Research On Online Classification Method Of Coal And Rock Drillability Of Coalmine Based On Mechanical Specific Energy

Most coalmines in China are gas mines,and gas disasters occur from time to time.Gas drainage in high gas coal seams is the main measure to prevent gas disasters in coalmines.Coalmine drilling rig,as the key technical equipment for gas drainage drilling operation,is of great significance for preventing gas disasters and ensuring safe and efficient production in coalmines.At present,the intelligent degree of coalmine drilling rigs in China is still relatively low.In the actual drilling process,drillers often judge the coal and rock types of the drilled strata according to the characteristics of drilling speed,slag return type and water return color,and adjust the drilling parameters of the drilling rigs according to personal experience.This not only requires drillers to have high experience level and strong sense of responsibility,but also with the increase of drilling depth,there is a high misjudgment rate in judging the drilled formation,and the adjustment of drilling parameters also shows a certain lag.Therefore,in view of the lack of corresponding online classification method of coal drillability in the process of gas drainage drilling in China's coalmines at present,this paper puts forward an online classification method of coal drillability based on Mechanical Specific Energy based on the National Key Research and Development plan "Unmanned Intelligent Drilling Technology for Underground Gas Prevention and Control",and carries out the following three aspects of research.(1)The bit-rock mechanics model is constructed.Based on elasticity and rock fragmentation,the mechanical models of bit breaking rock by pressing and shearing are established.The mathematical relationship between drilling parameters(drilling pressure,torque)and physical and mechanical properties(compressive strength,shear strength)of drilled coal and rock is derived.(2)The variation law of drilling speed and Mechanical Specific Energy when drilling different materials under different drilling conditions is revealed.With the help of finite element simulation software ABAQUS,the simulation analysis model of bit rock breaking is established,and the rock breaking process of bit under different drilling conditions is simulated and analyzed,and the variation law of drilling speed and Mechanical Specific Energy when bit drills different materials is obtained.(3)An on-line classification method of coal drillability based on Mechanical Specific Energy is proposed.Drilling parameters and Mechanical Specific Energy are closely related to the drillability of drilled coal strata.The mapping relationship between drilling parameters and Mechanical Specific Energy and drillability of drilled coal strata can be constructed by using Artificial Neural Network algorithm.The classification accuracy and running time are taken as the standards to test the generalization of two kinds of drillability evaluation indexes and the learning ability of three kinds of Artificial Neural Network algorithms.The results show that:(1)The Mechanical Specific Energy is more stable and generalizable.(2)The classification accuracy and operating efficiency of the Extreme Learning Machine are higher,and the learning ability is stronger.