KR101962341B1 - Construction method of cast-in-place concrete pile with semi-spherical end - Google Patents

Abstract

The present invention relates to a method to construct a cast-in-place concrete pile with a hemispherical front end surface, which forms the cast-in-place concrete pile with a hemispherical front end surface by depositing concrete into a through-hole with a hemispherical bottom surface in a side to increase a front end support force of the concrete pile so as to reduce a construction cost and period. According to the present invention, the method to manufacture a cast-in-place concrete pile with a hemispherical front end surface comprises: a through-hole formed by drilling the ground by a predetermined depth and having a height equal to a diameter; a rebar net or member inserted into the through-hole; and an in-place concrete deposited into the through-hole to form the hemispherical front end surface. The hemispherical front end surface is formed in a base rock which is bedrock with hardness equal to or greater than that of a soft rock.

Description

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a method of constructing a pile of a cast-in-place concrete having a semi-spherical cross section,

The present invention relates to a method and apparatus for reducing the cost of construction and shortening of air by increasing the bearing capacity of a concrete pile without forming a hole in the lower part of the hole by forming a concrete pile having a hemispherical cross section by pouring concrete into the pore hole having a hemispherical bottom surface. The present invention relates to a method of constructing a pile of a cast-in-place concrete having a hemispherical cross-section as far as possible.

The concrete pile is placed in the perforation hole, and the pile is inserted into the concrete pile. The concrete pile is inserted into the perforation hole. do.

These piles are less noise and vibration, and they can be used for large diameter and long pile construction.

In recent years, construction of on - site concrete piles has been carried out steadily due to increasing complaints about noise and vibration, and demand for large - diameter piles due to superstructure of buildings.

The concrete piles installed in the field secure the bearing capacity by the frictional force and the end bearing force. In order to improve the pile bearing capacity, pile depth is increased to increase the frictional force or to increase the bearing capacity by designing the large diameter pile.

However, in this case, there is a problem that the construction cost and the construction period greatly increase due to the increase of the excavation depth or the pile diameter.

Accordingly, in order to solve the problem of such a conventional on-site concrete pile, Japanese Patent Application No. 10-0990201 discloses a technique of expanding a lower portion of a perforation hole using an air hammer slidably protruding outward, 10-1643659 discloses a technique for expanding only the pile tip to increase the tip end supporting force.

However, since the registered technologies have a horizontally expanded bottom surface, the tip area is limited to only πr ² , which limits the increase of the tip end supporting force.

In order to solve the above-mentioned problems, the present invention provides a method of constructing a pile of a cast-in-place concrete having a hemispherical cross-section capable of increasing the end bearing capacity without increasing the pile bottom area.

According to a preferred embodiment of the present invention, there is provided a drill hole having a hemispherical bottom surface formed by excavating a ground to a predetermined depth and having the same height as a diameter; A reinforcing net or steel frame member inserted into the perforation hole; And a pierced hole formed in the perforation hole to form a hemispherical end surface; The semi-spherical cross-section is for constructing a piling-type concrete pile having a semi-spherical cross-section formed in a bedrock, which is a rocky rock bedrock, wherein (a) the pile is pierced with auger screw bit by inserting the ingot into the ground, Forming a perforation hole; (b) inserting a second hammer bit having a hemispherical tip in the perforation hole, and forming a hemispherical bottom surface by drilling the bedrock under the soil layer to the tip of the pile; (c) inserting a reinforcing net into the perforation hole; And (d) placing a concrete pile inside the perforation hole so as to form a semi-spherical end surface at the tip; Wherein when the rock is deeper up to the depth of drilling, the soil layer is pierced with the auger screw bits in the step (a), the drill is pierced to the upper end of the hemispherical bottom surface with the first hammer bit whose tip is a horizontal surface, And the second hammer bit is replaced with the second hammer bit by lifting the hammer bit to the ground.

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According to another preferred embodiment of the present invention, in the step (b), the hemispherical front end section is operated at a speed of 50% or less of the high-pressure compressor capacity used for the first hammer bit during the second hammer bit operation. The present invention provides a method of constructing a punched concrete pile.

According to another preferred embodiment of the present invention, a guide bit is protruded from a lower end of the second hammer bit, thereby providing a method of constructing a pierced concrete pile having a semi-spherical cross section.

According to the present invention, by placing the concrete in the perforation hole having a hemispherical bottom surface and forming a cast pile having a semi-spherical cross section, the area of the pile of the concrete pile is increased by contacting with the ground, .

Accordingly, it is possible to sufficiently secure the allowable supporting force of the pile by a simple process without a procedure for drilling the lower part of the perforated hole, and it is possible to reduce the construction cost and drastically shorten the construction period, and reduce the environmental pollution by reducing the number of high pressure compressors.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view showing a pile of a cast-in-place concrete having a hemispherical cross-section formed by the present invention; FIG.
FIG. 2 is a view showing a reaction force acting on the tip of a pile due to an upper load according to the shape of the tip of the pile. FIG.
FIG. 3 is a table showing pile tip area and tip bearing capacity according to pile diameter before and after application of the present invention.
FIG. 4 is a view showing an equipment setting state for a method of constructing a field-cast concrete pile having a hemispherical end face according to the present invention. FIG.
5 is a view showing a second hammer bit for forming a hemispherical bottom surface in the perforation hole;
FIGS. 6 to 9 are diagrams showing a stepwise process for a method of constructing a field-cast concrete pile having a hemispherical end face according to the present invention. FIG.
10 shows an embodiment of a first hammer bit;
11 is a view showing a ground drilling process when the rock layer is deep to an excavation depth.
12 is a front view showing a second hammer bit in which a guide bit is formed;
13 is a screen showing the result of numerical analysis modeling according to the present invention.
14 is a view showing a vertical displacement distribution diagram according to the present invention.
15 is a view showing a vertical stress distribution diagram according to the present invention.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings and preferred embodiments.

2 is a view showing a reaction force acting on the tip of a pile due to an upper load according to the shape of the tip of the pile, and FIG. 3 is a cross- Is a table showing the pile tip area and the tip bearing capacity according to the pile diameter before and after application of the present invention.

As shown in FIG. 1, the field-poured concrete pile having a hemispherical cross-section formed according to the present invention is formed by excavating the ground 1 to a predetermined depth and has a hemispherical bottom surface 101 having the same height as the diameter A perforation hole 10; A reinforcing bar 2 or a steel frame member inserted into the perforation hole 10; And a pouring concrete (3) pierced in the perforation hole (10) to form a hemispherical end surface (31); . ≪ / RTI >

The present invention provides a method of constructing a pile of a cast-in-place concrete having a semi-spherical cross section capable of increasing the end bearing capacity by increasing the pile tip area without spreading the lower part of the pore hole formed in the ground.

The perforation hole 10 is formed by excavating the ground 1 to a predetermined depth in order to form an in-situ concrete pile, and has a hemispherical bottom surface 101 convex downward.

Accordingly, the front end face 31 of the cast concrete poured in which the spotted concrete 3 is cast in the perforation hole 10 can be formed in a hemispherical shape.

Therefore, the tip of the concrete pile is in direct contact with the ground (1) and the area supported by the acupressure is greatly increased compared to the conventional planar pile tip.

Specifically, when the radius of the semi-spherical distal end surface of the concrete pile 31 (the radius of the hole 10) of the r, surface area of the semi-spherical distal end surface 31 is a 4πr ^2/2. Therefore, the tip area of a pile of the same pore size with a pile tip area of πr ² is doubled.

Therefore, the pile yield can be greatly reduced in the case of unit piles, and the design load can be satisfied even if the single pile is drilled with a diameter smaller than the existing pile diameter. Therefore, it is possible to reduce the construction cost and the construction period, and the number of high-pressure compressors can be reduced, thereby reducing environmental pollution.

A reinforcing net (2) or a steel frame member is inserted into the perforation hole (10).

If the site-cast concrete pile is a permanent pile, the reinforcing net 2 or the reinforcing net 2 and the steel frame member (not shown) may be inserted into the perforation hole 10.

If the pile is used as a pile as in the case of a pile-in-place concrete pile method, the steel member can be inserted into the pile hole 10.

The present invention will be described with reference to FIG.

2 (a), when the pile tip is hemispherically shaped as compared with the conventional pile placed on the ground in which the pile-line cross-section is in a horizontal plane, the reaction force acting on the tip of the pile due to the upper load .

The pile bearing capacity of the pile was estimated to be 625kgf / ㎠ = 625tf / ㎡ according to the basic design criterion (2009) of the pile, based on the rock strength of 50MPa. Is shown in FIG.

In FIG. 3, P and EP are respectively referred to as existing on-site concrete piles and on-site concrete piles constructed according to the present invention.

3, in the conventional percussion rotary drill (PRD) method, piles having diameters of Φ1,000 mm, Φ1,200 mm, and Φ1,500 mm have diameters of Φ800 mm, Φ1,000 mm, Φ1, 200 mm, which is very economical.

The height of the hemispherical bottom surface 101 and hemispherical end surface 31 may be the same as the radius of the perforation hole 10.

If the heights of the hemispherical bottom surface 101 and the hemispherical front end surface 31 are smaller than the radius of the perforation hole 10, the tip end bearing capacity decreases and the tip end bearing force decreases.

If the heights of the hemispherical bottom surface 101 and the hemispherical top surface 31 are larger than the radius of the perforation hole 10, the pile tip area is increased. However, since the pile is supported by frictional force, The supporting force can be rather reduced.

Therefore, it is preferable to form the hemispherical bottom surface 10 of the perforation hole 10 and the front end surface 31 of the cast concrete pile in the hemispherical shape having the same diameter in the width and height direction so as to maximize the tip end supporting force.

The hemispherical leading end surface 31 can be formed in the bedrock 12, which is a rocky rock bedrock.

In order to maintain the shape of the hemispherical bottom surface 101 of the perforation hole 10 formed by excavating the ground until the concrete is poured, the hemispherical bottom surface 101 should be formed in a hard rock bed of more than soft stone.

Accordingly, the hemispherical end surface 31 can be formed in the ground 1 which is soft rock, plain rock or light rock.

FIG. 4 is a view showing a state of equipment setting for a method of constructing a pile of a cast-in-place concrete having a hemispherical end face according to the present invention, and FIG. 5 is a view showing a second hammer bit for forming a hemispherical bottom face in the perforation hole. 6 to 9 are diagrams showing a stepwise process for a method of constructing a pile of a cast-in-place concrete having a hemispherical end face according to the present invention.

The present invention relates to a method of constructing the above-mentioned on-site concrete pile with reference to FIG. 1 to FIG. 3.

In the present invention, the hemispherical bottom surface 101 of the perforation hole 10 should be formed in the hard ground 1 over the soft rock. Therefore, it is possible to construct by Percussion Rotary Drill (PRD) method, which can ensure the perforation speed, maintains the accurate verticality, and is excellent in precision construction and can reliably construct the bedrock (12) regardless of the ground conditions.

In the method of constructing a pierced concrete pavement having a hemispherical cross section according to the present invention, the following steps are carried out: (a) The piercing hole 42 is drilled into the ground 1, 10) (Fig. 6).

4, a pile driver 4 is installed at a position where the perforation hole 10 is formed and a screw rod 41 to which an ingress 42 is mounted for protecting the pile of the soil layer 11, The perforation hole 10 is formed by inserting the ingather 42 while piercing the soil layer 11 with the auger gusset bit 11 having the auger bit 43 at the lower end thereof.

(B) The hemispherical bottom surface 101 is formed by inserting the second hammer bit 45 having a hemispherical tip in the perforation hole 10 and then piercing the bedrock 12 under the soil layer 11 to the tip of the pile ( 7).

In the step (b), the casing rod is left on the ground 1 and the screw rod 41 is pulled up to the ground to remove the auger bit 43, and the second hammer bit 45 having a hemispherical tip is mounted.

The bed hammer 12 is pierced with the second hammer bit 45 to form a hemispherical bottom surface 101 at the lower end of the perforation hole 10.

5 (a) shows a front view of the second hammer bit 45 for forming the hemispherical bottom surface 101 at the lower end of the perforation hole 10.

As shown in the bottom view of FIG. 5 (b), the second hammer bit 45 can be used by mounting a hemispherical perforation bit 451 at the tip of the T4 hammer bit.

The T4 hammer bit is easy to perforate even when the ground conditions are hard as well as the soil layer 11, such as a thick gravel layer, a soft rock layer, an intermediate layer layer and an amber layer.

In the step (b), the ground 1 is excavated by rotating the T4 hammer bit, which is an air hammer mounted on the pile driver 4, while being struck by the compressed air, and the excavated soil is discharged with compressed air.

After completion of the punching, the slurry is removed from the perforation hole 10 by using a mechanical pump, and the residual slime is removed by an air surging operation while injecting clean water.

After the step (b), a KODEN test is performed to confirm the vertical and perforation diameters of the perforation hole 10, and it is possible to confirm whether or not the hemispherical shape of the bottom end surface is properly maintained.

Next, (c) the reinforcing net 2 is inserted into the perforation hole 10 (FIG. 8).

The reinforcing net 2 can be installed in the perforation hole 10 while being assembled in advance on the ground and maintaining the vertical degree.

Finally, (d) concrete 3 is poured into the perforation hole 10 to construct a pierced concrete pile so that a hemispherical end face 31 is formed at the tip (FIG. 9).

In the step (d), the concrete 3 may be installed in the perforation hole 10 by using a trestle pipe so that material separation does not occur.

The poured concrete is cured to form a hemispherical end surface 31 at the tip of the pile.

FIG. 10 is a view showing an embodiment of the first hammer bit, and FIG. 11 is a diagram showing a ground drilling process when the rock layer is deep to the excavation depth.

The soil layer 11 is pierced with the auger bit 43 in the step (a), and then the first hammer bit 44 having a horizontal front end is pierced with the upper part of the hemispherical bottom surface 101 The first hammer bit 44 can be lifted to the ground and replaced with the second hammer bit 45. [

In the case where the rock layer is not as deep as the excavation depth, even if the second hammer bit 45 having a hemispherical tip is drilled, there is no problem in securing the vertical degree. However, when the rock layer is deep to the excavation depth, Is to penetrate the weathered rock 13 or to be formed to a deep depth in the bedrock 12, it is difficult to ensure verticalness when drilling a rock bed with only the second hammer bit 45 having a hemispherical tip.

Therefore, in this case, the soil layer 11 is punctured by the auger bit 43 (Fig. 11 (a)), and then the first hammer bit 44, which is a general hammer bit, The weathered rock 13 is pierced to the upper part of the bottom surface 101 (FIG. 11 (b)).

10 (a) and 10 (b) show a front view of the first hammer bit 44 and a bottom view of the plane puncturing bit 441 of the first hammer bit 44, respectively.

The first hammer bit 44 is configurable as a regular T4 hammer bit with a planar perforation bit 441 at its tip.

Then, the second hammer bit 45, which is a hemispherical hammer bit, is replaced in the hemispherical bottom surface 101, and then the hemispherical tip is punctured to form a hemispherical bottom surface 101 (FIG. 11C).

The first hammer bit 44 and the second hammer bit 45 can be coupled to the screw rod 41 by pin coupling, thereby facilitating equipment replacement.

Further, since the drilling operation can be carried out only by replacing the hammer bits 44 and 45, the work is simple and the workability is excellent.

In operation (b), the second hammer bit (45) may be operated at 50% or less of the high-pressure compressor capacity used for the first hammer bit (44) to perform the drilling.

When forming the hemispherical bottom surface 101, the ground should be gradually pierced in a manner of keeping the hemispherical shape well maintained. Accordingly, the second hammer bit 45 allows only about half of the high-pressure compressors to operate when the first hammer bit 44 is operated.

That is, the high pressure compressor is operated 100% to the upper part of the hemispherical bottom surface 101 using the first hammer bit 44, and the hemispherical bottom part 101 using the second hammer bit 45 is operated to the high pressure compressor by 50% Can be reduced and operated.

For example, in the case of a 640 hammer, when six boring high-pressure compressors are punched with a general hammer bit T4, which is the first hammer bit 44, a drilling operation is performed. The hemispherical T4 hammer bit, which is the second hammer bit 45, is operated by only three high-pressure compressors.

12 is a front view showing a second hammer bit in which a guide bit is formed;

As shown in FIG. 12, a guide bit 452 may protrude from the lower end of the second hammer bit 45.

If the ground 1 is not uniform and one side 1 is harder, if the tip of the hammer bit is hemispherical like the second hammer bit 45, it may be difficult to maintain the perpendicularity.

Therefore, the guide bit 452 having a diameter smaller than that of the hemispherical perforation bit 451 may be protruded below the hemispherical perforation bit 451 of the second hammer bit 45 to maintain the verticality by maintaining the center during the excavation have.

FIG. 13 is a view showing a result of numerical analysis modeling according to the present invention, FIG. 14 is a view showing a vertical displacement distribution diagram according to the present invention, and FIG. 15 is a screen showing a vertical stress distribution diagram according to the present invention.

Fig. 13 shows a result of numerical analysis modeling performed to examine the structural stability of a cast pile installed in the present invention.

The numerical modeling conditions are as follows.

- Near ground: Soft stone

- Soft rock uniaxial compressive strength: 50MPa

- Allowable end bearing capacity per unit area (q _a ): 625 tf / ㎡

- Permissible friction force per unit area (f _s ): 49.4 tf / ㎡

- Soft stone penetration length: 6.0m

- Permissible bearing capacity of the nave of the pile

Φ = 1,000 mm

Supporting capacity of tip (tip area): 923tf (1.477㎡)

Friction (Friction force per 1m): 904tf (150.7tf)

Total permissible bearing capacity: 1,827tf (load)

As a result of the numerical analysis, the vertical settlement amount is 19.7 mm, which is within 25 mm of the settlement allowance standard, and it is understood that the stability is secured.

15 shows that the hemispherical tip of the pile contributes to the load support (the normal stress at the pile tip is 553.0 tf / m2).

1: ground 10: perforation hole
101: hemispherical bottom surface 11: soil layer
12: bedrock 2: reinforcing net
3: (cast in place) Concrete 31: hemispherical cross section
4: file driver 41: screw rod
42: Inching 43: Auger screw bit
44: 1st hammer bit 441: Planar perforated bit
45: second hammer bit 451: hemispherical perforation bit
452: Guide bit

Claims (7)

A perforation hole 10 formed by excavating the ground 1 to a predetermined depth and having a hemispherical bottom surface 101 having the same height as the diameter; A reinforcing bar 2 or a steel frame member inserted into the perforation hole 10; And a pouring concrete (3) pierced in the perforation hole (10) to form a hemispherical end surface (31); And the hemispherical leading end face 31 is for constructing a cast-in-place concrete pile having a semi-spherical cross-section formed in the bedrock 12 as a rocky rock-
(a) forming a perforation hole (10) in the soil layer (11) by drilling with an auger bit (43) while inserting the ingress (42) into the ground (1);
(b) inserting a second hammer bit (45) having a hemispherical tip in the perforation hole (10) and then drilling the bedrock (12) under the soil layer (11) to the tip of the pile to form a hemispherical bottom surface (101);
(c) inserting the reinforcing net (2) into the perforation hole (10); And
(d) constructing a concrete pile (3) in the interior of the perforation hole (10) so as to form a hemispherical end face (31) at the tip; , ≪ / RTI >
In the case where the rock is deeper to the excavation depth, the soil layer 11 is punctured with the auger bit 43 in the step (a), and then the first hammer bit 44 whose tip is in a horizontal plane, Wherein the first hammer bit (44) is lifted to the ground and replaced with the second hammer bit (45). The method of claim 1, wherein the first hammer bit (44) is replaced with the second hammer bit (45).
The method of claim 1,
Wherein the first hammer bit (44) is operated at a rate of 50% or less of the high-pressure compressor capacity used in the first hammer bit (44) during the operation of the second hammer bit (45) Construction method of concrete pile.
The method of claim 1,
And a guide bit (452) protruding from the lower end of the second hammer bit (45). delete delete delete delete

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