JPH0711633A - Construction method of pile with bag, and enlarging excavation device - Google Patents

Abstract

PURPOSE:To display large bearing force according to a design. CONSTITUTION:Bearing ground is expandingly excavated by a preboring method, and after gravel in an excavated hole is removed, an existing pipe loaded with a bag body to the peripheral surface of the front end thereof is settled, and after that, a hardening fluid is injected in the bag body to develop a bulb of consolidation of foundation in the front end of the pile. A bit having expansion excavation blades 4 is mounted to the front end of a rod 1 with a screw, a casing 6 is so mounted that the screw and bit are surrounded thereby, and volume of a hollow section in the casing 6 is at least the same or more than that of an expanded excavation hole 12. Accordingly, even if a bearing layer is a sand gravel ground, the bag body can be surely expanded up to a specific shape.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of constructing a pile with a bag in which cement milk or concrete is injected into a bag attached to the tip of the pile to form a rooted bulb.

[0002]

2. Description of the Related Art Conventionally, a bag is attached to the end of a ready-made pile, and the pile is sunk in the ground that has been enlarged and excavated by the pre-boring method. A method of forming a bulb is known. This construction method is disclosed, for example, in JP-A-62-215719 and JP-A-62-63721.

Expanding excavation by the conventional method is carried out, for example, in FIGS.
It was carried out by a drilling device as shown in. First, in the apparatus of FIG. 5, a bit 2 having an enlarged excavating blade 4 is attached to the tip of a rod 1 having a stirring arm 10. This device has a mechanism in which the enlarged excavation blade is opened in the support layer to perform the enlarged excavation, and the excavation liquid and the earth and sand injected from the tip of the bit are stirred by the enlarged excavation blade to form the enlarged excavation hole 12. Further, the apparatus shown in FIG. 6 has a high pressure jet nozzle 11 at the tip of the rod 1.
This equipment excavates by jet water, and in the support layer 1
The mechanism is such that high-pressure jet water of 00 kg / cm ² or more is laterally jetted to form the enlarged drill hole 12.

[0004]

As described above, the expanding excavation method in the conventional method has been carried out by mixing the excavated earth and sand with the excavation liquid to form mud and make it into a slurry. That is, when the excavated earth and sand is made into a slurry and floated, the earth and sand are moved above and below the bag when the bag is inflated. However, in these expansion excavation methods, when the support layer is sand ground, clay ground, etc., it is easy to make a slurry and the bag can be expanded 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 excavation hole, which hinders the expansion of the bag body and prevents the bag from expanding to a predetermined shape. Therefore, in such a case, there was a phenomenon that the bearing capacity of the pile could not be achieved as designed.

The present invention is intended to solve the above-mentioned problems, and the bag body can surely expand to a predetermined shape even if the support layer is gravel ground, and the support force as designed is exhibited. The present invention provides a construction method and a drilling device that can be used.

[0006]

According to the present invention, the prefabricated boring method is used to expand and excavate the supporting ground, and after removing the gravel in the excavation hole, the prefabricated pile with the bag body attached to the outer peripheral surface of the tip is sunk. After that, a method for constructing a bag-equipped pile, characterized by injecting a solidifying fluid into the bag body to form a root-consolidating bulb at the tip of the pile, and an enlarged excavating blade at the tip of a rod having a screw. In the enlarged excavation device, a bit having a hole is attached, and further, a casing is attached so as to surround the screw and the bit, and the volume of the hollow portion in the casing is at least equal to or larger than the volume of the enlarged drill hole. is there.

A description will be given below with reference to the drawings. FIG. 1 is a conceptual diagram of the excavation process of the present invention. First, as shown in (a), the excavation device excavates the ground straight with a diameter about 10 cm larger than the pile diameter to reach the support layer. Then, as shown in (b), the enlarged excavation blade 4 at the tip of the bit is opened to perform the enlarged excavation for a predetermined length. After that, as shown in (c), the gravel 13 of the enlarged excavation portion is settled on the bottom of the enlarged excavation hole 12 by natural fall, the enlarged excavation blade is opened, and rotated near the bottom of the enlarged excavation hole so that it is moved to the upper portion. As much as possible, all the gravel is taken in the installed casing 6. Finally, as shown in (d), the excavator is pulled out to remove the gravel from the enlarged excavation hole.

After the above steps, the pile with bag is sunk in the excavation hole, and the solidifying fluid is injected into the bag body in the enlarged excavation hole and expanded to form the root-fixing bulb. By removing the gravel from the enlarged excavation hole in this manner, the bag can be surely inflated to a predetermined shape. Next, the excavation device of the present invention will be described with reference to FIGS.
4 shows. In the excavating device of the present invention, a bit 2 is attached to the tip of a rod 1 having a screw 3, and an enlarged excavating blade 4 is attached to the bit. And further,
The casing 6 covers the bit and the screw from immediately above the enlarged excavating blade.

The rod is hollow so that drilling fluid such as water can be injected from the bit at the tip. A screw is attached to the outer circumference of the rod by welding. The screw should be at least the part covered by the casing, not the entire length of the rod. A bit is attached to the tip of the rod, and the bit is attached with an enlarged excavating blade by a pin 5. This enlarged excavating blade has a structure that can be opened and closed by operation from the ground. The expanding digging blade is in a closed state as shown in FIG. 3 when straightly digging, and is in an open state as shown in FIG. 4 when expanding digging in the support layer. As an example, the enlarged excavating blade has a mechanism that opens and closes by a gear 8 as shown in FIG. This gear has a structure in which a rod is made into a double pipe and fixed to the inner pipe 9, and is rotated by an operation from the ground. Further, instead of using gears or the like, a mechanism may be used in which the enlarged excavating blade and the rod are connected by an arm and opened and closed by an operation from the ground. In any case, the structure may be such that the enlarged excavating blade is opened and closed by an operation from the ground.

The casing 6 for taking in the earth and sand is attached to the rod, but is independent of the rod, and the casing does not rotate together with the rotation of the rod. This is because the soil on the screw cannot be carried upward when it is rotated. Therefore, in order to prevent the rotation of the casing during excavation, it is effective to provide a protrusion such as a rib on the outside of the casing so as to bite into the surrounding ground during excavation. The material of the casing is usually a steel pipe. The inner diameter of the casing must be slightly larger than the outer diameter of the screw, and the thickness of the casing must be 9 mm or more in terms of rigidity. Further, the length of the casing needs to be long enough to capture all the gravel in the enlarged excavated portion.

The earth and sand taken into the casing is conveyed upward by a screw, but it is preferable to attach a slip-preventing plate 7 to the bit so that the earth and sand once taken in does not slip off. In this case, it is necessary for the plate to have a structure that opens only in the direction in which the soil is taken in.

[0012]

The present invention will be described in detail below with reference to examples. After the pile with bag was constructed on the gravel ground by the construction method of the present invention, a loading test was conducted. The excavation device having the structure shown in FIG. 2 was used for the construction method of the present invention. That is, a rod having a double pipe structure with an outer diameter of 200 mm is attached with a screw having an outer diameter of 600 mm, and the tip bit is also set to have an outer diameter of 600 mm.
I installed it. The enlarged excavating blade has a structure that opens and closes with a gear. The casing has an outer diameter of 650 mm and a thickness of 9
A steel pipe of mm was used, and the length was set to 5.6 m in consideration that almost all the earth and sand in the expanded excavation part could be taken in.

The pile used was an SC pile having an outer diameter of 500 mm and a length of 15 m, and a nylon bag having an outer diameter of 900 mm and a length of 3 m was attached to the tip. On the other hand, as a comparison, piles of the same use were constructed on the same ground by the conventional method,
A cargo test was conducted in the same manner. The excavator used in the conventional method is shown in FIG. 5, and has an outer diameter of 20 with a stirring arm.
It was assumed that the 0 mm rod and the bit with an outer diameter of 600 mm were installed so that the outer diameter was 860 mm when the outer diameter was enlarged.

As a result of the load test, the piles constructed by the construction method of the present invention had an ultimate bearing capacity of 800 tons, whereas the piles constructed by the conventional construction method had an ultimate bearing capacity of 600 tons.
It was ton. Furthermore, as a result of excavating the piles after the test, the piles constructed by the method of the present invention had root-fixing bulbs formed in a predetermined shape, whereas the piles constructed by the conventional method had a predetermined shape. Only about 70% of the rooting bulb was created.

[0015]

According to the construction method and the excavating device of the present invention,
Even if the support layer is gravel ground, reliable expansion and excavation can be performed, and the bag body can be surely inflated to a predetermined shape. Therefore, a large supporting force as designed can be expressed.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a construction method of the present invention.

FIG. 2 is a cross-sectional view of the enlarged excavation device of the present invention.

FIG. 3 is a view of the enlarged excavating blade of the present invention in a closed state.

FIG. 4 is a view showing a state in which the enlarged excavating blade of the present invention is opened.

FIG. 5 is a conceptual diagram of a conventional method.

FIG. 6 is a conceptual diagram of a conventional method.

[Explanation of symbols]

 1 ・ Rod 2 ・ Bit 3 ・ Screw 4 ・ Expansion excavating blade 5 ・ Pin 6 ・ Casing 7 ・ Slip-preventing plate 8 ・ Gear 9 ・ Inner tube 10 ・ Stirring arm 11 ・ Nozzle 12 ・ Expansion drilling hole 13 ・ Gravel

Claims (2)

[Claims] 1. A support ground is enlarged and excavated by a pre-boring method, and after removing gravel in the excavation hole, a prefabricated pile with a bag is attached to the outer peripheral surface of the tip, and then the solid is fixed in the bag. A method for constructing a pile with a bag, which comprises injecting a binding fluid to form a rooted bulb at the tip of the pile. 2. A rod having a screw is provided with a bit having an enlarged excavating blade attached to the tip thereof, and a casing is attached so as to surround the screw and the bit so that the hollow volume in the casing is at least the enlarged excavation hole. Drilling rig characterized by being equal to or larger than the volume of