structure.
The conventional infusion bag 40 shown in FIG. 7 (a) has a structure in which upper and lower circular base fabrics are stitched together at the peripheral edges thereof, and has a small stretch allowance. A double diameter is used. However, in this structure, when the reinforcing bar is inserted into the pile hole (Fig. 8 (a)) and the bag is pressed against the pile bottom, the surrounding portion is bent to the hole wall side (Fig. 8 (b)), and the bent portion is Concrete wraps around between the hole walls.

  On the other hand, in the contra-rotating bag structure of FIG. 7 (b), since the allowance in the vertical direction is large, even if the bag diameter is slightly larger than the pile diameter (for example, pile diameter +20 cm). Since the compressive force of the pile bottom can be obtained sufficiently, the concrete can be prevented from wrapping around without being bent to the hole wall side. That is, even if the reinforcing bar with the bag of the inverted bag structure is inserted into the pile hole (FIG. 8 (c)) and the bag is pressed against the pile bottom, the surrounding portion does not bend to the hole wall side (see FIG. 8 (d)), it is possible to prevent the wraparound of concrete.

FIG. 9 is a view for explaining a method of arranging the slime discharge hose on the pile bottom.
The slime at the bottom of the pile is placed when the pile body concrete is placed and hardened, and then the cement milk is pressurized and injected from the injection hose through the pile body to inflate the bag. It is pushed out to the ground through a plurality of holes of a slime discharge hose disposed on the back surface.
FIG. 9A is an arrangement view of a conventional slime discharge hose at the bottom of the pile, and only one slime discharge hose 50 is arranged outside the bag. However, when there is a large amount of slime, it cannot be discharged sufficiently. Therefore, as shown in FIG. 9B, the slime discharge hose 51 is bent and arranged in an arbitrary shape to increase the area where the discharge hose hits the pile bottom. Moreover, as shown in FIG.9 (c), the number of discharge hoses is increased and it arrange | positions to a pile bottom. By adopting such a configuration, slime can be discharged effectively.

A plurality of slime discharge hoses can be installed and arranged through the back side of the injection bag, and the injection bag can be prevented from falling by hanging the injection bag with the slime discharge hose.
FIG. 10 is a diagram for explaining an example in which an infusion bag is suspended by a slime discharge hose.
The slime discharge hose 60 passes through the inside of the reinforcing bar from the ground side and passes through the back side of the injection bag 61. By using two or more slime discharge hoses, the injection bag is suspended and the bag extends downward, It can prevent falling.

Next, an embodiment that can eliminate the need for a steel frame will be described.
FIG. 11 is a diagram illustrating an example of an embodiment in which water is poured into an infusion bag.
FIG. 11 (a) shows a state where the excavation of the enlarged-diameter pile has been completed. There is a mud cake on the hole wall, and there is a lot of slime on the bottom of the pile, which is fragile. A reinforcing bar with an injection bag installed at the tip is inserted into the pile hole (FIG. 11B). An injection bag may be installed through a steel frame. After inserting the reinforcing bar rod to a fixed position or the bottom, water is injected into the injection bag under pressure to expand the bag over the entire bottom surface of the enlarged diameter (FIG. 11 (c)). Next, when pile main body concrete is laid (FIG. 11 (d)), the injection bag is pressurized and compressed by the weight of the pile, and the water in the bag is discharged through the injection hose. Next, an injection material such as cement milk is pressurized and injected into the bag through the injection hose to expand the bag, and the pile tip ground is pressurized and reinforced. At this time, the slime is discharged through a slime discharge hose disposed through the back of the bag.

Drawing 12 is a figure explaining other examples of an embodiment which puts water into an infusion bag.
FIG. 12 (a) shows a state where the excavation of the enlarged-diameter pile has been completed. There is a mud cake on the hole wall, and there is a lot of slime on the bottom of the pile, which is fragile. An injection bag is set in the pile hole (with water) with a weight or the like (FIG. 12A). Next, a reinforcing bar rod is inserted into the pile hole (FIG. 12B), water is injected from the injection hose into the injection bag, and the bag is expanded over the entire bottom surface of the enlarged diameter (FIG. 12C). Subsequently, when pile main body concrete is laid (FIG.12 (d)), an injection bag will be pressurized and shrunk with the weight of a pile, and the water in a bag will be discharged | emitted through an injection hose. Next, an injection material such as cement milk is pressurized and injected into the bag through the injection hose to expand the bag, and the pile tip ground is pressurized and reinforced. At this time, slime is discharged through the slime discharge hose disposed through the back of the bag (FIG. 12 (e)).

FIG. 13 is a view for explaining an injection method into a bag.
FIGS. 13 (a) and 13 (b) are diagrams for explaining a conventional injection method, in which cement milk or the like is injected from one side of the injection hose (injection hose A in the figure) from the ground side (FIG. 13 (a)). Then, pressure injection is performed to compress and compress the pile bottom (FIG. 13B). In this process, slime is discharged through the slime discharge hose. However, in this method, cement milk is injected from one side and the injection bag is inflated from one side so that the whole is finally inflated. Therefore, there is a possibility that a phenomenon of inflating will occur.

  FIGS. 13C and 13D are diagrams for explaining the injection method of the present embodiment, in which cement milk is injected from one side of the injection hose (injection hose A in the figure) and from the opposite side (injection hose B in the figure). The air is extracted (FIG. 13 (c)), and then cement milk is injected from both sides of the injection hoses A and B and pressurized (FIG. 13 (d)). By such an injection method, the bag can be inflated evenly.

  According to the present invention, it is possible to cope with a construction method in which a large amount of slime accumulates, an enlarged diameter pile, a pile with a lot of excavation, etc., eliminating the sneak of slime and concrete on the back of the injection bag, and reliably reinforcing the pile tip ground Therefore, the industrial utility value is great.

It is a figure explaining the structure of the steel frame of this embodiment. It is a figure explaining the other example of the steel frame of this embodiment. It is a figure explaining the construction method of the cast-in-place pile when there is much excessive digging of this embodiment or there are many slimes. It is a figure explaining the construction method of the cast-in-place pile in the case of the diameter-expanded pile of this embodiment. It is a figure explaining the injection bag of this embodiment. It is sectional drawing which showed the example of the injection bag of a contra-rotation bag body structure three-dimensionally. It is a figure for demonstrating the advantage of a contra-rotating bag structure. It is a figure for demonstrating the advantage of a contra-rotating bag structure. It is a figure explaining the arrangement | positioning method in the pile bottom of a slime discharge hose. It is a figure explaining the example which hangs an injection bag with a slime discharge hose. It is a figure explaining the example of embodiment which puts water into an injection bag. It is a figure explaining the other example of embodiment which puts water into an injection bag. It is a figure explaining the injection | pouring method to a bag. It is a figure for demonstrating the existing tip preload cast-in-place pile method. It is a figure explaining the proposed steel frame. It is a figure explaining the construction method of the existing cast-in-place pile.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Pile hole, 2 ... Reinforcing bar, 3 ... Steel frame, 6 ... Main reinforcement, 7 ... Band reinforcement, 10 ... Extension arm, 11 ... Hook side

Claims (6)

In the infusion bag that is installed at the bottom of the steel frame attached to the tip of the rebar bar and presses and compresses the pile tip ground by injecting the injection
It has a contra-inverted bag structure in which one half of a hollow tubular body having both ends opened is folded inward of the other half, and a tubular member is attached in the opening of the contra-inverted bag body, and an injection tube is passed through the tubular member. The injection bag is characterized in that the injection material is injected from the injection tube through the tubular member between the inner portion and the outer portion that are folded. The injection bag according to claim 1, wherein the contra-rotating bag body has a diameter slightly larger than a pile diameter, and prevents the slime and concrete from entering the back side of the pile bottom. The infusion bag according to claim 1, wherein the contra-rotating bag is folded and extends in a longitudinal direction by injection of an injecting material. The infusion bag according to claim 1, wherein the infusion bag is made of a thick woven fabric and is covered with a non-woven fabric bag. It consists of a contra-reversal bag body in which one half of a hollow tubular body having both ends open is folded inside the other half, and a tubular member is mounted in the opening of the contra-rotating bag body, and an injection tube is mounted through the tubular member An infusion bag adapted to inject an injection material from an injection tube through the tubular member between the folded inner portion and outer portion is attached to the bottom of the frame, and is a steel frame disposed at the end of the reinforcing bar rod,
The steel frame has a braided structure of a plurality of ring-shaped frame sides and a plurality of vertical frame sides that connect the ring-shaped frame sides in the vertical direction, omitting a cross-shaped arm on the bottom surface of the frame, A steel frame in which a tubular member of an infusion bag can be inserted. It consists of a contra-reversal bag body in which one half of a hollow tubular body having both ends open is folded inside the other half, and a tubular member is mounted in the opening of the contra-rotating bag body, and an injection tube is mounted through the tubular member A steel frame in which a tubular member of an injection bag in which an injection material is injected from the injection tube through the tubular member between the folded inner part and outer part is inserted and attached from the lower central part is attached to the end of the reinforcing bar rod Attach and install in the borehole,
Injecting an injection material from one injection hose into the injection bag, and venting air from the other injection hose arranged on the opposite side of the injection hose;
A step of pressurizing and compressing the ground by injecting injection material from the injection hose on both sides to inflate the injection bag,
Of tip-reinforced cast-in-place piles including

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