The aim of the work is to study the use of slag aggregate concrete for the construction of monolithic concrete lining of mine workings. In the coal industry the average of 10-15 m of development workings are constructed to extract 1,000 tons of coal. The monolithic concrete is 97-98% of the total material consumption for the construction of vertical shafts in Kuzbass; lining costs being 50% of the total cost of shaft construction, which are directly dependent on the material consumption and cost. Considering the amount of annually produced coal in Kuzbass mines, it becomes obvious that the cement consumption in the industry amounts to several million tons, the consumption of the aggregates is about ten million cubic meters. It was found that 25-30% of concrete-lined mine workings are relined annually. This is due to the concrete destruction under the influence of unfavorable operating conditions, especially the destructive action of mine water. Therefore, the problem of production of concrete capable of withstanding these phenomena seems quite relevant.
To determine the tendency of a coal seam to bunts or other dynamic phenomena -caving, sudden spills of coal, shock bumps -use is made of its seismic activity (noise) [1][2][3][4] and the nominal strength index, determined from the depth of pene~ation of a pointed object into the seam under the effect of a standard force [5,6]. It is assumed that the noise, i.e., the number of fissures arising per unit time during working of the seam reflects the capacity of the seam to undergo brittle fracture. The greater the seismic activity the more readily will the seam fracture and the sooner will it lose stability. Therefore periods of high seismic activity indicate a heightening of the danger of dynamic phenomena. Although very primitive, such a viewpoint is useful because it agrees closely with practical experience: dynamic phenomena are actually manifested during higher seismic activity; this enables one to make a practical seismic prediction of the burst proneness of a seam from variations of the noise [1][2][3][4]. As regards the second parameter (the nominal strength index), it is assumed that it reflects mainly the natural strength of the coal seam: the greater the depth of penetration of the point, the weaker the seam and the more likelihood of the occurrence of dynamic phenomena [5]. This parameter is used for making local forecasts of the likelihood of a burst, the aim being to determine in good time the tendency of coal seams or their individual sectors to exhibit dynamic phenomena [6].It was of interest to determine to what extent both these parameters, which characterize from different angles the strength of a coal seam and its tendency to fracture, depend on rock pressure and to what extent they are mutually correlated. In 1967 a great number of seismic measurements were made by the procedure described in [4] in the steep burst-prone Devyatka seam (sector No. 78, Yunkom colliery, 716 level), accompanied simultaneously by strength measurements with an instrument designed by G. N. Feit [5]. Furthermore, in this sector episodic observations of the pressure curve were made using a hydraulic transducer designed by L. 13. Famin [7]. In the 10 months of these observations the face advance was 400 m.The strength determinations were performed in the lower part of the working-in the cross-hole of the haulage road and in the first and second benches. * The measurement lines were located in the gate ends of the face, in the middle part, and in the foot of the corresponding benches. The measurements were made once per day: in the first and second benches the measurement sites were located at 2 m intervals along the strike of the seam. In the cross-hole of the haulage road the measurements were less regular owing to the nonuniform advance of the latter. Measurements were performed at the surface of the working face; at each measurement point we made five measurements of the depth of penetration and then found the mean value. This Value, l, is one of the correlation parameters.The seismic measurements were made [1-4] with a ...
Experience of routine prediction and observation of gas bursts and other dynamic phenomena reveals that they sometimes occur when there are no observed changes in the strength properties or lithology of the seam. Changes in the physical properties of a seam can favor the development of dynamic phenomena, but are apparently not the leading factor in the creation of a burst-prone situation.Therefore it seems necessary to pay particular attention to processes occurring in the rock during the driving of mine workings, to the laws of roof and floor convergence, to the laws of variation of the process of brittle fracture of a coal seam under changing rock pressure, and to the temporal and spatial features of these processes during the period preceding the dynamic phenomena. The success of seismoacoustic prediction of bursts and shock bumps [1,2] assures us that this is a very promising route for developing a theory of gas bursts, shock bumps, and rock fails, and for further improvements in our methods of routine prediction of the danger of these phenomena.Dynamic phenomena occur in zones of a seam which a re being worked with anomalous increase in disintegration of the coal [3][4][5]; according to the current method of prediction [5], this zone is regarded as burst-prone throughout its length.A rise in pressure on the face zone can be due to an increase in the length of the main roof rock cantilever overhanging the working. The descent of the main roof rock can be very nonuniform. It sufficiently stiff layers are encountered in the roof rock, roof descent is held up, the size of the hanging roof cantilever increases, and the pressure on the face zone of the seam increases; simultaneously there is also an increase in the brittle fracture of the face zone, and this is quickly detected by seismoacoustic equipment which detects a rise in the noise level. If the pressure of the hanging cantilever of main roof rock is so great that the face zone of the seam and the supports of the immediate roof cannot sustain it, the immediate roof rock may fall into the worked-out area.When the hanging cantilever of main roof rock breaks off, the face zone of the coal seam is suddenly relieved of load, and, as investigations have shown [7], there may be a gas burst; the probability of this increases with the difference between the pressures on the face zone before and after breakaway of the rock cantilever, i.e., with the length of the hanging cantilever of roof rock.Consequently, the period of extraction operations before breakaway of the rock cantilever and during actual descent of the main roof is liable to dynamic phenomena.To make successful routine predictions of the risk of dynamic phenomena, it is necessary to examine the zone of the seam worked with long hanging rock cantilevers. An effective approach to studying and to determining the interval of descent of the main roof is correlation analysis of seismoacoustic observations, which enables us to study the periodic components of the process of coal disintegration in extraction wor...
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