Numerical Analysis Of Load And Wear Of Shield Disc Cutters Based On DEM

With the continuous expansion of urban scale and the rapid increase of population,subway construction has become one of the important directions of urban development.Shield machine is the most advanced tunneling equipment at present,which effectively improves the working environment of construction personnel.It has the advantages of high degree of mechanization,safety and reliability,and is widely used in underground engineering construction.Because of its excellent rock breaking performance,disc hob is widely used as rock breaking tool for shield and TBM.However,in practical engineering,hob wear is one of the most common losses in shield construction,which seriously affects the construction efficiency.This paper belongs to the research content of "973" project of the Ministry of science and technology of the people’s Republic of China "theory and control research on long distance safe driving of large diameter shield under complex conditions"(No.: 2015cb057802)".The simulation of rock breaking by cutter is carried out by discrete element software edem.Combined with the test data,the three-dimensional force and wear of rock breaking by hob are analyzed:(1)Based on the bonding contact model in the discrete element software edem,the simulation rock specimen is established by API method.The virtual uniaxial compression and Brazilian splitting tests are carried out on the rock specimen.The bonding parameters of four rock specimens with different strength are obtained by repeatedly adjusting the bonding parameters.The uniaxial compression of rock in the virtual simulation and indoor test are compared and analyzed The failure modes of the test and Brazilian splitting test prove that the discrete element method is feasible to simulate the uniaxial compression and splitting tensile test of rock.(2)Through the function of motion state setting in edem,the rolling circle cutting model considering the rotation of hob around its axis and the revolution around the center of cutter head is established.The indoor experiment of rock breaking circle cutting is carried out.The threedimensional force of hob in numerical simulation and indoor experiment is compared and analyzed,and the rationality of calculating the three-dimensional force of hob in this paper is demonstrated.(3)Two driving sections with similar geological parameters and obvious differences in driving parameters in mingle parking tunnel of Shenzhen Metro Line 6 are selected to calibrate the simulation wear coefficient and predict the wear amount respectively.The prediction results are compared with the measured data to demonstrate the rationality of the numerical model in predicting the hob wear when the driving parameters change.(4)The rock breaking simulation of hob with different parameters(rock strength,penetration,cutterhead speed,cutting angle,flat grinding state,etc.)is carried out.The impact effect at the moment of contact between hob and rock mass and the three-dimensional stress variation law of hob during rock breaking are analyzed.The vertical force,cutting angle and cutting speed of hob considering the changes of rock strength,penetration,cutterhead speed and other parameters are given The fitting formula of rolling force is obtained,and some results are verified by CSM model.(5)Based on the Archard wear model,this paper analyzes the hob wear under different working conditions,studies the abnormal wear such as the cutter ring fracture by using the dem-fem coupling method,and obtains the influence law of rock strength,penetration,cutter head speed,rock breaking state and other factors on the cuttes wear.