Non-contact rock sound wave speed detection method

Abstract

The invention provides a non-contact rock sound wave speed detection method belonging to rock physics research field. The method is as follows: laser pulses produced by a laser pulse generator bombard the surface of a to-be-measured object to form ultrasonic wave in the to-be-measured object, at the same time, a laser vibration measurement instrument laser head is used for detecting vibration signals on the surface of the to-be-measured object on the other side of the to-be-measured object and converting the vibration signals into electrical signals, then ultrasonic wave waveform is drawn according to the electrical signals, and finally, the ultrasonic propagation speed in the to-be-measured object can be calculated according to the first arrival time of the ultrasonic wave. By use of the non-contact rock sound wave speed detection method, laser vibration experiments on a variety of core samples can be performed, rock core sound wave speed data can be obtained without damages to rock core, the rate of repeated use of the rock core is improved, the number of repeated core mining is reduced; sound wave speed value of any position of the rock core can be calculated by the method, a rock core speed field can be established according to the results, and study on anisotropic characteristics of the rock core can be facilitated.

Description

technical field [0001] The invention belongs to the field of rock physics research, in particular to a method for non-contact detection of rock acoustic wave velocity. Background technique [0002] Rock ultrasonic velocity testing technology: Rock acoustic velocity is an important index for rock mass quality evaluation. The methods for measuring acoustic velocity can be basically divided into three categories: resonance method, pulse method and interference method. The commonly used testing method is the ultrasonic pulse method. Ultrasonic-time method is used to test the sound wave velocity of rock. This method mainly uses elastic pulse, that is, the propagation time of elastic wave in solid medium to calculate the velocity. For the specific method, see figure 1 , that is, the transmitting probe transmits an ultrasonic pulse with a center frequency of 0.5 MHz, and measures the initial arrival time of the longitudinal and transverse waves of the pulse through the rock sample ...

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Problems solved by technology

[0020] However, usually the rock ultrasonic velocity test needs to cut the rock core sample into a regular shape (square, cylindrical, etc.) according to the requirements of the test equipment before performing the velocity test. The accuracy of the velocity data obtained by the test is received by the acoustic probe and The influence of factors such as the coupling degree of the core sample and the attenuation ability of the core sample itself to ultrasonic waves. Such a test method destroys the integrity of the core obtained by drilling, and also consumes a lot of manpower and time on the processing of the core sample.

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