SU949594A1 - Method of checking stressed condition in mountain rock mass - Google Patents

Description

(54) METHOD OF CONTROLLING A STRESSED

CONDITIONS IN THE MASSIF OF MOUNTAIN BREEDS

The invention relates to methods for controlling stress in a rock massif and can be used in mining and in studying features of a genetic structure, for example, for the purposes of earthquake prediction, as well as landslides.

A method of controlling stress in a rock massif is well known, based on the drilling of boreholes (boreholes), the selection of core from them and its investigation in laboratory conditions.

However, this method is not only laborious and expensive, but also does not have sufficient accuracy in determining the stress state, since after taking the core from the array its state changes irreversibly.

There is a known method for studying the stress state in a rock massif, based on the emission and recording of the seismic frequency range fluctuations C1.

With this method, a source of elastic waves and a receiver of seismic waves are placed on the surface. Therefore, the remoteness of the source and receiver of seismic waves from

of the studied object of rocks, the use of sufficiently long reflected waves by yogis does not allow to follow the necessary changes in the elastic properties of rocks under the influence of the stresses developed in them, which, in turn, does not allow a confident prediction of the occurrence of mountain a strike or earthquake.

The closest in technical essence to the present invention is a method of controlling the stress state in an array of rocks, based on the placement of separate acoustic signals and sound-receiving shells in different wells drilled in the studied rocks, radiation and recording of elastic oscillations of the C21 sound frequency.

The known method is not intended to control the stress state in a rock massif, but by analogy with the breakthrough Ql, it is possible to evaluate the absolute values of stresses in their massif during the recalculation process.

However, the known method does not allow to determine the time of onset.

30 critical stresses, after which the investigated section of the rock massif is transformed into a plastic state. The purpose of the invention is to control the stress state in time and to detect the moment of occurrence of the critical (plastic) state in the rock mass at the prediction of natural disasters - landslides, rock bumps and earthquakes. The goal is achieved by the method of controlling the stress state in an array of rocks based on placing sound-emitting and sound-receiving projectiles separately in different wells drilled in the studied rocks, emitting and recording elastic oscillations of sound frequencies, which means a continuous radiation mode the amplitude of monochromatic harmonic signals simultaneously at least at two frequencies in the sound range, the stress state in the rock mass in Each time point is determined by the ratio of the stresses to a discontinuity 6p and (op by the expression .oe s) RC) where n is the ratio of the stresses to the discontinuity pf, -1 and fij are the emission frequencies; initial signal levels at these frequencies; fi fn registered one-time signal levels; d is the distance between the sound and the sound intake: shells, and the beginning of the critical state in the rock mass is determined by the moment when n ceases to be a constant value. The method is carried out as follows. Into a group of existing (or specially drilled) wells, for example, in two wells, Sound-emitting and sound-bending, shells are placed separately. When studying landslides and mountain blows, the depth of the projectiles is chosen to be equal to the depth of the stressed massif. Similarly, the depth of the sleeves of the rows is chosen in the study of stresses in the area of the focus area of the focal earth. In the case of investigation of the stress state of the rocks of the source center, earthquakes (the ones with a greater depth of penetration are hampered at the maximum possible depth corresponding to the actually achieved wells with the existing technology of their penetration. Thus, in the latter case, the stress state of the source investigate indirectly - according to the stressed state of the overlying rocks. The sound-emitting and sound-receiving shells are separated from each other by a given distance, r. With the help of the sound of the sound and the elastic sound. Frequencies are emitted continuously into the rocks at a constant level Lp of the original signal, at least at two fixed frequencies f 1 f 7. The levels of signals passing through the rocks are recorded with a sound-receiving projectile. The signal level L at a distance g from the sound-emitting sound Yes, it is defined by the expression L Uo-Meqrr-8, fe8dL, r, (where d is the sound absorption coefficient of the medium at frequency f. Hence, the sound absorption coefficient of the medium ctj, at a certain fixed frequency f, is equal to Up-f-IOgci r 9, 88 g and a tensile stress is established thereto (er and 6 pf, for example, at frequencies f, and f, j, respectively., - c, bvg Pf, bof -tf -Weqir „b, b8 g V -.4 where A is the proportionality coefficient. Within the limits of elastic deformations, the ratio pf and pfA, determined from relations (3) and (4), is constant and equal to 4/44-V °° l, s, (of, the transition to plastic deformations that precede irreversible deformations -; landslides, rock bursts and earthquakes; this ratio ceases to be constant because of the occurrence; at this moment, the nonlinearity of the media & 1. The proposed method is much more reliable than the method of core research prediction, as it allows accurate The moment of onset of an irreversible change in the rock mass.

Claims (2)

1.naiteHT US 3898610, 0 cells.340-15.5, publ .1973. 2.Pritsker L.S. Some methodical features of crosshole sounding on the tone signal. - Exploration and protection of mineral resources, 5 1977, 8, p.21 (prototype).