| With the increasing mining depth and scale of coal resources,mining stress has gradually increased its influence on the geological balance of original coal and rock.In China,natural disasters such as rock burst occur frequently due to operation errors and intensified mining.Under the influence of mining stress and stress concentration will occur,leading to the further development of coal crack and the expansion of the coal,mining can lead to large space mining stress field change more complex,when mining stress concentration is higher,the increased risks of shock,are more likely to induce impact ground pressure disasters,such as serious casualties and equipment damage.The reason is that the distribution law of mining stress field under different mining conditions is not clearly understood or grasped.The purpose of this paper is to study the experimental study of the change law of drilling parameters in the process of drilling coal and rock under the influence of mining stress,and to reflect the change trend of mining stress through the change law of drilling parameters,and then to predict the possibility of rock burst occurring in local coal.Based on the analysis of force model and dynamic model of drill pipe in the process of drilling coal and rock,the influence of mining stress on drilling parameters,namely drill pipe torque and cuttings quantity,as well as the relationship between coal particle size and cuttings quantity are deduced.By establishing the mechanical model of mining stress distribution,the position of the stress peak in the stress concentration area and the expression of the change function of mining stress under the influence of mining stress are deduced.Based on the analysis of the theory of water injection and pressure relief in coal seam,the relationship among the physical quantities in coal rock system is determined.Through simulation test in laboratory,coal is under the influence of mining stress was analyzed in the well drilling drilling parameter changes in the process of coal and rock specimens law trend,control of a single variable change the stress state of coal is coal specimen in other force,the drilling speed is constant control change only under the condition of different axial compression,confining pressure,the drilling parameter change rule.Through underground experiments,the change law of drilling parameters before and after coal seam water injection was studied,and the influence of mining stress on the change of cuttings,coal particle size and drill pipe torque in the process of drilling coal rock was analyzed,and whether coal seam water injection changed the redistribution of mining stress was also analyzed.Combining theoretical analysis with experiment,the higher the mining stress,the larger the drill pipe torque and the drilling cuttings,the larger the cuttings,the larger the coal particle size,the more the mining stress increases and then decreases to a stable level with the further away from the mining face.The experimental test and data processing analysis show that the amount of cuttings,coal particle size and drill pipe torque produced by drill pipe drilling coal body samples are positively related to the mining stress of coal body.The cuttings amount of drill pipe drilling with the deeper the cuttings depth is The size of coal chips and drill pipe torque increase gradually,then increase to a certain value,then decrease gradually and maintain stability.Through the variation of drilling parameters,it can be judged that the stress concentration area of mining stress is located,and the peak stress in the underground is about 7m away from the mining face.Through water injection into coal seam,the amount of cuttings,coal particle size and drill pipe torque peak value are all reduced and the peak position moves back in the process of drilling water injection.Therefore,the stress concentration area of coal seam water injection to reduce mining stress is very feasible.This paper has 44 figures,14 tables and 72 references. |
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