Study On The Evolutionary Characteristics Of Cutting Force Acting On Conical Pick And Performance Evaluation Of Roadheader

With the continuous development of the coal industry and the increase in the number of urban underground projects,there is a growing demand for large-scale and rapid excavation to obtain new ore bodies,and cantilever boring machines have been popularly used in rock excavation in the past decades because of their many advantages,such as high productivity,high reliability,construction flexibility and environmental protection.However,the low efficiency of breaking hard rock and the high consumption of the pick have hindered the large-scale use of roadheading machines in hard rock mines.Therefore,it is extremely important to systematically study the evolution characteristics of rock cutting force of the pick,optimize the cutting parameters and evaluate the performance of rock cutting capacity of roadheading machines based on reasonable rock cutting indexes to improve the economics of rock excavation.Based on rock cutting test and the numerical simulation of continuous cutting,this paper thoroughly explores the influence of rock physical and mechanical properties and cutting parameters on the evolution characteristics of rock cutting force of the conical pick,and establishes the prediction model of the evolution characteristics of rock cutting test and continuous cutting simulation respectively;based on the study of the definition of rock cut-ability and the evolution characteristics of force in the process of rock cutting,the standard of rock cut-ability is formulated.Based on the definition of rock cutability and the evolution characteristics of rock cutting,the performance of roadheader is evaluated by testing and grading criteria.It provides theoretical and experimental basis for improving rock cutting performance of roadheader and promoting its use in rock excavation.In view of the characteristics of the rock intrusion of conical pick,a professional test device is designed to lay the foundation for the study of the evolutionary characteristics of the rock cutting force of conical pick,the numerical simulation analysis of rock cutting and the standard test of rock cuttable and the formulation of grading standard.Eight types of rocks of different strengths are cut on the intrusive rock device using conical picks of different geometries.It is found that the maximum chip production is preceded by small chip avalanches,and the cutting forces showed sawtooth shape fluctuations and similar force evolution characteristics in brittle rocks.Based on the statistical analysis,it is found that there are significant statistical relationships between the peak point,penetration rate,upper and lower limits of cutting force and the physical and mechanical properties of the rock during the cutting force evolution.Finally,a cutting force evolution model is established using the characteristic points of force evolution.The comparison shows that the model can reasonably predict the evolution of the cutting force and reflect the characteristics of brittle rock crumbling.Based on the finite element method,the process of continuous cutting of the conical pick is simulated.Firstly,the material properties of the continuous surface cap model and the parameters of the conical pick cutting model are accurately calibrated using experimental rock mechanics parameters.The evolution curves of the cutting force under different cutting parameters are obtained by simulation,and the features are extracted based on statistical and spectral analysis.The results show that there are strong linear relationships between rock volume,peak force,average force,work done by the pick,standard deviation,root mean square and depth of cut,and all of them increase with the increase of depth of cut;There are strong exponential relationships between peak force,average force,work done by the pick,standard deviation,root mean square and cutter angle,and all of them increase with the increase of attack angle.The rake angle is negative when the friction between the pick and the rock is large,the influence on the characteristic value of rock cutting is especially obvious;the rock volume,peak force,average force,work done by the pick,standard deviation and root mean square are influenced by the cut slot,and they increase logarithmically with the increase of the line spacing,and when the line spacing reaches 5 times of the depth of cut,the values tend to be constant,that is,the cut slots no longer influence each other.Based on the findings of the rock cutting test of conical pick and the numerical simulation of continuous rock cutting,the standard test method and procedure of rock cutability were developed,and the rock cut-ability grading standard was formulated by considering the existing cutting power distribution of roadheader and the main parameters of the pick.The cut-ability test was carried out on 17 kinds of rocks,and the classification was discussed according to the classification standard.The results show that,in general,the higher the strength of the rock,the more difficult it is to cut,but there are also cases where the compressive strength and tensile strength are greater but easier to cut,and the use of cutting force and energy specific energy as the criteria for classification of rocks is obviously better than the classification of rock strength.