JP4232743B2 - Rotating penetrating pile and its construction method - Google Patents

Description

  The present invention relates to a rotary penetrating pile with wings that can rotate and penetrate into the ground, and a construction method thereof.

  Conventionally, it is used in a rotating penetrating steel pipe pile construction method in which a steel pipe pile provided with one or a plurality of rotor blades at the tip of the steel pipe pile is rotated so as not to generate excavation residual soil during construction or to a minimum. Various steel pipe piles with rotor blades have been developed. As for the tip structure, there are a structure in which one or a plurality of spiral blades are attached to the tip of the pile, and a structure in which a plurality of flat plate blades are attached. Each has a tip open type and a tip closed type.

  For example, Patent Document 1 describes a structure in which a wing made of two or three fan-shaped flat plates is attached by cutting out the tip of a pile spirally.

  In Patent Document 2, a flat steel plate obtained by dividing a donut-shaped steel plate having an outer diameter of 1.5 to 2.5 times the outer diameter of the steel pipe is attached to the upper side of the steel pipe pile, and the tip is opened. Is described.

  Patent Document 3 describes a rotary penetrating pile on the outer peripheral surface of the tip of a hollow pile wound with a curved spiral blade.

In Patent Document 4, the tip of a steel pipe is cut out in a spiral shape, and the outer diameter is 1.5 to 3 times the outer diameter of the steel pipe pile, and the inner diameter is 0.4 to 0.9 times the inner diameter of the steel pipe pile. The one with a spiral wing attached is described.
Japanese Patent Laid-Open No. 10-102489 Japanese Patent Laid-Open No. 11-036295 JP 2001-077332 A JP 2001-193063 A

  In steel pipe piles with rotor blades used for the rotary intrusion steel pipe pile method, it is expected that the tip bearing capacity will be improved by the wing part, high bearing capacity is obtained, penetration is good, and the wing strength is sufficient. It is required to be excellent in economic efficiency.

  In general, an open-end type is advantageous for construction of large-diameter steel pipe piles with a diameter of 800 mm or more. However, for example, in the case of a spiral blade represented by the example of Patent Document 4, the angle between the plane perpendicular to the steel pipe axis direction and the spiral blade is Since the penetration amount per rotation is equal to the inside and outside of the steel pipe, the amount of earth and sand taken into the steel pipe may be blocked to obstruct the penetration.

  In the example of Patent Document 3, the included angle is not 0 °. However, since the interval between the rotor blades is the same inside and outside the steel pipe, the amount of penetration and the amount of earth and sand taken into the steel pipe are also the same, so the same phenomenon as described above occurs.

  On the other hand, for example, in the open tip type flat blade represented by the example of Patent Document 2, it is difficult to cause clogging, but the propulsive force in the rotation construction is small, and in particular, the penetration property in the hard layer is inferior.

  Patent Document 1 states that by defining the step of the spiral blade attachment portion within a predetermined range, it is excellent in penetrability and high support force can be obtained. When formed, if the outer diameter of the wing is increased in order to obtain a high support force, the penetration becomes worse, and the resistance from the ground and the proof strength of the wing against the support force become problems.

  The invention of the present application is based on the background as described above, and the shape of the wing is devised. The purpose is to provide a pile and its construction method.

The rotary penetrating pile according to claim 1 of the present application is a rotary penetrating pile having a wing having an outer diameter larger than the outer diameter of the steel pipe pile at the tip of the steel pipe pile, and the disk having a substantially conical surface as the wing is divided into two. The two semi-disc shaped wings are mounted symmetrically at a predetermined mounting angle θ with respect to a plane perpendicular to the axis of the steel pipe pile, and the plane perpendicular to the axis of the steel pipe pile in the normal direction of the steel pipe pile and the wing The nip angle η formed by the surface of the blade gradually increases from the downward direction to the horizontal or upward direction from the beginning to the end of the blade, and the bottom angle (α) of the blade and the mounting angle (θ) are
0 ° ≦ θ−α ≦ 5 °
And it is characterized in that has a relationship.

  The “substantially conical surface” mentioned here includes the case of a complete conical surface, and is not limited to the case where the surface is smoothly continuous, but is actually a polygonal pyramid surface. It is meant to include the shape.

  Further, the attachment angle θ is considered as an angle formed by a straight line passing through the center of the steel pipe with a cross section perpendicular to the steel pipe axis and a straight line connecting the height difference between the start blade and the rear blade on the steel pipe. With regard to the included angle η, with the plane perpendicular to the axis of the steel pipe pile as the basis, the downward angle is considered negative and the upward direction is considered positive. It gradually increases until it becomes horizontal (the included angle η = 0) or upward (the included angle η is positive).

Since the surface of the spiral wing of a conventional rotary penetrating pile is on a flat surface, the proof strength of the wing is related to the resistance or supporting force from the ground. Is controlled by the coefficient (b · t ² ) / 6 (t is the plate thickness, b is the width, but in this case, the width b should be considered in any direction of the wing in terms of resistance from the ground or bearing capacity. Can do that.)

  In the case of the present invention, since the plate constituting the wing has a conical surface as a whole, the section modulus is greatly improved as compared with the case of a plane regarding resistance or supporting force from the ground, and the same section performance is obtained. The plate thickness is reduced, improving economics and improving penetration.

  In addition, the bearing capacity of the ground depends on the shear strength near the wing at the tip of the pile, and in the case of unconsolidated sand and gravel, a confining effect is obtained by the shape of the wing that forms a conical surface. Supporting force is improved.

  In addition, the end of the wing is positioned below the tip of the pile, making it easier to penetrate the pile, and the other end of the wing is horizontal (perpendicular to the pile) or above it. improves.

  In addition, since the wing is attached to the tip surface instead of the outer peripheral surface of the hollow pile, the bending acting on the attachment position is small against the vertical resistance from the ground, and the wing is attached to the outer peripheral surface. Compared to the case, the stability of the blade mounting part is high.

  Furthermore, in the present invention, the included angle η formed by the surface perpendicular to the axis of the steel pipe pile in the normal direction of the steel pipe pile and the surface of the blade is gradually increased from the downward direction to the horizontal or upward direction from the start end to the end of the blade. In other words, it is possible to obtain a large propulsive force by mounting the wings so that the wing overhanging direction gradually or downwards from the downward direction, and the ground excavation function is improved. Rotating and penetrating construction can be performed with relatively little rotational force even on the ground.

The rotary penetrating pile according to claim 2 of the present application is a rotary penetrating pile having a wing having an outer diameter larger than the outer diameter of the steel pipe pile at the tip of the steel pipe pile, and a donut-shaped disk having a substantially conical surface as the wing. Two split donut disk-shaped wings are mounted symmetrically at a predetermined mounting angle (θ) with respect to a plane perpendicular to the axis of the steel pipe pile, and perpendicular to the axis of the steel pipe pile in the normal direction of the steel pipe pile. The included angle (η) between the surface of the blade and the surface of the blade gradually increases from the lower end to the horizontal or upward from the beginning to the end of the blade, and the bottom angle (α) of the blade and the mounting angle ( θ)
0 ° ≦ θ−α ≦ 5 °
And it is characterized in that has a relationship.

  The difference from claim 1 is that the overhang width of the wing in the steel pipe is small, and the resistance to the intake of earth and sand from the tip is reduced. That is, by opening the inner diameter side of the blade, the earth and sand can be taken into the steel pipe pile more smoothly during the rotation penetration, and the construction of no soil or low soil can be performed efficiently. These can be properly used according to the ground conditions.

In the rotary penetrating piles according to claim 1 and claim 2, θ-α is an angle formed by a plane perpendicular to the steel pipe normal direction and the steel pipe axis direction at the rear end of the blade, and this angle should be 0 ° or more. For example, it has been confirmed by construction tests that the clumps at the leading edge of the following blades loosen and the penetrability increases. However, when the angle is approximately 5 ° or more, the support layer is loosened and adversely affects the supporting force. Therefore, the above range is preferable.

  That is, when θ−α <0 °, the trailing edge of the blade also faces downward, so that the soil passing in the rotating direction is difficult to pass through, and a closed state is likely to occur between the rotating blade and the rotating blade. In particular, when there are cobblestones, the downward wings will hold the cobblestone, and the penetration will be greatly reduced.

  On the other hand, when θ-α> 5 °, a tendency that the supporting force on the sand ground is lowered starts to appear. This is presumed that tan5 ° = 0.09, and when θ−α> 5 °, the silt material having a friction coefficient μ = 0.1 or less on the blade surface does not contribute to the supporting force.

  Also, in the construction, when θ-α> 5 °, the trailing edge of the blade becomes resistance at the time of rotational penetration, and the rotational torque necessary for rotational penetration in the vicinity of a particularly hard support layer increases. For this reason, a construction machine with a large output is required, which is uneconomical.

According to a third aspect of the present invention, in the rotary penetrating pile according to the first or second aspect , the projected blade width of the wing projecting outward from the steel pipe is gradually expanded from the leading end to the trailing end of the wing. .
By making the overhanging width of the steel pipe outward in the blade start end smaller than the blade end, the penetration into the ground can be improved.

Further, when penetrating into hard ground, the load transmitted to the steel pipe pile, since in many cases the starting end side of the blade to share the larger load than the terminal side, by a B _s <B _e as shown in FIG. 5 to be described later The load sharing can be averaged, and the supporting force of the ground can be effectively extracted.

  This structure also reduces the difference between the maximum (generally occurring at the start side) and the minimum (generally occurring at the end side) of the cross-sectional force generated at the joint between the blade and the steel pipe. The blade thickness required to obtain the force can be reduced, and economical member design becomes possible.

According to a fourth aspect of the present invention, in the rotary penetrating pile according to the second or third aspect , the projected blade width of the blade projecting in the steel pipe inward direction is gradually reduced from the leading end to the trailing end of the blade. .

In an open-ended rotary pile, it is necessary to take in an appropriate amount of earth and sand into the steel pipe (quantitatively, depending on the ground, the amount necessary to penetrate the steel pipe). The blade that projects into the steel pipe at the start side has the function of taking the soil into the steel pipe, and the end side has a function to push the taken-in soil into the steel pipe. It becomes larger and the rotational penetrability decreases. Therefore, by the wing span b _s and the rear-side blade width b _e a starting end which protrudes steel pipe inside as shown in FIG. 5 to be described later with b _s> b _e, upon uptake while maintaining capture performance Rotational resistance can also be improved.

However, reduction of the extreme wings termination width for lowering the push performance into steel, in this case the diameter of the opening suitably 0.3 to 0.8 of the steel pipe diameter, b _e / b _s = 0 It is suggested from the model experiment results that .4 to 0.9 is appropriate.

The construction method of the rotation penetration pile which concerns on Claim 5 of this application is penetrated in the ground, if the rotation penetration pile which concerns on Claim 1, 2, 3 or 4 is rotated around a pile axis | shaft. Is.

The rotary penetrating piles according to claims 1 to 4 are provided with two blades on the tip surface for rotary penetrating into the ground, and are constructed by a method similar to that of conventional rotary penetrating piles. It is intended mainly for construction without soil removal.

  According to the present invention, the wing attached to the tip surface of the pile forms a conical surface that spreads downward, and further, the wing extension direction is attached so as to gradually change from downward to horizontal or upward, Since a large propulsive force can be obtained and the excavation function of the ground is improved, it is possible to perform a rotational penetration construction with a relatively small rotational force even on a well-tightened high-density ground.

  Moreover, the cross-sectional performance of the blade with respect to the force in the vertical direction is improved, and a large proof stress is obtained. When the same proof strength is obtained, the blade thickness can be reduced. Since the wing is attached to the tip of the pile, the mounting stability is high.

  In addition, since the wings are not in the same plane, the wings do not slip at the position where the layer changes, and the angle of the blade tip is larger than that of a flat plate or spiral plate, so the penetration performance is improved and the cobblestone is gathered in the center and the steel pipe The performance of taking in is improved.

  Since the surface of the wing that contacts the ground is a conical surface that spreads downward, the support force can be improved by the confining effect.

By making the bottom angle α of the blade and the mounting angle θ satisfy 0 ° ≦ θ−α ≦ 5 °, the penetrability can be improved and the adverse effect on the supporting force can be reduced.

In the invention according to claim 3 , the projected blade width of the blade projecting outward from the steel pipe gradually increases from the leading end to the trailing end of the blade, so that the load sharing in the blade is averaged and the bearing force is effectively increased. Therefore, economical member design is possible.

In the invention according to claim 4 , the projected blade width of the blade projecting in the steel pipe inward direction is gradually reduced from the start end to the rear end of the blade, thereby optimizing the amount of sand and sand taken into the steel pipe. Rotational resistance during loading can be improved while maintaining the above.

According to the invention according to claim 5 of the present application, since the rotary penetrating piles according to claims 1 to 4 are rotationally penetrated into the ground, the penetrability is high and the workability is improved as compared with the conventional pile construction by rotary penetration. Can be planned.

  FIG. 1 and FIG. 2 show one embodiment of a rotary penetrating pile of the present invention, in which the tip of a steel pipe pile 1 is cut out and two blades 2 are attached to the tip surface 3 thereof.

  Each wing 2 has a shape in which a steel disk having a substantially conical surface is divided into two parts, and intersects the pile tip surface 3 cut out as described above when viewed from the front. Inclined and welded. The attachment angle at this time is θ, and the two blades 2 are attached symmetrically so that the crossing angle of the blades 2 becomes 2θ.

  In the construction, the steel pipe pile 1 as the rotating penetrating pile is pressed into the ground while rotating, thereby being penetrated into the ground. Moreover, penetration resistance is eased because earth and sand are taken in into the inside of the steel pipe pile 1 from the opening part which arises in the front-end | tip of the steel pipe pile 1. FIG.

Further, in the present invention, the included angle η formed by the surface perpendicular to the axis of the steel pipe pile 1 and the surface of the blade 2 in the normal direction of the steel pipe pile 1 is considered, and the included angle η is downward from the start end to the end of the blade 2. In the figure, η _s is the included angle at the starting end (downward and is considered as a negative value with respect to the plane perpendicular to the axis of the steel pipe pile), η _e Is the included angle (so that it becomes 0 or a positive value).

  In this way, the included angle η formed by the plane perpendicular to the axis of the steel pipe pile in the normal direction of the steel pipe pile and the surface of the wing increased gradually from the bottom to the horizontal or upward from the beginning to the end of the wing. Thus, as described above, a large propulsive force can be obtained and the excavation function of the ground is improved, so that the rotation penetration construction can be performed with a relatively small rotational force even in a well-tightened high-density ground.

  FIG. 3 shows the relationship between the base angle α of the blade 2 and the mounting angle θ. As described above, the base angle α is 0 ° ≦ θ−α ≦ 5 ° in relation to the mounting angle θ, so that the penetrability is increased and the adverse effect on the supporting force is reduced. be able to.

  In order to obtain this effect economically, the base angle α is generally in the range of 5 ° ≦ α ≦ 20 °, and from this, θ becomes 5 ° ≦ θ ≦ 25 °. The range of the base angle α is a range that can be economically processed when a thick plate of t = 16 to 100 mm is pressed.

  FIG. 4 shows the relationship between the two blades 2 attached to the front end surface of the pile. The distance between the start and end of two adjacent blades 2 is the distance H between the portion projecting outside the steel pipe and the steel pipe. In the case of the open-ended bladed steel pipe pile 1 having an opening 4 with a gap h projecting inward and h <H, so that the amount of earth and sand taken in is smaller than the amount of penetration per revolution. The effect of preventing blockage during construction can be expected.

FIG. 5 shows an embodiment of a rotary penetrating pile according to claims 3 and 4 .

As described above, the relationship between the projecting width B _e in overhang width B _s and wing 2 termination to the steel pipe outward in the blade 2 start end, by such a B _s <B _e, a load sharing It can be averaged, and the supporting force of the ground can be effectively extracted.

As also described above, that the relationship between the projecting width b _e in overhang width and blade 2 termination to the steel pipe in the direction of the wings 2 start is made to be b _s> b _e, sediment Rotation resistance at the time of uptake can be improved while maintaining the uptake performance.

It is a front view of the pile front-end | tip part which shows one Embodiment of the rotation penetration pile of this invention. It is a vertical sectional view in the rotation penetration pile of FIG. It is a vertical sectional view for explaining the relation between the bottom angle α of the blade and the mounting angle θ. It is the perspective view seen from the pile front end side for demonstrating the relationship between the two wing | blades attached to the pile front end surface. It is a top view which shows one Embodiment of the rotation penetration pile which concerns on Claims 3 and 4 of this application.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Steel pipe pile, 2 ... Wing, 3 ... Tip surface, 4 ... Opening

Claims (5)

In a rotary penetrating pile having a wing whose outer diameter is larger than the outer diameter of the steel pipe pile at the tip of the steel pipe pile, a semi-disc shaped wing obtained by dividing a disk having a substantially conical surface as the wing is an axis of the steel pipe pile. Are attached symmetrically at a predetermined mounting angle (θ) with respect to a plane perpendicular to the plane, and the included angle (η) between the plane perpendicular to the axis of the steel pipe pile and the surface of the blade in the normal direction of the steel pipe pile , Gradually increasing from the downward direction to the horizontal or upward direction from the beginning to the end of the blade, and the base angle (α) of the blade and the mounting angle (θ) are:
0 ° ≦ θ−α ≦ 5 °
Rotating penetrating pile characterized by the relationship . In a rotary penetrating pile having a blade having an outer diameter larger than the outer diameter of the steel pipe pile at the tip of the steel pipe pile, a half donut disk-shaped wing obtained by dividing a donut-shaped disk having a substantially conical surface as the wing is divided into a steel pipe. Two sheets are mounted symmetrically at a predetermined mounting angle (θ) with respect to a plane perpendicular to the axis of the pile, and the angle between the plane perpendicular to the axis of the steel pipe pile and the surface of the wing in the normal direction of the steel pipe pile ( η) is gradually increased from the downward direction to the horizontal or upward direction from the beginning to the end of the blade, and the bottom angle (α) of the blade and the mounting angle (θ) are
0 ° ≦ θ−α ≦ 5 °
Rotating penetrating pile characterized by the relationship . The rotary penetrating pile according to claim 1 or 2 , wherein the projected blade width of the blade projecting outward from the steel pipe gradually increases from the leading end to the trailing end of the blade. The rotary penetrating pile according to claim 2 or 3 , wherein the projected blade width of the blade extending in the steel pipe inward direction is gradually reduced from the start end to the rear end of the blade. Construction method of the rotary penetration piles, characterized in that the rotary penetration pile according to claim 1, 2, 3 or 4, wherein, going to penetrate into the soil in if rotated pile axis.

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