JPS621922A - Measurement of displacement of driven pile - Google Patents

Abstract

PURPOSE:To exactly obtain the penetration and rebound amounts of a pile immediately by a method in which a change in acceleration when driving a pile is measured by an accelerometer attached to the pile, and the change of acceleration so measured is subjected to two times' integration in an integrator to calculate the amount of displacement. CONSTITUTION:An accelerometer 10 is attached to a pile, a change of acceleration is measured each time striking is applied by Diesel hammer, etc., and the measured values are sent out to an integrator 2. The output of acceleration is subjected to two times' integration in the integrator 10 and converted into displacement output, and the displacement output is sent out to a recorder 3. The signals of displacement from the integrator 2 are recorded on a paper by the recorder 3 and displayed. The penetration and rebound amounts of the pile can thus be exactly obtained immediately.

Description

[Detailed Description of the Invention] [Industrial Application] The present invention provides a formula for determining the dynamic bearing capacity of a pile during pile driving, in which the number of words required for calculation is calculated based on changes in pile head displacement. This relates to a displacement measurement method for determining the amount of penetration and rebound at the pile head.

[Conventional technology]

When driving steel pipe piles, concrete piles, etc. with a diesel hammer, hydraulic hammer, etc., and determining whether or not the pile has a specified bearing capacity at a specified design depth or driving depth, use the following formula. The dynamic bearing capacity calculation formula shown is used.

2-eol ef ...- (1) However, Ru: Dynamic ultimate bearing capacity of the pile A: Actual cross-sectional area of the pile E: Young's modulus of the pile S: Amount of penetration of the pile K: Amount of rebound of the pile N: Average N value of the circumferential surface of the pile U: Perimeter of the pile KS: Amount of rebound at the tip of the ground Ko: Amount of rebound due to the elasticity of the pile l: Length of the pile eO: Correction coefficient ef: Equation (1) above the correction coefficient , Equation (2) is a one-dimensional wave equation, which is currently considered to be an accurate force value, among various equations such as the one-dimensional wave equation and the Hiley (formerly Ley) equation as a dynamic support force calculation equation. Equation (1) is a precise solution, and equation (2) is an approximate solution. Also, among these two equations, (
It has been reported that the precise solution of Equation 11 is in good agreement with the results of *experiments and loading tests.

Examples of these are shown in Table 1.

Table 1 In Table 1, the affixed paper is the measurement method shown in FIG. 4, and the optical displacement meter is the measurement method shown in FIG. 7. Both are conventional measurement methods. From the change in pile head displacement measured using these methods, the penetration amount s1 rebound amount at the pile head (rebound amount Ko due to the elasticity of the pile body, rebound amount Ks at the tip of the ground) can be found using equation (1) or (2).
The dynamic bearing capacity of a driven pile can be calculated using the formula.

In Figure 4, (10) is the pile body, (11) is the paper attached with adhesive tape (12) to the side of the pile head, (13)
is a pencil, and (14) is a ruler that supports the pencil (13), which is supported horizontally by a support (15).

In this pasted paper method, the operator moves the pencil (13) along the ruler (14) every time the pile body (10) is struck, and records the displacement change of the pile body.

FIG. 5 is a diagram showing the results of piling on land using this method, and FIG. 6 is a diagram showing the results of piling on land using this method. In addition, Figure 6+1 records the displacement change of the pile body on board the pile driving ship.

Next, FIG. 7 shows the configuration of an optical displacement meter system. In the figure, (16) is the targera 1- pasted on the stake body (10), which is painted white and black. (17
) is an optical measurement device installed on the quay;
), it consists of a camera (19) having a telephoto lens (18), an amplifier (20) that amplifies the imaging signal, a recording device (21), and an output device (22).

(23) is a hammer.

This method optically captures the displacement caused by driving the pile body (10), converts it into an electrical quantity, and outputs it.
This is a method of capturing and recording the image using a camera (19).

FIG. 8 is a diagram of the results recorded by this method.

In the figure, K shows the rebound amount of the entire pile, Ks shows the rebound amount of the tip ground, and Ko shows the rebound amount due to the elasticity of the pile body.

[Problem that the invention seeks to solve]

The problems with conventional pile displacement measurement methods are as follows.

(1) In the case of the pasted paper method ■ A fixed point is required to fix the pencil, but this cannot be achieved due to the ground vibrations that occur during pile driving.

■ Since the values of Ko and Ks cannot be separated, (
2) Only an approximate solution to the equation can be applied, resulting in extremely inaccurate measurement accuracy.

■ It is necessary to reset the pencil after each stroke, which is dangerous for the worker.

(2) In the case of optical displacement measurement method ■ A fixed point is required to fix the camera, but in the case of land piling, it is necessary to be at least 25+n Ii' away from the measuring device because it is affected by ground vibration. However, the limit distance is 100r due to reasons such as accuracy of measurement results.
Within n. Furthermore, in the case of offshore piling, the camera must be fixed on land.

■ Calibration between target and camera takes time.

■ Measuring equipment is expensive.

61 ■Night measurement is not possible.

The present invention has been made to solve the above problems, and provides a method for measuring the displacement of driven piles that can obtain highly accurate measurement results regardless of whether piles are driven on land or at sea, and that can be carried out at a relatively low cost. The purpose is to obtain.

[Means and effects for solving the problem] The method for measuring the displacement of a driven pile according to the present invention involves attaching an accelerometer to the pile body and measuring changes in the acceleration of the pile body during pile driving using the accelerometer. If the measured value is further integrated twice using an integrator, the amount of penetration and the amount of rebound necessary for calculating the dynamic support force calculation formula shown in equation (1) can be immediately and accurately determined.

〔Example〕

Hereinafter, the method of the present invention will be explained with reference to the drawings.

FIG. 1 is an explanatory diagram of the method of the present invention. In the figure (1)
is an accelerometer that can be easily attached to the pile body (10) using an appropriate attachment member with adhesive or the like, and is used to measure the change in acceleration per stroke of %l' by a diesel hammer, hydraulic hammer, etc. . (2) is an integrator that integrates the measured acceleration output of the accelerometer (1) twice and converts it into a displacement output. It also has various adjustment functions to accommodate the acceleration and displacement characteristics of pile drivers such as diesel hammers and hydraulic hammers. There are two types of integration methods: analog integration method and digital integration method. (3) is a recorder and an integrator (2
) is recorded on paper. In addition, accelerometer (1)
and the integrator (2) are communicated by wireless or wired communication such as a telemeter.

FIG. 2 is an experimental example illustrating the method of the present invention.

As shown in the figure, a steel pile (10) (20 mm φXi, 500 mm 1) is suspended by a piano wire (5) from a fixed beam (4), which is a fixed point. An accelerometer (1) was attached to the end of this pile body (10), and a steel hammer (63.2 mmφ x 150 mm1) was similarly suspended from the fixed beam (4).
) to the tip of the pile body (10). At the time of B, the acceleration generated in the pile body (10) is measured with the accelerometer (1),
The value is integrated twice by an integrator (2) to obtain the displacement. The graphs in FIGS. 3(,) to (,) show temporal changes from acceleration changes to displacements in this manner. Third
In Figure (c), curve A is the displacement determined by the method of the present invention, and curve MB is the displacement determined by the optical displacement meter method, but this is to the extent that there is no practical problem in determining displacement from acceleration changes as in the present invention. It can be seen that the fJ degree of can be sufficiently guaranteed.

〔Effect of the invention〕

According to the present invention, the following effects can be achieved.

(1) There is no need to secure a fixed point as in the conventional pasting assembly method and optical displacement meter method.

(2) It can be applied regardless of whether it is pile driving on land or at sea, and can be measured with the same accuracy as the optical displacement meter method.

(31 Since the values of Ko and Ks can be measured separately, it is possible to apply the highly accurate dynamic support force calculation formula shown in equation (1).

(4) The accelerometer is adjusted in advance and attached to the pile body, and since it is easy to handle, the calibration time can be significantly shortened.

(5) Remote measurement can be performed by wireless communication between the accelerometer and the integrator using a telemeter or the like.

(6) It is about 1/8 cheaper than the optical displacement meter method.

(7) Measurement at night is also possible.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the method of the present invention, Figure 2 is a configuration diagram of the experimental apparatus, Figures 3 (,) to (C) are hail diagrams showing the results measured with the experimental apparatus of Figure 2, Figures (a) and (b) are front and side views of the conventional example, Figures 5 and 6 are displacement diagrams obtained by the method shown in Figure 4, and Figures 7 (a) and (b) are other diagrams. A side view of the conventional example and a detailed view of the measuring device, and FIG. 8 is a diagram of the amount of displacement determined by the method of FIG. (1): Accelerometer, (2): Integrator, (3): Recorder,
(10): Pile body. Agent Patent Attorney Tadashi Sato Year 1 Figure 1 WA-600 Old ■ 130o○ Figure 2 Interval (msec) (as/mountain) 1 hour (+, uu+) l Figure 5 Figure 6 Engraving of drawings (no changes in content) Figure 4 Amended drawing 1゜(,b) Figure 7 (b) Figure 8 Procedural amendment (dragon) Dear Commissioner of the Japan Patent Office, February 28, 1986,
Display of incident Patent application No. 249035 of 1985, name of invention Method for measuring displacement of driven piles, ? Ill? Relationship with the case of a person who makes corrections Patent applicant address 88 Ono-cho, Tsurumi-ku, Yokohama, Kanagawa Prefecture Name
Nippon Steel Pipe Works Co., Ltd. Representative: Naosuke Ozawa 4, Agent address: 21-19 Toranomon-chome, Minato-ku, Tokyo Date of amendment order: February 5, 1986 (shipment date)
(February 25, 1986) Draft 6, drawings subject to amendment. 7. Contents of the amendment Figure 4 of the drawings will be amended as shown in the attached amended drawing. Above = 134-

Claims (1)

[Claims] An accelerometer attached to the pile body measures the change in acceleration of the pile body during pile driving, and the change in acceleration is calculated by an integrator.
A method for measuring the displacement of a driven pile, which is characterized in that the displacement is calculated by integraling the displacement.