JPH1122355A - Casing head for excavation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make excavation smooth and efficient, by providing projections for keeping a gap on the outer periphery of a cylindrical body equipped with excavating bits to reduce the frictional resistance of the earth pressure. SOLUTION: A casing head 11 is formed of a casing no and a cylindrical body with the same diameter with the casing. Excavating bits 13 are provided at the front end of the body, the gap between the casing 10 and the wall 16a of a hole 16 is kept at the outer periphery thereof, and a plurality of projections 14 are provided to reduce the frictional resistance of the earth pressure. When ground is excavated by the bits 13 while keeping the gap, as the wall 16a of the hole 16 is pressed to the outside, the soil of the wall face is compacted and the wall face is stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a casing head for excavation used for excavating a pile hole or the like with a casing in civil engineering work or building construction work.

[0002]

2. Description of the Related Art Conventionally, in general, when a pile hole or the like is excavated by a casing in civil engineering work, building construction work, or the like, as shown in FIG. Is attached to the lower end of the casing 3, the casing 3 is supported by the press-fitting device 4, set vertically, and the inside of the casing 3 is excavated and discharged by a hammer grab 5 or a screw. The casing 3 is pressed into the ground by excavating with the bit 2 at the lower end of the casing head 1 by applying a rotating force and a pressing force to the casing 3.

At this time, the bit 2 projects slightly (about 1 cm) outside the outer periphery of the casing head 1 so that a pile hole slightly larger than the diameter of the casing 3 can be excavated. It is configured to reduce the frictional resistance due to the earth pressure acting on the outer periphery of the casing 3 during excavation. However, as the excavation proceeds, the earth pressure acting on the outer periphery of the casing 3 gradually increases. Tightening increased frictional resistance and eventually made drilling impossible.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a casing head for excavation which can reduce the frictional resistance acting on the casing and perform excavation reliably and smoothly.

[0005]

In order to solve the above-mentioned problems, according to the present invention, a gap between a casing and a hole wall is secured on the outer periphery of a cylindrical body having a drill bit at the tip. Is provided with a projection for the housing.

According to the casing head having the above-described structure, the outer peripheral projections press the hole wall during the excavation rotation, and the soil on the wall is compacted and stabilized, so that the earth pressure acting on the casing becomes very small. Friction resistance is also reduced, and excavation can be performed reliably and smoothly.

[0007] In the present invention, it is desirable that the projection is spirally disposed on the outer periphery of the casing head. According to a preferred aspect of the present invention, the protrusion is
It has an outer surface that is inclined so that the rear side in the excavation rotation direction becomes gradually higher toward the circumferential direction of the body. According to a specific configuration aspect of the present invention, the protrusion is
It is formed to have a substantially crescent cross section.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, reference numeral 10 denotes a cylindrical casing for excavating a casing, 11 denotes a casing head for excavation attached to a lower end of the casing 10, and 12 denotes a casing which is rotated and pressed by the casing 10. This is a press-fitting device called a full-circle rotating machine for applying force. The press-fitting device 12 uses the hydraulic pressure to
0 is held from the surroundings, and a rotating force and a pressing force are applied to the casing 10 in that state, and a known one can be used.

As can be seen from FIGS. 2 and 3, the casing head 11 has a cylindrical body 10a having the same diameter as the casing 10, and a drill bit 13 is provided at the tip of the body 10a. A plurality of projections 14 are provided on the outer periphery of the body 10a to secure a gap between the casing 10 and the hole wall 16a of the pile hole 16 to reduce frictional resistance due to earth pressure.

The protrusion 14 presses the hole wall 16a of the pile hole 16 excavated by the bit 13 to compress the soil on the wall surface and stabilize the condition of the wall surface, thereby forming the casing 10 and the hole. The gap for reducing frictional resistance is secured between the wall 10a and the wall 16a. The shape is not particularly limited as long as it has such a function. Outer surface 1 that is smoothly inclined so that the rear side in the rotation direction becomes gradually higher.
4a. Projection 1 of the illustrated embodiment
Reference numeral 4 denotes a crescent having an outer surface 14a having an arc shape or a cross-sectional shape similar thereto, and a plurality of projections 14 are spirally attached to the outer periphery of the body 10a. Therefore, the outer surface 14 of each of the protrusions 14
The radius of curvature of a is smaller than the radius of curvature of the cylindrical surface of the body 10a.

The height of the projection 14 (the body 10a)
Is preferably equal to or slightly larger than the length h of the bit 13 projecting outward from the outer peripheral surface of the body 10a. Particularly, when excavating soft ground, It is better to make it a little higher.

The casing excavation using the casing head 11 having the above-described structure is performed in the same manner as the conventional one shown in FIG. At this time, as the casing head 11 excavates and rotates, the projections 14 on the outer periphery press the hole wall 16a outward to consolidate the soil on the wall surface and stabilize the state of the wall surface. 16a and a sufficient gap will be secured.
The earth pressure acting on the casing 10 becomes very small and the frictional resistance is reduced, so that the excavation can be performed reliably and smoothly. If the height of the projection 14 is higher than the bit 13,
Since the diameter of the hole wall 16a is slightly enlarged by the projection 14, excavation can be performed more smoothly. The above casing 10
Are connected in sequence according to the excavation depth.

In the above embodiment, the projection 14 is spirally mounted on the outer periphery of the casing head 11, but the mounting position does not necessarily have to be spiral, but may be circumferential. The circumference may be single or multiple. Alternatively, they can be mounted in other regular or irregular arrangements. The length of the casing head 11 is naturally determined to be optimal according to the number of protrusions, their arrangement, and the like.

[0014]

As described above, according to the present invention, by providing a simple means of providing a projection on the outer periphery of the casing head, the frictional resistance due to the earth pressure acting on the casing during excavation is reduced, and the excavation is performed. It can be performed reliably and smoothly.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part in a use state showing an embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is a sectional view taken along line AA of FIG. 2;

FIG. 4 is a sectional view showing a conventional excavation method.

[Description of sign]

 Reference Signs List 10 casing 10a body 11 casing head 13 bit 14 protrusion 14a outer surface 16a hole wall

Claims (4)

[Claims] 1. A cylindrical body having an excavating bit at a tip thereof, and a clearance between a casing and a hole wall provided on an outer periphery of the body to reduce frictional resistance due to earth pressure. An excavating casing head having a projection. 2. The casing head according to claim 1, wherein a plurality of projections are spirally arranged. 3. The casing head according to claim 1, wherein the projection has an outer surface inclined such that a rear side in a digging rotation direction becomes gradually higher in a circumferential direction of the body. thing. 4. The casing according to claim 3, wherein said projection has a substantially crescent-shaped cross section.