JP2009249893A - Rotary press-in pile and construction method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive rotary press-in pile and a construction method therefor for reducing construction load when excavating an intermediate layer to improve excavation performance and achieving high supporting force after reaching a supporting layer. <P>SOLUTION: This rotary press-in pile is provided with a steel pipe pile and one or a plurality of excavation bits attached to a tip of the steel pipe pile. By merely changing the direction of rotation of the rotary press-in pile when excavating the intermediate layer and the supporting layer, the excavated sediment is pushed outside the steel pipe pile and is taken into the inside of the steel pipe pile. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a rotary press-fit pile using an open end pile and a construction method thereof.

In general, one of the foundation pile construction methods for supporting structures is a rotary press-fit steel pipe pile construction method using open-ended piles.
In rotary press-in construction of open-ended piles, when excavating the intermediate layer, it is necessary to prevent pile tip clogging with increasing construction depth and reduce the construction load. In addition, after reaching the support layer, it is necessary to reliably close the lower end portion of the open-ended pile to obtain a large support force.

  Conventionally, for example, Patent Document 1 proposes a blade structure of a casing construction top pipe that distributes the excavation blade of the casing construction top pipe into three rows of an outer cutter, a central cutter, and an inner cutter. The technique disclosed in Patent Document 1 creates a flow for taking in the earth and sand excavated from the outer side of the front pipe by the blade structure of the front pipe for casing method. Furthermore, the technique disclosed in Patent Document 1 aims to improve the excavability by equalizing the wear of each excavating blade.

  Further, Patent Document 2 proposes a rotary press-fit steel pipe pile in which a plurality of excavation bits are provided in the circumferential direction at the lower end, and the excavation rib is fixed in the pipe of the steel pipe pile so as to be point-symmetric with respect to the steel pipe center. Has been. The technique disclosed in Patent Document 2 excavates and agitates earth and sand taken into a steel pipe with excavation ribs. The disclosed technique of Patent Document 2 aims to remove the blockage in the steel pipe when the intermediate layer is rotationally press-fitted by a drilling rib, and to promote the blockage in the steel pipe when the support layer is stopped.

Registered Utility Model No. 2520117 JP 2007-284866 A

  However, the construction method of the blade structure of the leading pipe for casing method described in Patent Document 1 is a technique of concrete piles, and concrete is used to prevent the inside of the pipe from being blocked by earth and sand taken inside the leading pipe. It was necessary to discharge the soil that had been taken in for placement. For this reason, in order to prevent sedimentation in the pipe, grab a soil removal device such as a screw auger, a chisel for crushing rocks and clods, a drilling bucket for scooping rocks and clods, and rocks and clods. It is necessary to provide a separate device such as a hamburger that raises to the ground. Thereby, the construction method using the blade part structure described in Patent Document 1 has a problem that the step of discharging soil is included, the construction time is prolonged, and the cost is increased. Furthermore, this blade structure has a problem that since the excavation blades are arranged in three rows, a large number of excavation blades are required and the cost is increased.

  Moreover, the rotary press-fit steel pipe pile to which the excavation rib of patent document 2 is fixed excavates and stirs the earth and sand taken in in the steel pipe with an excavation rib. However, for example, when excavating highly viscous ground or hard ground, excavation and agitation with the excavation ribs are difficult, and the tip clogging tends to be remarkable.

  Therefore, the present invention has been devised in view of the above-described problems, and its purpose is to omit the soil removal process, to reduce the work load during excavation of the intermediate layer, improve the excavation performance, An object of the present invention is to provide an inexpensive rotary press-fit pile capable of obtaining a high support force after reaching the support layer and a construction method thereof.

  In order to solve the above-mentioned problems, the present inventor includes a steel pipe pile and one or a plurality of excavation bits attached to the tip of the steel pipe pile, and at the time of intermediate layer excavation and support layer excavation Has invented a rotary press-fit pile that can push the excavated earth and sand to the outside of the steel pipe pile and take in the inside just by changing the rotation direction of the steel pipe pile.

  That is, the invention according to claim 1 of the present application includes a steel pipe pile and one or a plurality of excavation bits attached to the tip of the steel pipe pile, and at least one of the excavation bits is used for excavation. The bit has an angle between the longitudinal direction and the tangential direction at the intersection of the central axis of the longitudinal direction and the outer periphery of the steel pipe pile, and at least this angle makes the excavation bit of the excavation bit face the inside of the steel pipe pile. It is characterized by being provided.

  The invention according to claim 2 of the present application is characterized in that an outer peripheral side protrusion width of the excavation bit is equal to or less than a friction cutter thickness.

  The invention according to claim 3 of the present application is characterized in that the excavation bit has excavation blades in the excavation direction and in the opposite direction.

  The invention according to claim 4 of the present application is the method for constructing the rotary press-fit pile according to any one of claims 1 to 3, wherein the excavation until the tip of the steel pipe pile reaches a predetermined depth. The rotary press pile is rotated in a direction that becomes an obtuse angle with respect to the outward longitudinal direction of the bit, and after reaching the stopping depth, the rotary press pile is rotated in the opposite direction of the direction. To do.

  The invention according to claim 5 of the present invention is characterized in that, in the above-described stopping, the tip of the steel pipe pile is made to reach the support layer and then reversely rotated.

  In the invention according to claim 6 of the present application, at the time of the above-mentioned stopping, immediately after reaching the tip of the steel pipe pile to the support layer, the excavation is advanced by reverse rotation, and after reaching the tip of the steel pipe pile to the support layer, It is characterized by stopping.

  In the present invention having the above-described configuration, it is possible to reduce the construction load and improve the excavation performance when excavating the intermediate layer without including the soil removal process during excavation.

  Further, in the present invention, by changing the rotation direction in the reverse direction when the tip of the rotary press-fit pile reaches the support layer, earth and sand can be taken inside the steel pipe pile when excavating the support layer of the steel pipe pile. As a result, when the steel pipe pile is stopped, the inside of the steel pipe pile is closed with the earth and sand that has taken in the tip of the steel pipe pile, and a high supporting force can be obtained. For this reason, in the past, after reaching the depth at which the tip of the steel pipe pile stops, for example, a process of driving the rotary press pile into the support layer deeply, The process of injecting soil cement is not necessary. By eliminating such a process, the process can be simplified and the construction period can be shortened in the construction of the rotary press-fit pile. Further, it is more effective if the depth at which the tip of the steel pipe pile is stopped is a support layer.

  Moreover, in this invention, since the effect mentioned above can be implement | achieved only by changing a rotation direction, the existing construction machine used for the rotation press-fit pile can be used. As a result, the process can be simplified, the construction period can be shortened, and the cost can be reduced.

  Hereinafter, as a best mode for carrying out the present invention, a rotary press-fit pile will be described in detail with reference to the drawings.

  FIG. 1 shows the configuration of a rotary press-fit pile 1 to which the present invention is applied. The rotary press-fit pile 1 includes a steel pipe pile 2 and an excavation bit 3 attached to the lower end of the steel pipe pile 2. This excavation bit has an excavation blade 12 over the entire length in the longitudinal direction L of the excavation bit 3 from the inside of the steel pipe pile. The rotary press-fit pile 1 is rotary press-fitted and penetrates into the ground. The rotary press-fit pile 1 may be inserted into the ground by an all-around swirler or the like (not shown).

  The steel pipe pile 2 is comprised with the hollow open end pile which the upper end and the lower end opened. The steel pipe pile 2 may be formed of any steel pipe such as a spiral steel pipe or a bending steel pipe.

  2 to 5, 6 (a) and 6 (b) are perspective views of the excavation bit 3 with the cutting edge 13 on the inner peripheral side of the steel pipe pile 2 of the excavation bit 3 as the front. As shown in FIG. 2, the excavation bit 3 includes a height direction H that is a direction from bottom to top in the drawing, a longitudinal direction L that is a direction from the front to the depth side in the drawing, and a right to left in the drawing. And a width direction W that is a direction toward the center.

  As shown in FIG. 2, the excavation bit 3 includes an excavation bit main body 11 and an excavation blade 12.

  The excavation bit body 11 is made of a material that can be easily welded directly to the steel pipe pile 2, such as a general structural steel rolled steel, a welded structural rolled steel, or a mechanical structural carbon steel.

The drilling blade 12 is, for example, a cemented carbide tip for a steel tool such as tungsten carbide, a general structural steel rolled steel subjected to heat treatment such as quenching or tempering, a rolled steel for welded structure, or a carbon steel for mechanical structure. Consists of hard materials such as. As an example of the excavation blade 12, for example, as shown in FIG. 2, only the lower end side in the height direction H of the excavation bit 3 may be formed of a hard material.
Further, the excavation bit 3 may be configured by cutting out the excavation blade 12 as a hard material by heat treatment such as quenching and tempering.

  As an example of the shape of the excavation bit 3, for example, as shown in FIG. 2, in the cross section in the longitudinal direction L of the excavation bit 3, h1> h2, and the lower side and the height on the front surface of the excavation bit 3 The angle φ formed with the long side of the lens may be an acute angle. As another example of the shape of the excavation bit 3, for example, as shown in FIG. 3, the excavation bit 3 is set so that the magnitude relationship between the heights h1 and h2 of the excavation bit 3 is h1> h2. The longitudinal direction L of the excavation bit 3 may be inclined at a height. As another example of the shape of the excavation bit 3, for example, as shown in FIG. 4, the magnitude relationship between h1 and h2 which is the height of the excavation bit 3 is h1> h2, and the width of the excavation bit 3 is The height of the excavation bit 3 and the inclination of the width of the excavation bit 3 may be inclined in the longitudinal direction L of the excavation bit 3 so that a certain magnitude relationship between w1 and w2 is w1> w2. As another example of the shape of the excavation bit 3, for example, as shown in FIG. 5, it may be a streamlined shape along the longitudinal direction L of the excavation bit 3, which is the direction in which earth and sand flow. As another example of the shape of the excavation bit 3, an inclination may be provided on the inner side of the steel pipe pile so that h2> h1 in FIG. As another example of the shape of the excavation bit 3, for example, as shown in FIG. 15, the cross-sectional shape in the longitudinal direction L of the excavation bit 3 may be a pentagon. In any case, it is desirable that the excavation bit 3 has a shape that reduces excavation resistance and smoothes the flow of earth and sand.

  As an example of the excavation bit 3, for example, as shown in FIG. 6A, the excavation bit is provided at both ends in the longitudinal direction L of the excavation bit 3 on the lower end side in the height direction H of the excavation bit 3. Three excavating blades 12 may be provided. As another example of the excavation bit 3, for example, as shown in FIG. 6B, the excavation bit 3 includes an excavation bit body 11 and an excavation bit 12 and an excavation bit 3a. You may comprise so that it may consist of the bit 3b for excavation provided with the bit main body 11 and the excavation blade 12. FIG. The excavation bit 3a is provided with an excavation blade 12 only at the lower end portion on the near side in FIG. 6B in the longitudinal direction L of the excavation bit 3a. Further, the excavation bit 3b is provided with an excavation blade 12 only at the lower end portion on the depth side in FIG. 6B in the longitudinal direction L of the excavation bit 3b. The excavation bit 3 may be configured by fixing the excavation bit 3a and the excavation bit 3b by welding or the like on the surface 16 having the same cross-sectional shape. Since the hard material used for the excavation blade 12 is very expensive, the manufacturing cost of the excavation bit 3 can be reduced by reducing the volume of the excavation blade 12.

  The number of excavation bits 3 may be one or plural. As for this excavation bit 3, it is desirable to arrange | position four or more pieces so that it may become point-symmetrical at the lower end of the steel pipe pile 2. FIG. If the number of excavation bits 3 is three or less, the burden per one increases, and the excavation performance decreases. As the number of excavating bits 3 increases, the cost increases, and the number of excavating bits 3 is determined by the balance between cost and excavation performance. Moreover, the excavation bit 3 can be equally disposed at the lower end of the steel pipe pile 2 to make the excavation load even and improve the construction efficiency. Further, when a plurality of excavation bits 3 are arranged at intervals, the excavation bits 3 may be the same or a mixture of different ones.

  FIGS. 7 (a), 7 (b), 8-11, 12 (a), and 12 (b) are steel pipe piles when the rotary press pile 1 is rotated in the rotational direction A or the rotational direction B. 2 and a plan view of the excavation bit 3. FIG.

  As shown in FIG. 12 (a), the excavation bit 3 has an outer projecting portion 14 b that is a portion projecting from the outer periphery of the steel pipe pile 2 and an inner portion that is a portion projecting from the inner periphery of the steel pipe pile 2. And a projecting portion 14a.

  In the excavation bit 3, the outer side surface in the radial direction of the steel pipe pile 2 is shown as 15b, and the inner side surface in the radial direction of the steel pipe pile 2 is shown as 15a.

  The excavation bit 3 has its upper surface 17 attached to the lower end of the steel pipe pile 2 by welding or bolt fastening via a welding flat bar or a holder (not shown).

  As shown in FIG. 7A, the point P is the point where the distance from the center O of the steel pipe pile 2 is longest on the radially outer surface 15b of the excavating bit 3. The excavation bit 3 is attached so as to have an outer peripheral side protruding width b which is the distance between this point P and the intersection of the outer periphery of the steel pipe pile 2 on the radial line of the steel pipe pile 2 passing through this point P. This outer peripheral protrusion width b is the excavation width of the earth and sand outside the steel pipe pile 2 by the excavation bit 3. Further, a point where the distance from the center O of the steel pipe pile 2 is the shortest on the radially inner side surface 15a of the excavating bit 3 is defined as a point Q. The excavation bit 3 is attached so as to have an inner peripheral side protruding width a which is the distance between this point Q and the intersection of the inner periphery of the steel pipe pile 2 on the radial line of the steel pipe pile 2 passing through this point Q. Yes. This inner peripheral side protruding width a is the excavation width of the earth and sand inside the steel pipe pile 2 by the excavation bit 3.

As the outer peripheral protrusion width b increases, the frictional force on the peripheral surface decreases, so that the necessary press-fitting rotational torque decreases. However, the peripheral surface friction cannot be recovered, and the supporting force is also decreased. However, since the amount of soil to be scraped increases, the resistance applied to each excavation bit 3 increases. On the contrary, when the outer peripheral side protrusion width b is reduced, the reverse phenomenon occurs. Therefore, in order to ensure the bearing force by peripheral friction after construction, the outer peripheral side protruding width b is, for example, when the pile diameter of the steel pipe pile 2 is less than 800 mm, following the setting of the thickness of the friction cutter in the road bridge specifications. Is preferably 9 mm or less, and 12 mm or less when the pile diameter of the steel pipe pile 2 is 800 mm or more.
On the other hand, the inner peripheral side protruding width a is preferably about the same as the outer peripheral side protruding width b from the balance of moments generated in the excavation bit 3 when the earth and sand are scraped by the bit.

  In the excavation bit 3, as shown in FIG. 7A, the intersection point between the central axis in the longitudinal direction L of the excavation bit 3 and the outer periphery of the steel pipe pile 3 is defined as an intersection point X. At least one of the tangential direction E of the outer periphery of the steel pipe pile 2 at this intersection X and the longitudinal direction L of the excavation bit 3 has an angle, and in particular, the angle θ is in the range of 2 ° to 45 °. It is desirable to become. Further, the angle θ other than the at least one is preferably 0 ° to 30 °, and may not be all 2 to 45 °. FIG. 8 shows a planar arrangement of the steel pipe pile 2 and the excavation bit 3 as an example in which the angle θ is 15 °. FIG. 9 shows a planar arrangement of the steel pipe pile 2 and the excavation bit 3 having an angle θ of 30 ° as an example. For example, as shown in FIG. 10, when the angle θ exceeds 45 °, for example, 50 ° or more, the angle with respect to the rotation direction A of the cutting edge 13 of the excavation bit 3 decreases, and the excavation performance deteriorates. For example, as shown in FIG. 11, when the angle θ is 0 °, the cutting edge 13 of the excavation bit 3 faces the rotation direction A, and excavation performance is improved. However, when the angle θ is at least 2 ° or more, a flow of earth and sand described later can be made, but when the angle θ is 0 °, a flow of earth and sand cannot be made.

  In the construction method using the rotary press-fit pile to which the present invention is applied, the rotary press-fit pile 1 is rotary press-fitted in the rotation direction A as shown in FIG. During excavation of the support layer 32, as shown in FIG. 13B, the rotary press-fit pile 1 is rotary press-fitted in a rotation direction B that is opposite to the rotation direction A. The support layer refers to a layer having sufficient thickness and hardness to block the lower end portion of the steel pipe pile 2 and stop the pile. The sufficient thickness here refers to a thickness at which the ground does not cause punching breakage or large subsidence with respect to a load generated at the tip in order to exert a supporting force that is a characteristic of a pile. The intermediate layer 31 refers to a layer until the tip of the steel pipe pile 2 reaches the support layer 32.

  First, the earth and sand flow D will be described in detail with reference to FIG. 12A and FIG. 13A when the intermediate layer 31 is excavated. The rotary press pile 1 is rotationally press-fitted in a rotational direction A that is an obtuse angle with the outward longitudinal direction L of the excavating bit 3. As a result, the ground is excavated by the excavating bit 3, and the steel pipe pile 2 is penetrated into the intermediate layer 31.

  At this time, the outer peripheral earth and sand 21a of the steel pipe pile 2 is excavated by the outer projecting portion 14b of the excavation bit 3 rotating in the rotation direction A. Since the outer peripheral side earth and sand 21a of the excavated steel pipe pile 2 is an obtuse angle between the outward longitudinal direction L of the excavating bit 3 and the rotation direction A, the outer side earth and sand 21a extends along the outer surface 15b of the excavating bit 3. And then flowed to the outside of the steel pipe pile 2. Further, the inner circumferential soil 22a of the steel pipe pile 2 is excavated by the inner projecting portion 14a of the excavation bit 3 that rotates in the rotation direction A. Since the inner circumferential side earth and sand 22a of the excavated steel pipe pile 2 is an obtuse angle between the outward longitudinal direction L of the excavating bit 3 and the rotation direction A, the outer surface 15b of the excavating bit 3 is Along the outside of the steel pipe pile 2. Thus, when the rotary press-in pile 1 is rotary press-fitted in the rotational direction A, the earth and sand at the tip of the steel pipe pile 2 is excavated by the excavation bit 3, and the excavated soil is along the outer surface 15 b of the excavation bit 3. Will be washed away.

  The steel pipe pile 2 reduces the earth and sand volume on the inner side of the steel pipe pile 2 by pushing out the inner circumferential soil 22a of the steel pipe pile 2 to the outside, thereby reducing the sediment density and lowering the friction on the inner peripheral surface. become. For this reason, the steel pipe pile 2 becomes difficult to block | close by reducing the earth and sand density of the inner periphery side earth and sand 22 of the steel pipe pile 2.

  The steel pipe pile 2 raises the earth and sand density of the outer side of the steel pipe pile 2 by pushing out the inner circumference side earth and sand 22a of the steel pipe pile 2 to the outside, and compacts the ground of the outer circumference. However, the excavation bit 3 acts as a friction cutter that reduces the friction between the steel pipe pile 2 and the outer peripheral earth and sand 21, so the construction load can be reduced.

  Thus, at the time of excavation of the intermediate layer 31, the steel pipe pile 2 can make it difficult to block the inner side by reducing the sediment density on the inner side. Moreover, the steel pipe pile 2 can reduce a construction load and improve excavability by reducing the outer peripheral surface friction.

  Next, when excavating to near the depth to stop, the sediment flow D will be described in detail with reference to FIGS. 12 (b) and 13 (b). The rotary press-fit pile 1 is rotationally press-fitted in a rotational direction B that is opposite to the rotational direction A. As a result, the ground is excavated by the excavating bit 3 and the steel pipe pile 2 is penetrated into the support layer 32.

  At this time, the outer peripheral earth and sand 21a of the steel pipe pile 2 is excavated by the outer projecting portion 14b of the excavation bit 3 rotating in the rotation direction B. Since the outer circumferential side earth and sand 21a of the excavated steel pipe pile 2 has an acute angle formed by the outward longitudinal direction L of the excavation bit 3 and the rotation direction B, the outer side sediment 21a extends along the inner surface 15a of the excavation bit 3. And then flowed into the inside of the steel pipe pile 2. Further, the inner circumferential soil 22 a of the steel pipe pile 2 is excavated by the inner projecting portion 14 a of the excavation bit 3 that rotates in the rotation direction B. Since the inner circumferential side earth and sand 22a of the excavated steel pipe pile 2 has an acute angle between the outward longitudinal direction L of the excavating bit 3 and the rotation direction B, the inner side surface 15a of the excavating bit 3 is Along the inside of the steel pipe pile 2. Thus, when the rotary press-in pile 1 is rotary press-fitted in the rotational direction B, the earth and sand at the tip of the steel pipe pile 2 is excavated by the excavating bit 3, and the excavated earth and sand is applied to the inner side surface 15 a of the excavating bit 3. Along the inside.

  The steel pipe pile 2 increases the sediment accumulation inside the steel pipe pile 2 by taking the outer peripheral side earth and sand 21a of the steel pipe pile 2 inside, thereby increasing the sediment density. For this reason, the steel pipe pile 2 will be obstruct | occluded gradually by increasing the sediment density of the inner periphery side sediment 22.

As described above, at the time of stopping, the inner side of the steel pipe pile 2 is increased in blockage with the increase in sediment density. In addition, after the front-end | tip of the steel pipe pile 2 reaches | attains the support layer 32, the depth which excavates by stopping the rotary press-fit pile 1, ie, the depth by which the lower end of the steel pipe pile 2 penetrates into the support layer 32 is rotation. It is determined by the supporting force to be acquired by the press-fit pile 1 and the hardness of the ground.
It is desirable that there is a layer as the support layer 32 at the depth to be stopped. In other words, it is desirable that when the steel pipe pile 2 reaches the support layer 32 when stopping, a high support force can be obtained. Even if the reverse rotation immediately before stopping is started after reaching the support layer 32 or just before reaching, the tip of the steel pipe pile 2 reaches the support layer 32 and piles on the support layer 32. As long as you can have the support of

  At the time of stopping the rotary press-fit pile 1, the steel pipe pile 2 penetrated into the support layer 32 takes the solid soil such as soil and gravel of the support layer 32 into the steel pipe pile 2, thereby Is surely blocked. For this reason, the rotary press-fit pile 1 can acquire a high support force.

  After stopping the rotary press-fit pile 1, the steel pipe pile 2 recovers the peripheral frictional force with the outer peripheral earth and sand 21 of the steel pipe pile 2 over time, and is integrated with the outer peripheral earth and sand 21 of the steel pipe pile 2. It will become.

  Note that the angle θ is not limited to the same angle in all the excavation bits 3 attached to the tip of the steel pipe pile 2 and is different, for example, 0 ° and 15 ° as shown in FIG. May be. The cutting edge 13 of the excavation bit 3 having an angle θ of 0 ° is oriented in the direction of rotation A and excavation performance is improved. Further, the cutting edge 13 of the excavating bit 3 having an angle θ of 15 ° has the outer peripheral side protruding width b of the steel pipe pile 2 and the inner peripheral side protruding width a of the steel pipe pile 2 and is excavated as described above. Can flow along the inner side 15a or the outer side 15b of the excavating bit 3 to the inside or outside of the steel pipe pile 2. By making the angle θ different from 0 ° and 15 °, the rotary press-fitting pile 1 to which the present invention is applied has high excavation performance, and the excavated earth and sand can flow at the tip of the steel pipe pile 2. Become.

  As described above, in the rotary press-fit pile 1 to which the present invention is applied, it is possible to reduce the construction load and improve the excavation performance when excavating the intermediate layer 32.

Moreover, in the rotary press-in pile 1 to which the present invention is applied, the tip of the steel pipe pile 2 is changed from the rotation direction A to the rotation direction B when reaching the predetermined depth, thereby excavating the steel pipe pile 2 to the stop depth. In, the earth and sand can be taken inside the steel pipe pile 2. At this time, the predetermined depth may be, for example, upward by a distance of about 1 to 5 times the pile diameter with respect to the stopping depth. Thereby, when the steel pipe pile 2 is stopped, it is possible to obtain a high support force by closing the lower end portion of the steel pipe pile 2 with the earth and sand taken in. For this reason, conventionally, for example, a process of driving the rotary press pile into the support layer deeply after the tip of the steel pipe pile reaches the support layer, for example, a process of driving the rotary press pile deep into the support layer, An injection step is not necessary. By eliminating such a process, the process can be simplified and the construction period can be shortened in the construction of the rotary press-fit pile.
Further, in the present invention, as in the prior art, when the support layer 32 is provided at the stopping depth, it becomes more effective. In this case, a support force stronger than that of the intermediate layer 31 can be obtained by the support layer 32.

  Moreover, in the rotary press-in pile 1 to which the present invention is applied, since the above-described effect can be realized only by changing from the rotational direction A to the rotary direction B, the existing construction machine used for the rotary press-in pile is used. can do. As a result, the process can be simplified, the construction period can be shortened, and the cost can be reduced.

  In the rotary press-fitting pile 1 to which the present invention is applied, when the angle θ formed by the excavation bits 3 is different from 0 ° and 15 °, the angles θ of all the excavation bits 3 are 15 °. When the resistance to rotation at the time is too large, the excavation bit 3 is replaced with one having an angle θ of 0 °, whereby a load such as rotational torque can be reduced.

It is a block diagram of the rotary press-fit pile to which this invention is applied. It is a perspective view which shows the example of the shape of a bit for excavation. It is a perspective view of the bit for excavation which gives the inclination of height to the longitudinal direction of the bit for excavation. It is a perspective view of the bit for excavation which gives the inclination of height and width to the longitudinal direction of the bit for excavation. It is a perspective view of the bit for excavation made into the streamline shape in the longitudinal direction of the bit for excavation. (A) is a perspective view of the excavation bit which shows the example of one excavation bit, (b) is a figure which shows the example of the excavation bit comprised by two excavation bits. (A) is a top view which shows arrangement | positioning of the steel pipe pile and excavation bit in an intermediate | middle layer, (b) is a top view which shows arrangement | positioning of the steel pipe pile and excavation bit in a support layer. It is a top view which shows the state which attached the bit for excavation to the steel pipe pile at an angle of 15 degrees. It is a top view which shows the state which attached the bit for excavation to the steel pipe pile at an angle of 30 degrees. It is a top view which shows the state which attached the bit for excavation to the steel pipe pile at an angle of 45 degrees. It is a top view which shows the state which attached the bit for excavation to the steel pipe pile at an angle of 0 degree. (A) is a figure for demonstrating the flow of earth and sand in an intermediate | middle layer, (b) is a figure for demonstrating the flow of earth and sand in a support layer. (A) is a figure for demonstrating the penetration method of the rotary press-fit pile in an intermediate | middle layer, (b) is a figure for demonstrating the penetration method of the rotary press-fit pile in a support layer. It is a figure which shows the example of arrangement | positioning of the excavation bit, Comprising: It is a top view which shows the case where the excavation bit is attached to the steel pipe pile at the angle of 0 degree and 15 degrees. It is a perspective view of the bit for excavation whose longitudinal direction cross section of a bit for excavation becomes a pentagon.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotation press pile 2 Steel pipe pile 3 Excavation bit 3a, 3b Excavation bit 11 Excavation bit main body 12 Excavation blade 13 Cutting edge 14a, 14b Outward projecting part 15a, 15b Outer side surface 16 Symmetric surface 17 Upper part 21 Outer side earth and sand 21a, 21b Outer periphery side earth and sand 22 Inner periphery side earth and sand 22a, 22b Inner periphery side earth and sand 30 Ground surface 31 Intermediate layer 32 Support layer

Claims (6)

Steel pipe piles,
Including one or more excavation bits attached to the tip of the steel pipe pile,
At least one excavation bit among the excavation bits has an angle between the tangential direction at the intersection of the central axis in the longitudinal direction and the outer periphery of the steel pipe pile and the longitudinal direction, and at least the angle formed by this The rotary press-fit pile, wherein the cutting edge of the excavation bit is provided toward the inside of the steel pipe pile.   The rotary press-fit pile according to claim 1, wherein an outer peripheral side protruding width of the excavation bit is equal to or less than a friction cutter thickness.   The rotary press-fit pile according to claim 1 or 2, wherein the excavation bit has excavation blades in the excavation direction and in the opposite direction. It is the construction method of the rotary press-fit pile described in any one of claims 1-3,
Until the tip of the steel pipe pile reaches a predetermined depth, the rotary press pile is rotated in an obtuse angle with respect to the outward longitudinal direction of the excavation bit, and the depth at which the tip of the steel pipe pile stops is stopped. Until reaching the above, the rotary press-in pile is rotated in the opposite direction to the above direction.   5. The method for constructing a rotary press-fit pile according to claim 4, wherein the rotary press-fit pile is reversely rotated after the tip of the steel pipe pile reaches the support layer at the time of the stopping.   At the time of the above-mentioned stop, immediately before the tip of the steel pipe pile reaches the support layer, the rotary press-fit pile is advanced by excavation by reverse rotation, and the tip of the steel pipe pile reaches the support layer and then is stopped. The construction method of the rotary press-fit pile of Claim 4 characterized by the above-mentioned.

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