JPH0711634A - Construction method of pile having bag body - Google Patents

Abstract

PURPOSE:To develop bearing force as designed by expanding a bag body surely up to a specific shape even if a bearing layer is a sand and gravel layer. CONSTITUTION:A curved push plate 1 with 10mm in thickness is mounted to the upper end of a screw rod of an excavation device. After the rod is rotated forwardly to make excavation up to a sand layer through a clay layer, the rod is reversely rotated up to a sand and gravel layer with specific depth to make expansion excavation, sand and gravel 8 mounted on a screw is slowly pulled up to the clay layer, and after the rod is rotated in such a state and is pushed against the clay layer, the rod is pulled out, and a pile body 5 is settled while inserting the pile body 5 in an expansible bag body 6. After that, hardener is injected into the bag body 6 from the ground to fix the pile body 5 to the sand and gravel layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for constructing a prefabricated pile having a bag body for injecting cement milk or concrete into a bag body attached to the tip of the pile to form expanded root-consolidating bulbs. is there.

[0002]

2. Description of the Related Art It is known that a bag is attached to a ready-made pile, and after the pile is sunk, a caking fluid is injected into the bag to expand and expand the bag. In this construction method, a pile with a bag is sunk in the ground that has been expanded and excavated by the pre-boring construction method, and thereafter, the solidified fluid is injected into the bag body to expand and expand the bag body. This construction method is disclosed, for example, in JP-A-62-2.
No. 15719 and Japanese Patent Laid-Open No. 62-63721.

In the conventional pre-boring tip expansion method,
For example, the excavation device as shown in FIGS. 6 and 7 is used. First, in the apparatus shown in FIG. 6, a bit having an enlarged excavating blade is attached to the tip of a rod having a stirring arm. This device has a mechanism in which the enlarged excavating blade is opened in the support layer to perform the enlarged excavation, and further the excavating liquid and the earth and sand injected from the tip of the bit are stirred by the enlarged excavating blade to form the enlarged excavation hole. Further, the apparatus shown in FIG. 7 has a high-pressure jet nozzle at the tip of the rod. This equipment excavates with jet water, and 100 kg /
The structure is such that high-pressure jet water of cm ² or more is jetted laterally to form an enlarged drill hole.

As described above, the conventional method of expanding and excavating is not a method of discharging the excavated earth and sand from the expanding excavation hole, but a method of stirring and mixing the excavating liquid with the excavating liquid to form mud, and forming a slurry. It was In other words, the excavated earth and sand is made into a slurry and floated to move the earth and sand above and below the bag when the bag is inflated. However, in these expansion excavation methods, when the support layer is sand ground or clay ground, it is easy to form a slurry and the bag can be inflated to a predetermined shape, but when the support layer is sand gravel ground, The large gravel cannot be floated and the gravel settles on the bottom of the enlarged drilling hole, which hinders the expansion of the bag and prevents the bag from expanding to a predetermined shape (see FIG. 3). Therefore, in such a case, there was a phenomenon that the bearing capacity of the pile could not be achieved as designed.

Therefore, a method of attaching a screw to the poling rod and discharging the gravel to the ground is generally used. However, when the excavation length becomes long, not all gravel in the excavation hole is carried to the ground even if such a screw rod is used, and most of the gravel is not pulled up to the ground and the screw rod and the hole wall There was a problem that it fell from the gap and remained in the enlarged drill hole.

[0006]

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned drawbacks of the prior art. Even if the support layer is gravel ground, the bag body can surely be inflated to a predetermined shape. Therefore, it is an object of the present invention to provide a method for constructing a pile with a bag that can develop a supporting force as designed.

[0007]

The present invention is directed to a screw on an auger bit and a gravel or cobblestone excavated by an excavator having a pressing plate at the upper end of the screw to pull up to soft ground by the screw, and the pressing plate is used. Gravel and boulders are pressed into the soft formation above the drill hole, and then a bag pile is sunk in the drill hole, and a solidifying fluid is injected into the bag body to expand the bag pile. It is a construction method.

The present invention will be described in detail below with reference to the drawings. The excavator used in this method is as shown in FIG. The excavator used in this method is provided with an auger bit 3 having an enlarged excavating blade 4 at its tip. The auger bit may have any shape as long as it has an enlarged digging blade.The enlarged digging blade is a hydraulic type that mechanically opens and closes, or a type that opens and closes by resistance to the surrounding soil by reverse rotation. It may be one. next,
A rod 10 having a screw 2 is connected directly above the auger bit. The length of the screw 2 needs to be a distance from the gravel ground, which is a supporting layer, to the soft clay ground above. With such a length, the gravel of the supporting layer can be pulled up to the upper soft cohesive ground. The upper part of the screw may be a rod of any shape as long as it can be connected to an auger motor, but the one having a stirring blade as shown in Fig. 1 stirs the excavated soil with muddy water to prevent collapse of the hole wall. It is preferable because it can be prevented.

Further, in the present invention, a pressing plate 1 is attached to the upper end of the screw for the purpose of pressing the raised gravel and cobbles against the clay layer.
The pressing plate has a length of about 10 mm and a height of 10 to 30 cm.
The iron plate is attached so as to contact the outer peripheral surface of the rod and the outer peripheral surface of the screw as shown in FIG. 1 (B). It is preferable that the pressing plate has a smooth curved surface as shown in FIG. 2 because the gravel can be easily pressed smoothly.

The gravel excavated by the auger bit on the support layer which is the gravel ground by using the digging device having such a structure is mounted on the blades of the screw, and rises. When the rising gravel hits the pressing plate, it is pressed against the soft ground on the outer periphery as the rod rotates. The pile used in this method is a pile with a bag, an example of which is shown in FIG. The bag body attached to the ready-made pile is a synthetic fiber such as nylon, polyethylene or vinylon, and the attachment portion of the bag body and the ready-made pile is attached with a band and an adhesive or a combination thereof. Moreover, it is preferable that the diameter of the bag body is slightly larger than the excavation diameter because the bag body is closely attached to the excavation wall surface and the frictional force between the excavation wall surface and the bag body is increased.

The pile is sunk in an enlarged excavation hole excavated by the excavator, and a consolidating fluid such as cement milk is injected from the ground through an injection pipe communicating with the bag body. The bag is inflated by the injection of the solidifying fluid. At this time, most of the gravel is already discharged upward from the enlarged excavation hole and pressed against the soft ground, so that the bag body can be expanded to a desired diameter without being obstructed by the gravel. Therefore, the pile constructed by this method can develop a high bearing capacity as specified. Further, since the gravel pulled up from the support layer is not pressed against the soft ground and is not discharged to the ground, there is also an effect that the amount of excavated soil is reduced.

[0012]

EXAMPLE An experiment was actually conducted using this invention. A conceptual diagram of the auger rod used in the test is shown in FIG. From the results of the boring survey, it was found that the test ground had a gravel layer as a supporting layer at a depth of 30 m or more. The excavation length was set to 31 m because the tip of the pile must be placed in the diameter gravel layer. Also, because there was a clay layer 8-10m above the gravel layer,
The screw length was 10 m. The rod on the upper part was equipped with a stirring blade, and the auger bit was a reverse expansion bit. The screw diameter was 500φ, the auger bit had an original diameter of 500, and the outer diameter when expanded was 800φ. The above-mentioned pressing plate was attached to the upper end of the screw.
As the pressing plate, an iron plate with a plate thickness of 10 mm is 150 x 220 m.
After cutting into a size of m, it is curved as shown in FIG.
It was attached to the upper end of the screw by field welding.

Pre-boring is 31m from the surface first
The normal rotation was excavated at 500φ without expanding, and the rod was rotated for 3 minutes while raising the rod for 3 to 4 m and waiting for the rotation torque to decrease. After that, reverse the rod and open the enlarged excavating blade from the surface to 26.5-31.
Extensive digging up to m, return the rod to normal rotation, slowly pull up the rod about 3 m as shown in Fig. 5 so as not to drop the gravel and boulders on the screw, and rotate the rod again as it is After pressing the gravel against the clay layer, the rod was pulled up and the pile was immediately sunk.

The sunk pile has a pile length of 30 m and a pile diameter of 500φ.
The SC pile, the bag is made of nylon, the bag length is 3 m, and the bag diameter is 860.
φ bag-equipped pile. Reinforcing rods with a diameter of 3 mm are wound around the pile surface inside the bag body in several stages so that the cement milk inside the bag hardens and the adhesion between the pile body and the hardened cement body increases. Has become. Further, this pile is provided with an injection pipe for injecting cement milk into the bag. In this experiment, the injection pipe was installed in the hollow part of the pile. After the pile was sunk, cement milk was injected into the tip bag part by a pump to form a bulb at the tip of the pile. The state is shown in FIG.

When the supporting force of this pile was measured, it was found that the desired supporting force was obtained. When the excavation survey was carried out, it was confirmed that the bag body at the tip swelled to the shape 800φ as excavated by the auger.

[0016]

[Comparative Example 1] This is the same as the example except that the rod screw and the pressing plate used in this comparative example are not provided.
The specifications of the tip bit, excavation length, excavation shape, and pile were also the same. After excavation, the rotation of the auger was stopped, the rod was gently pulled up, the pile was quickly laid down, and the solidified fluid was injected to expand and expand the bag. However, the injection pressure was excessively increased before the injection of a predetermined amount, so the injection was abandoned.

When the bearing capacity of the pile was measured, the bearing capacity was low. After that, the pile was excavated, and as a result, gravel was accumulated in the excavation hole as shown in FIG. It was found that the bag could not be inflated at the prescribed injection pressure.

[0018]

By using the construction method of the present invention, even if the support layer is gravel ground, by pushing the excavated gravel against the soft clay layer in the middle, the pile with bag can be surely expanded to a predetermined diameter. . Therefore, a high supporting force as designed can be expressed. Moreover, since the gravel is not pulled up to the ground, the amount of residual soil treatment is small.

[Brief description of drawings]

FIG. 1 shows an example of an excavating device used in the present invention.

FIG. 2 shows an example of an excavator used in the present invention.

FIG. 3 is a conceptual diagram when construction is performed by the construction method of the present invention.

FIG. 4 is an example of a pile with a bag used in this method.

FIG. 5 is a conceptual diagram of the construction method of the present invention.

FIG. 6 is a conceptual diagram of a conventional method of construction using a reversing expansion drill bit.

FIG. 7 is a conceptual diagram of a conventional method using a high pressure jet.

FIG. 8 is a conceptual diagram when the conventional construction method is used.

[Explanation of symbols]

 1 Pressing Plate 2 Screw Rod 3 Enlarging Head 4 Enlarging Drilling Blade 5 Pile Body 6 Bag Body 7 Enlarging Drilling Hole 8 Gravel 9 Stirring Blade 10 Rod 11 Rebar 12 Cement Milk 13 Wire Rope 14 Injection Pipe 15 Wire Rope Stopper 16 Nozzle 17 Injection tube

Claims (1)

[Claims] 1. A gravel or boulder excavated by an excavator having a screw on an auger bit and a pressing plate at the upper end of the screw is pulled up to a soft ground layer above the excavation hole by the screw, and the gravel is pressed by the pressing plate. A method for constructing a pile with a bag, which comprises pressing a cobblestone or boulder into a soft formation, and then burying the pile with a bag in an excavation hole and injecting a solidifying fluid into the bag to inflate the bag.