JP2020037857A - Construction method of steel pipe pile - Google Patents

Abstract

To provide a construction method of a steel pipe pile which can enhance construction performance to the ground having a riprap layer or a boulder layer.SOLUTION: This steel pipe pile driving method for driving a steel pipe pile 1 into the ground having a riprap layer and/or a boulder layer by using a vibration pile driving machine 3 comprises a process for arranging a high-pressure water jet nozzle 7 which can inject high-pressure water 11 having water pressure exceeding 50 MPa at a tip external peripheral part of the steel pipe pile 1, stopping vibration pressure-insertion when the steel pipe pile arrives at least at the riprap 15 layer or the boulder layer at the vibration pressure-insertion of the steel pipe pile 1, imparting a preset vertical load suitable for regulating the movement of ripraps 15 or boulders by a tip of the steel pipe pile 1, and crushing the ripraps 15 or the boulders by injecting the high-pressure water 11 from the high-pressure water jet nozzle 7.SELECTED DRAWING: Figure 1

Description

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

Methods for placing steel pipe piles include a hitting method, a vibration method, and a press-fitting method.
However, in the ground having a rubble layer or a boulder layer, there is a high risk of damaging the pile due to high penetration resistance, and rubble and boulder rocks receiving the force from the pile move and the vertical force is applied. Is not transmitted well, and it becomes difficult to cast in any of the methods.

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 using an advance drilling method using an earth auger, replacing the part with sand, and driving a pile again. Has been taken.
As another method, Patent Literature 1 proposes a method of improving the driving performance by attaching wear-resistant steel to the tip of a pile.

Japanese Patent No. 3735225

  The advance drilling method using the earth auger requires equipment for advance drilling, excavated rubble, and soil transportation, which increases construction space and cost. , There is a problem that the construction period becomes longer.

  In addition, in Patent Document 1, although the durability of the pile itself at the time of driving is improved by attaching wear-resistant steel to the tip of the pile, rubble and boulders receiving the force from the pile move and the vertical force is applied. The problem of not being transmitted well has not been solved. Therefore, construction becomes difficult especially in the case where the rubble layer is on the surface, such as the rubble mound used for the foundation of the harbor structure and the solidification.

  The present invention has been made in order to solve such a problem, and an object of the present invention is to provide a method of constructing a steel pipe pile capable of improving the 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 placing a steel pipe pile on a ground having a rubble layer and / or a boulder layer by a vibration pile driving machine,
A high-pressure water jet nozzle capable of injecting high-pressure water having a water pressure of more than 50 MPa is disposed on the outer periphery of the tip of the steel pipe pile, and when the steel pipe pile is subjected to vibration press-fitting,
When the tip of the steel pipe pile reaches at least the rubble layer or the boulder layer, vibration press-fitting is stopped, and a preset vertical load suitable for restricting the movement of rubble or the boulder by the tip of the steel pipe pile is applied. The method further comprises a step of crushing the rubble or the boulders by applying high-pressure water from the high-pressure water jet nozzle to the tip of the steel pipe pile.

(2) Further, in the apparatus according to the above (1), high-pressure water mixed with an abrasive is injected.

(3) Further, in the above-mentioned (1) or (2), after the steel pipe pile is driven to a predetermined depth, the injection material injected from the high-pressure water jet nozzle is switched from water to cement, It is characterized in that cement is injected into the pile tip ground to improve the ground.

(4) In the above-mentioned (3), 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 connected to the steel pipe pile. The cement is injected into the ground surrounding the pile while raising along the outer peripheral surface of the pile to improve the ground.

(5) Further, in the above-mentioned (1) to (4), high-pressure water is injected obliquely downward inside the steel pipe pile.

(6) Further, in the above-mentioned (1) to (4), a plurality of the high-pressure water jet nozzles are disposed so as to be directed diagonally downward inside the steel pipe pile and diagonally downward outside the steel pipe pile. It is characterized by injecting high-pressure water.

(7) Further, in the above-mentioned (1) to (6), the injection port of the high-pressure water jet nozzle is arranged to be located at a distance of up to 100 mm from the tip of the steel pipe pile. Things.

In the present invention, a high-pressure water jet nozzle capable of injecting high-pressure water with a water pressure of more than 50 MPa is disposed on the outer periphery of the tip of the steel pipe pile, and when the steel pipe pile is subjected to vibration press-fitting,
At least when reaching the rubble layer or the boulder layer, the vibration press-fitting is stopped, and a vertical load suitable for restricting the movement of the rubble or the boulder is given by the tip of the steel pipe pile, and the high-pressure water is applied. By providing the step of crushing the rubble or boulder by jetting high-pressure water from a jet nozzle, the rubble or boulder can be suppressed so as not to move, and the rubble or boulder can be reliably crushed. The workability on the ground having the rubble layer or the boulder layer can be improved. Further, by reliably crushing the rubble or the boulder, 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 | summary of the apparatus used for the construction method of the steel pipe pile of embodiment. It is an explanatory view of an example of the ground used as a construction object 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 the other aspect of the steel pipe pile which concerns on embodiment. It is a graph which shows the examination result of arrangement of the injection mouth of the high pressure water jet nozzle concerning an embodiment. It is explanatory drawing explaining the arrangement | positioning of the injection opening of the high pressure water jet nozzle used for the construction method of the steel pipe pile of embodiment. FIG. 6A is an AA view of FIG. 6B.

Prior to the description of the method for constructing a steel pipe pile according to the present embodiment, equipment used for the method for constructing a steel pipe pile will be outlined.
As shown in FIG. 1, the vibration pile driving machine 3 used for press-fitting the steel pipe pile 1 is attached to the upper part of the steel pipe pile 1 via the chucking portion 5 to apply vibration to the steel pipe pile 1 and to pile the pile. The steel pipe pile 1 is penetrated into the ground by reducing peripheral frictional force and tip resistance.

As shown in FIG. 1, a high-pressure water jet nozzle 7 is provided on the outer periphery of the tip of the steel pipe pile 1.
The high-pressure water jet nozzle 7 is capable of jetting high-pressure water having a water pressure of more than 50 MPa (for example, more than 50 MPa and 300 MPa or less), and is detachably provided on the outer periphery of the tip of the steel pipe pile 1. In the present embodiment, four high-pressure water jet nozzles 7 are provided at positions 90 ° apart on the outer periphery of the steel pipe pile 1.

  In order to prevent the high-pressure water jet nozzle 7 from being damaged during the press-fitting of the steel pipe pile 1, a cylindrical protection member 9 is provided at the tip of the steel pipe pile 1. Avoid contact with

The number of high-pressure water jet nozzles 7 to be arranged is not limited to four, and may be one or two if the pile diameter is small, for example. Further, three or four or more may be discretely arranged.
Further, as will be described later, when the high-pressure water jet nozzle 7 injects the high-pressure water 11, the vibration is stopped. Therefore, when the number of the high-pressure water jet nozzles 7 is smaller than the pile diameter, After injecting the water 11, the steel pipe pile 1 may be slightly rotated to inject the high-pressure water 11.

  With respect to the direction in which the high-pressure water 11 is ejected from the high-pressure water jet nozzle 7, the high-pressure water 11 may be ejected vertically downward, or may be ejected toward the inside of the steel pipe pile 1. By injecting inward, the pile can be smoothly driven without rubble or boulder clogging the inside of the steel pipe pile 1. However, it is desirable that the blowing angle θ of the high-pressure water 11 be 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 direction of the high-pressure water 11 may be alternately between the inside and the outside.
However, when the injection directions of the high-pressure water jets directed alternately between the inside and the outside are largely different, the rubble or the boulders are not sufficiently crushed, and it becomes difficult to rotationally press-fit the steel pipe piles. On the other hand, if the difference in the jet direction of the high-pressure water jets directed alternately between the inside and the outside is small, the crushed portions of the rubble or the boulders overlap, resulting in inefficient construction. Therefore, it is desirable that the angle difference between the inside and outside of the high pressure water jet in the injection direction with respect to the radial direction of the steel pipe pile be within 10 ° to 30 °.

As will be described later, in the construction method of the present invention, a mode in which the material supplied to the high-pressure water jet nozzle 7 is switched from water to cement 25 and the ground is improved by injecting the cement 25 (see FIG. 4D). It is conceivable that, in such an embodiment, a high-pressure water jet nozzle 7 that jets outward is preferable because ground improvement can be performed over a wide range.
As the direction of the high-pressure water jetting, three modes, that is, vertically downward, inside of the steel pipe pile, and outside of the steel pipe pile are considered, but any one of these three directions, any two directions, or three directions All directions may be used.

The high-pressure water jet nozzle 7 is connected to a supply pipe 13 for supplying jet water.
Normally, water is supplied from the supply pipe 13, but an abrasive may be mixed into the water in order to increase the cutting force of the rubble 15 and the boulders.
Silica sand can be used as the abrasive, but other materials such as steel slag, steel grit, fused alumina, and garnet can also be used.
In addition, as the abrasive, the hardness of abrasive particles 300-2000 (HK, Knoop hardness), D50 (specified by JIS Z 8815, a sieving test method to measure the particle size distribution of powdery substances) The particle size at which the cumulative frequency of the powdery substance becomes 50%) A material having a particle size of 200 μm to 1000 μm is preferable.

  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 collecting after the steel pipe pile 1 is constructed. For example, the high-pressure water jet nozzle 7 may be temporarily attached to the protection member 9 by a lock pin or spot welding, and after construction, the water jet hose may be pulled off from the ground by pulling a water jet hose from the ground. Good.

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

A method for constructing a steel pipe pile according to the present embodiment will be described with reference to FIG.
When the steel pipe pile 1 is subjected to vibration press-fitting, when the tip of the steel pipe pile 1 reaches the rubble layer 23, the vibration of the vibration pile driving machine 3 is stopped, and the movement of the rubble 15 is regulated by the tip of the steel pipe pile 1. Set an appropriate preset vertical load. Then, the vertical load is applied to the rubble layer and / or the boulder layer from the tip of the steel pipe pile 1.
Whether or not the tip of the steel pipe pile 1 has reached the rubble layer 23 can be known from an increase in the penetration resistance of the pile. In addition, if the depth of the rubble layer 23 is known in advance by a preliminary survey conducted prior to the installation of the steel pipe pile, the rubble layer 23 was reached by both the depth and the penetration resistance. You can know.

The setting of the vertical load and the application of the vertical load to the rubble layer and / or the boulder layer suppresses the rubble 15 from moving so that when the high-pressure water 11 is injected, the rubble 15 can be crushed reliably. That's why.
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, and may be the own weight of the steel pipe pile 1 or a load larger than that. In that case, an additional weight may be used.

With the movement of the rubble 15 regulated, the high-pressure water jet nozzle 7 injects the high-pressure water 11 to crush the rubble 15 (see FIG. 3A). When the number of high-pressure water jet nozzles 7 is small, it is possible to crush the rubble 15 over the entire circumference along the tip of the steel pipe pile 1 by slightly rotating the steel pipe pile 1 and injecting the high-pressure water 11. it can. In addition, even if the rubble 15 is not completely crushed by the high-pressure water 11, a crack that can be broken by vibration press-fitting may be formed.
When the rubble 15 is crushed or cracked by the high-pressure water 11, the vibration of the vibrating pile driving machine 3 is restarted, and the rubble layer 23 is subjected to vibration press-fitting (see FIG. 3B). When the press-fitting is performed to some extent, the vibration of the vibrating pile driving machine 3 is stopped again, and the high-pressure water 11 is injected by pressing the rubble 15 by applying the above-described preset vertical load (see FIG. 3C). Such an operation is repeated until the rubble layer 23 is passed.

As described above, the injection direction of the high-pressure water 11 may be vertically downward, but by arranging it toward the inside of the steel pipe pile 1, the pile is not clogged with the rubble 15 or the boulder, so that the pile is smooth. Casting becomes possible.
Further, a plurality of high-pressure water jet nozzles 7 may be attached to the outer side of the tip of the steel pipe pile 1 so that the high-pressure water 11 is jetted in a direction of alternating between the inside and the outside of the steel pipe pile 1.

After passing through the rubble layer 23, the vibration of the vibratory pile driving machine 3 is restarted, and the pile penetrates into the supporting ground (see FIG. 3D).
When the vibration press-fitting is completed, the high-pressure water jet nozzle 7 is removed from the tip of the pile, pulled up together with the supply pipe 13, and the construction is completed.

As described above, according to the steel pipe pile construction method of the present embodiment, the rubble 15 can be suppressed so as not to move, and the rubble 15 can be reliably crushed. Workability can be improved. In addition, 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.
Although the above description has described the construction of the steel pipe pile 1 on the ground with the rubble layer 23, the same applies to the construction on the ground with the boulder layer.

When the high pressure water 11 is used when passing through the rubble layer 23, the surrounding ground is disturbed by the water pressure, so that the supporting force of the steel pipe pile 1 (supporting force = tip supporting force + pile and ground peripheral surface) (Frictional force) may be weakened.
To solve this problem, after the pile is driven to a predetermined depth, the material supplied to the high-pressure water jet nozzle 7 is switched from water to cement 25, and the cement 25 is injected into the pile tip ground to improve the ground. Thereby, the tip supporting force of the pile can be increased.
When the cement 25 is injected into the pile tip ground, the cement 25 is injected while rotating the steel pipe pile 1 around the center axis of the pile to improve the ground, thereby supporting the entire ground around the steel pipe pile 1. Performance can be increased.

Further, the steel pipe pile 1 is driven to a predetermined depth (see FIGS. 4A to 4C), and the material supplied to the high-pressure water jet nozzle 7 is switched from water to cement 25, and the cement 25 is placed on the pile tip ground. After the soil is improved by injecting the cement, the high-pressure water jet nozzle 7 may be removed from the tip of the steel pipe pile 1 and the soil may be improved by injecting the cement 25 into the pile surrounding ground while raising the pile (FIG. FIG. 4D).
Thereby, the frictional force between the steel pipe pile 1 and the peripheral surface of the ground increases, and the tip supporting force of the steel pipe pile 1 can be further increased.
In addition, since the disturbance of the ground occurs basically only at the location where the high-pressure water 11 is sprayed, the section where the cement 25 is sprayed on the pile surrounding ground and the ground is improved is sprayed with the high-pressure water 11. For example, only the section with the rubble layer 23 may be used.

  When it is expected that the cement will be improved by injecting the cement 25 to the pile tip ground or the pile peripheral surface, the high-pressure water jet nozzle 7 can be sprayed toward the outside of the pile to improve the ground in a wide range. It is possible to do.

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

A protection member 9 is provided to prevent damage to the high-pressure water jet nozzle 7 due to contact with rubble, boulders, earth and sand, but at the tip of the high-pressure water jet nozzle 7 to reduce the possibility of damage. It is conceivable to arrange a certain injection port at a position higher than the tip of the protection member 9.
On the other hand, when the distance from the injection port of the high-pressure water jet nozzle 7 to the target increases, 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 and the crushing depth of the target (concrete) was experimentally examined. FIG. 5 is a graph showing the results, in which the vertical axis represents the crushing depth (mm) and the horizontal axis represents the distance (mm) from the nozzle orifice to the target.
As shown in FIG. 5, the crushing ability is maintained up to a distance (SOD) of 100 mm, while the crushing ability is significantly reduced at a distance (SOD) of 150 mm or more.

FIG. 5 shows the results when the discharge pressure of the water jet was 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 a boulder, the transmitted energy by the water jet is not different from that of concrete, so it may be considered to have the same tendency.
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. 6, the tip of the steel pipe pile at the injection port of the high-pressure water jet nozzle 7 (the tip of the protection member 9). It is preferable that the distance L from the upper side be located between L and 100 mm.
Although the lower limit of the distance to the target (SOD) is theoretically 0 (zero), the steel pipe to be press-fitted in rotation may be slightly inclined. desirable.

DESCRIPTION OF SYMBOLS 1 Steel pipe pile 3 Vibration pile driving machine 5 Chucking part 7 High-pressure water jet nozzle 9 Protective member 11 High-pressure water 13 Supply pipe 15 Rabbits 17 Ripstone mound 19 Seawall 21 Support layer 23 Ripstone layer 25 Cement

Claims (7)

A method for constructing a steel pipe pile in which a steel pile is driven by a vibrating pile driving machine on a ground having a rubble layer and / or a boulder layer,
A high-pressure water jet nozzle capable of injecting high-pressure water having a water pressure of more than 50 MPa is disposed on the outer periphery of the tip of the steel pipe pile, and when the steel pipe pile is subjected to vibration press-fitting,
When the tip of the steel pipe pile reaches at least the rubble layer or the boulder layer, the vibration press-fitting is stopped, and a preset vertical load suitable for restricting the movement of the rubble or the boulder by the tip of the steel pipe pile is applied. A method for constructing a steel pipe pile, comprising a step of applying high-pressure water from the high-pressure water jet nozzle to crush the rubble or the boulders, while applying the steel pipe pile to the steel pipe pile.   The method for constructing a steel pipe pile according to claim 1, wherein high-pressure water mixed with an abrasive is injected.   After the steel pipe pile is driven to a predetermined depth, the injection material injected from the high-pressure water jet nozzle is switched from water to cement, and the soil is improved by injecting cement into the pile tip ground. Item 3. The method for constructing a steel pipe pile according to item 1 or 2.   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 pulled up along the outer peripheral surface of the steel pipe pile, while cementing the pile peripheral ground. The method for constructing a steel pipe pile according to claim 3, wherein the soil is improved by injecting the soil.   The method for constructing a steel pipe pile according to any one of claims 1 to 4, wherein high-pressure water is injected obliquely downward inside the steel pipe pile.   The plurality of high-pressure water jet nozzles are arranged, and high-pressure water is jetted diagonally downward inside the steel pipe pile and diagonally downward outside the steel pipe pile, respectively. Construction method of the steel pipe pile described in the paragraph.   The method for constructing a steel pipe pile according to any one of claims 1 to 6, wherein the injection port of the high-pressure water jet nozzle is located between the tip of the steel pipe pile and 100 mm upward.