JPS6230908A - Pile-head displacement measuring apparatus for pile driving - Google Patents

Abstract

PURPOSE:To measure displacement of pile-heads easily and safely, by measuring acceleration of the pile-head for each driving stroke and obtaining the required value by double analogue integration. CONSTITUTION:Change of acceleration per each impact is measured with an accelerameter 1 attached on a pile-head setter 8. An output of this acceleration is modulated into an FM or an AM electric wave with a telemeter transmitter 2 attached to the pile-head setter 8 and it is transmitted to a telemeter-receiver 4 installed in a measuring area. In the receiver, the electric wave is received for converting it into the specified electric signal. A transient recorder 5 converts an analogue electric signal from the receiver 4 into a digital signal for recording. Next, an analogue integrator 6 makes double integration of the analogue output prom the recorder 5 for a deviation output. By this arrangement, penetration and rebound amounts necessary for a discrimination equation of dynamic holding force of pile can immediately be obtained. And, the deviation output from an analogue integrator 6 is plotted on an X-Y graph of a X-Y recorder 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for measuring displacement at the head of a sleeper bed necessary for calculating a determination formula for determining the dynamic bearing capacity of a pile.

[Conventional technology]

Determined by driving a steel pipe pile, concrete pile, etc. using a diesel hammer, hydraulic hammer, etc. using a one-dimensional wave equation to determine whether the pile has a specified bearing capacity at a specified design depth or driving depth. In the dynamic support capacity determination formula, it is necessary to measure the penetration amount (N value) at the head of the bed and the rebound amount (the amount of rebound due to the elasticity of the antibody, the amount of rebound at the tip of the ground) as shown by the following formula: be.

Here, Ru: Ultimate bearing capacity of the pile A: Actual cross-sectional area of the pile E: Young's modulus of the pile K: Amount of rebound of the pile N: Average N value of the circumferential surface of the pile U: Director of the pile 1: Length of the pile e (1t e l : Correction coefficient To know the value of K in the above formula, change the displacement of the pile head by 4
need to be measured. As a conventional measurement technique, there is the following lulr method.

(1) Paste paper method (2) Optical displacement old method 1-, RL! (Figure 2 shows the configuration of the 11 pasted paper methods (
al (b).

In the figure, (10) is a stake, (11) is two sets of adhesive sticks (12) attached to the side of the pile head, (13) is a pencil, and (14) is a pencil supporting the pencil (13). Using a ruler, place a post (1
5) The first one is supported horizontally.

In this pasted paper method, a ruler (14) is installed horizontally on a support (15) installed near a driven pile (10).
+4) (While moving the pencil (13) along this line at a constant speed, touch the paper (11) -!- attached to the side of the pile head -.
This is a method to record the estimated penetration ¥ and bound f1; (the sum of the elastic compression of the pile and the ground at the tip of the pile).

Figure 3 shows daily galley 7 recorded using this method. .

Next, FIGS. 4(a) and 4(b) show the configuration of the optical displacement meter system of (2) above. In the figure, (16) is a pile (
10) There are two targets attached, painted in white and black. (17) is installed on the quay.'i1. r-optical measuring device, shown in detail in Figure 4()1)-4', 1
Uni, a telephoto lens (18) and an azure camera (19),
Shooting 18! (The bar 43 is made up of an amplifying amplifier (20), a recording device (21), and an output device (22). (2
3) is a hammer 3°.In this method, the displacement caused by driving the pile (10) is optically captured, and this is converted into an electric mouse and output is attached to the pile (10). Shil
-Painted in white and black, it'lt'lt'nt get it (1)
6) was captured with a camera (19) and recorded using the 3° offset method. Figure 5 shows the 17 day gerano recorded using this method. Riba 'nondo ¥ of the ground, KO shows a 41 rebound rat on the antibody bullet f1.

[Problems that the invention attempts to solve] The problems of the prior art are as follows. 3゜ (1) In the case of the pasted paper method ■ It is necessary to keep the pencil stationary for each stroke, so it is difficult for the operator to do so. is dangerous.

■A fixed point is created near the driven pile using a support and a ruler, but it cannot be a precise fixed point because of the ground vibrations that occur during impact. Therefore, the accuracy of the measurement results is extremely poor and lacks reliability.

(2) In the case of optical displacement meter method ■Measuring equipment is expensive.

- Since the camera must be fixed at a fixed point, it is necessary to keep it at a distance of 50111 mm or more from the driven pile due to driving vibration when applying on land. Furthermore, in the case of construction at sea, it is basically extremely difficult to obtain a fixed point.

■If the target attached to the antibody shifts or becomes stiff, the measurement will be interrupted and the stake driving operation will also be interrupted.

"Means and effects for solving the problems" In the present invention, 1
- To measure the displacement of the pile head during pile driving, first attach it to the pile head, measure the change in acceleration during impact with an accelerometer, transmit the output of that acceleration with a secondary transmitter, and measure it. Receive it with a telemeter receiver installed at the location. Next, this signal (Matrunen 1-Recordte 5
As well as recording myself (this, with an analog integrator, 2 points j7
Without converting it into displacement, the range of penetration and rebound required for calculating the equation for determining the dynamic bearing capacity of the pile can be immediately obtained.

〔Example〕

FIG. 1 is a block diagram of an embodiment of the present invention, and in the figure (
1) is an accelerometer that can be easily attached to the pile head using an appropriate attachment member with adhesive, etc.
This measures the change in acceleration for each strike made by a hydraulic hammer or the like. (2) is a sub telemeter transmitter attached to the head of the telemeter, which modulates the output of the accelerometer (1) into FM or AM radio waves and transmits them to the telemeter receiver described later. (3) is a power supply that supplies the necessary power to the accelerometer (1) and the telemeter transmitter (2). (4) is a telemeter transmitter (2
Telemeter receivers (3 units) installed at the measurement location several tens of meters away from the telemeter receiver receive the FM or AM radio waves emitted from the telemeter and convert it into a predetermined electrical signal. (5) performs digital L conversion (7) to record the analog electrical signal from the transient recorder.It also has a function of digital output if necessary.

(6) is an analog integrator that integrates the analog output (acceleration output) from the transient 17 coder (5) twice to produce a displacement output. In addition, it has an integral time constant adjustment function and an analog integral output adjustment function in order to correspond to the acceleration and displacement characteristics depending on the characteristics of pile drivers such as diesel/'1 hammer and hydraulic hammer. (7) is an x-y recorder that converts the displacement output from the analog integrator (6) into an x-y recorder. In addition, (8) in the figure shows the head attachment part.

〔Effect of the invention〕

The method of the present invention is that when determining the dynamic bearing capacity of a pile, the acceleration, which is completely unrelated to the numerical value required for calculating the determination formula, is measured for each impact, and analog integration is performed twice. It is used to find the required numerical value, and is effective in the following cases.

(1) Displacement can be easily determined by simply measuring the acceleration of the head of the sleeper and integrating it twice. Also, there is no need to worry about interrupting measurement work or piling work.

(2) The measuring device can be made inexpensive.

(3) Work is safe because it uses a telemeter (wireless remote measurement) method.

(4) It is not affected by pile driving vibration, so it can be applied to both mariners and land-based construction. 1

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional example, in which FIG. 1A shows a front view and FIG. 2B shows a side view. Figure 3 is a diagram of data recorded using the method shown in Figure 1, and Figure 4 is a block diagram of another conventional example, where (a) is a side view and (b) is a detailed diagram of the measuring device. shows. FIG. 5 is a diagram of data 17t recorded by the method of FIG. (1): Accelerometer (2): Telemeter transmitter (4): Telemeter receiver (51: I-Langien) to 17 coder (6):
analog integrator

Claims (1)

[Claims] The change in acceleration of the pile head during pile driving is measured by an accelerometer attached to the pile head, and the output of the accelerometer is then received by a telemeter receiver installed at the measurement location using a telemeter transmitter. A method for measuring the displacement of a pile head during pile driving, characterized in that the signal is integrated twice by an analog integrator via a transient recorder.