JP6943272B2 - Construction method of steel pipe pile, steel pipe pile - Google Patents

Description

The present invention relates to a method of driving a steel pipe pile into the ground by a rotary press-fitting machine, and particularly to a method of constructing a steel pipe pile suitable for a ground having a rubble layer or a boulder layer, and a steel pipe pile.

There are a striking method, a vibration method, and a press-fitting method as a method for driving steel pipe piles.
However, in the ground with a rubble layer or a boulder layer, there is a high risk of damaging the pile due to the high penetration resistance, and the rubble and boulders that receive the force from the pile move and force in the vertical direction. Is not transmitted well, so it is difficult to place the pile with either method.

As a solution to such a problem, a method of excavating a rubble layer or a boulder layer with a diameter larger than the pile diameter by a preliminary excavation method using an earth auger, replacing the part with sand, and placing a pile again is possible. Has been taken.
Further, as another method, Patent Document 1 proposes a method of improving the driving performance by attaching wear-resistant steel to the tip of the pile.

Japanese Patent No. 3735225

The advanced excavation method using an earth auger requires equipment for advanced excavation, excavated rubble, and soil transportation, which increases the construction space and cost, and also sets a pile driving machine again after sand replacement to pile the pile. There is a problem that the construction period is long because the construction period is long.

Further, in Patent Document 1, by attaching wear-resistant steel to the tip of the pile, the durability of the pile itself at the time of driving is improved, but the rubble and boulders that receive the force from the pile move and the force is applied in the vertical direction. The problem that is not transmitted well has not been solved. Therefore, construction is difficult especially in cases where the rubble layer is on the surface, such as the rubble mound used for harbor structural foundations and root consolidation.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a method for constructing a steel pipe pile and a steel pipe pile capable of improving workability on a ground having a rubble layer or a boulder layer.

(1) The method of constructing a steel pipe pile according to the present invention is a method of driving a steel pipe pile into the ground having a rubble layer and / or a boulder layer by a rotary press-fitting machine.
When a high-pressure water jet nozzle capable of injecting high-pressure water having a water pressure of more than 50 MPa is provided on the outer peripheral portion of the tip of the steel pipe pile and the steel pipe pile is rotationally press-fitted.
When the tip of the steel pipe pile reaches at least the rubble layer or the boulder layer, the vertical load and the rotational speed acting on the steel pipe pile are regulated by the rotary press-fitting machine, and the movement of the rubble or boulder is regulated by the tip of the steel pipe pile. It is characterized by comprising a step of injecting high pressure water from the high pressure water jet nozzle to crush the rubble or boulders by setting a value suitable for the above.

(2) Further, the above-mentioned item (1) is characterized in that high-pressure water mixed with an abrasive is sprayed.

(3) Further, in the above (1) or (2), while cutting crushed rubble and / or boulders by injecting high-pressure water from the high-pressure water jet nozzle with a bit arranged at the tip of a steel pipe pile. It is characterized by having a process of press-fitting steel pipe piles into the ground.

(4) Further, in any of the above (1) to (3), after the steel pipe pile is driven to a predetermined depth, the injection material to be ejected from the high-pressure water jet nozzle is changed from water to cement. It is characterized in that the ground is improved by injecting cement onto the ground at the tip of the pile by switching.

(5) Further, in the above (4), after the ground improvement of the pile tip ground is completed, the high pressure water jet nozzle is removed from the outer peripheral portion of the tip of the steel pipe pile, and the removed high pressure water jet nozzle is removed from the steel pipe pile. It is characterized in that the ground is improved by injecting cement onto the ground around the pile while pulling it up along the outer peripheral surface of the pile.

(6) Further, in any of the above (1) to (5), the high-pressure water is jetted diagonally downward inside the steel pipe pile.

(7) Further, in any of the above (1) to (5), a plurality of the high-pressure water jet nozzles are arranged diagonally downward inside the steel pipe pile and diagonally downward outside the steel pipe pile. It is characterized by injecting high-pressure water toward each of them.

(8) Further, in any of the above (1) to (7), the injection port of the high-pressure water jet nozzle is arranged so as to be located between the tip of the steel pipe pile and 100 mm above. It is a feature.

(9) Further, the steel pipe pile according to the present invention is arranged on the outer peripheral portion of the tip of the pile to prevent damage to the high-pressure water jet nozzle capable of injecting high-pressure water having a water pressure of more than 50 MPa and the high-pressure water jet nozzle. It is characterized by including a cylindrical protective member of the above and a cutting bit arranged on a surface of the protective member in contact with the ground.

(10) Further, in the above-mentioned item (9), the cutting bit is arranged so as to sandwich the tip of the high-pressure water jet nozzle, so that the cutting bit also serves as the protective member. Is.

In the present invention, a high-pressure water jet nozzle capable of injecting high-pressure water having a water pressure of more than 50 MPa is provided on the outer peripheral portion of the tip of the steel pipe pile, and the steel pipe pile is rotationally press-fitted.
At least when the rubble layer or boulder layer is reached, high-pressure water is discharged from the high-pressure water jet nozzle at a preset vertical load and rotation speed suitable for restricting the movement of the rubble or boulder by the tip of the steel pipe pile. By providing the step of injecting and crushing the rubble or boulder, the rubble or boulder can be suppressed so as not to move, and the rubble or boulder can be reliably crushed. It is possible to improve the workability on the ground having a layer. Further, by surely crushing the rubble or boulders, the steel pipe pile can be driven in the vertical direction, and a stable foundation structure can be constructed.

It is explanatory drawing explaining the outline of the equipment used for the construction method of the steel pipe pile of an embodiment. It is explanatory drawing of an example of the ground which is the object of construction in an embodiment. It is explanatory drawing of the construction method of the steel pipe pile which concerns on embodiment. It is explanatory drawing of the construction method of another aspect of the steel pipe pile which concerns on embodiment. It is explanatory drawing explaining the outline of another aspect of the apparatus used for the construction method of the steel pipe pile of embodiment. Note that FIG. 5A is an arrow view AA of FIG. 5B. It is explanatory drawing explaining the outline of another aspect of the apparatus used for the construction method of the steel pipe pile of embodiment. Note that FIG. 6A is an arrow view BB of FIG. 6B. It is a graph which shows the examination result of the arrangement of the injection port of the high pressure water jet nozzle which concerns on embodiment. It is explanatory drawing explaining the arrangement of the injection port of the high pressure water jet nozzle used in the construction method of the steel pipe pile of embodiment.

Prior to the explanation of the steel pipe pile construction method according to the present embodiment, the equipment used in the steel pipe pile construction method will be outlined.
As shown in FIG. 1, the rotary press-fitting machine 3 used for rotary press-fitting of the steel pipe pile 1 is attached to the upper part of the steel pipe pile 1 via a chucking portion 5 to apply rotational force and pressure input to the steel pipe pile 1. However, the steel pipe pile 1 is pierced into the ground.

Further, as shown in FIG. 1, a high-pressure water jet nozzle 7 is arranged on the outer peripheral portion of the tip of the steel pipe pile 1.
The high-pressure water jet nozzle 7 is capable of injecting high-pressure water having a water pressure of more than 50 MPa (for example, more than 50 MPa and less than 300 MPa), and is detachably arranged on the outer peripheral portion of the tip of the steel pipe pile 1. In the present embodiment, two high-pressure water jet nozzles 7 are provided at positions 180 ° apart from the outer circumference of the steel pipe pile 1.

In order to prevent the high-pressure water jet nozzle 7 from being damaged during the rotary press-fitting of the steel pipe pile 1, a cylindrical protective member 9 is provided at the tip of the steel pipe pile 1, and the high-pressure water jet nozzle 7 is made of earth and sand as much as possible. I try not to touch it.

The number of high-pressure water jet nozzles 7 to be arranged is not limited to two, and may be one, or three or more may be arranged discretely.
However, since the steel pipe pile 1 is rotated by the rotary press-fitting machine 3, the entire circumference can be covered by the rotation of the steel pipe pile 1 even if the number of high-pressure water jet nozzles 7 is reduced.

Regarding the ejection direction of the high-pressure water 11 from the high-pressure water jet nozzle 7, it may be ejected vertically downward, or it may be ejected toward the inside of the steel pipe pile 1. By injecting inward, the inside of the steel pipe pile 1 is not clogged with rubble or boulders, and the pile can be smoothly driven. However, it is desirable that the blowing angle θ of the high-pressure water 11 is within 30 ° in the pile center direction with respect to the pile axis direction (see FIG. 1).

Further, when a plurality of high-pressure water jet nozzles 7 are attached, the blowing directions of the high-pressure water 11 may be alternated between the inside and the outside.
However, if the injection directions of the high-pressure water jets directed alternately inside and outside are significantly different, the rubble or boulders are not sufficiently crushed and it becomes difficult to rotationally press-fit the steel pipe pile. On the other hand, if there is little difference in the injection direction of the high-pressure water jets that are alternately directed to the inside and the outside, the crushed parts of the rubble or boulders will overlap, resulting in inefficient construction. Therefore, it is desirable that the angle difference in the injection direction with respect to the radial direction of the steel pipe pile circle of the high-pressure water jet directed alternately inside and outside is within 10 ° to 30 °.

As will be described later, in the construction method of the present invention, the supply material to the high-pressure water jet nozzle 7 is switched from water to cement 25, and the cement 25 is injected to improve the ground (see FIG. 4D). Therefore, in such a mode, it is preferable to have a high-pressure water jet nozzle 7 that injects outwards because it is possible to improve the ground in a wide range.
There are three possible directions for ejecting high-pressure water: vertically downward, inside the steel pipe pile, and outside the steel pipe pile. One of these three directions, any two directions, or three directions. It may be in all directions.

A supply pipe 13 for supplying jet water is connected to the high-pressure water jet nozzle 7.
Water is normally supplied from the supply pipe 13, but in order to increase the cutting force of rubble and boulders, an abrasive may be mixed with the water.
As an abrasive, silica sand can be applied, but as other materials, steel slag, steel grit, molten alumina, garnet, etc. can also be applied.
In addition, as an abrasive material, in the sieving test method for measuring the particle size distribution of powdery substances specified by Abrasive particle hardness 300 to 2000 (HK, Noup hardness) and D50 (JIS Z 8815). , Particle size at which the cumulative frequency of the powdery substance is 50%) A material having a particle size of 200 μm to 1000 μm is suitable.

The high-pressure water jet nozzle 7 can also inject cement 25 or the like used for ground improvement.

The high-pressure water jet nozzle 7 may be detachably attached to the protective member 9 when the steel pipe pile 1 is constructed and then collected. For example, the high-pressure water jet nozzle 7 may be temporarily attached to the protective member 9 by a lock pin or spot welding, and the water jet hose may be pulled from the ground after construction so that the water jet nozzle 7 can be peeled off from the protective member 9. good.

Next, the construction method will be specifically described.
As an example of construction of a steel pipe pile on the ground having a rubble layer and / or a boulder layer, which is the target of the present embodiment, as shown in FIG. 2, it was constructed on a rubble mound 17 formed by the rubble 15. In the revetment 19, there is a case where a steel pipe pile 1 for reinforcement is constructed up to the support layer 21 through the rubble mound 17 on the sea side of the revetment 19. In the following description, a case where the steel pipe pile 1 is constructed on the ground having the rubble layer 23 made of the rubble 15 as shown in FIG. 2 will be described.

As shown in FIG. 3, the method of constructing the steel pipe pile according to the present embodiment is that when the steel pipe pile 1 is rotationally press-fitted and reaches the rubble layer 23 (see FIG. 3A), the tip of the steel pipe pile 1 is reached. Set to a preset vertical load and rotational speed suitable for restricting the movement of the rubble 15.
Whether or not the tip of the steel pipe pile 1 has reached the rubble layer 23 can be known from the increase in the penetration resistance of the pile. In addition, if the depth of the rubble layer 23 is known in advance by the preliminary survey conducted prior to the placement of the steel pipe pile, the rubble layer 23 was reached by both the depth and the intrusive resistance. Can be known.

The vertical load and the rotation speed are set / changed so that the rubble 15 is restrained from moving so that the rubble 15 can be reliably crushed when the high-pressure water 11 is injected.
Therefore, as the vertical load, an appropriate load may be set in advance according to the size of the rubble 15 constituting the rubble layer 23, or the weight of the steel pipe pile 1 may be used, or a load larger than that may be used. In that case, an additional weight may be used.
Further, regarding the rotation speed, the rotation speed may be zero, that is, the rotation may be stopped, and even when the rotation is performed, the rotation speed is usually slower than the rotation speed at the time of penetrating the rotation. However, when the rotation speed immediately before reaching the rubble layer 23 is slow, the high-pressure water 11 may be injected without changing the rotation speed.
The rotation for crushing rubble may be continuously rotated in the same direction, for example, 360 ° may be rotated, and then 360 ° may be rotated in the opposite direction and returned. Further, the rotation angle may be changed according to the position and number of the attached high-pressure water jet nozzles.

With the movement of the rubble 15 restricted, the high-pressure water 11 is injected from the high-pressure water jet nozzle 7 to crush the rubble 15. The example shown in FIG. 3B is an example in which the rubble stone 15 is crushed along the shape of the steel pipe pile 1 by injecting high-pressure water 11 while slowly rotating the steel pipe pile 1.
When the rubble layer 23 is thick, the steel pipe pile 1 is not rotated, and the rubble 15 is held down by the tip of the steel pipe pile 1, and high-pressure water 11 is sprayed to crack or crush the rubble 15. Then, the steel pipe pile 1 may be rotated and penetrated a little, and then the rotation may be stopped and the high-pressure water 11 may be injected repeatedly.

As described above, the injection direction of the high-pressure water 11 may be vertically downward, but by arranging the high-pressure water 11 toward the inside of the steel pipe pile 1, the pile is smoothly filled with rubble 15 or boulders. Placing is possible.
Further, a plurality of high-pressure water jet nozzles 7 may be attached to the outside of the tip of the steel pipe pile 1 so that the injection direction of the high-pressure water 11 is alternately directed to the inside and the outside of the steel pipe pile 1.

After passing through the rubble layer 23, the steel pipe pile 1 is returned to a rotation speed or the like suitable for rotational penetration and rotationally penetrates to the supporting ground (see FIG. 3C).
When the rotary penetration is completed, the high-pressure water jet nozzle 7 is removed from the tip of the pile and pulled up together with the supply pipe 13 to complete the construction.

As described above, according to the construction method of the steel pipe pile of the present embodiment, the rubble stone 15 can be suppressed so as not to move, and the rubble stone 15 can be reliably crushed. Workability can be improved. Further, by crushing the rubble 15, the steel pipe pile 1 can be driven in the vertical direction, and a stable foundation structure can be constructed.
The above description describes the construction of the steel pipe pile 1 on the ground with the rubble layer 23, but the same applies to the construction on the ground with the boulder layer.

When high-pressure water is used when passing through the rubble layer 23, the surrounding ground is disturbed by water pressure, so that the bearing capacity of the steel pipe pile 1 (supporting force = tip bearing capacity + friction between the pile and the ground surface). It is also possible that the force) becomes weaker.
To solve this problem, after driving piles to a predetermined depth, the material supplied to the high-pressure water jet nozzle 7 is switched from water to cement 25, and cement 25 is injected into the ground at the tip of the pile to improve the ground. As a result, the bearing capacity at the tip of the pile can be increased.
When injecting cement 25 into the ground at the tip of the pile, the cement 25 is injected while rotating the steel pipe pile 1 around the central axis of the pile to improve the ground, thereby improving the bearing capacity of the entire ground around the pile. Can be increased.

Further, the steel pipe pile 1 is driven to a predetermined depth (see FIGS. 4A to 4C), the material to be supplied to the high-pressure water jet nozzle 7 is switched from water to cement 25, and the cement 25 is placed on the ground at the tip of the pile. After the ground improvement is performed by injecting cement 25, the high-pressure water jet nozzle 7 may be removed from the tip of the steel pipe pile 1 and pulled up while the cement 25 is injected into the ground around the pile to improve the ground (. See FIG. 4 (d)).
As a result, the frictional force between the steel pipe pile 1 and the ground peripheral surface is increased, and the tip bearing capacity of the steel pipe pile 1 can be further increased.
Since the ground is basically disturbed only at the place where the high-pressure water 11 is sprayed, the cement 25 is sprayed on the ground around the pile and the high-pressure water 11 is sprayed in the section where the ground is improved. It may be only the section where the rubble layer 23 is present, for example, the section where the rubble layer 23 is present.

When it is expected that cement 25 will be injected into the ground at the tip of the pile or the peripheral surface of the pile to improve the ground, the ground can be improved over a wide area by enabling the injection from the high-pressure water jet nozzle 7 toward the outside of the pile. It becomes possible to do.

In the above description, the high-pressure water 11 is sprayed when passing through the rubble layer 23, but when the steel pipe pile 1 is driven into a hard layer such as a supporting ground in addition to the rubble layer 23 and the boulder layer, The high-pressure water 11 may be injected, and the present invention does not exclude this.

Further, as shown in FIG. 5, a cutting bit 27 may be arranged at the tip of the protective member 9, and in this way, the rubble and / or boulders may be crushed by the high-pressure water jet, and the tip of the steel pipe pile may be further arranged. The construction speed can be increased by cutting rubble and / or boulders with the cutting bit 27 arranged in the ground and press-fitting a steel pipe pile into the ground.
Further, as shown in FIG. 6, the cutting bit may be arranged so as to sandwich the tip of the high-pressure water jet nozzle 7, and may be a protective member-combined bit 29 that also serves as a protective member.
In this case, a cutting bit 27 may be provided at the tip of the steel pipe pile 1 in addition to the protection member combined bit 29.

A protective member 9 is provided to prevent the high-pressure water jet nozzle 7 from being damaged by contact with rubble, boulders, and earth and sand, but the tip of the high-pressure water jet nozzle 7 is provided to reduce the possibility of damage. It is conceivable that the injection port in the above is arranged above the tip of the protective member.
On the other hand, if the distance from the injection port of the high-pressure water jet nozzle 7 to the target becomes large, there is a concern that the crushing ability may decrease. Therefore, the relationship between the distance (SOD) from the injection port of the high-pressure water jet nozzle 7 to the target object and the crushing depth of the target object (concrete) was experimentally investigated. The graph showing the result is shown in FIG. 7, where the vertical axis shows the crushing depth (mm) and the horizontal axis shows the distance (mm) from the nozzle injection port to the target.

Note that FIG. 7 shows the results when the discharge pressure of the water jet is set to 200 MPa. If the discharge pressure changes, the crushing depth changes accordingly, but the relationship between the distance to the target (SOD) and the crushing depth of the target (concrete) is the same, and crushing up to a distance (SOD) of 100 mm. Ability tends to be maintained.
Further, even if the target is rubble or boulders, the energy transmitted by the water jet is the same as that of concrete, so it can be considered that the tendency is the same.
Therefore, from the above results, in order to maintain the crushing ability of rubble and boulders by the high-pressure water jet, as shown in FIG. 8, the tip of the steel pipe pile at the injection port of the high-pressure water jet nozzle 7 (the tip of the protective member 9). The distance L from the upper side to the upper side is preferably arranged so as to be located between L = 100 mm.
The lower limit of the distance to the target (SOD) is theoretically 0 (zero), but in reality, the steel pipe to be rotationally press-fitted may tilt slightly, so it is desirable to keep a distance of about 10 to 20 mm. ..

1 Steel pipe pile 3 Rotating press-fitting machine 5 Chucking part 7 High-pressure water jet nozzle 9 Protective member 11 High-pressure water 13 Supply piping 15 Scrap stone 17 Scrap stone mound 19 Revetment 21 Support layer 23 Scrap layer 25 Cement 27 Cutting bit 29 Protective member combined bit

Claims (8)

A method of constructing a steel pipe pile in which a steel pipe pile is driven into the ground having a rubble layer and / or a boulder layer by a rotary press-fitting machine.
When a high-pressure water jet nozzle capable of injecting high-pressure water having a water pressure of more than 50 MPa is provided on the outer peripheral portion of the tip of the steel pipe pile and the steel pipe pile is rotationally press-fitted.
Tip of the steel pipe pile, when reaching at least the rubble layer or boulder layer, the rotational speed that acting on the steel pipe pile from the rotary press fit machine to restrict the movement of rubble or boulder by the tip of the steel pipe pile The vertical load is set to the own weight of the steel pipe pile or a load larger than that, and the rubble or the boulder is suppressed so as not to move, and high-pressure water is injected from the high-pressure water jet nozzle. A method for constructing a steel pipe pile, which comprises a step of crushing the rubble or the boulder. The method for constructing a steel pipe pile according to claim 1, wherein high-pressure water mixed with an abrasive is injected. 1. Or the method for constructing a steel pipe pile according to 2. After driving the steel pipe pile to a predetermined depth, the injection material injected from the high-pressure water jet nozzle is switched from water to cement, and cement is injected into the ground at the tip of the pile to improve the ground. The method for constructing a steel pipe pile according to any one of Items 1 to 3. After the ground improvement of the pile tip ground is completed, the high-pressure water jet nozzle is removed from the outer periphery of the tip of the steel pipe pile, and the removed high-pressure water jet nozzle is pulled up along the outer peripheral surface of the steel pipe pile while cementing the pile peripheral surface ground. The method for constructing a steel pipe pile according to claim 4, wherein the ground is improved by injecting. The method for constructing a steel pipe pile according to any one of claims 1 to 5, wherein high-pressure water is sprayed diagonally downward inside the steel pipe pile. Any one of claims 1 to 5, wherein a plurality of the high-pressure water jet nozzles are arranged to inject high-pressure water diagonally downward inside the steel pipe pile and diagonally downward outside the steel pipe pile, respectively. Construction method of steel pipe pile described in the section. The construction of the steel pipe pile according to any one of claims 1 to 7, wherein the injection port of the high-pressure water jet nozzle is arranged so as to be located between the tip of the steel pipe pile and 100 mm above. Method.

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