JP2004239701A - Weight fall buffer in rigidometer of ground - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable coping with rigid ground in a wide range without exchanging shock absorbing material and further improve measurement precision, in an apparatus for measuring rigidity of a ground based on reaction force from the ground and displacement of the ground to the impact force which is generated by dropping a weight 3 and transmitted to the ground A through the shock absorbing material. <P>SOLUTION: A compound coil spring 19 having a plurality of upper and lower coils different in spring rate is used as the shock absorbing material. On a substrate of low rigidity, a reaction force waveform which is ready in buffering action of the coil of small spring rate can be obtained. Also on a ground of high rigidity, a reaction force waveform which is ready in buffering action of a coil of large spring rate can be obtained. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a device for measuring the rigidity of the ground such as a road or a track, and more particularly, to a weight in a weight drop-type rigidity measuring device that drops a weight and measures the rigidity of the ground using the impact force. The present invention relates to a fall buffer.
[0002]
[Prior art]
As a method for measuring the rigidity of the ground, a method called a flat plate loading test has been known for a long time. This is a method in which a load is applied to a circular loading plate having a diameter of 30 cm placed on the ground, and the rigidity of the ground is measured from the relationship between the magnitude of the load and the displacement of the loading plate (ground), and the rigidity of the ground is evaluated. As the value, a value obtained by dividing the load strength (value obtained by dividing the applied load by the area of the loading plate) at a displacement of 0.125 cm obtained from the displacement curve by 0.125 cm (K value) (K value) Seeking. However, in the flat plate loading test, a large reaction force device such as a heavy machine which receives a reaction force of the load applied to the loading plate is required, and the test time is also several hours.
[0003]
Therefore, it has been conventionally performed to more simply measure the rigidity of the ground using a weight drop type rigidity measuring device. This stiffness measuring device drops a weight on a load scale placed on the ground via a loading plate, and transmits the impact force of the weight to the ground via the load meter and the loading plate. , And a displacement of the ground is detected by displacement detecting means. As the K value for evaluating the rigidity of the ground, the load strength when the ground displacement is a predetermined value (the value obtained by dividing the measured value of the ground reaction force by the load meter by the area of the loading plate, as in the flat plate loading test). ) Divided by the predetermined value.
[0004]
In addition, in the weight drop type stiffness measuring device, a cushioning material is installed in the transmission path of the impact force to prevent the measured value of the ground reaction force from fluctuating due to disturbance of the data waveform due to sudden impact or bounce due to impact force. It is arranged so that the impact force of the weight is transmitted to the ground while being cushioned by the cushioning material. Conventionally, a rubber material is used as a cushioning material.
[0005]
Here, the ground reaction force changes in such a manner as to draw a mountain-shaped waveform under the influence of the buffering action of the cushioning material, and the above-mentioned K value is obtained by using the peak value of this waveform as a measured value of the ground reaction force. In this case, in order to adjust the measurement conditions, the time from the start of the rise of the reaction force waveform to the peak (peak time) falls within a predetermined range on the ground having various stiffnesses, and the cushioning material has a linear deformation range (elastic range). It is desired that the peak be reached in the state where the buffering action is performed.
[0006]
However, the deformation characteristics of rubber materials are basically non-linear and the elastic range is narrow, so it is necessary to frequently replace the rubber material according to the rigidity of the ground. Even so, there was a difference in characteristics among the individual rubber materials, and the obtained data was easy to vary and was very difficult to handle. In most cases, the measurement of ground stiffness is performed outdoors, but since rubber materials are easily affected by temperature, data may vary depending on temperature, and rubber materials may deteriorate over time from a relatively early stage. And there was also a problem in terms of durability.
[0007]
Therefore, in order to solve the above-mentioned problem, it has been considered to use a coil spring having a wide elastic range, being hardly affected by air temperature, and having excellent durability as a cushioning material. However, at construction sites such as roads and tracks, the rigidity of the ground varies greatly from place to place, so it is not possible to cope with the elastic range of the coil spring. It has to be replaced with a different coil spring. That is, it is necessary to use a coil spring having a large spring constant in a high-rigid ground in which the ground reaction force is large, and to use a coil spring having a small spring constant in a low-rigid ground in which the ground reaction force is small.
[0008]
In addition, the inventor of the present application has come to realize that it is effective to suppress the impact force transmitted to the ground at first and stabilize the ground to obtain more accurate data.
[0009]
Prior art documents related to the present application include, for example, the following.
[0010]
[Patent Document]
Patent No. 2506282
[Problems to be solved by the invention]
In view of the above points, the present invention provides a weight falling buffer in a ground rigidity measuring device capable of coping with a wide range of rigid ground without replacing the cushioning material and further improving measurement accuracy. That is the challenge.
[0012]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the weight drop buffering device in the ground rigidity measuring device of the present invention drops the weight, and transmits the impact force of the weight to the ground via the cushioning material. In a device for measuring the rigidity of the ground based on a reaction force from the ground to the force and a displacement of the ground, a composite coil spring having a plurality of upper and lower coil portions having different spring constants is used as the cushioning material. .
[0013]
Here, there are at least two coil portions, a coil portion suitable for measurement of a relatively (relatively) low rigidity ground and a coil portion suitable for measurement of a high rigidity ground than the low rigidity ground. A composite coil spring is used as a cushioning material, and a spring constant of the coil portion suitable for the measurement of the ground with high rigidity is set to be larger than a spring constant of the coil portion suitable for the measurement of the ground with low rigidity. In this way, on low-stiffness ground, the reaction force waveform peaks while the coil portion having a small spring constant performs a buffering action, and on the high-stiffness ground, the coil portion having a large spring constant has a buffering action. The reaction force peaks in the running state. And, even if the reaction force becomes large in the ground of high rigidity, the rising of the reaction force waveform becomes steep due to the buffering action of the coil portion having a large spring constant, so that the peak time falls within a predetermined range similarly to the ground of low rigidity. . Therefore, it is possible to cope with a ground having a wide range of rigidity without replacing the cushioning material.
[0014]
Also, during a predetermined period at the beginning of the rise of the reaction force from the ground, a buffer action is performed by the coil part having the minimum spring constant of the plurality of coil parts, and thereafter, the reaction from the ground is performed while being buffered by the other coil parts. If the composite coil spring is configured so that the force reaches a peak, the impact force transmitted to the ground can be initially suppressed. Therefore, more accurate data can be obtained by stabilizing the ground, and the measurement accuracy is improved. It has two coil portions, a coil portion having a relatively small spring constant suitable for measurement of the ground having relatively low rigidity and a coil portion having a relatively large spring constant suitable for measurement of ground having relatively high rigidity. When a composite coil spring is used, the impact force transmitted to the ground can be initially suppressed to a low level by the buffering action of the coil part having a relatively small spring constant (the coil part having the minimum spring constant) on the ground having high rigidity. . In addition, by adding a coil portion having a smaller spring constant than a coil portion having a relatively small spring constant, it is possible to initially suppress the impact force transmitted to the ground even on a low-rigid ground.
[0015]
The above-described composite coil spring can be configured by connecting a plurality of independent coil springs having different spring constants. In this case, each coil spring is the above-mentioned coil portion. Further, the composite coil spring may be constituted by unequal-pitch coil springs. In this case, the coil portions are constituted by portions having different pitches.
[0016]
Further, in the present invention, the “ground” generally means a roadbed, a road surface, the ground, a pavement surface, and the like. The stiffness measuring device of the present invention can be applied to, for example, measuring the stiffness of a roadbed under a sleeper such as a railway, a road, a landslide before construction of a structure, a ground in a structure, a road surface of an airport, and the like. It is.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows a weight drop type rigidity measuring device for measuring the rigidity of the ground. This device includes a load cell 2 placed on the ground A via a disk-shaped load plate 1, a weight 3 dropped on the load cell 2, and a weight 3 attached above the load cell 2. And a locking mechanism 4 for removably locking.
[0018]
The load cell 2 is a load cell having a cylindrical strain body 5 made of metal and a top plate member 6 and a bottom plate member 7 mounted on both upper and lower ends thereof. Is fixed. A strain gauge (not shown) is attached to the inner peripheral surface of the strain generating element 5, and a load is applied via the strain gauge due to the strain of the strain generating element 5 generated by a vertical load acting on the load cell 2. Is output.
[0019]
Further, an acceleration sensor 8 that is positioned at the center of the bottom plate member 7 and detects acceleration in the vertical direction is fixed inside the load cell 2. Then, the acceleration signal output from the acceleration sensor 8 is transmitted to the external data processing device 9 together with the load signal, and the acceleration detected by the acceleration sensor 8 is integrated twice to obtain the vertical displacement of the ground A. I have to. It is also possible to provide a speed sensor instead of the acceleration sensor 8 and calculate the vertical displacement of the ground A by integrating once the speed detected by the speed sensor.
[0020]
A disk-shaped auxiliary plate 10 is fixed on the top plate member 6 of the load cell 2, and the weight 3 is externally vertically movably inserted into a guide rod 11 erected on the auxiliary plate 10. . The weight 3 can be lifted by gripping a knob 12 fixed to its upper end.
[0021]
The locking mechanism 4 includes an operation lever 15 pivotally mounted on a support member 13 attached to the guide rod 11 so as to be position-adjustable via a shaft 14. An engaging piece 17 is provided on the upper end of the weight 3 to engage with a flange 16a at the upper end of the cylindrical body 16 so that the weight 3 can be locked at an upper position. The operation lever 15 is urged by a spring 18 in a direction in which the locking piece 17 engages with the flange 16a. By gripping the upper part of the operation lever 15 and swinging the operation lever 15 in the direction of arrow P in the figure, the locking piece 17 is detached from the flange 16a, and the weight 3 is directed toward the load meter 2. To fall.
[0022]
When the weight 3 falls on the load meter 2, the impact force of the weight 3 is transmitted to the ground A via the load meter 2 and the loading plate 1, and the reaction force from the ground A to the impact force is applied to the load meter 2. Then, the reaction force is measured, and the displacement of the ground A is measured.
[0023]
In the transmission path of the impact force to the ground A, a cushioning material constituting the weight falling shock absorber of the present invention is arranged so that a sudden impact is not applied to the ground A. In the present embodiment, a plurality of cushioning members composed of a composite coil spring 19, which will be described in detail later, are arranged on the upper surface of the auxiliary plate 10 on the load cell 2 so as to surround the guide rod 11. The reaction force and displacement of the ground A change due to the cushioning action of these cushioning members so as to draw a mountain-shaped waveform as illustrated in FIG. Then, the peak value of the reaction force and the displacement are set as the respective measured values, and the mass and the drop height of the weight 3 are adjusted so that the measured value of the displacement becomes the predetermined value zs. A value (K value) for evaluating the rigidity of the ground is obtained by dividing the measured value of the force by the area of the loading plate 1) by the predetermined value zs. However, even if the weight and the drop height of the weight 3 are adjusted, it is difficult to obtain a displacement that exactly matches the predetermined value. Therefore, by changing the mass and the falling height of the weight 3, a measurement is performed to obtain a displacement sandwiching the predetermined value, and the K value is obtained by proportional distribution. The predetermined value zs of the displacement is based on 0.125 cm of a flat plate loading test performed using a loading plate having a diameter of 30 cm. When the diameter of the loading plate 1 is not 30 cm, the diameter of the loading plate 1 is set to φs. , 0.125 cm multiplied by the diameter ratio (φs / 30) with respect to the load plate having a diameter of 30 cm is set as the predetermined displacement zs.
[0024]
Here, in order to adjust the measurement conditions, the time from the start of the reaction force waveform rise to the peak (peak time TP) when the measurement of the displacement becomes the predetermined value zs on the ground having various rigidities is performed. It is desired that the peak is set within a predetermined range (about 6 to 10 msec), and furthermore, the buffer reaches a peak in a state where the cushioning material performs a buffering action in a linear deformation region (elastic region).
[0025]
Accordingly, in the present embodiment, as shown in FIG. 2, a composite coil spring 19 having an upper first coil portion 19a and a lower second coil portion 19b having a larger spring constant as a buffer, as shown in FIG. Is used. Note that the first and second coil portions 19a and 19b may be arranged upside down. When such a composite coil spring 19 is used, in a region where the ground reaction force is relatively small, the first coil portion 19a is mainly elastically deformed as shown in FIG. After the ground reaction force is increased and the first coil portion 19a is completely compressed, only the second coil portion 19c is elastically deformed as shown in FIG. Therefore, when the measurement is performed on the ground having high rigidity, as shown in FIG. 4, the ground reaction force gradually rises due to the buffering action of the first coil portion 19a for a predetermined period at the beginning of rising, and then the second coil A waveform is drawn which rises rapidly and reaches a peak while receiving the buffering effect of the portion 19b.
[0026]
Here, the spring constant of the first coil portion 19a is a relatively small value suitable for measurement on the ground having relatively low rigidity, that is, the measured value of the displacement on the ground having relatively low rigidity becomes the predetermined value zs. When such a measurement is performed, the reaction force waveform is set to a peak in a state where the first coil portion 19a performs a buffering action, and the peak time TP is set to a value that falls within a predetermined range. The spring constant of the second coil portion 19b is set to a relatively large value suitable for measurement on a relatively stiff ground, that is, the measured value of displacement on a relatively stiff ground is a predetermined value zs. When the first measurement is performed, the reaction force waveform is set to a peak value in a state where the first coil portion 19a performs the buffering action, and the peak time TP is set to a value within the predetermined range. Therefore, it is possible to deal with a wide range of rigid ground without replacing the cushioning material. Further, in the measurement on the ground having high rigidity, the impact force transmitted to the ground is initially suppressed low by the buffering action of the first coil portion 19a, so that the ground can be stabilized and more accurate data can be obtained. Measurement accuracy is improved. In the case of low rigidity ground, a buffering action of the ground itself can be obtained, so that the initial impact force does not have to be suppressed by the buffer material, but if necessary, a coil having a smaller spring constant than the first coil portion 19a may be used. The part may be added to the composite coil spring 19.
[0027]
In the above-described embodiment, the first and second coil portions 19a and 19b are formed by independent coil springs, respectively, and the two coil springs are joined by welding or the like to manufacture the composite coil spring 19. . However, the composite coil spring 19 is not limited to this. For example, as shown in FIG. 3, the composite coil spring 19 may be formed by an unequal pitch coil spring. In this case, the narrow pitch portion becomes the first coil portion 19a having a small spring constant, and the wide pitch portion becomes the second coil portion 19b having a large spring constant.
[0028]
Further, in the above embodiment, the plurality of composite coil springs 19 are arranged so as to surround the guide rod 11, but the guide rod 11 is loosely inserted into the inner circumferential space of a single composite coil spring having a larger coil diameter. It is also possible to arrange in such a way.
[Brief description of the drawings]
FIG. 1 is a diagram showing an entire configuration of an embodiment of a rigidity measuring device according to the present invention.
2A is a diagram showing a composite coil spring used as a cushioning material of a weight drop buffer in the rigidity measuring device of FIG. 1, FIG. 2B is a diagram showing a low load state of the composite coil spring, and FIG. The figure which shows the high load state of a coil spring.
FIG. 3 is a diagram showing another embodiment of the composite coil spring.
FIG. 4 is a view showing waveforms of a ground reaction force and a displacement measured by the rigidity measuring device of FIG. 1;
[Explanation of symbols]
A: Ground 2: Load cell 3: Weight 19: Composite coil spring 19a: Coil portion with a small spring constant 19b: Coil portion with a large spring constant

Claims (5)

Dropping the weight, transmitting the impact force of the weight to the ground via the cushioning material, in a device for measuring the rigidity of the ground based on the reaction force from the ground and the displacement of the ground against this impact force,
A weight falling shock absorber in a ground rigidity measuring device, wherein a composite coil spring having a plurality of upper and lower coil portions having different spring constants is used as the shock absorbing material. The composite coil spring has at least two coil portions, a coil portion suitable for measuring a ground having low rigidity and a coil portion suitable for measuring a ground having higher rigidity than the ground having low rigidity. The weight drop buffer device in the ground rigidity measuring device according to claim 1, wherein the interaction of the two coil portions enables the rigidity of the ground having a wide range of rigidity from the ground having high rigidity to the ground having low rigidity. . The composite coil spring performs a buffering action by a coil section having a minimum spring constant of the plurality of coil sections for a predetermined period at the beginning of the rise of a reaction force from the ground, and thereafter receives a buffering action by another coil section. 2. The weight fall buffer device according to claim 1, wherein the reaction force from the ground reaches a peak. The ground rigidity measuring apparatus according to any one of claims 1 to 3, wherein the composite coil spring is configured by joining a plurality of independent coil springs each serving as the coil part. Weight drop shock absorber in. The weight drop buffer device according to any one of claims 1 to 3, wherein the composite coil spring is constituted by an unequal pitch coil spring.

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