R.I. Shishkov
Kuzbass State Technical University, Kemerovo Russian Federation
S.M. Tagiev
Kuzbass State Technical University, Kemerovo Russian Federation
A.V. Remezov
Kuzbass State Technical University, Kemerovo Russian Federation
DETERMINATION OF PARAMETERS
REFERENCE PRESSURE
Annotation: This article describes the laws determining the reference pressure parameters derived by Russian scientists and researchers .
Keywords: stress,
slaughter, reference pressure, the array.
The issue of full
disclosure laws of formation of the stress state of the rock massif in various
geological conditions up to now and for a long time to be relevant. However,
the need to determine the parameters are constantly present in the mining
practice. The author sees the solution to the problem of determining the
reference pressure, by determining factors, dependencies, and the specific
conditions that determine the parameters of the concentration ratios and
deconcentration stresses in columns excavation sites in specific areas.
When deciding on
the distribution of stresses in the array of problems during excavations taken
following, fundamentally differing types of stress state of coal and rocks
intact array:
- Is seen as an
array of elastic continuous medium, in which the vertical stress equal weight
strata γH rocks and horizontal μ / (1-μ) γH, where μ - Poisson
coefficient equal to 0.2-0.3 sandstones, siltstones and mudstones for 0.25-0.4
and 0.2-0.35 for coal;
- Is seen as an
array of plastic medium in which both vertical and horizontal stresses are the
same and equal to the weight column γH rocks;
- The array is
regarded as elastic-plastic medium in which the voltage can be determined from
the expression:
= 
, (1)
where α- angle of dip, hail; η- lateral thrust
coefficient of rocks, the value of which depends on the depth and the depth of
300-400m, according to experimental studies of sandstones 0.3-0.5 for 0,35-0,6
siltstones and mudstones 0.4- 0.7.
Some researchers
suggest that the form of the stress state in the pristine array is primarily
dependent upon the depth if at shallow depths plastic rock properties are weak
and the array can be regarded as an elastic solid medium, the sufficiently deep
plastic deformation can lead to equalize stresses to the value γH. Therefore, in general, the array
should be regarded as elastic-plastic medium with changing the depth ratio of
lateral thrust. On fields with a sloping and steep fall formations also,
apparently, it is necessary to take into account the possibility of significant
changes in the stress state of the array due to tectonic forces. Therefore, to
determine the stress state of the array in a variety of geological conditions
necessary to carry out special investigations of mine.
According
P.V.Egorova [1, C.78] found that in a number of the earth's crust horizontal
array voltage exceeds the vertical. This is explained by the ongoing tectonic
processes. In many fields, rock masses tectonic stresses exceed 2-4 times
gravity, particularly at shallow depths. Prof. P.V.Egorov, summarizing field
observations stress state of rocks by unloading on a number of fields prone to
rock bursts, set changes depending on the amount of horizontal stress with
depth:
+
=27+0,7H (2)
The decision V.G.
Gamoshinskogo [2], it is considered axisymmetric problem, but in addition
attempt to take into account the crushing of the edge formation zone. As a
result, they are offered the support of the pressure distribution curve ahead
of the long stope, which consists of two branches: the ascending in the
direction from the bottom to the array and downlink.
For the
descending branch of the accepted formula A.N. Dinnik:
(3)
k - where stress
concentration factor at the edge of the reservoir.
For the ascending
branch of the formula is offered at a fixed slaughter:
, (4)
c- where coal clutch; f- coefficient of friction of coal for
coal; h - half the capacity of coal seam; ξ-
coefficient of lateral pressure; t - time; T - rheological coefficient
characterizing the stress relaxation time when coal destruction.
However,
according to A.A.Borisova formula (3) and (4) are not suitable for the main
mode - mode steady motion overlying rock strata [3, C.185].
In conclusion we
can say the following: the problem of determining the reference pressure is
reduced in the end to the calculation of the coefficients of concentration and
deconcentration of stress in specific areas of the pillars excavation sites.
The calculations involve the use of geomechanical models of the medium, which
differ in the degree of manifestation of the account of the rheological
properties of rocks: elastic, elastic-plastic and plastic model.
Bibliography:
1. P. V.
Egorov,G. G. Stumpf,A. A. Renev,Yu. A. Shevelev,I. V. Morukov,V. V. Sydorchuk, Geomechanics.State.
the establishment of the Kuzbass. GOS. tehn.Univ. of Illinois-Kemerovo,2002. P.
339.
2. Kamasinski VG
rock pressure on shallow coal seam in the area of production.Coal,1957, No. 6, P.
16-23.
3. Borisov A. A.
rock Mechanics and arrays. – Moscow: Nedra, 1980. P. 360