The selection standing waves of microseismic field according to the physical modeling

Fedin K.V.

A.A. Trofimuk Institute of Petroleum Geology and Geophysics SB RAS, Novosibirsk, Russia

Fedin.konstantin@gmail.com

There are many problems associated with the construction and operation of pipelines, namely local failure, corrosion, washing, freezing soil, subsidence, etc. leading to deformation or loss of strength. In recent years, developed a method of inspection of buildings and engineering structures, allowing for different times of the field recordings of MS in different parts of the objects to determine the values ​​of natural frequencies and mode shapes to study the standing waves formed in the plants under the influence of microseismic vibrations [1-2].

This paper describes a technique of physical modeling method, a survey of buildings and structures standing waves by using multi-temporal records of microseismic field applied to the problem of the influence of subsidence on the pipeline system, and give some experimental results.

The objects of investigation are steel, aluminum and copper pipes. After a series of preliminary experiments on the quality factor of the material, it was decided to choose the copper pipe as a further object of the study. Obtained images of the flexural modes of vibration of copper pipe with a 50-cm of the tube on the 150th cm, in increments of 1 cm on 5t synchronous recordings, which is approximately 3.25 seconds, set at the edges of foam rubber.

The considered frequency range from 0 to 6.1kGts. The parameters investigated were the following copper pipe, 18mm diameter and 1mm thickness and length 2metra. Then, to simulate a system of pipes, pipe was rigidly fixed with five clips from the edges of the tube and then in increments of 50cm. The measurements were performed between the second and fourth clamp to start the central clamp was removed, so that the resulting system of 4 clips without center, in order to confirm the theoretical possibility of the existence of oscillations of the individual, between 2m and 4m straps. The results show that the edges of the picture can be seen bending vibration nodes of standing waves, which may indicate the existence of rigid fastening of the sample.

Next, to simulate the pipeline system, has been fixed clamp the central portion of the pipe.According to the results noticeably influence of the clamp, each part of the pipeline system varies independently of the other part, with the frequency increasing order modes. It can be seen third node oscillations at the edges and center. You may notice that the right of the picture more intense due to the fact that the reference sensor in the measurement process was located to the right of the central mounting.

To simulate land subsidence in the central part, a central clamp was placed rubber gasket.The results of this experiment showed that the node is lost flexural vibrations in the center, that is, copper tube oscillates as a whole, between 2m and fourth clamps. You can also see that the bending vibrational modes are much higher. Q-factor of the picture has become much worse. You can also replace the sharp disappearance of the intensity of 56 to 61cm, this place is fixing the reference sensor.

Was carried out computer simulations of the process. These physical simulations agree well with the computer [3].

References:

1. Emanov, Seleznev VS, Bach A. etc. Detailed engineering and seismological studies of buildings and structures standing waves / Problems of regional geophysics: Geophysical Conference Proceedings. - Novosibirsk: LLC "Printing of Siberia", 2001.

2. RF patent № 2150684. Method of recording time to a single measurement of multi-accounts / Emanov, Seleznev VS, Kuz

3. Abaqus Student Edition / http://www.simulia.com/academics/student.html