JP4051677B2 - Off-the-shelf pile head - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a ready-made pile embedding excavation head that is used when a steel or concrete cylindrical or column-shaped ready-made pile is installed in the ground.
[0002]
[Prior art]
Conventionally, the ready-made pile embedding method includes forming a pre-made pile insertion hole in the ground by excavating the ground using a screw auger with a drilling bit fixed at the tip, and then into the ready-made pile insertion hole. There is a so-called pre-boring method for inserting ready-made piles.
[0003]
As the excavation head used in this conventional pre-boring method, for example, one having a structure as shown in FIGS. 4 and 5 is used (for example, Patent Document 1). This excavation head 3 fixes two spiral blades 12 spirally arranged around a hollow central axis 10 in which a liquid agent injection path 11 is formed at the center, and is fixed in a symmetrical arrangement with a pitch shifted by 180 degrees. A plurality of excavation bits 16 project from the lower end edge of each spiral blade 12 and the lower end of the central shaft 10.
[0004]
Further, a part of the spiral blade 12 is notched to form an enlarged bit support part 13, and the enlarged bit 15 is pivotally supported by the enlarged bit support part 13 with a longitudinal pivot shaft 14. The pivot shaft 14 is vertically oriented parallel to the central axis 10, and the enlargement bit 15 rotates on a plane orthogonal to the central axis 10, and is always in the spiral direction of the spiral blade 12. The angle is inclined.
[0005]
When forming a pre-boring-type ready-made pile embedding hole, as shown in FIG. 6 (a), the excavation head 3 is fixed to a support shaft 4 made of, for example, a screw auger and pushed into the ground while being rotated forward, The ground is excavated by the excavating bit 16 and excavated to a predetermined depth while the excavated soil is discharged upward by the spiral blade 12.
[0006]
After drilling to a predetermined depth, as shown in FIG. 6 (b), the excavation head 3 is reversed, the surrounding ground is cut by the expansion bit 4, and a solidified material such as cement milk is mixed and injected therein, so-called soil cement. Create an enlarged bulb 2 by Thereafter, as shown in FIG. 6 (c), the excavation head 3 is rotated forward to accommodate the enlarged bit 4, the excavation head is pulled out, and the ready-made pile 1 before solidifying the enlarged bulb 2 as shown in FIG. 6 (d). To insert.
[0007]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-350473
[Problems to be solved by the invention]
In general, embedding a pile using a drilling head requires that a ready-made pile is embedded at a predetermined depth at a predetermined angle and that excavation efficiency is high. For this reason, the conventional off-the-shelf pile embedding drill head is provided with a plurality of excavation bits on the left and right sides of the central axis, and the positions thereof are between the excavation bits on both sides from the center of rotation. By making the distances different from each other and changing the excavation position of each excavation bit, efficient excavation is performed.
[0009]
However, in recent years, it has been demanded that the depth of embedded piles is long, and as the depth increases, the direction of excavation tends to be distorted, and in contact with adjacent piles and obstacles in the deep part. In other words, there is a problem that it may not be possible to embed up to a predetermined depth.
[0010]
In view of such a conventional problem, the present invention has been made for the purpose of providing a ready-made pile embedding excavation head that can reduce the deviation of the excavation direction during excavation.
[0011]
[Means for Solving the Problems]
In order to solve the conventional problems as described above and achieve the intended purpose, the invention according to claim 1 is characterized in that a spiral spiral wing is provided around the central axis, and a drilling bit is provided at the lower end. A prefabricated pile embedding excavation head that is detachably fixed to the lower end of the rotary spindle, and the spiral blades are provided around the central shaft with a pitch shifted by 180 degrees, and the lower edges of the spiral blades Are arranged symmetrically with respect to the rotational axis of the central axis, and a plurality of excavation bits project from the lower edges of the spiral blades and the lower end surface of the central axis, Is the distance from the central axis except for the two most excavating bits, the excavation bit on one side and the excavation bit on the other side of the rotation axis of the central axis. Are placed in staggered positions, One both sides that the rotation axis as a boundary, sum of the product of the distance to each drilling bit center from the rotation axis and the width of each drill bit is substantially equal on both sides that the boundary of the central axis It is in having constituted so that.
[0012]
By configuring in this way, the sum of the torques when excavating bits on both sides centering on the rotation axis becomes equal, and straightness when excavating while raising the excavated soil with a screw auger by rotating forward Will be better.
[0013]
In addition, the right and left excavation bits excavate at different positions, and excavation efficiency is improved.
[0014]
The feature of the invention according to claim 2 is that, in addition to the configuration of claim 1 , each spiral blade protrudes from the outer periphery of the spiral blade at the periphery of the spiral blade, and the proximal end side of the spiral blade is opposite to the spiral blade. The present invention has an enlarged bit supported rotatably on an inclined surface along the surface.
[0015]
By configuring in this way, the soil removal resistance when excavating using the present excavation head is reduced, and straightness is maintained even when the expansion bit is provided.
[0016]
According to a third aspect of the invention, in addition to the configuration of the second aspect , the enlarged bit is provided in a symmetrical arrangement on both upper and lower surfaces of the spiral blade. By comprising in this way, the cross-sectional area of an expansion bit can be enlarged in the state where earth discharge resistance is less, and the ground disturbance effect by an expansion bit becomes large.
[0017]
A feature of the invention according to claim 4 is that , in addition to the structure of claim 2 or 3 above, a stopper with which the back surface abuts when the enlarged bit stands is provided on the forward rotation front side of the enlarged bit mounting position. The stopper has a height substantially the same as the thickness of the enlarged bit and a length in the radial direction of the head rotation that is substantially the same as the width of the enlarged bit. Is an inclined surface that reaches the surface of the spiral blade.
By configuring in this way, when the earth is removed by the spiral blade during forward rotation, the expansion bit is positioned at the back of the inclined surface, and the earth removal resistance can be reduced.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of the present invention will be described with reference to FIGS.
[0019]
FIG. 1 shows an outline of an excavation head according to the present invention, and reference numeral 20 in the drawing denotes a central axis of the excavation head A. The central shaft 20 has a hollow cylindrical shape having a liquid agent injection path 21 at the center, as in the conventional example described above, and is provided with a male connection portion 23 for connection to the rotary support shaft 22 at the upper end.
[0020]
Around the central axis, two spiral blades 24 formed by spirally forming a strip-shaped steel plate are integrally fixed. The two spiral blades 24 are installed on the target with the spiral pitch shifted by 180 degrees, the lower ends protrude downward from the lower end of the central shaft 20, and the lower end edges 25 are on a straight line passing through the rotation axis. And symmetrically arranged around the rotation axis.
[0021]
Excavation bits 26, 26,... Project from the lower edges of the spiral blades 24 in the respective spiral extension directions. A liquid agent discharge port 27 is opened at the lower end of the central shaft 20, and a pair of central portion excavation bits 28 project from both sides of the discharge port 27. Each central excavation bit 28 is directed in the same direction as the excavation bit 26 at the lower end of the spiral blade 24 on the side close to each spiral blade 24.
[0022]
Each of the excavating bits 26 and 28 has a rotation axis, that is, an excavation bit on one side and an excavation bit on the other side on both sides of the central axis 20 as a boundary. However, except for the two outermost drill bits, the distance from the rotation axis to the center in the bit width direction is staggered, and the width of each drill bit and its rotation axis The sum of the product with the distance is set to be approximately equal on both sides of the central axis.
[0023]
That is, as shown in FIG. 3, the widths of the excavation bits 26 and 28 on the left side of the central shaft 20 are B1 to B4, the distances from the rotation axis at the center of each bit are L1 to L4, and the excavation bit 26 on the right side. When the width of 28 is B5 to B8, and the distance from the rotation center of each bit center is L5 to L8,
L1 ・ B1 + L2 ・ B2 + L3 ・ B3 + L4 ・ B4
= L5 ・ B5 + L6 ・ B6 + L7 ・ B7 + L8 ・ B8
The width and the protruding position of each excavation bit are set so that the torque during excavation is equal on the left and right.
[0024]
Enlargement bits 31 are provided on the outer peripheral edge portions of the spiral blades 24 on the lower side of the treetop from the mid-height of the excavation head A. As shown in FIG. 2, each of the enlarged bits 31 is raised in the rotational radial direction of the spiral blade 24 from the position where it is directed in the circumferential direction of the spiral blade 24 and falls inward from the peripheral edge thereof, and the tip thereof is spiral blade. It is attached so that it can rotate between the position which protruded from the outer periphery of 24.
[0025]
Each of the enlarged bits 31 is used in the same orientation on both the upper and lower surfaces in the arrangement that sandwiches each of the spiral blades 24, and the base end portion 32 is formed in a substantially semicircular shape, and the semicircular circular center portion is formed at the center of the semicircle. A pivot hole 33 is opened.
[0026]
Enlarged wing support fittings 34 are fixed to the enlarged bit attachment positions of the spiral wings 24, respectively. The metal fitting 34 is fixed so as to fill a space in which a part of the spiral blade 24 is cut out, and a flat plate portion 34 a whose upper and lower surfaces are substantially the same as the upper and lower surfaces of the spiral blade 24, and an edge of the flat plate portion 34. The flat plate portion 34a is fixed at substantially the same inclination angle as the spiral inclination angle of the spiral blade 24.
[0027]
The stopper portion 34b is used when the excavation head A is rotated forward, that is, when the excavation head A is rotated so that the excavated sediment is conveyed upward by the spiral blade 24 (in this specification, the rotation is the normal rotation in this direction). , The rotation in the opposite direction is the reverse rotation), and has a dimension substantially the same as the width a of the enlarged bit 31 and the protruding height is substantially the same as the thickness b of the enlarged bit 31. The same dimensions are formed. The front side in the forward rotation direction of the stopper portion 34b is a gently inclined surface 34c that reaches the upper surface or the lower surface of the spiral blade 24.
[0028]
The stopper portion 34b is configured so that when the enlarged bit 31 rises in the direction of the turning radius of the excavating head A on the rising surface on the flat plate portion 34a side, the back surface thereof comes into contact with the rising surface to maintain the rising state. When the excavation head A is rotated forward, the expansion bit 31 is tilted to the circumferential side of the spiral blade by the resistance of the surrounding ground. When the excavation head A is rotated in the reverse direction, the rotation radius is increased by the resistance of the surrounding earth and sand. The rear surface is brought into contact with the stopper portion 34b to prevent the rotation and maintain the rising state.
[0029]
The excavation head A configured as described above is used in place of the excavation head used in the above-described conventional pre-boring method, and the ground is excavated by the excavation bits 26 and 28 by rotating the excavation head in a normal direction. The pile insertion hole is formed while being earthed by 24. At the time of excavation, as shown by the solid line in FIG. 2, the enlarged bit 31 is tilted to the moving rear side of the stopper portion 34 b and is housed in a position along the upper and lower surfaces of the spiral blade 24. And after excavating to a predetermined depth, in order to form the expansion bulb | ball in the conventional construction method mentioned above, it pulls up reversely rotating. As a result, the enlarged bit 31 rises as indicated by the provisional line in FIG. 2 and protrudes from the outer periphery of the spiral blade 24 to disturb the periphery of the leading hole. At the same time, a bulb is formed by injecting a solidifying agent such as cement milk.
[0030]
【The invention's effect】
As described above, in the ready-made pile embedding excavation head according to the present invention, the sum of the products of the width of each excavation bit and the distance from the rotation axis is substantially equal on both sides of the rotation axis. With this configuration, the sum of the torques during excavation of the excavation bits on both sides centering on the rotation axis becomes equal, and the straightness when excavating while raising the excavated soil with a screw auger is increased Get better.
[Brief description of the drawings]
FIG. 1 is a side view showing an example of an excavation head according to the present invention.
FIG. 2 is a bottom view of the excavation head shown in FIG.
FIG. 3 is an enlarged bottom view showing a drill bit part of the drill head shown in FIG. 1;
FIG. 4 is a side view showing a conventional drilling head with an enlarged bit.
FIG. 5 is a cross-sectional view taken along line AA in FIG.
FIG. 6 is a cross-sectional view schematically showing the steps of a conventional pre-boring method.
[Explanation of symbols]
A Drilling head 20 Center shaft 21 Liquid agent injection path 22 Rotating support shaft 23 Male connecting portion 24 Spiral blade 25 Lower end edge 26 Drilling bit 27 Liquid agent discharge port 28 Center portion drilling bit 31 Expansion bit 32 Base end portion 33 Pivoting hole 34 Expanded wing support bracket 34a Flat plate portion 34b Stopper portion 34c Inclined surface

Claims (4)

In a ready-made pile embedding excavation head that is provided with a spiral spiral wing around the central axis, has a drilling bit at the lower end, and is detachably fixed to the lower end of the rotary support shaft,
The spiral blade is provided with two pieces around the central axis with a pitch shifted by 180 degrees, and the lower edges of the spiral blades are arranged symmetrically with respect to the rotational axis of the central shaft,
A plurality of excavation bits projecting from the lower edge of the spiral wings and the lower end surface of the central shaft;
The excavation bit includes the excavation bit on one side of the rotation axis of the central axis and the excavation bit on the other side excluding both excavation bits located on the outermost sides. The sum of the product of the width of each excavation bit on both sides of the rotation axis and the distance from the rotation axis to the center of each excavation bit installed at positions where the distances from the center are staggered A prefabricated pile embedding excavation head characterized by being configured to be substantially equal on both sides of the central axis.   Each spiral blade is provided with an enlarged bit that protrudes from the outer periphery of the spiral blade at the periphery of the spiral blade, and the base end of the spiral blade is rotatably supported on an inclined surface along the surface of the spiral blade. The ready-made pile embedding excavation head according to claim 1.   The ready-made pile embedding excavation head with an expansion bit according to claim 2, wherein the expansion bit is provided in a symmetrical arrangement on both upper and lower surfaces of the spiral blade.   A stopper is provided on the forward rotation front side of the enlargement bit mounting position so that the back surface abuts when the enlargement bit stands, and the stopper is substantially the same height as the enlargement bit, and the length in the head rotation radius direction is the enlargement 4. The ready-made pile according to claim 2, wherein the pile is formed to have substantially the same length as the width of the bit, and an inclined surface that reaches the surface of the spiral blade on the front side of the stopper when the head rotates forward. Drilling head for embedding.

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