| In recent years,with the high development of coal mine equipment assembly capacity,owing to its exceptional advantages of high recovery rate of coal resources, good working conditions,improving coal quality and achieving high production efficiency,the long face with large mining height technology is gradually applied to production practice.Nevertheless,enlarging mining height and lengthening mining faces bring more difficulties of surrounding rock controlling.Therefore,through theoretical analysis, simulation tests and field experiments and other means, from the aspects of the mining stope surrounding rock activity mechanism of the long face with large mining height, surrounding rock stress distribution, roof structure and Law of motion, the dynamic relationship of support-surrounding rock system, the analysis of support suitability and the optimization of working face layout,this paper systematically studied the strata movement law of the long and comprehensive mining face with large mining height and the dynamic control technology of the support surrounding rock system,which provide reference for the further promotion and application of the long face with large mining height technology.This paper obtained the following main achievements:(1)Established overall mechanical model of the surrounding rock of the long and fully mechanized mining face with large mining height, initial breaking of main roof,the cycle fracture of proof sinking and the stress distribution of surrounding rock are discussed. In addition, definited the deflection surface equation about proof sinking, acquired the maximum subsidence point of the proof, the expression of roof stress is established. With the increase of the working face, the peak pressure of the abutment pressure of the long face has increased and its position moves to the coal pillar. At the same time,the mining height has no apparent impact on the stress distribution of lateral coal entity.(2) relationship between supports and surrounding rock reflects the movement rule of surrounding rock and support performance, adaptability and mutual influence between the structure.The stability of the support system, depends on the stability of the bracket-immediate roof system.Roof subsidence is inversely proportional to support working resistance relations;As for immediate roof with soft and broken rock, roof subsidence is small because a given deformation of basic roof is absorbed by the immediate roof.(3) With the increase of mining height and working face length, original overlying structure is damaged,which may become a part of the caving zone. Combining with 2-508 long and comprehensive mining face with large mining height,using key strata theory and the composition of strata on mining stope as well as lithologic parameter,we can choose C3、C7、C16 as key rock stratum,and then calculating The load and fault throw of each layer by step.(4)As for long face with large mining height, with the increasing of face support resistance,shear stress concentration area gradually decreases,the concentration of stress reduces, Stress range extends to the whole roof control area. But when support resistance reaches some certain value, the effect of improving the stress concentration is not so obvious. When setting load is low, increasing the setting load to reduce roof subsidence has a distinct role. With the increase of setting load, roof subsidence gradually reduced, but the reduced rate getting smaller and smaller.(5)The main factors of stope roof instability are:distance between roof bar end and coal wall, working resistance, dipping angle, old roof pressure or not, the total thickness of the immediate roof. With the increase of the distance between roof bar end and coal wall, caving arch parameters (the height of caving zone and tip-to-face distance) are increasing and show non-linear relationship. The distance between roof bar end and coal wall should be controlled below 0.6m, which can prevent coal call caving as well as the end caving. It is approximate hyperbolic relationship between the working resistance of the support and roof subsidence.The horizontal of resistance support should not be less than 280KN and the working resistance of support should not be less than 7600KN.The support dipping angle should be controlled at about 80°(6) The contrasting with mine pressure measurement of the long face and the ordinary face shows:the stepping range of main roof breaking down is more inconsistent,with bigger range and uniform dynamic load; the interval of periodic weighting is shorth,and the pressure does not appear strong, dynamic load factor is small.The pressure the support of long face with large mining height bore is mainly static load, the roof weighting step of the long face as follows:the longest nose section, followed by the tail section, face central shortest.the roof weighting step of working face shows asymmetrical distribution.(7)By establishing the mechanical model of roof control,using theoretical calculations to analyse the working face support resistance and conduct field measurement.The range of support working resistance is between 6000KN and 8000KN, a small number of support working resistance is over or close to 13000 KN(safety valve opening pressure); On several stage,such as passing the pillar,normal stoping and closing working,the max support working resistance is range from 6000KN to 9000kN,which indicts that support utilization rate is low and the surplus coefficient is bigger. According to on-line monitoring data analysis,support working resistance shows normal distribution.Along the working face length direction,the pressure on central support is bigger than that on two ends,the pressure on machine tail is below that on head. Working face the nose and tail support working resistance is mainly between 6000 KN and 8000KN, central support working resistance is mainly concentrated between 6000KN and 9000 KN. Working face length increases, the roof pressure significantly subjoins. |
PDF Full Text Request