JPH042730B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a vibration experiment method using actual ground for analyzing the stability of the ground and structures during an earthquake.

[Conventional technology]

Conventionally, the following methods have been generally used to actually measure the behavior of earthquakes and structures during earthquakes.

Earthquake observation method: Seismometers and other instruments are installed on the ground and structures, and measurements are taken after waiting for an actual earthquake to occur.

Vibration experiment method: Vibration is excited by a vibrator or rocket installed on the ground (or structure), or by explosives buried in the ground, and measured using the same instruments as above.

Indoor test method: A certain part of the ground is sampled and the above physical properties are determined through indoor tests of the specimen.

[Problem that the invention seeks to solve]

However, when it comes to actual measurement of behavior during a major earthquake, the probability of being able to actually measure it is extremely low, and the strain and acceleration levels that can be generated are too low to be applicable in reality.
There were problems such as technical limitations in the sampling method and doubts about test accuracy.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention sets an excitation area in advance, excavates a groove that reaches deep into the ground around the area, and distinguishes the excitation area from the outside area when conducting a vibration experiment. It is characterized by being able to obtain the behavior of the ground or structures in their natural state that corresponds to the behavior of the ground or structures during an actual major earthquake.

〔Example〕

An embodiment of the present invention will be described with reference to the drawings.
In FIGS. 1 and 2, A in the figures is a preset vibration region, and instruments 1 such as a seismometer, a pore water pressure gauge, and an earth pressure gauge are buried in the ground. Typically, this involves drilling a hole deep into the ground, placing corded instruments in the hole, and then backfilling the hole. In addition, the embedding of instruments will be determined as appropriate depending on the direction of vibration.

On the other hand, around the excitation area A, a continuous groove 2 is excavated in a circular manner reaching deep into the ground (for example, 50 m deep). The depth of the groove 2 in this case should be appropriately set according to the type of ground, the size of the measurement target area, etc. Moreover, the groove 2 may be excavated with an excavating machine such as a BW machine.

The groove 2 separates the vibration region A from the non-vibration region B outside the vibration region A, and a vibration device 4 is placed on the ground surface of the vibration region A via a concrete mat 3.

Although the inside of the groove 2 may be left as is, it is desirable to fill the groove with muddy water in order to protect the groove wall surface. Further, the vibration device 4 is capable of applying vibrations in various directions such as horizontal, vertical, and torsional vibrations. Further, the concrete mat 3 is made of reinforced concrete and has a thickness of about 1 m, and is connected to the ground surface by driving small stakes between it and the ground surface to prevent it from slipping.

Then, the vibration excitation device 4 is activated and vibrated. In this case, the applied vibration will not propagate outward from the groove 2, but will be limited to the excitation area A, and the behavior equivalent to a large earthquake will occur in the excitation area despite the relatively small excitation force. This will occur over the entire ground of A. Therefore, by actually measuring its behavior with instruments 1 such as a seismograph, it is possible to analyze the stability of the ground during a major earthquake.

In the above embodiment, the behavior of the ground was actually measured, but it goes without saying that the behavior of a structure built on the ground surface or the like can also be actually measured using instruments installed on the structure.

In addition, if the ground to be investigated is deep and there is a soft stratum at the top, piles 10 or continuous underground walls that penetrate the soft stratum P and reach the ground Q to be investigated are placed on the lower surface of the concrete pine 3, as shown in Figure 3. The vibrations can be directly transmitted to the survey target ground Q through the piles 10 or underground continuous walls, or the soft stratum P in the excitation area A can be improved to strengthen and improve the ground as shown in Figure 4. Just set it to R.

Furthermore, if you set up the seismometer as is after conducting experiments in this way, it will be convenient for long-term earthquake observation.

〔Effect of the invention〕

According to the present invention, a groove is dug around the excitation area to limit the area where vibration occurs, so even with a small excitation force, the behavior equivalent to that during a large earthquake can be generated in the ground or structure. Therefore, it is possible to actually measure the strain and acceleration that would occur in the ground and structures during a major earthquake, which greatly contributes to stability analysis. Furthermore, it is useful for directly evaluating the validity of conventional seismic analysis methods, making it extremely effective in seismic design.

[Brief explanation of drawings]

Figures 1 and 2 are for explaining one embodiment of the present invention. Figure 1 is a side sectional view of the ground, Figure 2 is a plan view of the same, and Figures 3 and 4 are surface layers, respectively. FIG. A... Vibration area, B... Non-vibration area, 1... Instruments such as seismograph, 2... Groove, 3... Concrete mat, 4
...Vibration device.

Claims (1)

[Claims] 1 In a vibration experiment method in which the ground is vibrated and the resulting behavior of the ground and structures is measured using instruments such as seismographs, an area to be vibrated is set in advance and a trench reaching deep into the ground is created around it. A vibration excitation experimental method characterized by excavating and thereby separating the excitation area from the outside area.