Research On Hydraulic Support Stability Of Large Mining Height

With the development of comprehensive coal mining technology,one-time mining full height technique becomes the main way in current thick coal seam mining area.As one of the most important equipment,the large mining height hydraulic support stability directly determines the safety and efficiency of coal mining.It has been proved by practices that the large height mining face is prone to occur roof fall,rib spalling,hydraulic support instability,and other security accidences.The changes of hydraulic support height,weight,gravity center and stress conditions increase high-end hydraulic support sensitivities to floor slope angle,and they also bring the new requirements for large mining height stability design and sliding advance method.In the case of thick coal seam mining,it requires that large mining height must have high quality components with large output pressure,flow rate,and power,and it also requires that the large mining height performance matches with corresponding condition,otherwise,large mining height support will be unstable,thus it will restrict safe and efficient coal production.Aiming at the characteristics of coal and rock,and special structure of hydraulic support in large height mining face,this paper proposes a set of complete schemes to improve large mining height stability,which includes physical characteristics analysis for surrounding rock,mechanical design for large mining height support,and control methods for large mining height support.First of all,this work studies overlying strata structure and key strata fracture position characteristics in large height mining face by adopting the key strata theory,and then studies requirements for large mining height which are brought by rib spalling and floor slope angle.Furthermore,this work works out the calculating method for large mining height working resistance,required support strength and potential rib spalling position,and explores the influence factors that the floor slope angle impacts on hydraulic support,and then figures out the prevent methods.Based on improvement for large mining height structure stability,this work establishes the force model of the support in the loading state,puts forward algorithms for calculating double-cylinders-support large mining height supporting force balance zone,summarizes the large mining height stability influence factors,and then proposes balance jack protection methods by improving the fitting accuracy between the four-link hole and shaft,and installing structural limit block.Taking advantages of genetic algorithm.the trajectory of the top beam of the hydraulic support is optimized in this work,and the end distance is reduced,so as to ensure and improve large mining height stability.Aiming at ZY15000/29/63 large mining height hydraulic support the mathematical model of the key components and the main large mining height circuits are analyzed and derived by advantages of hydraulic system theory.Targeting at high failure probability of balance loop and structure under the conditions of pressure varying sharply and bad operating environment,a novel balance circuit is designed in this work to realize jointly interaction between balance and prop circuits,therefore to improve balance mechanism's stability and support's adaptability.Aiming at large impact on the roof and new characteristics of big prop cylinder's size.large flow and momentum during support littering process,a position servo control system for support cylinders is established to control littering velocity of support cylinders,so as to realize large mining height contacting with root,and avoid support impacting on the roof.Analytical formulation of the residual supporting force of support cylinders is deduced,and an independent control circuit for sliding advance with pressure is designed to realize and maintain the stability during large mining height sliding advance with operating pressure.Taking ZY 15000/29/63 large mining height as test object,this work verifies the proposed theory and design methods in large height mining face of No.3 Hongyang Mining company.The performance of the balance circuit,position servo control system for support cylinders,and large mining height sliding advance with operating pressure system is verified with the simulation tool of AMESim.By using Matlab,the Bode curves of the prop in the down-shift-rise working cycle is plotted,and the stability of the hydraulic control system of the large mining height hydraulic support is analyzed.The results show that the theory and methodologies developed in this work is feasible and they have important guiding significances and application values for improving the safe and efficient mining of thick coal seam in coal mine.