RU2162149C1 - Method of determining rock stability in supporting of mine workings - Google Patents

Abstract

FIELD: mining industry. SUBSTANCE: method includes unloading of working at tested district, determination of initial rate of residual deformation increment of rocks in zone to be supported, and evaluation of rock stability depending on value of said rate. In so doing, pair determinations are carried out preliminarily in two unsupported breakage faces of values of mean initial rate Vc of displacement of mine working contour proportional to initial rate of increment of residual deformations of rocks of zone to be supported and time ts of its stable state. Then, determined for these breakage faces are constants a and b of empirical dependence and mean initial rate Vc of displacement of mine working contour at tested district. With use of given empirical dependence and obtained constants a and b in this dependence, time ts of stable state of mine working of tested district is calculated. Rock stability at this district is evaluated by comparison ts with reference values of time of working stable state for concrete classes of rock stability. EFFECT: higher accuracy of determination of rock stability under conditions of shortage in data on rock mass properties, for instance, at new deposits and ore fields. 2 cl, 4 dwg, 1 tbl

Description

 The invention relates to the mining industry and is intended to determine the stability of the rocks during the fastening of mine workings, mainly in conditions of lack of information about the properties of the massif, for example, in new deposits and ore fields.

 There is a method of controlling the stability of the sides of quarries (Muller L. The Rock Slide in the Vaiont Valley // Rock Mechanics & Engeneerig Geology, 1964, 2, p. 148-212), including measuring rock deformations, determining the initial strain increment rates during unloading and assessment of rock stability by their size.

 The disadvantage of this method is the impossibility of its application in underground mine workings due to a significant difference in the nature of the development of rock displacement in the sides of open pits, where displacements of rock blocks along sliding surfaces are realized, in contrast to mine workings, where inelastic displacements of rocks near the output contour lead to softening them, destruction and dumping. In new fields, with a lack of data on the properties of the massif, there is little information on the values of the rates of increment of deformation of rocks corresponding to different classes of their stability, which negatively affects the accuracy of determining the stability of rocks when implementing the known method.

A known method for determining rock stability (Bieniawsky ZT Case studies: prediction of rock mass behavior by the geomechanics classification // Second Australia - New Zealand conference on geomechanics, 1975, p. 36-41), including the measurement of parameters related to rock stability : rock strength, core output, water inflow, the distance between cracks, their opening and occurrence elements, empirically determining the time t _{at a} stable standing of a mine and assessing rock stability by comparing it with the reference values of standing time for specific classes of failure rock solidity.

The disadvantage of this method is the non-specific nature of the empirical relationship of the parameters measured in the experimental section with the rock stability when determining the rating numerical rating, which determines the time t _{at the} stable standing of the mine in the experimental section. This leads to the subjectivity of the assessment of individual parameters, the summation of measurement errors by six parameters and negatively affects the accuracy of determining the stability of rocks.

 The closest in technical essence and the achieved result to the proposed method is a method for determining the stability of a fixed mining (a. From. USSR N 1089259, E 21 C 39/00, published in BI N 16, 1984), including unloading the excavation at the experimental site , determination of the initial rate of increment of residual deformations of the rocks of the fixed zone and assessment of the stability of the rocks by its value.

 The disadvantage of this method is the lack of accuracy in determining the stability of rocks: only two categories of stability (stable and unstable) are distinguished, while in world and domestic practice five categories of stability of rocks are accepted (Bulychev N.S. Mechanics of underground structures in examples and tasks .- M .: Nedra, 1989, p. 75). In addition, the known technical solution involves measuring the initial increment rate of residual deformations of rocks in local areas of the massif interacting with the spacer beam, which is technically more difficult than measuring the initial displacement rate of the output contour. And since stresses and strains are unevenly distributed along the perimeter of the working section, the measurement process does not take into account the influence of the characteristics of the stress-strain state (SSS) of the massif, the strength and disturbance of the rocks on their stability. All this reduces the accuracy of determining the stability of rocks.

 The practice of exploiting underground deposits during their exploration and development shows that often emergency situations in mine workings and destruction of the roof support are associated with insufficient accuracy in assessing rock stability.

Technical task: improving the accuracy of determining the stability of rocks during fastening of mine workings in the absence of data on the properties of the massif, for example, in new deposits and ore fields due to the use of the empirical dependence of time t _{at a} stable standing of the mine from the average initial speed V _{to the} displacement of its contour, the constants a and b of which characterize the intensity of unloading deformations of the massif, reflect the influence of the features of the SSS of the massif, the strength and structural disturbance of the rocks on their stability I have a more detailed definition of the stability of rocks on the experimental plot in the range of five classes of rocks stability.

The problem is solved in that in the method for determining the stability of the rocks during the fastening of the mine workings, including unloading the workings in the experimental section, determining the initial increment rate of the residual deformations of the rocks of the fixed zone and assessing the stability of the rocks depending on the magnitude of this speed, according to the invention, are preliminarily at least two loose faces paired determination values average initial velocity V _{to the} bias generation circuit which is proportional to the initial velocity at ascheniya residual strain sawmills fixed zone, and then the time t _at its steady standing. After that, the constants a and b of empirical dependence are determined for these faces
t _y = a / (V _k - b),
where t _y is the time of steady standing of the mine, s;
a is a constant, m;
V _to - the average initial displacement rate of the output circuit, m / s;
b - constant, m / s.

Then, the average initial velocity V is determined _{to the} displacement of the excavation contour in the experimental section, after which, according to the indicated empirical dependence and the constants a and b obtained in the loose faces of this dependence, the time t is calculated _{for the} stability of the standing of the excavation in the experimental section and the rock stability is assessed by comparing t _y with reference values of the time of steady standing of the mine for specific classes of rock stability.

In this case, an increase in the accuracy of determining the stability of rocks during fastening of mines under conditions of a lack of data on the properties of the massif is achieved by determining the constants a and b of the empirical dependence of the time t _{at a} stable standing of the mine on the average initial velocity V _{to the} displacement of its contour, which integrally characterize the intensity of unloading deformations of the massif and indirectly reflect the influence of the peculiarities of the VAT of the massif, strength and structural disturbance of the rocks on the time of stable standing of the mine, which, in the end ohm result, determines the stability of rocks as a classification feature. This allows you to evaluate the stability of the rocks in the experimental plot in the range of five classes of rock stability.

In very unstable rocks, it is advisable to measure the initial velocities V _{to the} displacements of the output contour using benchmarks installed on the bottom of the face.

Under these conditions, the time t _{at a} stable standing of the workings is very short, usually less than an hour, and therefore it is impossible to measure the displacement speeds of the working circuit during this period, evaluate the stability of the rocks and fix. Under these conditions, the rate of displacement of the development loop on the bottom of the bottom of a fixed mine is quite informative, which is close in magnitude to the average initial velocity V _{to the} displacement of the contour of a loose mine. In this direction, primary collapse occurs in very unstable rocks. Consequently, in very unstable rocks, it is possible to measure with sufficient accuracy by the benchmarks installed on the bottom of the face, both the initial speed V _{to the} displacement of the output contour, and the time t _{at a} stable working position to determine the constants a and b of the indicated empirical dependence, which greatly simplifies the implementation of the method in these conditions.

The essence of the technical solution is illustrated by an example of determining the stability of rocks during fastening of mine workings, drawings and a table, where: in FIG. 1 shows a cross section of a mine working; in FIG. 2 - a longitudinal section through the excavation; in FIG. 3 is an example of an approximation of the empirical dependence of time t _{for the} stability of a working stand in an unsecured face from the average initial velocity V _{to the} displacement of its contour according to 18 preliminary measurements at the VT field; in FIG. 4 - an example of determining the stability of rocks in a particular experimental section of the VT field according to the indicated empirical dependence presented in logarithmic coordinates; in table - classification of rocks of the "VT" field by stability.

 The proposed method is implemented as follows.

At the field, where it is supposed to determine the stability of the rocks during the conduct and fastening of the mine workings, at least two loose faces for preliminary measurements are selected. Deadlock workings in obviously unstable rocks are most suitable, where it is possible to directly measure the time t of _the stability of their standing (from the moment of formation to the primary collapse). In the massif of rocks 1 on the circuit 2 of the mine 3 lay the benchmarks 4 and measure the initial velocity V ₁ - V _{4 the} displacement of the circuit 2 of the mine 3 (Fig. 1, 2). Then, their average value is determined by calculation - the average initial speed V _{to the} displacement of the circuit 2 of mine 3. The unloading of the rock mass 1 is carried out by the formation of mine 3, which is one of the main schemes of perturbation of the VAT array for geomechanical observations used for instrumental measurements of strain increments at large bases (Kurlenya M.V., Popov S.N. Modern methods for diagnosing the stress state of rocks by its perturbation // Mechanics of rocks and mechanized supports. Novosibirsk: IGD SO A N USSR, 1985, p. 56-62). Then, the time t is measured there _{at the} steady standing of the mine, fixing at a distance the moment of primary rock collapse, after which the constants a and b of the indicated empirical dependence are determined for loose faces (Fig. 3). Due to the hyperbolic nature of this dependence, two loose faces are sufficient for preliminary measurements and calculation of the constants a and b.

To determine the stability of production in the experimental plot, the well-known empirical dependence t _у = a / V _к - b) is used, the constants a and b of which were determined. In the experimental section, the average initial velocity V _{to the} displacement of the excavation circuit is determined based on the measurement of the initial velocities V ₁ - V _{4 of the} displacement of the circuit 2 of the excavation 3 in the experimental section (Fig. 1, 2), if it is not fixed, or based on the measurement of the initial velocities V _6, V _7, when installed lining 5. Then calculated by said empirical relationship obtained in loose and faces the constants a and b depending on time t that _{in the} resistant output and standing stability is evaluated by comparing rocks t _y with reference values Majestic time t _y1, t _{y2, y3} t, t _y4 (Fig. 4) stable standing openings corresponding to the boundaries of stability of specific classes of rocks (IV), as defined in the work Bieniawski ZT, Agoshkova MI, Bulycheva N. FROM. and etc.

Changes in the experimental plot of values of parameters such as the departure l, m, height h, m and half-span B, m of the working cross-section as compared with preliminary measurements, require calculation of the corresponding corrections to the reference values of time t _{at a} stable standing of the working.

In very unstable rocks that collapse immediately after excavation, it is not always possible to measure the initial velocity V ₁ -V _{4 of the} displacement of circuit 2 (Fig. 1, 2) to determine their average value V _k , but it is quite large, even in a fully fixed mine when l = 0, the initial velocity V ₅ displacement of the contour 2 on the chest 6 of the face (Fig. 2). This allows you to use the directly measured value of V ₅ to assess the stability of the rocks in the manner described above.

As an example, the determination of rock stability during the fastening of the mine workings of the exploration and development mine of the VT deposit of the Tselinny GCC with an empirical dependence (Fig. 3) of the type
t _y = 0.24 / (V _k - 2.5 · 10 ^-7 ).

As can be seen in FIG. 4, in the logarithmic coordinate axes, it is close to a linear dependence. The boundaries of the rock stability classes for excavation with a height of h = 4.1 m and a span of B = 2.2 m (section in the sinking of 14.12 m ² ), corresponding to the reference values of the time values t _y1 , t _y2 , t _y3 , t _y4 ( Fig. 4) sustainable standing workings are shown in the table.

The average initial displacement rate of the output circuit V _k * = 7.1 · 10 ^-5 m / s (Fig. 4), measured at the experimental site in the mine, corresponds in empirical dependence t _y * = 3.3 · 10 ³ s (55 min) , which according to the table allows us to classify the breed as very unstable rocks (V). Actual rock collapse occurred after 58.5 minutes. Similarly, the stability of rocks is determined during the fastening of mine workings for other classes of rock stability.

 It can be seen from the example that the use of the present invention allows one to achieve a sufficiently high accuracy in determining rock stability and classify them according to five categories of rock stability under conditions of insufficient data on the properties of the massif, namely, in new deposits and ore fields.

Claims (2)

1. The method of determining the stability of the rocks during the fastening of the mine workings, including unloading the workings at the experimental site, determining the initial increment rate of the residual deformations of the rocks of the fixed zone and assessing the stability of the rocks depending on the size of this zone, characterized in that they are preliminarily produced in at least two loose paired definitions of the average initial velocity V _{to the} displacement of the output contour, proportional to the initial rate of increment of residual deformations of rocks th zone, and then time t _at its stable standing, after which constants a and b of empirical dependence are determined for these faces
t _y = a / (V _k - b),
where t _y is the time of steady standing of the mine, s;
a is a constant, m;
V _to - the average initial displacement rate of the output circuit, m / s;
b is a constant, m / s;
then determine the average initial speed V _{to the} displacement of the output contour in the experimental section, after which the time t _{at the} stable standing of the excavation in the experimental section is calculated _{from the} empirical dependence and the constants a and b obtained in the loose faces and the rock stability in it is evaluated by comparing t _y with reference values of the time of steady standing of the mine for specific classes of rock stability.  2. The method according to claim 1, characterized in that in very unstable rocks, the initial displacement rates of the output contour are measured by reference points installed on the bottom of the face.

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