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Urgency
The technology of a coal mining on mines means losses of coal in security pillars. It, so-called, operational losses which reach 5-10 % from industrial stocks of coal of a mine field. This parameter can be lowered essentially if to make dredging coal from security pillar is whole at repayment of horizon. I also am devoted to the decision of this extremely actual problem magistracy work.
The decision of tasks
For an establishment of parameters of working off it is whole it is necessary to solve the following tasks:
The analysis of existing ways of working off of flat thin coal layers and design procedures of parameters is put in a basis of work is whole also chambers, research by a method of boundary elements tensely - deformed conditions of system "roof - whole - ground " and generalization of results by methods of mathematical statistics, including the plural correlation analysis.
Theoretical substantiation of geometrical parameters of chamber system of development it is whole
The contact task for system "roof - whole - ground» is relative driller-screw dredging is solved a method of boundary elements. Working loading - weight of breeds. Settlement circuits contain different quantity of chambers in the block due to what the picture tensely - deformed conditions at different stages of clearing works are established. Thus it is necessary to take into account, that the full cycle of technological operations concerning working off by installations BZM-1̀ of one chamber in width a = 2,1 m and length l = 30 m makes 6 hours.
Modules of elasticity of coal and breeds of a roof and ground in analysis the moments it is determined under the formula (1)
Et=E/(1+Ft) (1)
Ft – function of creep
Ft=δt1-α/(1-α) (2)
t - time, second.
A=nα+(n-1)β (3)
n - quantity of chambers in the block;
a - width of the chamber, m;
b - width between chamber whole, m.
Between blocks of chambers remain basic wholes width b1, having not less, than a double stock of a fortress. For between chamber it is whole, which can collapse after working off of all block, the factor of a stock which is equaled to unit is supposed. The size A should be such that during development of the block the roof kept stability. The criterion of stability is size of rapprochement of ground and a roof of chambers. In analyzed conditions she should not exceed 3,5 s-m as at the big displacement as mine supervision testify, there is a landslide of breeds of a roof in the chamber.
For a quantitative estimation of a degree of influence of the factor of time results of two decisions for the same settlement circuit - received are compared on the basis of the mentioned model linearly - hereditary environments and at use of model of the elastic environment without taking into account changes of deformation properties of breeds from time. It appears, that the maximal rapprochement of ground and a roof of the chamber because of creep of breeds increases in 1,85 times.
For definition of probability of loss of stability of chambers the pressure found by calculation are estimated by criterion of destruction which looks like
R=σgran-(σekv)max>=0 (4)
For function R the normal law of distribution, therefore probability collapse passes of breeds of a roof it is defined under the formula
P=1/2-F(η) (5)
Results of calculation of probability of loss of stability of the first chamber are resulted depending on depth of development driller-screw by way at a = 2,1́, b = 1,2 m, m = 0,8 m, n = 3. At depth of development Í = 160 m the probability collapse does not exceed 0,1. Not casually maximal moving and pressure in roof, ground and wholes does not exceed in this case boundary values.
On depth Í = 220 m the probability collapse a roof reaches 0,65. Therefore during time extracting layers on depth more than 220 m in analyses mountain - geological conditions with the purpose of increase of reliability of works are desirable to reduce width of chambers or to increase width is whole.
In case of extraction by combines at a = 4,0́, b = 0,6 m, b1 = 1,2 m, m = 1,2 m, n = 3 and at presence wooden based on depth Í = 220 m make probability of loss of stability 0,14.
The author, having lead calculation and the analysis for set of variants and various mountains - geological conditions, has come to following conclusions.
Owing to the correlation analysis of the given 180 variants of calculation the equations of regress for the maximal values of rapprochements of a roof and ground in percentage of capacity of a layer are established.
Plural correlation relations of the received dependences have values 0,904 … 0,985, and sizes of criterion of Fisher much more than one-percentage borders of deviations that testifies about close enough correlation of researched sizes with the varied parameters and the statistical importance of the established connections.
Conclusions
The basic conclusions of a technique the following:
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