JP3926364B2 - Construction method of tip-reinforced cast-in-place piles - Google Patents

Description

  The present invention relates to a method for constructing a tip-reinforced cast-in-place pile in which an injection bag is provided at the tip and inflated at the bottom of the pile.

  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. 4 is a diagram for explaining a previously proposed tip preload unit, FIG. 4 (a) is a diagram showing the unit, FIG. 4 (b) is a diagram showing a state of being built in a pile hole bottom, and FIG. It is a figure which shows the state which pressed the unit against the pile bottom.
A steel frame 3 is attached to the tip of the reinforcing bar 2 with a wire. An injection bag 4 is attached so as to surround the steel frame 3, and a protective sheet or the like is provided on the outside thereof, although illustration is omitted. Cement milk is injected into the injection bag 4 from the ground through the injection tube 5, the injection tube expansion / contraction mechanism 6, and the injection hose 7. In addition, the slime discharge hose 9 having a plurality of holes through which slime flows is attached to the surface of the injection bag 4 that contacts the ground and connected to the slime discharge pipe 8, and the slime at the bottom of the pile is discharged to the ground. Yes.

  As shown in FIG. 4 (b), a rebar cage 2 is built in the excavated pile hole 1, and as shown in FIG. 4 (c), the steel frame is crushed at the bottom of the pile with the weight of the rebar cage and the injection bag is Expand to the entire pile bottom. As will be described later, when the reinforcing bar 2 is lifted in this state, the injection tube expansion / contraction mechanism 6 slides and the injection bag 4 is left on the bottom of the pile. To inflate the infusion bag and pressurize and compress the pile tip ground. The slime at the bottom of the pile is driven out through the discharge hose 9 and the slime discharge pipe 8 by the applied pressure at this time.

FIG. 5 is a diagram for explaining a method for constructing cast-in-place piles.
FIG. 5A shows a state in which the excavation of the pile hole has been completed, and the pile bottom is brittle with a lot of slime. Insert a steel frame with a steel frame at the tip of this pile hole and a rebar cage with a tip preload unit consisting of an injection bag (Fig. 5 (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. 5 (c)), the reinforcing bag is lifted to a predetermined position while leaving the injection bag on the pile bottom (FIG. 5 (d)). Next, after placing and hardening the concrete, the cement milk is pressurized and injected from the injection pipe that passes through the pile body (Fig. 5 (e)) to inflate the injection bag, and the pile tip ground is pressurized and compressed. Strengthen. With the pressure at this time, the slime flows into the slime discharge hose disposed through the back surface of the bag and formed with a plurality of holes, and is discharged to the ground through the slime discharge pipe 8.
JP 2003-171930 A

  The tip preload unit used in the past uses a commercially available hard vinyl chloride pipe (hereinafter referred to as a polyvinyl chloride pipe) as an injection pipe and a slime discharge pipe, and this polyvinyl chloride pipe is in units of 4 m. In actual use, a length of several tens of meters is required. Therefore, as shown in FIG. 6, a method of sufficiently applying and bonding an adhesive with the socket 10 is used, but a connection failure occurs in this portion. In particular, in the case of an injection tube, cement milk cannot be injected at the time of pressurized injection to the tip preload unit. PVC pipes are cheap and strong, but on the other hand, they are difficult to bend and are difficult to handle because the unit of length is determined to be 4 m, which is a great deal of labor for workers. Moreover, since the joining with a socket is needed, the problem has arisen in the certainty of the construction precision.

  In addition, after crushing the tip preload unit at the bottom of the pile, an injection tube expansion / contraction mechanism is provided to lift the reinforcing bar cage and leave the injection bag at the bottom of the pile. As shown in FIG. 7, the injection tube expansion / contraction mechanism comprises a steel slide tube 15, the injection hose 7 is connected to the lower end via an O-ring 16, and the injection tube 5 is slid to the upper end via an O-ring 17. It is possible to fit. The injection tube 5 is marked 1m from the tip so that the injection tube is arranged over the entire length of the slide tube, and grease is applied to the injection tube so that the injection tube slides sufficiently. ing. However, when the injection tube is in contact with a reinforcing steel basket, the sliding of the injection tube is hindered, and the expansion / contraction mechanism does not function sufficiently.

  The injection pipe and slime discharge pipe are installed inside the reinforcing bar. If it is installed outside the reinforcing bar cage, the PVC pipe may be destroyed by rolling when the reinforcing bar cage is dropped into the pile hole, and the concrete to be placed does not go well to the back side of the PVC pipe. Therefore, it is necessary to install the injection pipe and the slime discharge pipe inside the reinforcing bar cage. However, the denser the reinforcing bar, the more complicated and difficult it is to connect. In addition, there is a problem of damage due to tremming of the tremmy tube.

  Moreover, the injection pipe and the slime discharge pipe are constructed of the same material PVC pipe, and are indistinguishable in appearance. For this reason, when cement milk is injected, there is a possibility that it is mistakenly injected into the slime discharge pipe.

  In addition, the rebar cage and the steel frame are connected by a wire, but there is a possibility that a hole will be made in the injection bag at the pointed portion of the wire when the steel frame is crushed and the steel frame is crushed . In addition, it takes a long time to join the wires, and there is a possibility that the injection bag may be accidentally damaged during binding. In addition, there is a similar problem because the injection pipe and the discharge pipe are connected to the rebar cage by a wire.

The present invention is intended to solve the above-described problems, and aims to improve construction accuracy and workability and to reliably strengthen the pile tip ground.
To that end, the invention of claim 1 lays a steel bar with a steel frame with an injection bag installed at the bottom into the excavation hole, crushes the steel frame at the bottom of the pile and expands the injection bag to the bottom of the pile. In the construction method of cast-in-place piles that pressurize the pile tip ground by injecting the injected material under pressure,
A flexible hard resin hose is used for an injection pipe for injecting an injection material under pressure and a slime discharge pipe, and a crushed stone having a particle size of 40 mm or less is put into a pile bottom in advance.
According to a second aspect of the present invention, the hard resin hose used for the injection pipe has a structure in which a reinforcing thread is wound around the outer periphery of the inner pipe and a wire is wound around the outer side through a transparent intermediate layer. It is characterized by.
The invention according to claim 3 is characterized in that the hard resin hose has no connection place from the ground to the bottom of the pile.
The invention according to claim 4 is characterized in that the hard resin hose is arranged by being bound by a binding band on the outside of the reinforcing bar cage.
The invention of claim 5 is characterized in that the hard resin hose is dyed so that it can be discriminated from for injection and for slime discharge.
The invention of claim 6 is characterized in that the steel frame is bound to a reinforcing bar with a binding band.

  By using a flexible hard resin hose for the injection pipe and slime discharge pipe, the present invention can be a single hose with no connection points from the ground to the bottom of the pile. The expansion and contraction mechanism of the pipe is no longer necessary, the construction accuracy and workability are improved, and the cement milk can be reliably injected under pressure. In addition, since the resin hose can be installed outside the reinforcing bar cage, the workability is greatly improved, and the resin hose is not damaged by the rolling of the tremy tube. Further, since the injection pipe and the slime discharge pipe can be distinguished by dyeing the resin hose, there is no mistake in the work site. In addition, since the binding band is used as a method for connecting the steel frame and the hose to the reinforcing steel basket, the workability is improved and the injection bag is not damaged.

Embodiments of the present invention will be described below.
FIG. 1 is a diagram illustrating a tip preload unit according to the present invention, and FIG. 2 is a diagram illustrating a hard resin hose used for an injection tube.
In FIG. 1, an injection bag 4 is attached so as to surround a steel frame 3 attached to the tip of a reinforcing steel basket 2, an injection material (for example, cement milk) is injected into the injection bag 4 through an injection tube, and piles are formed with a slime discharge pipe The basic configuration for discharging the slime at the bottom is the same as that shown in FIG. 4, but in the present invention, first, a flexible hard resin hose is used as the injection tube 20 and the slime discharge tube 21. Is different.

  As shown in FIG. 2, the hard resin hose used for the injection pipe 20 is formed by winding a reinforcing thread 26 around an inner pipe 25 made of resin, forming an intermediate layer 27 made of transparent resin thereon, It is wound and has a structure in which a protective layer 29 made of a transparent resin is coated on the outermost layer, and the resin is made flexible by adding a plasticizer to vinyl chloride.

  The outline of the manufacturing process of the hard resin hose used for the injection pipe 20 is as follows. Inner pipe molding in which a plasticizer is added to vinyl chloride extruded from an extruder and the resin molded by the winder is cooled while being cooled through a cooling water tank. After winding the reinforcing yarn through the knitting machine while feeding the wound pipe, the intermediate layer is formed through the extruder, and the intermediate layer and the knitting process are wound up by the winder while cooling through the cooling water tank. After winding the wire with a wire coiling machine while feeding out the pipe, form a protective layer (outer skin) through the extruder, wind up with a winder while cooling in a cooling water tank, and make it into a product from the outer shell and wire coiling molding process The maximum length of 100m is possible. It is preferable to use an injection hose having a thickness of 2 to 8 mm.

  The hard resin hose used for the slime discharge pipe 21 is obtained by eliminating the winding process of the reinforcing yarn and the winding process of the wire in the manufacturing process of the hard resin hose of the injection pipe. The slime discharge hose preferably has a thickness of 2 to 5 mm. Of course, if necessary, the reinforcing resin or wire may be wound around the hard resin hose used for the slime discharge pipe 21 to increase the strength.

  Since the flexible hard resin hose can be manufactured long enough, it can be a single hose from the ground to the injection bag and from the ground to the bottom of the pile, and it is not necessary to connect with a socket as in the past, Workability is greatly improved. In addition, the injection tube and the slime discharge tube are dyed in different colors, for example, by adding a dye to the resin in the manufacturing process, so that the injection tube and the slime discharge tube are not mistaken at the work site.

  By using the hard resin hose of the present invention, in the case of an injection tube, a conventional expansion / contraction mechanism is not required, the cost can be reduced, and there is no hindrance to cement milk injection. The hard resin hose used for the injection pipe has an instantaneous maximum withstand pressure pressure in the air of 3.5 MPa, can sufficiently withstand a preload pressure of 1.5 MPa applied on the ground, and is not damaged.

  In the case of the slime discharge pipe, a large load is applied, but this force only discharges the slime through a plurality of holes opened in the portion attached to the injection bag, so a flexible hard resin hose with a thickness of 2 to 5 mm is used. By using it, there is no hindrance to slime discharge.

  In addition, since the hard resin hose of the present invention is flexible, there is no risk of damage even if it is arranged outside the reinforcing bar cage, and the concrete can sufficiently wrap around the back side of the hose. Therefore, in the present invention, both the injection pipe and the slime discharge pipe are arranged outside the reinforcing bar cage, and a binding band 30 made of plastic as shown in FIG. 3 is used for binding to the reinforcing bar cage instead of the conventional wire. This binding band is a commercially available one, and the band is formed with a jagged surface, and is a well-known one that does not loosen when inserted into a binding portion and tightened. As described above, the injection pipe and the slime discharge pipe are arranged outside the reinforcing bar cage and are attached with the binding band, so that the workability is remarkably improved. 3 is also used to attach the steel frame 3 to the reinforcing bar cage. Since the binding band does not have a pointed portion like a conventional wire, there is no risk of damaging the injection bag. In addition, since there exists a possibility that an injection | pouring bag may contact and tear when there is a sharp stone etc. in a pile bottom, it is desirable to throw a crushed stone with a particle size of 40 mm or less into a pile bottom beforehand. This crushed stone can be preloaded to balance.

  According to the present invention, workability is remarkably improved and construction accuracy is improved, so that the pile tip ground can be surely strengthened, and the industrial utility value is great.

It is a figure explaining the tip preload unit of the present invention. It is a figure explaining the hard resin hose for injection pipes. It is a figure explaining a binding band. It is a figure explaining the tip advanced loading unit previously proposed. It is a figure explaining the construction method of a cast-in-place pile. It is a figure explaining the connection of a PVC pipe. It is a figure explaining an injection pipe expansion-contraction mechanism.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 ... Steel bar, 3 ... Steel frame, 4 ... Injection bag, 20 ... Injection pipe, 21 ... Slime discharge pipe, 25 ... Inner pipe, 26 ... Reinforcement thread, 27 ... Intermediate layer, 28 ... Wire, 29 ... Protective layer , 30 ... A unity band.

Claims (6)

A steel slab with a steel frame with an injection bag installed at the bottom is built in the excavation hole, the steel frame is crushed at the bottom of the pile, the injection bag is spread to the bottom of the pile, and the injection material is injected under pressure. In the construction method of cast-in-place piles that pressurize the pile tip ground,
Use of a flexible hard resin hose for the injection pipe for injecting the injection material and the slime discharge pipe, and a crushed stone having a particle size of 40 mm or less is put into the pile bottom in advance. Construction method of piles. The hard resin hose used for the injection pipe has a structure in which a reinforcing thread is wound around the outer circumference of the inner pipe and a wire is wound around the outer side through a transparent intermediate layer. The construction method described. The construction method according to claim 1, wherein the hard resin hose has no connection portion from the ground to the bottom of the pile. The construction method according to claim 1, wherein the hard resin hose is arranged by being bound by a binding band on an outer side of a reinforcing bar. The construction method according to claim 1, wherein the hard resin hose is dyed to make it possible to distinguish between injection and slime discharge. The construction method according to claim 1, wherein the steel frame is bound to a rebar cage with a binding band.

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