JPH02171420A - Method of measuring displacement of fitted pile to be fitted during construction and device therefor - Google Patents

Abstract

PURPOSE:To aim at enhancing the measuring accuracy by providing a displace ment sensor, an acceleration sensor and an inertial weight to a pile to be driven so as to measure a virtual penetrating length and a rebound value, and by computing the measured value so as to obtain practical values. CONSTITUTION:An inertia weight 9 supported at both ends by springs 7, 7 and dash pots 8 is provided in a casing 6 mounted on a pile 2. A displacement meter 10 which moves together with the inertia weight 9 is provided in the casing, and an accelerometer is provided to the weight 9. Then, during the pile 2 being driven, a relative displacement and a relative acceleration between the pile 2 and the weight 9 are measured. Thereafter, a displacement within an accelerometer during an infinitesimal time is integrated twice, and then a virtual displacement is corrected so as to obtain an actual displacement. With this arrangement, a precise drive-in length of the pile and a rebound value may be measured, and they may be safely measured at a lower cost even during use of a sound shield cover and during working on the water, which cannot be measured conventionally.

Description

[Detailed description of the invention] <Industrial application field> The disclosed technology is used for driving foundation piles for construction work such as buildings and civil engineering ditch structures to obtain sufficient supporting force when driving piles into the ground. It belongs to the technical field of state measurement technology.

SUMMARY OF THE INVENTION Therefore, the present invention provides a method for managing the driving piles used for the foundations of the above-mentioned construction work when driving the piles into the ground by applying impact force with a hammer. This invention relates to a displacement measuring method for measuring the penetration amount and rebound amount on the outside of the driven pile in order to obtain the supporting force of the pile using the hammer formula for A case is directly fixed to the side of the driven pile, or is attached so as to be replaceable, and a displacement h1 sensor is installed inside the case to measure the amount of penetration and rebound through the case. A weight with large inertia is provided in the case, an accelerometer is provided in the way 1~, and the acceleration of the accelerometer is integrated twice,
The displacement of a hammered pile in construction work can be obtained by combining or subtracting the amount of displacement with the amount measured by the displacement meter sensor and calculating the exact amount of penetration and rebound by 1q to obtain the hammer formula. This invention relates to a measuring method and device.

<Prior art> In pile driving work, confirming whether the driven/ν pile has the specified support horn is called 1-pile driving control, and this management method includes the so-called hammer formula. There is a dynamic bearing capacity formula for piles called .

The hammer formula is calculated from the impact energy of the hammer, the resulting amount of force of the pile into the ground, and the amount of elastic deformation between the pile and the ground (referred to as the amount of rebound). It has been proposed.

Although there is still much debate about the reliability of the hammer formula, it is still used today, partly because the measurement management is simple and no other suitable method has been established. Commonly used.

<Problems to be Solved by the Invention> The measurement method is as shown in FIG. 8, by attaching a reference beam 1 to a pile 2, using the beam 1 as a support, and recording a pencil 3 for each impact on the pile 2. Move the paper to the 4th side and apply the penetration amount S to the 4th side of the paper such as graph paper attached to the stake 2 as shown in Figure 9.
This is done using a primitive method of recording one rebound mC. Therefore, this management method has the following problems.

Firstly, there is a drawback that recording is taken directly under the pile driver during pile driving, which is dangerous.Secondly, when using a soundproof cover (which covers the entire pile), The soundproof cover must be opened during measurement, and the cover must be opened when the noise is at its loudest when the ball is stopped (final hit), so there is no point in installing the cover, and thirdly,
There was a problem that it could not be applied to work on the water surface such as the sea, lake surface, river surface, etc., and fourthly, it was difficult to systemize by automatic recording.

Until now, methods for measuring the amount of pile penetration and rebound have been introduced, such as optical methods and methods that directly measure displacement, but no method has been put into practical use. Recently, a management system has been developed in which an acceleration sensor is attached near the head of the pile and the acceleration at the time of impact, which is 1q, is integrated twice to determine the amount of penetration and rebound.

Since the acceleration, which changes drastically due to the impact, is read and analyzed at extremely short time intervals such as 1/1000 seconds, it is expensive because it requires high-performance training equipment and analysis technology. Despite this, it also had the disadvantage that very high accuracy could not be expected.

<Purpose of the Invention> The purpose of the present invention is to consider the problems of pile driving management based on the above-mentioned prior art as technical issues to be solved, and to complete a measurement management system that satisfactorily addresses each of these problems. The record management computer has
In addition to the above-mentioned pile penetration amount and rebound amount, the impact energy of the hammer can be input at the same time, and the hammer formula can be selected arbitrarily and the pile support amount obtained from that formula can be calculated in real time. The purpose of this invention is to provide an excellent method for measuring the displacement of piles during impact, which will benefit the field of measurement technology available in the construction industry.

<Means/effects for solving the problem> In order to solve the above-mentioned problem, the structure of the present invention, which is based on the scope of the above-mentioned patent claims, is to solve the above-mentioned problem. When using the hammer formula to manage the driving of piles in order to maintain sufficient bearing capacity in the ground, the impact energy of the hammer, the amount of penetration of the pile into the ground, and the amount of rebound are When measuring (elastic deformation amount) as a displacement amount, the case of the measuring device is fixedly attached to the side surface of the driven pile in advance, or is attached in a removable manner, and the displacement sensor is fixedly installed inside the case. A way 1~ with a large inertial force having an acceleration sensor is arranged by a spring and a dashpot so as to be able to swing vertically, etc., and a striking force is applied to the driven pile by a hydraulic hammer or the like, and the case is attached to the driven pile together with the The displacement sensor measures and detects the amount of penetration and rebound on the child support, while the acceleration sensor measures the displacement within a minute time.
The actual penetration amount and rebound amount can be obtained by summing and adding and subtracting both data, and the hammer formula for the driven pile is obtained.
This is a technical measure that enables proper pile driving management.

Basics of Hammer Formula> If the weight of the hammer is W and the falling height is H, then the impact energy F per impact on the pile is expressed as W+-1.

If the falling height of the hammer cannot be measured visually, such as with a hydraulic hammer, for example, a non-contact switch can be installed at two points on the casing at different heights near the impact point, and the height of the hammer passing there can be measured. If the falling speed of the hammer is determined from the time and the distance between two points, the impact energy F can be found from v 2 F= (1) g where ■: the falling speed of the hammer and the acceleration of the ql food.

The energy E given to the ground through the pile is
R: Ground penetration resistance (pile support) S: Pile penetration amount C: Elastic deformation amount of the ground and pile (rebound amount), E=f (s+'c/2) (2> expressed.

In addition, elastic deformation energy: R-C/2 is the average of the maximum deformation amount C from the initial deformation amount O.

Therefore, from the balance between the impact energy F of the hammer and the energy E due to the resistance of the ground, WH=R(s
/2) (3), the bearing capacity of the ground R
is, H R= (
4) It is given by s0c/2.

In addition, in the case of a hydraulic hammer, WV2/2g R= (5
>s0c/2.

However, in practical use, formulas (4) and (5>) are developed into various formulas, taking into account the effects of pile caps, cushions, etc. installed between the hammer and the pile.

This invention aims to accurately detect the amount of penetration and rebound of a pile under the input conditions so that any hammer formula can be applied.

<Background of the principle of the invention> Since the amount of penetration during pile driving and the amount of rebound (during elastic deformation) are both amounts of displacement, a potentiometer (displacement meter) that satisfies frequency response is required. It is sufficient to measure using .

However, in reality, since the ground is also photographed when the pile is driven, there is a problem in that it is difficult to obtain a fixed point for measuring displacement.

In contrast, this invention applies the principles of seismometry and acceleration reduction, using a way 1 to 4) with a certain amount of mass as a fixed point, and measuring displacement using its inertial force. .

That is, a displacement meter is attached to the weight, and the amount of displacement of the pile is determined from the relative displacement between the way 1 and the pile and the absolute displacement of the weight itself.

In this case, the weight does not follow vJ8 in the high frequency range, and even if it does move, it will only capture images at low frequencies.

Therefore, we attached an accelerometer to the weight and measured the acceleration by 2.
By integrating the weight twice, the amount of movement is captured, so that even if the weight moves a little, there is no problem in terms of the measurement principle.

<Embodiment> Next, one embodiment of the present invention will be explained based on the drawings as follows.

The embodiment shown in FIG. 1 shows the principle aspect of a pile circumference fixed type in which a measuring device 5 according to the invention of this application is attached to a pile 2, and the measuring device 5 has a cylindrical case (or a rectangular case). It consists of a weight 9 whose both ends are supported by a spring 7, 7 and a dashpot 8, and a suitable potentiometer (displacement meter) 10 which moves integrally with the weight 9.

Therefore, an accelerometer (not shown) is attached to the weight 9 [
Save it.

In the above configuration, when a striking force is applied to the pile 2 by a hydraulic hammer or the like, the case 6 is displaced together with the pile 2, whereas the weight 9 tends to stay at its original position due to inertia force.

Therefore, a relative displacement occurs between the pile 2 and the weight 9,
This is detected by the potentiometer 10.

On the other hand, the weight 9 also tries to move in response to the external force, but because it is suspended by the spring 7.7 and the dashpot 8, it vibrates at a period with a low natural motion number.

Since the accelerometer can be used simply by detecting the movement of the weight 9, changes in acceleration are small, and displacement can be detected relatively easily by integrating the acceleration twice.

Note that the combination of the dashpot 8 and the spring 7 is selected in advance depending on the damping conditions of the system.

First, the actual displacement of pile 2 due to the impact of the hydraulic hammer is the second
As shown in the figure, it is assumed that the penetration is and the amount of elastic deformation (rebound Inc).

On the other hand, in the records measured by the measuring device 5, the amount of penetration S' and the amount of elastic deformation (rebound i > c
' shall be expressed as.

That is, the movement of the weight 9 causes a deviation in the reference line, and the potentiometer 10 detects C' and S'.

On the other hand, since way l-9 changes in a very short time (1/several seconds), taking the average acceleration and setting it as α, d2x = (X (6) dt
' dx = v = αt (7) t x = 1/2 αt2 From the relationship (8), the displacement mx after one hour is determined.

Here, V: speed, t: elapsed time.

Therefore, the settlement is and the rebound mc in FIG. 3 are obtained by the following equations.

Subsidence amount (penetration amount > s = s' + 1/2 αt22 (9) rebound amount c = c' + 1/2 αt, ' (10)
The embodiment shown in Fig. 4.5.6.7 shows an embodiment of the measuring device 5' that is considered to be effective in cases where it is difficult to recover the detection part, such as in underwater piling construction. , the detecting section (measuring device 5') and the stake 2 are separated and are of a non-fixed type, and the detecting section (measuring device 5') is suspended by hooking a wire row 111 to a case 6'.

In this embodiment, the measuring device 5' includes wheels 12, 12...
The measuring wheel unit 13 is comprised of a case 6' holding a measurement detecting section having a . . .

Accordingly, the case 6' is attached to each measuring ring 12 by means of pressing the stake 2 or other means depending on the position where the case 6' is hung.
For moderate pressing, ensure that the resistor 2 is always pressed with force.

In this embodiment, in addition to the means of pressing with the horizontal component of the weight due to the relationship between the hanging position of way 1~ and the position of the center of gravity, magnets 13' are attached to the lower surface of case 6' at appropriate intervals so as not to come into contact with resistor 2. Even if horizontal movement of the pile 2 occurs during driving, the measuring wheel unit ~13 is prevented from separating from the pile 2.

However, in this case, the pile 2 is applicable only to a steel pile, and when the pile is made of a non-magnetic material such as the concrete pile 1, a ring-shaped guide is used on the outer circumference of the pile (not shown). This allows you to deal with horizontal shots.

The measuring wheel unit 13 is elastically displaced in the direction perpendicular to the pile 2 via the spring 7 in the case 6' (the state in which it is pressed by the spring).
It is equipped with a sensor that not only follows the horizontal displacement of a small pile, but also takes care to ensure that the horizontal displacement does not cause errors in the detection of vertical displacement.

The relative displacement between the pile 2 and the measuring device 5' can be determined from the rotation angle of the measuring wheel unit 13, and an angular displacement sensor (such as an encoder) is attached to the shaft of the measuring wheel 14. It is.

In this case, since the case 6' and the measuring wheel unit 13 themselves are the way 1~, the acceleration sensor 4/16 is attached to the measuring wheel unit 13 as shown in FIG.

The measuring ring 14 can follow the displacement of the pile 2 using the measuring device @5'.
The first condition is that the measuring wheel 14 is as light as possible, and secondly that the measuring wheel 14 and the stake 2 are as light as possible.
The frictional force is large, and thirdly, the angular displacement sen +j
15, the shaft resistance must be small, and other conditions must be met.

Among these, the friction of the measuring wheel 14 has a large effect on measurement accuracy.

Therefore, in the measuring device 5', for example, a rubber-like magnet is attached to the measuring wheel 14 in the shape of a tire for use with steel piles.

For concrete piles, a tire-shaped structure is used in which a highly adhesive material such as soft rubber is attached as a resistor.

In order to reduce the weight of the measuring wheel 14, the measuring wheel 14 is made of lightweight material such as Plus Deck or aluminum.
In order to increase the friction between the measuring wheel 14 and the stake 2, the shaft diameter is made as small as possible, and the bearing seal structure is designed to reduce resistance.

<Effects of the invention> When performing the fixing of driven piles in construction work, etc., the adopted hammer formula has the effect of reliably obtaining supporting force even though it is a simple device. In order to measure the penetration amount and rebound amount using devices installed in parallel, it can be applied to work on the coast, the sea, lakes, rivers, etc., even when using a safe and soundproof cover. The excellent effect is that it can also be systematized.

In addition, with respect to the apparent penetration amount and rebound amount determined by the displacement meter, the displacement of the weight is also measured by integrating two times using the acceleration sensor of the weight, which is swingably provided inside the case with a spring or dashpot. The amount of penetration on the child rest that is measured and obtained by a displacement meter, and
Another advantage is that by adding or subtracting the rebound amount, more accurate actual penetration amount and rebound amount can be obtained, and the displacement measurement device does not require high-performance measuring equipment or complex analysis techniques. , it also has the advantage of not increasing costs.

Therefore, as a result, the accuracy of pile driving work etc. is improved, the construction period is shortened, climbing accuracy is good, construction can be done at low cost, and records etc. can be kept well. is also played.

[Brief explanation of the drawing]

The drawings are detailed explanatory diagrams of the invention of this application, and FIG. 1 is a partial cross-sectional side view of one embodiment, FIG. 2 is a graph showing the amount of penetration and rebound of the same driven pile, and FIG. 3 is a graph showing the amount of penetration and rebound of the same driven pile. 4 is a plan view of another embodiment, FIG. 5 is a partial sectional side view of the same, FIG. 6 is a partial sectional side view of the measuring wheel unit, and FIG. 7 is a partial sectional side view of the measuring wheel unit. Enlarged partial cross-sectional plan view,
FIG. 8 is a perspective view of measuring the penetration distance and rebound amount based on the prior art, and FIG. 9 is a graph diagram of the d penetration amount and rebound amount based on the prior art. 2... Driven pile, S... Penetration amount, C... Rebound amount, 10.
...Displacement sensor (potentiometer), 9...Way 1~, s', c'...Displacement amount 6...Case, 12...Roller, Applicant: Civil engineering? iJt research center

Claims (8)

[Claims] (1) When driving a driven pile by applying impact force to the driven pile with a hammer, use the hammer formula for managing the driving of the pile to obtain the pile supporting capacity against the ground of the driven pile. In the displacement measurement method for penetration amount and rebound amount, the penetration amount and rebound amount are measured by a displacement sensor attached to the pile, and the displacement amount of a weight with a large inertial force attached to the displacement sensor is calculated from an accelerometer. 1. A method for measuring displacement of a driven pile in construction work, characterized in that accurate penetration amount and rebound amount of the driven pile are obtained by obtaining the displacement amount. (2) When driving a driven pile by applying impact force to the driven pile with a hammer, use the hammer formula for managing the driving of the pile to obtain the pile supporting capacity against the ground of the driven pile. In the measuring device used for the method of measuring displacement of penetration amount and rebound amount, a displacement sensor is fixed in a case attached to the above-mentioned driven pile, and a weight with a large inertial force having an acceleration sensor is swingably arranged. A device for measuring displacement of driven piles in construction work. (3) The method for measuring displacement of a driven pile in construction work according to claim 2, wherein the case is fixed to the driven pile. (4) The method for measuring the displacement of a driven pile in construction work according to claim 2, wherein the case is removably attached to the driven pile. (5) The method for measuring the displacement of a driven pile for construction work according to claim 4, characterized in that a magnet is attached to the case. (6) The method for measuring the displacement of a driven pile for construction work according to claim 4, wherein the driven pile is made of a magnetic material. (7) The method for measuring the displacement of a driven pile in construction work according to claim 4, wherein the case is attached to the driven pile via a roller. (8) The method for measuring the displacement of a driven pile in construction work according to claim 4, wherein the driven pile is made of a non-magnetic material and is provided with a guide for a case.