Research On Cutting Fracture Characteristics Of Rock Plate With Different Constraints

The main disposable energy source in China is coal,which is mainly underground mining.The roadway is the main transportation channel to ensure the continuous production of coal.Cutting power increasing is the main method that was adopted for improving the hard rock broken ability of roadheader.In contrast,cutting power increasing of the roadheader certainly increasing the weight and volume of roadheader.Meanwhile,the manufacturing process and strength of cutting tools have not been improved,that will be lead to the cutting tool wear aggravated and the driving cost increased,thus leading to the reduction of tunnel excavation efficiency.Research on the new cutting method for breaking hard rock,improve the cutting ability and efficiency,reduce the power and weight of the roadheader have great significance to reduce the production cost in the process of tunnel excavation.The diamond saw and conical pick combined rock cutting method was proposed in the paper.First,the diamond saw was used to slit rock for obtaining rock plate.Second,the cutting tool was adopted for cutting and breaking the rock plate.The method can increase the cutting ability and excavation efficiency of cutting head,so as to improve the driving speed of the roadway obviously.In this paper,rock plates cutting with conical pick was taken as research object,the theoretical analysis and numerical method was adopted for researching the rock break process by conical pick.The rock plate cutting test-bed was built for research the influence factor of rock plate fracture and peak cutting force,provide theoretical and experimental basis for diamond saw and conical pick combined rock cutting method applied in tunnel excavation.On the basis of studying the characteristics,physical properties and mechanical properties of rock,the factors that influenced on the cutting process and cutting forces were researched.Based on the elastic thin plate theory,the mechanical model of the rock plate under the action of cutting tools was established.The boundary conditions for sides and corner points under different constraints are given.Based on the diamond saw and conical pick combined rock cutting method,the rock plate conditions that was often occurred in the tunnel excavation was studies.The solution for rock plate bending was carried out by different boundary condition.The position with maximum deflection and maximum bending moment was obtained,and the fracture position of the rock plate was forecasted.The rock cutting numerical simulation model was built.By combining damage model and penetration failure,crack propagation and fragment separation in the rock cutting process was successfully simulated under the action of conical pick.The research results of the test point failure mechanism shown that tensile failure is mainly reason lead to rock fracture.It is same to the theoretical analysis results.The influence of cutting speed,cutting depth and rock elastic modulus on the fragmentation separation in the cutting process were researched by simulation method.Moreover,the influence of rock compressive strength and cutting depth on cutting force and specify energy are studied.The rock plate cutting test-bed was built,which mainly includes the cutting module of the rock plate,the signal collecting component and hydraulic power system.The experiment plan for study single factor influenced on the cutting performance of conical pick in the rock cutting process was worked out,including rock properties,rock plate thickness,cutting depth,width and height of the rock plate influenced on the fracture results and peak cutting forces.Rock properties were obtained by uniaxial compressive strength test and Brazil splitting method.The rock cutting test results show that for three fixed rock plate,the peak cutting force increased exponentially with increasing rock compressive strength,the thickness of the rock plate and the cutting depth of the conical pick.With the increase of the width and height of the rock plate,the peak cutting force exponentially decreased.For the two adjacent sides fixed rock plate,the peak cutting force increased linearly with increasing compressive strength of rock,increased exponentially with increasing thickness of the rock plate and the cutting depth of the conical pick,decreased exponentially with increasing width and height of the rock plate.For the one side fixed rock plate,the peak cutting force increased linearly with the increasing rock compressive strength and the cutting depth of the conical pick,increased exponentially with the thickness of the rock plate and width of the rock plate,decreased linearly with increasing height of rock plate.The numerical model that rock plate broken by single conical pick was built by finite element method,and rock plate fracture process was simulated.The simulation results show that when the main generated on the rock plate,the cutting force reach to the maximum value.Tensile failure is the reason lead to rock plate fracture also,through the failure model of the rock test points.In the simulation,the stable peak cutting force is studied.The simulation results show that stable peak cutting force increased with the increasing compressive strength of rock,the larger size corresponding to the minimum rock plate.The influence of cutting positon,cutting angle and confining pressure on peak cutting force are also studied in the simulations.The peak cutting force increased and the decreased with increasing cutting angle and confining pressure,increased with decreasing cutting position.The peak cutting force that obtained from the three constrained conditions were compared,the results show that peak cutting force increased with the increasing fixed edge number under the same cutting parameters.In this paper,the conical pick cutting force and the rock plate fracture result were obtained by means of the experiment that were carried out on the rock plate cutting test bed.That provide the experimental basis for the diamond saw and conical pick combined cutting method in the roadway.The correction of the numerical simulation method was verified by the comparison between numerical results and experimental results.That provide a new idea and method for researching rock cutting in microcosmic.It demonstrated that diamond saw and conical pick combined cutting method can effectively reduce the cutting force,by comparison between the cutting forces that obtain from traditional rock cutting method and new cutting method.Diamond saw and conical pick combined cutting method can effectively improve the cutting efficiency.