Research On Dem Parameter Determination Methods And Its Application In Coarse-Grained Soil Compaction Simulations

The reasonable determination of discrete element parameters is the key to whether the discrete element model can accurately reflect the real behavior of particles.At present,the two widely used methods,direct measurement method and virtual calibration method,are still lack of systematic verification,which makes their selection controversial.Therefore,this paper designed experiments to obtain discrete element parameters based on the principles of direct measurement method and calibration method,compared the application results of deformation,stress and particle movement of the two methods from the macro and micro level of particles,verified and compared the effect of the two methods,and contributed to the efficiency and reliability of discrete element parameter determination.Finally,the relevant results were applied to the discrete element simulation of subgrade vibration compaction,the main conclusions are as follows:(1)According to the principles of direct measurement method,calibration method and relevant literature,the inclined plate test,collision test,stacking test and calibration model were designed in this paper.With the help of these experiments,the discrete element parameters of disk particles and ball particles were obtained.These results are the same when the recovery coefficient and the friction coefficient between particles and plate are determined by direct measurement method and calibration method.For the results of friction coefficient between particles,the difference between the two methods is 10%-25%,and the results of yang’s modulus are significantly different,but they are in the same order of magnitude.(2)The disk particle penetration test and ball particle vibration compaction test designed in this paper were simulated by discrete element method.The application results of the parameters determined by the two methods in the two-dimensional and three-dimensional discrete element models were compared.The results are as follows: in the two-dimensional discrete element model,the results of the direct measurement method and the calibration method make the changes of the strength on the particle surface in the numerical simulation consistent with the test,but in reproducing the displacement changes of a single particle,the proximity between the calibration method and the test is 33.3% higher than that of the direct measurement method.In the three-dimensional discrete element model,the accuracy of calibration method in reproducing the macro and micro mechanical response of particle system is 37.6% higher than that of direct measurement method.(3)The following conclusions are obtained in the discrete element simulation of vibration compaction of coarse-grained soil subgrade.The vertical displacement of particles with particle size less than 40 mm is more vulnerable to the excitation force.Particles with particle size of 40-160 mm act as a skeleton,and the vertical displacement changes significantly only when the excitation force is large.In terms of frequency,the vertical displacement of particles with particle size of 5-40 mm is the largest when the frequency is 28 Hz,while it is the smallest at 35Hz;the frequencies of35 Hz,28Hz and 28 Hz maximize the vertical displacement of particles with particle sizes of 40-80 mm,80-120 mm and 120-160 mm respectively.Therefore,the vertical displacement of particles with different particle sizes corresponds to different vibration frequencies.