JPS6323331B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an apparatus for applying vibration to a pile using a vibrator and driving the pile into the soil.

[Conventional technology]

Conventionally, there is a pile driving device that utilizes vibration in the axial direction of a pile, that is, longitudinal vibration.

In contrast, a device has been proposed that drives a pile using vibration in a direction perpendicular to the axis of the pile, that is, lateral vibration.

FIG. 1 is a diagram showing a pile driving device that uses lateral vibration. In this pile driving device, a vibrator 2 that rotates an eccentric shaft to generate lateral vibration is placed near the tip inside a hollow pile 1, and the vibrator 2 applies lateral vibration to the pile 1. The axis of the pile 1 is caused to revolve, and the pile 1 is made to sink. In this case, the soil reaction force that resists the sinking of the pile 1 is generally thought to include a tip resistance force acting on the tip of the pile 1 and a frictional resistance force acting on the side surface of the pile 1. By applying lateral vibration to pile 1, soil can be removed at the tip of pile 1, and a predetermined gap can be formed between pile 1 and the soil on its side, which reduces tip resistance and frictional resistance. can reduce the force,
It is possible to sink the pile 1 using a small force other than the lateral vibration force such as the own weight of the pile 1 or a pressing force.

[Problem that the invention seeks to solve]

By the way, Figure 2 shows the condition of pile 1 when the pile 1 is driven into the soil by applying lateral vibration to the pile 1 using the vibrator 2.
2 is a graph showing the relationship between the vibration acceleration α at the tip of the pile 1 and the penetration speed v of the pile 1. As is clear from this graph, the larger the vibration acceleration α, the more the penetration speed v
becomes larger, and the penetration efficiency of the pile 1 improves.

Further, FIG. 3 is a graph showing the relationship between the penetration depth d of the pile 1 and the vibration acceleration α when the pile 1 is driven into the soil while keeping the excitation force of the vibrator 2 constant. As is clear from this graph, when the excitation force of the vibrator 2 is kept constant, when the penetration depth d is small, the vibration acceleration α is large, and as the penetration depth d becomes large, the vibration acceleration α is small. Become,
The vibration acceleration α gradually approaches a constant value. This is expressed as the vibration acceleration α = aω ² , where a is the amplitude of the vibration of the pile 1 and ω is the rotational angular velocity of the vibration of the pile 1, and when the excitation force of the vibrator 2 is kept constant. When the penetration depth d is small, the resistance force of the soil is small, so the amplitude a becomes large, and as the penetration depth d becomes large, the resistance force of the soil becomes large, so the amplitude a becomes small, and the penetration As the depth d increases, the resistance force of the soil approaches a constant value, and the amplitude a
This is because the value approaches a constant value.

Furthermore, when driving the pile 1 into the soil by applying lateral vibration to the pile 1 using the vibrator 2, the ground vibration generated in the surrounding ground due to the pile driving is greater than when driving the pile with a conventional vibrohammer. Although it is small, ground vibration still occurs. Figure 4 is a graph showing the relationship between the vibration acceleration α and the magnitude S of the ground vibration generated in the surrounding ground when the pile 1 is driven into the soil by applying lateral vibration to the pile 1 using the vibrator 2. be. As is clear from this graph, as the vibration acceleration α increases, the magnitude S of the ground vibration increases.

Therefore, by keeping the excitation force of the vibrator 2 constant,
When driving the pile 1 into the soil, at the start of driving, that is, when the penetration depth d is small, the vibration acceleration α becomes large, so while the penetration speed v is large, the magnitude of ground vibration S becomes large; As the depth d increases, the vibration acceleration α decreases, so the magnitude S of the ground vibration decreases, while the penetration speed v decreases. Therefore, in order to reduce the magnitude S of ground vibration when the penetration depth d is small, if the excitation force of the vibration exciter 2 is set small, the vibration acceleration α when the penetration depth d is large will be reduced. Therefore, the penetration speed v becomes small.On the other hand, if the excitation force of the vibrator 2 is set large in order to increase the penetration speed v when the penetration depth d is large, the penetration speed v becomes small when the penetration depth d is small. Since the vibration acceleration α increases, the magnitude S of ground vibration increases. In this way, in the case of pile driving using lateral vibration, there is a contradiction between the penetration speed v and the magnitude S of ground vibration.

This invention was made to solve the above-mentioned problems, and when the penetration depth d is small, the magnitude S of ground vibration does not increase, and when the penetration depth d is large, the It is an object of the present invention to provide a pile driving device in which the speed v does not become small.

[Means for solving problems]

In order to achieve this object, the present invention provides a device for driving the pile into the soil by applying vibration to the pile using a vibrator, in which the vibrator applies vibration in a direction perpendicular to the axis of the pile. using
a vibration accelerometer that detects vibration acceleration at the tip of the pile; a comparator that calculates a comparison value between the detected value of the vibration accelerometer and a preset target value of vibration acceleration; means for changing the excitation force of the vibrator to maintain the vibration acceleration at a constant value.

[Effect]

In this pile driving device, the vibration acceleration is controlled to a constant value, so when the penetration depth d is small, the amplitude a becomes large, and the detected value of the vibration accelerometer becomes larger than the target value, so the vibration exciter When the excitation force becomes small and the penetration depth d is large, the amplitude a becomes small, so the detected value of the vibration accelerometer becomes smaller than the target value, so the excitation force of the vibrator increases, and the vibration acceleration is maintained at a constant value, that is, at the target value.

〔Example〕

FIG. 5 is a diagram showing a piling device according to the present invention. In the figure, 3 is an eccentric shaft of the vibrator 2, 4 is a fixed part of the vibrator 2, and 5 is a hydraulic motor of the vibrator 2. The hydraulic motor 5 rotates the eccentric shaft 3.
6 is a hydraulic hose connected to the hydraulic motor 5; 7 is a hydraulic source that supplies pressure oil to the hydraulic motor 5 via the hydraulic hose 6; 8 is an electromagnetic flow rate provided between the hydraulic source 7 and the hydraulic motor 5. The flow control valve 8 controls the amount of pressurized oil supplied from the hydraulic source 7 to the hydraulic motor 5 . 9 is a vibration accelerometer attached to the vibrator 2; 10 is a comparator to which a target value α _p of vibration acceleration is set; 11 is a cord connecting the comparator 10 and the vibration accelerometer 9; calculates the comparison value between the detected value of the vibration accelerometer 9, that is, the vibration acceleration α, and the target value α _p . Reference numeral 12 denotes an amplifier that amplifies the output signal of the comparator 10, and the flow rate control valve 8 is controlled by the output signal of the amplifier 12. 13 is a relief valve provided between two pipes connected to the hydraulic motor 5.

In this piling device, a vibration accelerometer 9 detects a vibration acceleration α, a comparator 10 calculates a comparison value between the vibration acceleration α and a target value α _p , and an amplifier 12 controls a flow control valve 8 according to the comparison value. Therefore, when the vibration acceleration α is larger than the target value α _p , the amount of pressure oil supplied from the hydraulic source 7 to the hydraulic motor 5 decreases in accordance with the comparison value, so the rotation speed of the hydraulic motor 5 decreases. As the rotation speed of the eccentric shaft 3 decreases, the excitation force of the vibrator 2, which is proportional to the square of the rotation speed of the eccentric shaft 3, decreases, and when the vibration acceleration α is smaller than the target value α _p , Since the amount of pressure oil supplied from the hydraulic source 7 to the hydraulic motor 5 increases according to the comparison value, the rotation speed of the hydraulic motor 5 increases, and the rotation speed of the eccentric shaft 3 increases, so that the vibration exciter 2 The excitation force increases. As a result, when the vibration acceleration α is larger than the target value α _p , the rotational speed of the eccentric shaft 3 decreases, so that
When the rotational angular velocity ω decreases and the vibration acceleration α is smaller than the target value α _p , the rotational speed of the eccentric shaft 3 increases, so the rotational angular velocity ω increases, so the vibration acceleration α becomes a constant value, that is, the target value α held at _p .

Therefore, at the start of pile driving, that is, when the penetration depth d is small, the resistance force of the soil acting on the pile 1 is small, so the amplitude a becomes large, and the vibration acceleration α becomes larger than the target value α _p . Since the amount of pressure oil supplied to the hydraulic motor 5 decreases, the rotational speed of the eccentric shaft 3 decreases, and the excitation force of the vibrator 2 decreases. As a result, the rotational angular velocity ω becomes smaller, the vibration acceleration α decreases, and the vibration acceleration α becomes the target value α _p
is equal to In this way, even if the amplitude a increases, the vibration acceleration α can be prevented from increasing, and therefore the magnitude S of the ground vibration can be prevented from increasing. Furthermore, when the penetration depth d is large, the resistance force of the soil acting on the pile 1 becomes large, so the amplitude a becomes small, and the vibration acceleration α becomes smaller than the target value α _p , so that the vibration acceleration α is smaller than the target value α p. Since the amount of pressurized oil increases, the rotational speed of the eccentric shaft 3 increases, and the excitation force of the vibrator 2 increases. As a result, the rotational angular velocity ω increases, the vibration acceleration α increases, and the vibration acceleration α
becomes equal to the target value α _p . In this way, even if the amplitude a becomes small, the vibration acceleration α can be prevented from becoming small, and therefore the penetration speed v can be prevented from becoming small.

〔Effect of the invention〕

As explained above, in the pile driving device according to the present invention, when the penetration depth d is small,
Since the excitation force of the vibrator is reduced, even if the amplitude a increases, it is possible to prevent the vibration acceleration α from increasing, thereby preventing the magnitude S of the ground vibration from increasing. , the magnitude of ground vibration S can be kept within the permissible limit, and when the penetration depth d is large, the excitation force of the vibrator increases, so even if the amplitude a becomes small, the vibration acceleration Since it is possible to prevent α from decreasing, it is possible to prevent the penetration speed v from becoming small, and it is possible to maintain penetration efficiency. As described above, the effects of this invention are remarkable.

[Brief explanation of the drawing]

Figure 1 is a diagram showing a pile driving device that uses lateral vibration, Figure 2 is a graph showing the relationship between the vibration acceleration α at the tip of the pile and the pile penetration speed v, and Figure 3 is a graph showing the relationship between the vibration acceleration α at the tip of the pile and the pile penetration speed v. A graph showing the relationship between the pile penetration depth d and the vibration acceleration α when the pile is driven into the soil with a constant vibration force. FIG. 5 is a graph showing the relationship between the vibration acceleration α and the magnitude S of ground vibration when a pile is driven into the pile, and FIG. 5 is a diagram showing a pile driving apparatus according to the present invention. DESCRIPTION OF SYMBOLS 1... Pile, 2... Vibrator, 3... Eccentric shaft, 5... Hydraulic motor, 7... Hydraulic source, 8... Electromagnetic flow control valve, 9... Vibration accelerometer, 10... Comparator.

Claims (1)

[Claims] 1. In a device for driving the pile into the soil by applying vibration to the pile using a vibrator, the vibrator is one that applies vibration in a direction perpendicular to the axis of the pile,
a vibration accelerometer that detects vibration acceleration at the tip of the pile; a comparator that calculates a comparison value between the detected value of the vibration accelerometer and a preset target value of vibration acceleration; 1. A pile driving device comprising means for changing the excitation force of a vibrator to maintain the vibration acceleration at a constant value.