RU2540694C1 - Method for determining natural stresses in mine rock body - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: method involves measurement of stresses in mine rock body beyond the limits of an influence zone of second (mining) working at different depth when using underground mine workings, build-up of charts (dependences) of variation of the obtained primary stresses with depth. In order to improve forecast accuracy of stresses, including at horizon depth, each of the primary stresses is divided into constant and variable (pulsating) components in time. Relationship between variation of constant component parts with depth is obtained; a law of variation of variable (pulsating) stresses in time is found; then, these component parts are added at the required depth and the required time.

EFFECT: improving forecast accuracy of stresses on lower horizons in the future and at use of measurement results in the past on upper horizons.

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Description

The invention relates to methods for determining natural stresses in a rock mass, which are used as boundary conditions when calculating stresses in rock structures and elements of development systems to assess their stability.

A known method of determining natural stresses, based on the hypotheses of their formation only under the influence of gravitational forces [1]. According to the hypothesis of A. Game, natural stresses do not exceed the gravity of a column of overlying rocks:

$${\sigma }_x={\sigma }_y={\sigma }_z=-\gamma H,\text{(one)}$$

where σ _z is the vertical component, MPa;

σ _x , σ _{y are the} horizontal components, MPa;

γ is the specific weight of the overlying rocks, MN / m ³ ;

H is the thickness of the overlying rocks, m

According to the hypothesis of A.N. The dynamics of the horizontal components depends on the lateral spread of vertical stresses λ

$${\sigma }_x={\sigma }_y=-\lambda \gamma H,\text{(2)}$$

,Where $$\lambda =\frac{\mu }{\mathrm{one}-\mu }$$

,

µ is the Poisson's ratio.

A disadvantage of the known methods is that they do not take into account the influence of tectonic forces that are involved in the formation of horizontal natural stresses.

Closest to the proposed method in terms of technical nature and the achieved result are various methods for directly measuring stresses in the studied massifs of rocks, based on partial and complete unloading of the massif and its hydraulic fracturing [1].

As a result of experimental work, we obtain

$${\sigma }_z=\lambda \gamma H,\text{(3)}$$

$${\sigma }_x=\lambda \gamma H+{\sigma }_{tx},\text{(four)}$$

$${\sigma }_x=\lambda \gamma H+{\sigma }_{t\mathrm{at}},\text{(5)}$$

where σ _tx , σ _tu are tectonic stresses acting along the X and Y axes.

A disadvantage of the known methods is that tectonic forces include a constant (independent of the measurement time) and variable components, which periodically changes in time with a cycle of 3.5 years, 11 years, 90 years, etc.

However, all known methods in the production of measurements and processing of the results do not allow to separate these components and the obtained result characterizes the stress state of the massif only at the time of measurement and when using this data after 5, 10 and 11 years, errors in calculating the stability of mountain structures can reach significant values.

The aim of the invention is to improve the accuracy of predicting stresses in the lower horizons in the future tense and when using the results of measurements in the past tense on the upper horizons.

This goal is achieved by the fact that the main stresses determined by known methods are divided into constant and variable (pulsating) components over time

$${\sigma }_x=(\lambda \gamma H+{\sigma }_{xt})+{\sigma }_{xtP},\text{(6)}$$

$${\sigma }_{\mathrm{at}}=(\lambda \gamma H+{\sigma }_{\mathrm{at}t})+{\sigma }_{\mathrm{at}tP},\text{(7)}$$

since σ _htp ≈σ _ut = σ _tp , we obtain the dependence of the changes in the constant components with depth, find the pattern of change of the variable (pulsating) stresses in time at the field in question, or take them as average for the region, and then summarize these components at the required depth and in right time.

The situation is facilitated by the fact that σ _mn are inherent in the entire earth's crust and their magnitude is the same both in the Urals and throughout the globe [2]. The deformation of the earth's crust and the associated σ _cr in the Urals and on the volcanic islands of the Pacific, Indian and Atlantic oceans in the equatorial zone, where GPS satellite correction stations are located, differ by no more than 5%.

As an example, let us consider the conditions for determining and predicting natural stresses at the Gaisky underground mine, where natural stresses were measured using the slit method, σ _{TP was} determined at a special training ground in the near-barrel yard on the mountains. 830 m.

Mountains., M Year Measured The constants σ ^p = σ _i σ _tn σ _z σ _x σ _y σ _tp

$${\sigma }_x^P$$

σ _y 830 1998 -22 -40 -19 -7 -33 -12 910 2004 -25 -42 -twenty -four -38 -16 1070 2008 -33 -49 -32 -9 -40 -23

Figure 1 shows the graphs of the constant stress components with depth, as in Figure 2 - graphs of σ _mn in 1998 and 2013 with projections to 2020 in the mines cities Krasnoturinsk, Nizhny Tagil, Berezovsky and Guy.

Information sources

1. Ralnikova M.V., Zoteev O.V. Geomechanics: Textbook. - M.: Publishing House "Ore and Metals, 2003. - 240 p.

2. Zubkov A.V. Periodic expansion and contraction of the Earth as a likely mechanism of natural disasters. - Lithosphere, 2013. No. 2, p.145-156.

Claims (2)

1. The method of determining natural stresses in a rock mass, including measuring stresses in a rock mass by known methods outside the influence zone of treatment (mining) work at various depths using underground workings, plotting (dependencies) changes in the main stresses obtained with depth, different the fact that to increase the accuracy of predicting stresses, including at a depth of the horizon, each of the main stresses is divided into constant and variable (pulsating) in time with leaving, they obtain the dependence of the change in the constant components with depth, find the pattern of change of the variable (pulsating) stresses σ _TP in time, and then summarize these components at the required depth and at the right time. 2. The method according to claim 1, characterized in that the graph of changes in σ _TP over time is taken as the average value for the region.

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