JPH0325566B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a first piston of a vibrating body in which a first piston and a second piston are formed at an appropriate distance in the axial direction, and a first piston in a vibrating machine casing in which a first oil chamber and a second oil chamber are formed. A second piston is housed in the chamber and a second piston is housed in a second oil chamber, and hydraulic oil is sealed in the second oil chamber to elastically support the exciter casing and the vibrating body, and the vibrator is driven by a hydraulic motor. Vibration is generated by alternately supplying pressure oil to both ends of the first piston at appropriate intervals via a rotation switching valve that acts to alternately switch the flow direction of pressure oil at intervals corresponding to the rotational speed of the hydraulic motor. It has a vibrator that generates vibrations of an appropriate frequency by relatively displacing the machine casing and the vibrating body in the axial direction at appropriate intervals, and a pile attached to the lower end of the exciter is pressed against the pile. This invention relates to a vibrating pile driving device that is driven into the soil by the vibrating pressure of an exciter. When driving piles into the soil using this type of vibratory pile driving equipment, the exciter must be vibrated at the same vibration frequency as the natural frequency of the entire vibration system including the vibratory pile driving equipment and the piles. It is known that sometimes the highest oscillating pressure is obtained. However, the natural frequency of this vibration system changes from moment to moment in response to the penetration resistance of the soil, which continuously changes as the pile penetration progresses. In order to efficiently drive at an appropriate penetration speed throughout the entire process, it is necessary to constantly control the vibration frequency of the vibrator to match the natural frequency of the vibration system that provides the maximum vibration pressure. However, in conventional vibrating pile driving equipment of this type, the operator visually judges changes in the state of pile penetration and corrects the vibration frequency of the pile driver based on that judgment (so-called intuition). Because I was
It is difficult to appropriately judge changes in the actual penetration situation and to appropriately and quickly change the working conditions in response to the changes so that the vibration frequency of the exciter matches the natural frequency of the vibration system. However, there was a problem in that the ability of the pile driving equipment could not be utilized to its full potential. In view of the problems of the conventional vibrating pile driving device as described above, the present invention aims to improve the efficiency of pile penetration work by vibrating a vibrator at a vibration frequency that provides the maximum vibration pressure. The purpose of this device is to provide a vibrating pile driving device having a basic configuration as shown in the header. A volume deviation generator for changing the volume of the oil chamber and a pressure amplitude detector for detecting the pressure amplitude in the second oil chamber are provided, and based on the volume change and pressure amplitude change of the second oil chamber, Detecting the relative relationship between the natural frequency of the entire vibration system and the current vibration frequency of the vibration exciter, and appropriately adjusting the rotation speed of the hydraulic motor in order to match the vibration frequency of the vibration exciter with the natural frequency of the vibration system. The invention is characterized in that it is equipped with a controller that controls the increase and decrease of the amount of water. Hereinafter, the vibrating pile driving device of the present invention will be explained based on an embodiment shown in the attached drawings. Fig. 1 shows a hydraulic resonance type vibrating pile driving device Z according to an embodiment of the present invention, and the vibrating pile The striking device Z has an exciter 1 which is vibrated by hydraulic pressure. The vibrating machine 1 includes a vibrating body 3 in which two pistons, a first piston 4 and a second piston 5, are integrally formed in a skewer shape at appropriate intervals in the axial direction of the rod part 3a, and a vibrating body 3 is formed inside the vibrating body 3. The exciter casing 2 has a first oil chamber 6 for accommodating the first piston 4 of the body 3 and a second oil chamber 9 for accommodating the second piston 5, and is connected to the main hydraulic power source. The high-pressure oil is supplied to the first oil chamber 6 through the rotary switching valve 15.
By alternately supplying the upper chamber 7 located on the upper end surface side of the piston 4 and the lower chamber 8 located on the lower end surface side of the piston 4 to move the vibrating body 3 up and down with respect to the exciter casing 2, the exciter 1 is vibrated at an appropriate vibration frequency to generate vibration pressure in the vertical direction.
The vibration frequency of the exciter 1 is appropriately set by appropriately increasing or decreasing the rotation speed of the hydraulic motor 16 for driving the rotary switching valve using a controller 30, which will be described later. Note that the first oil chamber 6 is hereinafter referred to as a vibration chamber 6. Further, hydraulic oil is sealed in an upper chamber 10 located on the upper end surface side of the second piston 5 and a lower chamber 11 located on the lower end surface side of the second oil chamber 9 housing the second piston 5. . This sealed oil is applied to the exciter casing 2
and acts as a hydraulic spring that elastically supports the vibrating body 3. Note that this second oil chamber 9 will be referred to as a spring chamber 9 below. By the way, in order to match the vibration frequency of the vibration exciter 1 with the natural frequency of the vibration system, the magnitude relationship between the current vibration frequency F of the vibration exciter 1 and the natural frequency f of the vibration system is checked and the detection result is used. Based on, for example, F<f
In this case, it is necessary to increase the vibration frequency F of the exciter 1 so as to bring it closer to F=f.
Therefore, in the exciter 1 of the pile driving device Z of the illustrated embodiment, the relationship between the hydraulic spring constant k of the spring chamber 9, the natural frequency f of the vibration system, and the mass m of the vibration system is f≒(√ k /2π)・(1/√ m), the hydraulic spring constant k changes in inverse proportion to the volume of the spring chamber 9, and the vibration frequency F of the exciter 1 is the natural vibration of the vibration system. Focusing on three points, the hydraulic pressure and pressure amplitude in the spring chamber 9 increase as F approaches the resonant frequency (that is, as F approaches the resonance frequency), and a larger vibration pressure can be obtained. A volume deviation generator 22 for generating a volume deviation in the spring chamber 9 and a pressure amplitude detector 26 for detecting the pressure amplitude of the spring chamber 9 are installed on the side of the spring chamber 9 to check the trend of variable values. , which inputs the output signals from the volume deviation generator 22 and the pressure amplitude detector 26 to the controller 30 as a control factor for the vibration frequency F. In addition, to briefly explain the configuration of this volume deviation generator 22, this volume deviation generator 22 has a first chamber 24 communicating with the upper chamber 10 of the spring chamber 9 and a second chamber 25 communicating with the lower chamber 11. It is composed of a stepped piston 23 that can change the volume of both chambers (that is, the volume of the spring chamber 9) by the same amount at the same time, and the piston 23 is controlled by a volume deviation generator of a controller 30 described later. The volume of the spring chamber 9, that is, the hydraulic spring constant k, can be changed at a constant cycle by moving the spring chamber 9 continuously or intermittently forward and backward at a very low speed at a constant cycle based on a control signal from the circuit. Further, in the illustrated embodiment, when the pressure amplitude value of the spring chamber 9 falls below a preset constant amplitude, the volume deviation generator control circuit 34 operates the volume deviation generator 22 and maintains the pressure amplitude constant. Although the operation is stopped when the amplitude is recovered above the amplitude, in other embodiments of the present invention,
It may be configured to operate continuously while the exciter 1 is in operation, regardless of the magnitude of the pressure amplitude in the spring chamber 9. Next, before controlling the vibration frequency F of the exciter 1, the vibration frequency F of the exciter 1 that can actually occur is determined.
Considering the form of the magnitude relationship between and the natural frequency f of the vibration system, there are two cases that can be considered as the form of this magnitude relationship. That is, when the current vibration frequency of the exciter 1 is F as shown in FIG.
The second case is when the natural frequency f ₁ of the vibration system is greater than the vibration frequency F (f ₁ > F), and the second case is when the natural frequency f ₂ is smaller than the vibration frequency F (f ₂ < F). ). Therefore, in the first case, the vibration frequency F is increased to approach the natural frequency f ₁ ,
In the second case, the vibration frequency F must be reduced to approach the natural frequency. Regarding these two cases, the natural frequency f of the vibration system, the vibration frequency F of the exciter 1, and the spring chamber 9 when the volume of the spring chamber 9 is alternately increased and decreased.
Table 1 shows the correlation between the pressure amplitude P and the pressure amplitude P.

【table】

[Table] First, in the first case where f(f ₁ )>F among non-resonant cases, when the spring chamber volume V is increased (that is, when the hydraulic spring constant k is decreased) The natural frequency f of the vibration system decreases and the natural frequency f
The deviation of the vibration frequency F of the exciter 1 becomes smaller, the pressure amplitude P of the spring chamber 9 increases, and conversely the spring chamber volume V
(i.e., when the hydraulic spring constant k is increased, the natural frequency f increases and the natural frequency f
The deviation of the vibration frequency F of the exciter 1 increases, and the pressure amplitude ΔP of the spring chamber 9 decreases. Therefore, in this first case, the spring chamber volume V always changes.
Rate of change α of pressure amplitude P in spring chamber 9 with respect to dV =
dP/dV is a positive value. In the second case where f(f ₂ ) < F during non-resonance, when the spring chamber volume V is increased, the natural frequency f decreases and the natural frequency f and the vibration frequency F As the deviation increases, the pressure amplitude P decreases, and conversely, when the spring chamber volume V is decreased, the natural frequency f increases, and the deviation between the natural frequency f and the vibration frequency F becomes smaller, resulting in a pressure amplitude P. increases. Therefore, in this second case, dP/dV=α always takes a negative value. That is, by checking the value of α=dP/dV, it is possible to determine the control form of the vibration frequency F of the exciter 1. Therefore, in the vibrating pile driving device Z of the illustrated embodiment, the controller 30
The value of dP/dV is checked, and the vibration frequency F is controlled to increase or decrease as appropriate depending on the result. In particular, in this embodiment, the natural frequency f of the current vibration system is assumed and stored in advance from the magnitude of the dP/dV value (that is, from the slope of the characteristic diagram depicting a parabola). It is written in a map of the circuit 33, and when a vibration frequency update control signal is issued, the frequency change range corresponding to the current dP/dV value is read from this map. Next, the action of the vibrating pile driving device Z of the illustrated embodiment will be explained using the control flowchart shown in FIG. Therefore, when the pile P is penetrated into the soil, the pressure amplitude detector 26
If it is confirmed by the detection signal from the spring chamber 9 that the pressure amplitude has decreased below a predetermined value (in other words, if the vibration pressure has become smaller than the predetermined value and the pile penetration speed has decreased), the volume deviation generator Control circuit 34
The volume deviation generator 22 is activated by a control signal from the . When the volume deviation generator 22 operates, first, the pressure amplitude change trend detection circuit 31
The volume deviation △ of the spring chamber 9 from the volume deviation generator 22
V and the pressure amplitude are input from the pressure amplitude detector 26, respectively. In this pressure amplitude change trend detection circuit 31, from the volume deviation △V and the pressure amplitude P, α=
The value of dP/dV is calculated to detect the change tendency of the pressure amplitude when the spring chamber volume is changed, and the detection result is inputted to the vibration frequency change range setting circuit 32. In the case of α0, the vibration frequency control circuit 3 increases or decreases the vibration frequency of the exciter 1.
5, but in that case, dP/dV
A predetermined vibration frequency change range is read out from the memory circuit 33 according to the value of . When the frequency change signal is input to the vibration frequency control circuit 35, the opening degree of the flow control valve 17 is appropriately adjusted via the torque motor 18 according to the change value, and the rotation speed of the hydraulic motor 16 is increased or decreased. The vibration frequency F of exciter 1 is the natural frequency
Bring it closer to f ₁ or f ₂ . By repeating this frequency change operation an appropriate number of times,
The vibration frequency of the exciter 1 can be brought as close as possible to the natural frequency of the current vibration system. When the deviation between the vibration frequency F of the exciter 1 and the natural frequency f of the vibration system becomes equal to or less than a predetermined value, the operation of the volumetric deviation generator 22 is stopped, and the vibration frequency changing operation is completed. In this way, when the vibration frequency of the exciter 1 matches or approaches as much as possible the natural frequency of the current vibration system, the vibration pressure is restored and the pile P is driven smoothly again at the appropriate penetration speed. can be included. Note that the rotation speed of the hydraulic motor 16 is constantly detected by a rotation speed sensor 19, and is controlled by a frequency feedback circuit 37 to ensure that the rotation speed returns to the rotation speed set by the vibration frequency control circuit 35. Feedback controlled. Further, the vibration frequency of the exciter 1 can be arbitrarily changed by manually switching the control system to the manual side using the automatic switching device 36, regardless of the natural frequency of the vibration system. Next, to explain the effects of the present invention, the vibratory pile driving device of the present invention changes the natural frequency of the vibration system due to a change in the penetration resistance of the soil. If the frequency deviation increases and the vibration pressure on the pile decreases, the vibration frequency of the exciter should be changed appropriately to approach or match the natural frequency of the vibration system as much as possible to reduce the vibration pressure. Since recovery is attempted, the pile can be driven effectively with greater vibration pressure throughout the entire process of penetrating work, and this has the effect of increasing the efficiency of pile penetrating work.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of a vibratory pile driving device according to an embodiment of the present invention, Fig. 2 is a diagram showing the relative relationship between the vibration frequency of the exciter and the natural frequency of the vibration system, and Fig. 3 is a diagram of the vibratory pile driving device. This is the control flowchart. 1... Exciter, 2... Exciter casing, 3...
... Vibrating body, 4... First piston, 5... Second piston, 6... First oil chamber, 9... Second oil chamber, 15...
...Rotary switching valve, 16...Hydraulic motor, 20...
...Pile.

Claims (1)

[Claims] 1 The first piston 4 and the second piston are spaced appropriately in the axial direction.
The first piston 4 of the vibrating body 3 forming the piston 5 is placed inside the first oil chamber 6 of the exciter casing 2 forming the first oil chamber 6 and the second oil chamber 9, and the second piston 5 are respectively housed in the second oil chamber 9, and hydraulic oil is sealed in the second oil chamber 9 to elastically support the exciter casing 2 and the vibrating body 3. Pressure oil is supplied to both ends of the first piston 4 at appropriate intervals through the rotary switching valve 15 which is driven and acts to alternately switch the flow direction of the pressure oil at intervals corresponding to the rotational speed of the hydraulic motor 16. The vibration exciter 1 has an exciter 1 configured to generate vibrations of an appropriate frequency by displacing the exciter casing 2 and the vibrating body 3 in an axial direction at appropriate intervals by alternately supplying the vibrator casing 2 and the vibrating body 3. A vibratory pile driving device is configured to drive a pile 20 attached to the lower end compression part of the pile 20 into the soil by the pressing force against the pile 20 and the vibration pressure of the vibrator 1, wherein the second oil chamber 9 A volume deviation generator 22 for changing the volume of the second oil chamber 9 by an external operation, and a pressure amplitude detector 26 for detecting the pressure amplitude in the second oil chamber 9 are provided. Said second oil chamber 9
The relative relationship between the natural frequency f of the entire vibration system and the current vibration frequency F of the vibrator 1 is detected based on the volume change (△V) and pressure amplitude change (△P) of the vibrator 1. 1 vibration frequency F is the natural frequency f of the vibration system
A vibratory pile driving device characterized by comprising a controller 30 that appropriately increases or decreases the number of revolutions of the hydraulic motor 16 in order to match the above.