This paper describes the new method for in-situ measurements of the most large-scale stress fields that are comparable to dimensions of deposits and mining leases. The method considers open cast mines and collapse zones of underground mining as disturbing cavities. The calculation of stresses is carried out thru measured deformations for the conditions of plane stressed state from the measured displacements of survey marks on the earth surface. GPS or GLONASS technology is used for the measuring. The results of in-situ study deformations of pit edges Pipe Udachnaya Mine (Sakha Republic, Russia) have been presented as an example of practical application of the method.
Rock pressure control with chamber mining involves ensuring stability of stope chambers while min~m4zlng the amount of ore in support pillars. We have studied the distribution of stresses in system elements of a mine with excavation of iron ore deposits of medium thickness (up to 20 m) and developed a new method for stress control of chambers and pillars.Rock beds of most iron ore deposits in the USSR and other countries are homogeneous, with horizontal stresses two or three times as high as vertical stresses [i]. No sagging "plates" or "beams" are created in the roof of the worked-out space. Vertical tensile stresses due to the weight of the hanging wall are compensated by the outward pressure of the horizontal stresses of the bed. The elements of the chamber workings are therefore destroye d by tangential stresses on the periphery of the worked-out space. This is confirmed by iron ore mining experience in the Urals, where the fracturing of pillars and chambers in strong monolithic rocks begins from the periphery at sites of concentration of maximum tangential stresses [2]. Field studies [3] have established that the strength of rocks under uniaxial and biaxial pressure is practically the same, i.e., the conventional Mohr's strength theory coincides with the first classical theory.In iron ore deposits the strength of chamber system elements can be estimated by the principal normal stresses at the periphery of the worked-out space.The stability of the hanging wall is provided when the compressive stresses at the contour of the roof are smeller than the bed's ultlmte compressive strength. Tensile stresses in the worked-out space roof are undesirable, because ultimate strength of the rock bed is very low.In absence of reliable methods of three-dlmenslonal modeling, we computed the principal normal stresses for a plane problem and then took into account the three-dimenslonallty of the worked-out space by introducing bulk coefficients.The plane modeling was constructed for the most stressed cross section of the worked-out space --cutting across i~s center. Since most iron deposit beds behave as a linearly elastic isotropic medium, the modeling was performed by the method of integral singular equations with the ELAST-2 program [4].Dip angles of the ore body were varied from 0 to 90". Initial bed stresses ware set equal to i, but in the analysis of the simulation results and a recalculation by superpositlon to biaxlal stressed state, the fact that the horizontal stresses are greater than the vertical stresses was adjusted for. The simulation also took into account the weight of the overburden and the weight of the collapsed rocks and introduced ~he outward pressure A -0.3 into the equations.The configurations of worked-out spaces in medium-thickness ore bodies worked by chambers followed by overburden collapse were divided into five types.i. The initial stage in ore body development. The worked-out space is described by a paralleleplped with a rectangular cross section (Fig. la).2. After a story is worked out and seal...
In article the actual problem of updating of the current legislation on designing for conformity to modern representations about an array of rocks is designated. Modern geodynamic movements play an important role in the formation of hazardous and emergency situations in surface and underground industrial and social facilities. Currently, in the regulatory documentation for the design of modern geodynamic movements are attributed to separate so-called areas of development of natural and technological processes, so the processes arising under the influence of modern geodynamic movements, are studied only for objects of high responsibility and only on additional request of the task, which is prepared by the customer. Prevention of dangerous development of building object destruction is possible at a stage of designing of constructions at performance of engineering researches. In most cases, engineering-geological and engineering-geodetic surveys are conducted without taking into account the factor of modern geodynamics, which is especially unacceptable in the design of social and industrial facilities, to which increased safety requirements are imposed. At present, the requirements of the standards do not fully correspond to the modern concept of rock mass, mobility of the upper crust of the Earth, which significantly complicates their application in practice. By results of researches it is revealed a number of the reasons of a deviation from requirements of standards for increase of safety of new building or operation of already existing responsible objects taking into account deformation processes under the influence of modern geodynamic movements.
The article presents an innovative procedure for the joint stress-strain and elasticity modulus analysis in high-strength rock masses with spacing from a few to tens meters. The procedure includes measurement of elastic convergence of rock walls due to deeper penetration of the foot of a vertical shaft and the analysis of measured displacements of check points along the shaft cross-section perimeter with subsequent two-stage solution of an inverse geomechanical problem. In the first stage, in the lobed diagram of measured displacements of check points, the azimuths of axes of the principal horizontal stresses in surrounding rock mass are determined. In the second stage, the process of deeper penetration of the shaft foot is modeled with different scenarios of the rock mass stress-strain behavior set as varied principal horizontal stresses at the known azimuths of their main axes. Then, the model and in-situ measurement results are compared using the analysis of variance ANOVA. The wanted variant of the stress-strain behavior and the associated modulus of elasticity, such that deviation of the actually measured displacements of check points from the model values is minimal, is identified by the extremum analysis of the experimental diagrams. The procedure was successfully tested in Vspomogatelny and Skipovoi vertical shafts of the Tenth Anniversary of Independence of Kazakhstan mine within Donskoy Mining and Processing Plant, in qualitatively different geological conditions: high-strength rock mass areas categorized as unstable and stable. In unstable rocks, the measured elasticity modulus Е = 3,5 ± 0,7 GPa made 6 %-16 % of the elasticity modulus in samples. In the stable rock mass, the measured modulus Е = 36,6 ± 7,7 GPa almost coincided with the elastic modulus of samples.
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