JPH10298988A - Pile driver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pile driver, by which the pile driving force and noise can be controlled at the same time so that the driving force is large and noise is low, and especially the noise can be minimized. SOLUTION: A lower end part of a pile 2 is guided by a leading body 4, and the leading body 4 is driven by a hammer. A pile is subjected to the downward push-in force by the reaction of centrifugal or linear acceleration of an accelerator 11 giving vibrational acceleration. In the case of using an eccentric rotor, the rotational angular speed ω of the eccentric rotor 24 of the accelerator 11 is calculated from the centrifugal reaction, mass of a pile or the like and resistance from the ground, and the control is conducted in such a manner as to attain a value a little larger than the rotational angular speed ω, whereby the vibrational noise of the accelerator 11 can be minimized. In the case of using rectilinear or linear accelerator, the control is conducted to attain more suitable acceleration according to the variety of oil pressure difference and the change of switching frequency. The interaction between the accelerator and the pile generates no impact sound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an improvement of a double hammer pile driver. More particularly, the present invention relates to a pile driving machine in which a hammer is a drop type and an accelerator is a vibration type to prevent generation of noise.

[0002]

2. Description of the Related Art A pile driving foundation is used for driving a pile into the ground to support an upper load. Among the construction methods using ready-made piles in this pile driving foundation, there is a method in which a hole is formed by an earth auger or the like before pile driving. A free-fall hammer is used as a pile driver for driving a pile into the hole. The impact noise between the falling hammer and the top of the ready-made stake is particularly disliked in urban areas. For this reason, a pile driver that has prevented the generation of noise is known, and has demonstrated its effectiveness in ground improvement work in urban areas. Such a pile driver that suppresses noise generation is known as a double hammer type pile driver.

[0003] The principle of the double hammer type pile driver is described in Japanese Patent Application Laid-Open No. 61-10624, Japanese Utility Model Publication No. 6-21957, and the like. In this pile driving machine, the lower end of a prefabricated pile of a cylindrical body is supported by a support or a conductor, and the main hammer falls in the cylindrical body and drives the support in the hole, and at the same time, the secondary hammer falls. Then hit the upper end and drive the ready-made pile.

Since the hammer hits the support at a deep position in the ground, in such a pile driving machine, noise is generated in a cylindrical body which is a ready-made pile, and most of the noise is eliminated in the ready-made pile and in the ground. . If the support precedes, the force required to drive the ready-made pile itself, which sinks under its own weight in most cases, can be weak, so there is little noise as a whole, and such a pile driver is suitable for use in urban areas It is.

On the other hand, there is known an ultrahigh frequency pile driving machine for driving a pile by causing a small weight piston to vibrate at a high frequency by hydraulic pressure using a cylinder as a reaction force. In this device, the noise is small, but the driving energy given to the pile by the vibrating body is small. For this reason, there is a possibility that the construction period until the completion of the driving becomes long, or the time until the completion of the driving becomes indefinite depending on the hardness of the ground, and the construction schedule may be deviated.

[0006] There is a demand for a pile driving machine which can perform a pile driving with a large driving energy and reliably, and can minimize noise. That is, there is a demand for a pile driver that can shorten the construction period while minimizing noise.

[0007]

SUMMARY OF THE INVENTION The present invention has been made based on such a technical background, and achieves the following objects.

An object of the present invention is to provide a pile driving machine having a large driving force and low noise.

Another object of the present invention is to provide a pile driving machine which has a large driving force and low noise, and can simultaneously control the driving force and the noise.

It is still another object of the present invention to provide a pile driving machine which has a large driving force, a small noise, and simultaneously controls the driving force and the noise to minimize the noise.

Still another object of the present invention is to provide a low cost pile driving machine which has a large driving force, low noise and a simple apparatus.

Still another object of the present invention is to provide a pile driving machine that can reduce the cost of the apparatus by simplifying the above control.

[0013]

Means for Solving the Problems To solve the above-mentioned problems, the following means are adopted. In the pile driving machine according to the present invention, the tip conductor that guides the pile by driving the lower end of the pile in which the hollow hole is formed by driving the pile into the excavated pile driving hole is driven by a hammer. . The tip conductor need not support the pile. Since the pile is also supported by the frictional force from the side by the ground, a gap is formed between the lower end of the pile and the leading conductor. The tip conductor can also support the pile.

The upper end of the pile is accelerated downward by the accelerator. The accelerator acts on the top of the pile. The accelerator includes an accelerating body capable of giving an acceleration to the accelerator main body. Accelerators do not impact the pile. That is,
The accelerator gives the pile a continuous acceleration. The accelerator is an eccentric rotating body or a linear moving body that generates a centrifugal force. The rotating body is supported by the accelerator main body and rotates eccentrically to generate centrifugal force. This centrifugal force acts on the pile as a reaction. The linear moving body is a piston or a vibrating body integrated with the piston. The piston is, for example, a high-frequency pile driver that is vibratoryly accelerated by a periodic fluctuation of a fluid pressure difference between both sides of the cylinder into which the piston is inserted.

As the rotating body, a plurality of small rotating bodies are used to simplify the strengthening structure of the apparatus main body. Each time the centrifugal energy is absorbed by the pile, the plurality of bodies that rotate independently of each other resonate and become in phase. in this case,
Since there is no need to mechanically connect the two bodies, the apparatus system is simple and can be provided at low cost. A plurality of bodies may be rotated in the same phase by coaxial coupling or the like. For example, two units are used as a unit in which two rotators are coaxially connected, and two units are made independent,
Resonating these two units by spontaneous excitation can shorten the time until resonance and reduce the cost of the apparatus relatively.

Since the accelerator does not give impact energy to the pile, that is, since the accelerator and the pile are substantially always integrated, no impact noise is generated at the time of collision.

The hammer is suspended from the accelerator by a wire, a portion of the wire is pulled downward by a pulley, and the pulley is driven downward by a hydraulic cylinder. As a result, the large energy obtained by the free fall of the hammer is instantaneously transmitted to the leading conductor in an instant, and the power is used for full driving. When an impulsive sound is generated, the impulsive sound is generated deep in the ground and absorbed in the ground, and the noise is extremely small and leaks to the outside world.

On the other hand, since the eccentric rotary accelerator and the pile do not basically separate from each other, no impulsive sound is generated between them. The pile in the pile driving hole, which has already been expanded and maintained by driving the leading conductor, is driven with relatively low force, so that no vibration noise is generated.

The average rotational angular velocity ω of the rotating body is

[0020]

(Equation 2) It is controlled so that By controlling the angular velocity to a minimum value or a value slightly larger than the angular velocity that satisfies this equation, even if a vibration sound is generated, the vibration sound can be minimized. This control can be performed by electric power control to be supplied to the electric motor or hydraulic control to be supplied to the hydraulic motor, so that the control is easy and the cost of the apparatus can be reduced.

Regarding the acceleration body, whether it is a linear moving body or an eccentric rotating body, its acceleration can be easily controlled.
The fluid pressure differential on either side of the piston is easily variable, as is known in the art, and the centrifugal force is also easily changed by changing the angular velocity, also as is known in the art.

[0022]

According to the pile driver according to the present invention, the noise is minimized. Since it is easy to change the acceleration of the accelerator, minimization of the accelerator and reduction of the pile driving ability are irrelevant. Changing the acceleration of the accelerator has no effect on the generation of noise.

[0023]

Next, an embodiment of the present invention will be described. FIG. 1 shows a basic structure of a pile driver according to a first embodiment of the present invention. The pile driving hole 1 is already formed in the ground to be driven by an excavator (not shown). The pile driving hole 1 guides the driving of the pile 2. The pile 2 is a pipe, and a hollow hole 3 penetrates the pile 2 in the axial direction. Pile 2
It can be supported by the leading conductor 4.

The leading conductor 4 is guided into the pile driving hole 4 and is driven downward gradually. The outer diameter of the leading conductor 4 is designed to be slightly smaller than the bore 1 of the pile, but the size relationship between the outer diameter of the leading conductor 4 and the inner diameter of the bore 1 is not a significant problem. This is because the hole 1 in the pile is not a hole found in metal drilling, but is rough-cut by an earth auger and the wall surface of the hole collapses, so that the inner diameter of the hole cannot be strictly defined.

The leading conductor 4 has a bottom 5, which supports the pile 2. The leading conductor 4 has a cylindrical portion 6, and the outer cylindrical surface of the cylindrical portion 6 forms the outer diameter of the leading conductor 4. The pile 2 is driven into the hole whose diameter has been increased by driving the leading conductor 4, but a complete gap does not occur between the pile 2 and the hole 7 above the bore 1.

It is more appropriate to think that the expanding ground near the inner surface of the hole 7 is pressed against the pile 2 because it is in the ground.
The ground exerts such pressures P and P ′ on the pile 2. The pressure P ′ is a pressure exerted on an action point at a position lower than the action point on which the pressure P acts.

When the pile is driven, the hammer 8 reciprocates in the pile 2 with a vertical component. FIG. 1 shows a case where the hammer 8 freely falls in the vertical direction. The gravity of the accelerator body 9 acts on the upper end of the pile 2. The accelerator 11 includes an accelerator main body 9 and a vibration motor 21. A winch 13 is fixedly provided on the accelerator body 9.

The winch 13 can be provided so as not to be directly fixed to the accelerator body 9 but to be relatively integrated with the accelerator body 9. The wire 14 having one end fixed to the winch 13 has the other end fixed to the hammer 8 via a group of pulleys. The group of pulleys includes a moving pulley 15 that can move vertically with respect to the main casing 2 substantially vertically below the winch 13.

The moving pulley 15 is rotatably supported on the upper end of the piston rod 17 of the hydraulic cylinder device 16. The moving pulley 15 is driven downward. A part of the wire 14 is pulled downward by the moving pulley 15. Movable pulley 15
Is received by the hydraulic cylinder device 16 in a downward driving force, and is pulled up by an upward tension of a part of the wire 14.

A fixed pulley 18 is fixedly provided on the accelerator body 9. The hammer 8 is suspended from the winch 13 by a wire 14 via a moving pulley 15 and a fixed pulley 18. The accelerator body 9 has a passage hole 19 through which the wire 14 passes. A chuck mechanism (not shown) for holding the pile 2 is not necessary in principle between the accelerator main body 9 and the pile 2 mounted on the pile 2, but a chuck mechanism is provided for safety. It is desirable.

The accelerator body 9 can be suspended by a suspension wire (not shown), and is supported by a leader (not shown) supported by a self-propelled vehicle so as to descend naturally. During the pile driving operation, the accelerator body 9 is placed in a state where it can fall naturally.

The accelerator 11 is fixedly provided at the upper end of the accelerator main body 9. As the accelerator 11, a commonly used vibration motor 21 is used. 1 of vibration motor 21
As shown in FIG. 2, the set includes an electric motor 22 and an eccentric rotator 24 attached to an output shaft 23 of the electric motor.

One set of vibration motors 21 includes one motor 2
2 and two eccentric rotating bodies 24 arranged symmetrically and coaxially with the electric motor 22 as a center position. The two eccentric rotating bodies 24 rotate in the same phase. Another set of vibration motors 21 is the same in structure and size as the other sets.

The two sets of vibration motors 21 are arranged symmetrically with respect to the vertical plane S (FIG. 1) including the portion of the wire 14 in the stake 2 for suspending the hammer 8. The eccentric rotors of the two sets of vibration motors 21 need not be constrained to be in the same phase. In other words, two sets of vibration motors 2
Synchronization of the two motors is not required.

At the start of the driving work, the accelerator 9 is mounted on the pile 2
It is placed on. It is not necessary to fix the pile 2 and the accelerator body 9. The hydraulic pulley 15 is operated by operating the hydraulic cylinder device 16.
Is driven downward. The drawing length of the wire 14 is adjusted by rotating the winch 13. The hydraulic cylinder device 1 is a hydraulic circuit (not shown) for driving the hydraulic cylinder device 16.
6. Free circulation circuit including 6.

That is, the valve in the circulation circuit is operated to make the circulation circuit free from the hydraulic pressure source. Ignore this because the resistance of the hydraulic circuit is substantially close to zero. By this operation, the hammer 8 falls freely. The free fall distance is twice as long as the movable pulley 15 is driven and descended.
The hammer 8 strikes the leading conductor 4 with an impact. The tip conductor 4 previously inserted into the pile inner hole 1 is driven downward in the pile inner hole 1 by an undefined distance while the inner surface of the pile inner hole 1 is slightly broken by this impact.

By repeating this impact, the tip conductor 4 gradually enters the ground. Since the impact sound is silenced in the pile 2 serving as a silencer and is dispersed in the air in a small amount, it still propagates into the air through the pile 2 with a low penetration degree.
At first, the hammer 8 is made to have a shorter falling distance.

On the other hand, the two motors 2 of the vibration motor 21
2 are driven independently. The two eccentric rotators 24 driven to rotate by one electric motor 22 rotate in the same phase. The two eccentric rotators 24 driven by the other motor 22 also rotate in the same phase.

Even if the eccentric rotating bodies 24 of the two sets of vibration motors 21 do not initially have the same phase, they gradually resonate each time the eccentric rotation energy is lost, and eventually rotate in the same phase. Become. The reaction of the centrifugal force generated by the accelerator 11 is transmitted to the upper end of the pile 2 via the accelerator body 9. The centrifugal force is expressed by the following equation when the two sets of vibration motors 21 are in a resonance state.

[0040]

(Equation 3) Here, the right side is the maximum value of the total centrifugal force added for the subscript n. In this embodiment, the mass m, the effective radius of rotation r, and the rotational angular velocity ω of each one eccentric rotator are:
Equal, regardless of the value of the subscript n. The overall centrifugal force, or left side, that appears substantially is represented by the left side and is n times the average effective centrifugal force.

This centrifugal force acts on the pile 2 downward.
The gravitational force M1g of the mass M1 of all objects placed on the stake 2 such as the accelerator 11, the accelerator body 9, and the hydraulic cylinder device 16 and the gravitational force M2g of the mass M2 of the stake 2 act on the stake 2 downward. . g is the gravitational acceleration. The stress in the ground acts on the cylindrical outer surface of the pile 2 in the horizontal direction as pressure.

The pressure is a complex function of the depth from the ground, but per unit length (in the case of multiplying the circumferential length per unit area) by dividing the integral value by the length of the penetrated stake 2 Is represented by P. When the coefficient of friction between the surface of the pile 2 and the soil constituent material is represented by μ, the resistance represented by μμLP acts on the pile 2 upward. L indicates the entry length of the pile 2. When the pile 2 is floating from the leading conductor 4 and the pile 2 does not sink, the balance of the force is expressed by the following equation.

[0043]

(Equation 4) From now on, when ω is calculated,

[0044]

(Equation 5) The accelerator 11 is controlled so as to have a value slightly larger than the rotational angular velocity thus obtained. The centrifugal acceleration that allows the pile 2 to sink down smoothly with minimum energy can be generated by the control of the accelerator 11. Thus, the pile 2 sinks following the sinking of the leading conductor 4.

The other piles 2 are sequentially connected to the upper end of the lower pile 2. The hardness of the ground changes with the depth. Corresponding to the hardness, the angular velocity ω of the eccentric rotating body of the accelerator 11
Control the increase or decrease of This control properly sets the minimum energy required for settling. Generation of vibration noise can be minimized and minimized. Since the pile 2 and the accelerator main body 9 are basically the same body, no impact sound is generated between the pile 2 and the accelerator main body 9.

A linear reciprocating body can be used as the accelerator. Since this linear reciprocating body is shown in detail in the above-mentioned Japanese Patent No. 2527674, the detailed description will not be repeated in this specification. The reciprocating body or vibrating body that is linearly accelerated is a so-called piston, and is vibratedly accelerated by a periodic fluctuation of a fluid pressure difference on both sides, for example, a hydraulic pressure difference.

Since such acceleration is continuous, no impact energy is given to the pile. The pulsation of the oil pressure difference can be easily generated by a well-known conventional technique. That is, the hydraulic pressure distribution can be easily performed by alternately switching and connecting the supply-side oil passage and the return-side oil passage that respectively communicate with the cylinder chambers on both sides of the piston. The frequency of the switching can be easily changed by changing the rotation angular velocity of the valve body which is the rotating body. The rotation speed control of the rotating body can be easily performed by using a servomotor.

[Brief description of the drawings]

FIG. 1 is a front sectional view showing the principle configuration of Embodiment 1 of a pile driver according to the present invention.

FIG. 2 is a side view showing the accelerator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Pile driving hole 2 ... Pile 3 ... Hollow hole 4 ... Lead conductor 5 ... Bottom 8 ... Hammer 9 ... Accelerator body 11 ... Accelerator 15 ... Moving pulley 16 ... Hydraulic cylinder 21 ... Vibration motor 22 ... Electric motor 24 ... Eccentric rotation body

Claims (10)

[Claims] The present invention is characterized in that a vertical component is formed by driving a stake ahead of a lower end of a pile having a hollow hole formed therein by driving the stake and leading a conductor to be driven into the pile driving hole. A hammer that reciprocates with an accelerator, and an accelerator that acts on the upper end of the pile with a vertically downward component, wherein the accelerator has an accelerator body, and a vertical component with respect to the accelerator body. A pile driver consisting of an accelerating body that can be given an acceleration for reciprocating motion. 2. The apparatus according to claim 1, wherein the hammer is suspended from the accelerator by a wire, a portion of the wire is pulled downward by a pulley, and the pulley is driven downward by a hydraulic cylinder. Characteristic pile driver. 3. The pile driver according to claim 1, wherein the accelerator is a vibrator that is linearly accelerated in a vertical direction. 4. The pile driver according to claim 1, wherein the accelerator is a rotating body that generates a centrifugal force on the accelerator body. 5. The pile driver according to claim 4, wherein a plurality of rotating bodies are provided. 6. The pile driver according to claim 5, wherein drive sources for driving at least two of the plurality of bodies are independent of each other. 7. The pile driving machine according to claim 6, wherein a single drive source drives at least two of the plurality of bodies. 8. The method according to claim 4, wherein the average rotational angular velocity ω of the rotating body is represented by the following equation: Pile driver characterized by satisfying the following. 9. The pile driver according to claim 8, wherein the average rotational angular velocity ω is controlled to be a minimum value that satisfies the expression or a value close to the minimum value. 10. The pile driving machine according to claim 3, wherein said vibrating body moves by alternately switching fluid pressures on both sides thereof.