SU840354A1 - Method of assessing the impact hazard of rock - Google Patents

Description

(54) METHOD FOR DETERMINING SHOCK HAZARDS

one

The invention relates to mining, is associated with testing the mechanical properties of rocks and can be used to predict the behavior of the massif on the outcrop contour in the workings in cases where the dynamic forms of near-surface rock layers occur under the action of stresses arising in the massif. shooters, jolts, etc., which are harbingers of stronger rock bursts in the future as the stresses in the massif increase.

A known method for simulating the state of a foam in an array in which artificial rock elements are artificially separated, for example, in the form of crushing cores into disks under the action of them. stress 1.

There is also known a method for determining the shock hazard of rocks, including loading the core with a uniform radial load over its cylindrical surface 2.

However, this method involves the reproduction of the arrows either by way of drilling the hole ("working out) and loading it

contour forces acting radially. A longitudinal load applied along the axis serves as a shield to prevent the core from breaking on the discs. At the same time, the mechanics1 of the arrows on the contour of the array prone to such phenomena in the workings is more complex and is determined by the state of the rock from the simultaneous interaction of normal and tangential stresses, the ratio of which is determined by the mining engineering situation and changes with it. In addition, the curvature of the contour of the hole being drilled significantly influences the redistribution of stresses and does not allow to reproduce the mechanism of arrows or rocks in a pure form. Accordingly, the use of simulation results for judging the properties of the rock in terms of impact hazard is not sufficiently objective.

The purpose of the invention is to improve the accuracy of shock hazard determination by increasing the reliability of reproducing the conditions of formation of arrows or an array without drilling rock.

Claims (2)

This goal is achieved by preliminarily extending the core with rigid sections with holes and additionally loading it in the longitudinal direction over the annular area, then changing the ratio of these loads to obtain the effect of separating the element in the surface layer, and by the nature of its separation shock hazard of rock. The drawing shows a core loading circuit. The core 1 drilled in the massif and machined at the ends is artificially extended with rigid sections 2 with holes 3, loaded through the sections in the longitudinal direction by applying uniformly distributed load PO over the annular area and thereby creating a stress concentration inside the core along the cylindrical surface in accordance with a hole diameter of 3 in sections 2. Regardless of loading in the longitudinal direction, the core is loaded in the transverse direction evenly distributed over the lateral cylindrical surface with a load PO. As a result, the core experiences a complex stress state in which normal and tangential stresses act simultaneously inside the core. Rigid sections with holes facilitate the most intense transfer of normal and tangential stresses to the surface layers of the core ends, due to the local concentration of stresses. As a result, with increasing loads, the concentration of normal and tangential at | (strains on rock elements 4) adjacent to the holes in rigid sections is created. Independent loading in the longitudinal and transverse directions allows changing the ratio of these stresses. necessary to obtain the effect of separation of the element of the surface layer of the rock, determined experimentally by repeatedly loading the core. The nature of the manifestation of the separation of the rock element (dynamic, calm) depends on the degree nor the brittleness of the rock. The very principle of imitating the separation of rock elements, based on the use of rocks directly, is due to the fact that it is difficult to create mechanical characteristics on artificial materials. In the case of a dynamic form of separation of the surface layer element, rock formations are able to and is shockproof when corresponding stresses occur in the array. With a smooth, quiet extrusion of an element of the surface layer of arrows, No workings have been made in this type of rock, the rock is not dangerous. Example. Hydraulic installations are used to load the core in the longitudinal and transverse directions. The test core has a diameter of 70-120 mm with a length of 2 dm. The range of loads created in the rock along the core axis (Pb) and perpendicular to it (P) is in the range of O-1500 kgf / cm. It has been established that massive varieties of lead ores under loading give a vigorous dynamic effect of separating the rock element in the form of arrows with strong sound and emission, while marble plastically squeezes out under loading and separation of the element occurs smoothly and calmly. Tests indicate the impact hazard of massive lead ore upon occurrence appropriate stress and non-hazardous marble. As a result of using the invention, the mechanism of separation of rock elements from the output contour is reproduced with the simultaneous simultaneous action of normal and tangential stresses, which makes it possible to give an objective assessment of the tendency of the rocks to dynamic phenomena in the form of arrows (in the initial stage) and destructive rock attacks (in the future ) and determine the possibility of their manifestation in the workings. In this case, the method allows to determine the ratio of the stress limit values at which the rock element is separated from the array contour. The invention also makes it possible to increase the safety of mining operations by using it in predicting the possibility of the occurrence of dynamic mass destruction in the workings. At the same time, the most effective prediction is possible even at the design survey stage, when there is only a core that is extracted from wells during exploration drilling. Such forecasting provides the greatest security, as it allows taking preventive measures to prevent rock bursts long before the commencement of mining operations by incorporating safe schemes and development systems in drafts and thereby virtually eliminating the appearance of rock bursts. Claim method for determining shock impact between rocks, including loading the core with a uniform radial load across its cylindrical surface, characterized in that, in order to increase the accuracy of shock hazard determination by increasing the reliability of reproducing the conditions of formation of the rock mass without drilling, the core is elongated with rigid sections with holes and. additionally load it in the longitudinal direction along the annular square, then