SU1765458A1 - Method of controlling stress in rocks adjoining mine working - Google Patents

Abstract

The invention relates to mining and m. used in the excavation of mine workings. The goal is to reduce the stress state of the rock mass surrounding the mining output by providing additional stress behind the unloading zone. The dimensions of the off-loading area of the marginal array are determined. The dimensions of the half-span of production are determined. A well is drilled for the unloaded zone of the marginal array. They charge it with charge B for a length equal to the size difference between the half-span of the output and the unloaded zone of the marginal array. The explosive charges are exploded. 7 silt

Description

The invention relates to mining, and more specifically to mining and the safety of mining operations therein. The invention can be used in enterprises where it is necessary to protect underground workings from destruction by rock pressure under conditions of rock creep or impact hazard.

There is a known method of controlling the stress state of rocks in an array surrounding the mine workings by creating an unloading slot in the marginal array. As a result of the rocks moving in the direction of the cavity of the gap, the stress in the rocks decreases.

This method has a significant drawback. In the marginal part of the array, provided with a gap, the compressive stresses decrease to zero, and in some cases they become tensile, unacceptable for exposures

As a prototype of the invention, a method of preventing rock bursts in a rock massif is taken, which includes the formation of discharge gaps outside the mine workings, while the discharge gaps form fractures perpendicular to the maximum stresses acting in the rock mass behind the mining zone.

However, the known method leads to the destruction of the fracture zone, when its compliance (compressibility) is lower than the compliance of the artificially destroyed part of the massif. In addition, this method is ineffective in low-resistant rocks, as it contributes to further weakening them,

The aim of the invention is to increase the safety of production by redistributing the stresses in the rocks around it. The invention is directed to the improvement of technical and economic indicators of proVI

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mining and mining operations, as well as to improve the safety of mining operations.

The goal is achieved by the fact that in the method of preventing rock bursts, including the formation of a zone of destruction of rocks beyond the contour of the excavation, the formation of these zones is carried out behind the unloaded part of the marginal massif; at the same time, the destroyed rock is left in the indicated zone and additional pressure is created by dilantancy of the rocks; dilantancy is created by blasting downhole charges.

An analysis of the distinctive features of the proposed solution showed that the location of the zone of destroyed rocks behind the unloaded part of the marginal massif made it possible to preserve the integrity of the boundary part of the massif; reduce stresses in the massif near the contour of the mine workings; transferring the concentration of stresses from the marginal part of the massif to the area of its all-round compression, in which the mass carrying capacity of the massif is much higher, and the impact hazard of rocks is reduced by their fragmentation; the destruction of the rock while preserving its mass in the zone of destruction made it possible to create additional stationary pressure due to the dilantancy of the rocks; increase the size of the protection zone, including the undisturbed, unloaded and destroyed loaded parts of the array; exclude the volume of drilling to compensate for the loosening of the rocks, which is necessary when unloading the massif in a known manner; The creation of additional pressure in the zone of destruction of rocks by their dilantancy allowed the explosive method of destruction of rocks to be used, as the most economical in comparison with special (mechanical) ones.

FIG. 1 shows the cross section of the mine workings and the surrounding rock mass surrounding it; in fig. 2 shows section A-A in FIG. 1 (the zone of destroyed rocks is located behind the discharge part of the marginal massif); in fig. 3 - stress diagrams in the marginal massif, when the zone of destroyed rocks is located behind its discharged part; in fig. 4 shows a section of a marginal array in which the zone of destroyed rocks is located between the discharged parts of the array; Fig. 5 shows the distribution of stresses in the marginal array when the fractured rocks are located between the discharged parts of the array; in fig. 6 - location of the zone of destroyed rocks in front of the discharge part of the array; in fig. 7 shows stress plots for the case of location

destroyed rocks in front of the discharge part of the array.

The marginal array represents the area from the production contour inward, within the influence of generation.

The zone of destroyed rocks with which the stresses in the massif are controlled is characterized by the size within which the artificial destruction of rocks is carried out.

The unloading part of the array is its part, within which it is necessary to reduce the stresses, i.e. the part of the marginal array in which the stress state is controlled.

The size of the discharge part of the array can be determined instrumentally, for example by ultrasound logging of wells, or regulated by instructive and design documents.

The size of the zone of destroyed rocks is defined as the difference in the size of the protective zone, which is equal to the half-span (radius) of generation, and the size of the unloaded part of the array.

The protection zone is a section of rocks of a production contour deep into the massif in which no rock bursts or other destruction should occur.

The method is carried out as follows.

From generation 1, a row of wells 5 with a length equal to the size of the protection zone is drilled through the production of the discharge part 3 adjacent to the contour 2 of the marginal array 4. The well 5 within zone 6 is charged with an explosive (EX) with an under-discharge length equal to the size of the discharge part 3 of the edge array.

4. By blasting charges B, a zone of destroyed rocks 7 is created. When the explosion is orthogonal to the plane of location of wells 5, the massif expands. Gaps appear in it, the total amount of which, according to the experiment, reaches 8–15 mm. At the same time, in the opposite direction, the rock between the wells 5 is compressed to fracture and moves the expanding gases to the middle of the gap between the wells.

5, fill the void gaps. After the explosion, the fractures cannot fully close, this is prevented by the destroyed rock 7.

In the zone of destroyed rocks 7, due to the additional expansion of the delatating rocks, the stress increases, while in the discharge part 3 it decreases.

The ha of FIG. 3 shows the stress plot 8 prior to applying the proposed method, dashed line) and the plot 9 after applying the method (solid line), which show that in zone 3 the voltage is reduced.

In practice, it is possible that voltage reduction is necessary in two parts of the array, for example, along the edges of the rear sight. Then the zone of destroyed rocks 7 is placed between the discharge zones 3 and 12 (Fig. 4). Plots 10 and 11 (Fig. 5) show a decrease in stresses in zones 3 and 12 after the application of the proposed method.

FIG. 6 shows the case when the unloaded zone must be created inside the marginal part of the array, for example, in the center of the rear sight. In this case, the method involves creating a zone of fractured rocks 7 before discharging part 3 of the array at circuit 2 of output 1. After applying the proposed method, the stresses in zone 3 are lower (plot 13) than before its use (plot 14, Fig. 7).

The use of the proposed method of controlling stresses in the surrounding rocks in comparison with the known one provides the following advantages: while ensuring the discharge of a rock zone, it does not destroy it, which is especially important for the rocks adjacent to the production contour; the creation of additional thrust in the rocks contributes to their stability; in all cases, an additional spread in one place and a decrease in stresses in another contribute to a decrease in the intensity of the stress, and hence the threat of destruction of the marginal part of the massif; The zone of destroyed rocks has an important contradictory property: providing an additional spread, the zone is malleable at stresses close to the ultimate strength of the rocks; compliance is ensured by seeing the rocks at the points of contact of the pieces; the array is not destroyed. The additional thrust is created by the dilantancy of the destroyed rocks, i.e. the property that led to the destruction of the rocks on the production contour, used to produce a positive effect. The cost of creating a protective zone for protecting production is reduced by reducing the volume of drilling and explosives consumption. Improving the stability of the marginal array allows for its support to apply lightweight lining instead of arched, concrete, etc.

The effect of the application of the proposed method in conditions of excavation of workings on impact-sensitive rocks is primarily of a social nature and consists in increasing the safety of mining operations.

In addition, the redistribution of stresses in the marginal part of an array of rocks in combination with light types of lining, such as anchor, can provide sufficient stability of development, in which prior to the application of the proposed method, metal arched or concrete lining was used. At the Krivoy Rog deposit, the volume of such workings is 10–20 km.

Taking into account the approximate costs of the proposed and known options for maintaining workings, we use the formula for calculating

20

(С-Сн) -Ен (К „-К),

where С and Сн is the reduced cost of maintaining 1 m of output according to known (rubles) and new (rubles) ways;

K - capital investment (); KN - the cost of research (thousand rubles);

Yong - regulatory efficiency ratio (, 15);

And - the volume of use of the new method (A 14000 m).

The estimated economic effect will be 3 14000- (287-275) -0.15 x x (90000) 146500 rubles.

Claims (1)

Invention Formula A method of controlling voltages in the surrounding rocks, including determining the size of the discharge zone of the marginal array, drilling wells, charging these wells with charges explosives and their blasting, characterized in that, in order to reduce the stress state of the surrounding rock mass by providing additional stress for the discharge zone, determine the size of the half-span of production, and the well is drilled beyond the discharge zone of the marginal array, while the wells are charged with charges of explosives a length equal to the size difference between the half-span of the excavation and the discharge zone of the marginal array. u / L7 ,,, ( FIG. 2 tfig z Fig.b  ;;. №  iA, i m FIG. 6 P B FIG. 7