SU1390356A1 - Method of determining phase velocities of elastic waves in rock when measuring its strained state - Google Patents

Description

(21) 4109290 / 22-03

(22) 06/16/86

(46) 23.04..88. Bul Number 15

(71) Institute of Physics of the Earth im.O.Yu.Shmidt

(72) G.A.Efimova, I.V. Zhukov and V.A. Kalinin

(53) 622.289 (088.8)

(56) Molotov L.V. On the dispersion of bulk waves in terrigenous rocks. Publishing house of the USSR Academy of Sciences. Physics of the Earth, 1966, No. 8, pp.36-46.

Volarovich MP et al. Physico-mechanical properties of rocks and minerals at high pressures and temperatures. - M .: Science, 1974, p.23-25.

(54) METHOD FOR DETERMINING THE PHASE VELOCIATIONS OF ELASTIC WAVES IN MOUNTAIN BREEDS WHEN CHANGING THEIR STRESSED CONDITION

(57) The invention relates to mining and is intended to study

properties and state of rocks. The purpose of the invention is to improve the measurement accuracy. When it is loaded, mountain rock is sounded with the help of elastic and sound. .Registered past pulses. The sound bases and the propagation time of elastic waves in the rock are measured. In addition, the phase spectra of the fragments of the detected pulses are determined at the initial voltage RD and the effective voltage P and the phase velocity is calculated for each fixed component of the spectrum. The duration of the analyzed fragment of the recorded pulse is chosen from the condition 21 / Cf, where 1 and C g, respectively, the power of the thinnest sounding layer and the speed of elastic waves in it under the voltage P. Thanks to this method, more sensitive parameters are used and constant contact conditions are provided during rock loading. 1 il.

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The invention relates to the mining business and is intended to study the properties and states of rocks by changing the speed of propagation of elastic waves in them.

The aim of the invention is to improve the measurement accuracy.

The drawing shows a measurement system for determining phase velocities in rocks.

The measuring system contains a pulse generator 1, a piezo transducer 2, a rock block 3, g: a receiver 4, an amplifier 5, an oscillator 6, an analog-to-digital converter 7, a processor 8, a time sector: eKTOp 9, spectrum analyzer 10 and press 11.

The operation of the measuring system is as follows.

The electric pulses emitted by the generator 1 excite a piezoelectric transducer 2 fixed on the wall of the rock block 3 and generating sound acoustic pulses. Elastic impulses passed through the rock block 3 are fed to the receiver 4, which is attached to the protruding edge of the sample, so that the axis passing through the centers of their radiator and receiver surfaces is strictly perpendicular to the face of the sample, which is necessary for Providing the conditions of a normal patient for a direct longitudinal wave. Electric pulses from the piezoelectric receiver are fed to amplifier 5, then to the oscilloscope b for visual control and in parallel to analog-digital converter 7 and the processor

8dl frequency analysis. To cut off the non-informative part of the pulse, the time interval being analyzed is set in the program for computerized calculation of phase spectra. It is also possible to use a temporary selector.

9 in combination with a spectrum analyzer 10. The investigated block of rock is placed between the plates of a hydraulic press 11.

The method is carried out as follows.

In the initial stress state of the rock, with zero pressing force or load imitating the background static voltage P, the rock is heard, the propagation time is determined

elastic pulse in the rock on the first entry of a direct longitudinal wave and at the same time determined the phase spectrum of the fragment of the recorded pulse.

The duration of the analyzed fragment of the recorded pulse is chosen from the condition

-g - 21 / s

R

five

0

five

0

five

0

five

0

five

where 1, SL is, respectively, the power and speed of elastic waves in the thinnest sounding layer, at the initial voltage P, then the rock is loaded before the voltage P, and P g: P Pd, where P d, is the ultimate strength of the rock. The phase spectrum of the corresponding fragment of the detected pulse is determined at a voltage P and the phase velocity for each fixed component of the spectrum is determined at a stressed state P by the formula

Cf; L (P) / (t + L F, / W;),

where C j is the phase velocity for frequency f; L (P) - change of sound base under load; t is the propagation time of the elastic waves at the initial voltage PJ;

a If. is the phase difference of the frequency fj at voltages x and w) is the cyclic frequency, wp

 2n / f ..

The proposed method allows to increase the accuracy of phase velocity measurements by using a more sensitive parameter (changing the signal phase), as well as providing constant contact conditions during the rock loading process.

Claims (1)

Invention Formula The method for determining the phase velocities of elastic waves in rocks when their stress state changes, including sounding of rocks when they are loaded using elastic pulses, registration of transmitted pulses, measurement of the sound base and the propagation time of elastic waves in the rock, characterized in that aim to improve measurement accuracy. additionally determine the phase spectra of the fragments of the recorded pulses at the initial voltage PO and the effective voltage P and determine the phase velocity for a fixed component of the spectrum using the formula Cf. L (P) / (t + J (G, / L);), voltage P; L (/. - phase difference frequency fj at voltages P and LU - cyclic frequency, w- ,, the duration of the analyzed fragment of the recorded pulse is chosen from the condition where cf. - phase velocity for often-. . . you f .; L (P) is the change in the base, sounding where 1 and C are respectively the power nor under load; jj most thin sound layer t is the propagation time of the pack and the velocity of the elastic waves in it at the other waves at the initial stress P, ten /.