Study And Application Of The Mechanism Of Rock Cutting With Dredging Cutters

The technology of rock cutting with cutters is widely applied in engineering fields such as mining,drilling and tunneling.Its application in dredging engineering is also increasing,because of its characteristics of high-efficiency,environmentally friendly and precise in rock excavation.As one of the most important rock excavating equipment in dredging engineering,cutter suction dredger is used to excavate medium strength rock gradually.Larger cutting size is required,and the cutting conditions are more complex in rock excavating with cutter suction dredger,compared with other rock cutting machines such as continuous miners,tunnel boring machines and PDC bit.It is of great practical significance and academic value to investigate the mechanism of rock cutting with cutters in dredging engineering.Therefore,this paper studies the mechanism of rock cutting with dredging cutters from three aspects of theory,experiment and numerical simulation.1.The failure mode and failure mechanism of rock in different cutting conditions are analyzed.Based on the existing theories and experimental results,a theoretical model named as the LPE model for calculating the tangential force on the chisel pick is established.The applicability of the LPE model is not limited by the rake angle.The LPE mode can accurately describe the relationship between the main cutting parameters and the tangential force in rock cutting,and can properly estimate the tangential force.Which are confirmed by experiments.2.The linear rock cutting experiments with chisel picks and conical picks are designed and performed,and the effects of various of cutting parameters on rock cutting is investigated using univariate method.The variation of cutting force with the rake angle,cutting width,cutting depth,skew angle,tilt angle,attack angle and conical angle of the cutter is obtained.The experimental results verify the correctness of the LPE model.Fractal analysis is used to analyze the rock debris produced in the experiment.The fractal dimension of the debris under different cutting conditions is calculated,and the relationship between fractal dimension of the debris and cutting parameters is revealed.3.A SPH simulation model for rock cutting is established with the magnitude of stress to determine the failure of rock,and the influence of cutting parameters and rock properties on tangential force is studied through numerical simulation.The functions to expressing the relationships between tangential force and rock properties,and between tangential force and cutting parameters are obtained by regression analysis of the simulation results.A regression model for estimating tangential force is also established.4.A discrete element model for simulation of rock is established with the magnitude of strain to determine the failure of rock,and with a new proposed contact model(the NET-BPM model)to deal with element bonds.The new model is verified by simulating direct tension test and uniaxial compression test of rock.Finally,the model is used to simulate the rock cutting experiment with the cutter,and the effect of the rake angle is studied.The fragmentation mode of rock and the variation of cutting force under different rake angle are obtained.The simulation results are in good agreement with the experimental results.5.A numerical simulation model for rock dredging with cutter suction dredger is established by applying the LPE model and the law of rock fragmentation in rock cutting.The peak torque on the cutter head calculated by this model is about 1.6 times of the average torque,which is in line with the actual situation.Then,the model is used to study the rock dredging with cutter head,and the relationship between the dredging loads on the cutter head and the dredging parameters,the number of arms and the number of teeth of the cutter head is obtained.Aiming at topic of rock cutting with dredging cutters,taking theoretical research as core target,experimental and numerical verifications as basic method,and application research as extension method,the mechanism of rock cutting is deeply studied.The research findings of this study are of great guiding significance both to the design of the dredging system of larger cutter suction dredger and the research on rock cutting machines.The research methods adopted in this paper can be used as references for the subsequent research on rock cutting and other research related to rock fragmentation.