Applied Mechanics and Materials Vols. 522-524

Abstract: According to the occurrence conditions of deeply inclined coal seam of 81206 working face in Yanya coal mine, methods including transmission rock theory calculation and numerical calculation based on the relationship between supports and surrounding rock are used to calculate and analyze. The proper working resistance of support is 5979.2kN and the supporting intensity is 0.8~0.95MPa. The regression equation associated with roof subsidence displacement , thickness of the coal seam, working face length and supporting intensity is accomplished, which provides theoretical basis for the support selection.

Abstract: Taking backfill material of underground mine as the object of study, this paper conducts the research on its strength characteristics by using uniaxial compressive strength testing machine at different cement-sand mass ratio and curing time and mass concentration which the method of experiment and theory analysis were used. The model of predicting the strength of tailings backfill was introduced, and its results were identical with the expreimental test after comparing. Therefore, the mathematical model can be used to estimate the strength of tailings backfill after assigning the specific value of tailing backfill. The tested results show that the uniaxial compressive strength of backfill rose with the increase of its concentration, cement-sand ratio, and the curing time; the strength of backfill was not enough to sustain the stope if the curing time is short and the cement-sand ratio is small.

Abstract: For composite thick seams have been incidents burst power disasters, and seriously affect the safety of the mine production.Based on the engineering background in coal mine, through the same mining conditions, stope mining process simulation which happens in single hard coal, soft coal and single composite thick Coal Seam of Island face were studied through comparative analysis by FLAC3D　numerical simulation technology. Tendency and trend of the pressure distribution results obtain through the comparative analysis . The research results has been applied in the actual coal mining.

Abstract: Based on the heterogeneity of rock, the application of the theory of elastic damage mechanics, the Biot seepage mechanics and the theory of effective stress, considering the rock damage before and after the crack extension and penetration, the numerical calculation model using software RFPA is established in this article. Through the simulation research of rock specimens under the conditions of different osmotic pressure difference of seepage damage law, results show that the permeability coefficient of the rock and the crack, expansion and penetration is directly related to, but also affected by the failure mode of the rock. Permeability changes obviously lags behind the rock damage and crack or fissure extension, permeability of kick also lags behind the peak strength of rock.

Abstract: There are many factors that influence filling body stability in partial-filling mining. In deep mining, filling rate and internal friction angle of filling body are the main factors that greatly influence both sides of plasticity zone breadth in the process of filling bodys deformation and destruction. Taking filling rate and friction angle as the main variables to make a numerical simulation analysis on the deep mine working face, we can find a conclusion that it shows a concave-down power exponent relationship between the width of plasticity zone and the filling rate; With lower filling rate, it shows a concave-up power exponent relationship with friction angle, and the relationship of power exponent will change into the linearity as the filling rate increase.

Abstract: The intermediate principal stress effect of the rock has been demonstrated. By analyzing true triaxial test results of Dunham dolomite and Mizuho trachyte, we studied relationship between minimum principal stress and the rock strength under the same intermediate principal stress coefficient, and the relationship between intermediate principal stress and the rock strength under the same minimum principal stress condition. Research shows that the minimum principal stress has a linear relation with the rock strength, the intermediate principal stress coefficient of a quadratic function relation with the rock strength. And the mathematic expression of the intermediate principal stress effect function was calculated.

Abstract: In this paper pre-cracked rock is used to study the strength affect by the coal rock internal fissures, through uniaxial compression tests to observe the different perspectives cracks on rock strength by using the precast specimens. The experimental results show that: the strength of specimens with crack angle increases, decreases and then increases, till reaches a maximum at 90°. Based on the force divided, destruction of different angles of prefabricated crack growth path can be divided into: shear failure, tensile failure and tensile shear composite damage.

Abstract: In order to study overlying rock movement rules of fully mechanized top coal caving mining with high cutting height, taking 8100 working face of Tongxin mine as the engineering background, basing on the similarity theory and similarity simulation experiment, the paper analyzed overlburdens deformation, failure and movement laws after mining. Through research, results obtained first cave pace of immediate and basic roof, three zones characteristics and overburden displacement characteristic, which could provide a basis for coal mining under similar conditions, a reference for studying overburden movement rules of fully mechanized top coal caving mining with high cutting height and a guide for safe production.

Abstract: With the sustained and rapid economic growth, the demand for mineral resources will continue to increase in China. In recent years, under the strategy of “going out”, it became an inevitable choice for Chinese enterprises to allocate resources effectively and explore the market actively in the whole world. Determining how to construct the evaluation index system to make an objective and reasonable evaluation of mining investment environment of the host countries is the main purpose of this paper. Based on the previous theoretical models, this paper establishes the optimized mathematical model and, to a certain extent, provides a objective basis for the national investment in overseas mining, by using Fuzzy Synthetic Evaluation and Analytic Hierarchy Process.

Abstract: The gob of small colliery has been one of the main factors threatening the safe production of coal mine. The repeated mining working face in a certain mine is the practical engineering background in this paper to study the influence of gob in small colliery on the mining of lower layer. By using the numerical simulation software FLAC^3D, the stress distribution law and the change of displacement during lower layer mining were analysed. It can be concluded from the analysis of field measurement data that: there is stress relief under the gob of small colliery because the distribution of coal is irregular resulting from the random distribution of gobs in small colliery, while the residual coal causes the effect of stress concentration on the lower layer mining; relatively large displacement appears in the caving zone of the upper layer by the roof of working face and the support should be strengthened appropriately during mining; meanwhile, the gob of small colliery can cause the nonuniform distance of periodic weighting in the roof, and segmented pressure behavior can be observed during the periodic weighting of the working face. Research results could provide some guidance to the safe and efficient production in repeated mining working face in the mining with similar conditions.