SU1113543A2 - Method of determining stressed state of rock massif - Google Patents

Description

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The invention relates to mining and can be used to control the injection state of a rock mass.

According to the main author. St. No. 1086160, a method for determining the stress state of an array of rocks is known, based on changing the stress state of rock samples by mechanical loading and registering electromagnetic emission pulses during the loading process, according to which the mechanical loading of the samples is carried out at a constant speed, the amplitude is measured pulses by electromagnetic emission, determine their mean amplitude, record the time of the appearance of a pulse, the amplitude of which is more than an order of magnitude greater than the average a plitudu pulses of electromagnetic emission, and a load value corresponding to this point, is judged on the magnitude of stress relieving the condition of the rock mass 11.

However, this method does not allow to determine the directions of the main strains and, therefore, is not very informative.

The aim of the invention is to increase the information content of the method by determining the direction of the main stresses.

This goal is achieved by the fact that, according to the method of determining the stress state of an array of rocks, the amplitude of electromagnetic emission pulses is additionally measured at a load equal to the magnitude of the stresses acting in the array, while the measurements are carried out on samples differently oriented with respect to the array, and The direction of action of the maximum and minimum main voltages is judged according to the direction of the load at which the maximum and minimum pulses of the electromagnetic em are recorded, respectively. SMAI.

The physical background of the invention is as follows. The dielectric rocks, the minerals of which have a crystalline structure, have a volume polarization, which is associated with the genesis of the rocks and human activity, and is explained by the presence of charged defects in the structure of the crystal lattice. The loading of such rocks is accompanied by electromagnetic emission in the form of short high-frequency pulses, resulting, for example, as a result of movement under the action of an applied load and the release of charged defects on the surface of cracks, primarily Dislocations. The movement of dislocations in rocks is hampered by the presence of other defects - screw dislocations, vacancies and interstitial sites; ions, whose concentration depends on the thermodynamic state in which the rocks in the massif are located,

in particular, from their stress-strain state. Under unchanged conditions, most dislocations are enveloped by clouds of point defects, which inhibit the movement of dislocations and fix them in the crystal lattice. In this case, under the influence of stresses acting in the array, the dislocations are arranged in chains, most of which are oriented perpendicularly to the direction of the maximum principal stress. Thus, the number and orientation of the fixed dislocations in rocks depend on the magnitude and direction of the maximum principal stress acting in

array.

In the process of loading a rock sample, when a load reaches the same magnitude as the stress acting in the array, previously bound dislocations are separated from the surrounding clouds and these dislocations move to the surfaces of the cracks, which is accompanied by an electromagnetic pulse of significant amplitude. In this case, the amplitude of a given pulse depends on the degree of coincidence of the direction of application of the load with the direction of action of the maximum principal voltage. In that case, if the direction of application of the load coincides with the direction of action of the maximum principal voltage, the pulse of electromagnetic emission has a maximum amplitude.

Thus, the detected laws. The dimension of the amplitude change of the electromagnetic emission pulses of rock samples from the degree of coincidence of the direction of application of the load with the direction of deistriction of the maximum principal voltage allows determining the directions of the main stress in the rock massif.

FIG. I shows the dependences of the amplitude variation of electromagnetic emission pulses for six differently oriented rock samples on the magnitude of the load; in fig. 2 - stress ellipse constructed from the obtained results.

The method is carried out as follows.

From oriented towards the array of core drilled from the studied area of the array, make a series of samples. Each sample received

load at a constant speed using a hydraulic press to a load equal to the magnitude of the voltage acting in the array, and determine the amplitude of the electromagnetic emission pulse generated by this load using an antenna and a selective voltmeter. In this case, each of the studied samples of the series is rotated at a certain angle relative to the initial position.

On fng. Figure I shows the characteristic change in the amplitude of the pulses of the electromagnetic emissivity of the samples from the direction of application of the load. The direction of the load at which the maximum amplitude pulse is recorded coincides with the direction of the maximum main voltage 6i, respectively, the direction of the load at which the electromagnetic emission pulse is minimal, is the direction of the minimum main voltage 6iH in FIG. Figure 2 shows a voltage ellipse constructed from the measured values of the amplitudes of the electromagnetic pulses. - Experiments were carried out on specimens of various rocks (marbles, limestones, salt rocks, etc.). Samples in the form of cores with a diameter of 45 mm and a length of 270 mm were kept for several hours under a load of P 150 kg / cm, and then loaded. Next, icepH was cut into b samples with a length of 45 mm. Each sample was again subjected to linearly increasing loading up to a load of 200 kg / cm with simultaneous recording of the amplitude of electromagnetic emission pulses. In this case, the first sample was rotated by an angle of 30 ° relative to its position in the first cycle counterclockwise, the orientation of the second sample remained the same, the subsequent samples were rotated through an angle of 30 ° clockwise relative to the previous one. Experiments have shown that when the load is repeated, when the load P on the sample is equal to I, the pulses of electromagnetic emission of considerable amplitude are observed, and the magnitudes of these pulses depend on the degree of coincidence of the direction of the repeated and initial loads. In the case when these directions coincide (sample number 2), the amplitude of the electromagnetic emission pulse is maximum.

Thus, the invention makes it possible to increase the information content of the method for determining the stress state of a rock mass by determining the direction of the principal stresses. This is what determines its technical and economic effect.

Claims (1)

METHOD FOR DETERMINING THE STRESSED STATE OF ROCK MASSIVA by author. St. No. 1086160, characterized in that, in order to increase information content, they additionally measure the amplitude of electromagnetic emission pulses at a load equal to the voltage acting in the array, while the measurements are carried out on samples differently oriented with respect to the array, and the direction of action of the maximum and minimum principal stresses are judged by the directions of the load at which the maximum n minimum pulses of electromagnetic emission are recorded respectively. 150 R Fit. 1 III3543