Vibration Round - Soil Model, Finite Element Analysis

For the purpose of probing into vibration compaction process,a three dimension FEA model of vibration drum-soil system was developed for the first time.The vibration compaction process is simulated by the model.By analyzing the characteristic of compaction process,it was reasonable to select the Drucker-Prager soil model because the Drucker-Prager model had considered the elasticity and the plasticity of soil.Then,the matrix expression of the constitutive model was deduced. The graded soil modulus of different dry density,moisture content and confining pressure was obtained through conventional triaxial compression test.The bivar fitting function of the modulus between the two independent variables,the dry density and the confining pressure, was obtained by using the TableCurve software.The two strength parameters of graded soil, the cohesive strength C and the internal frictional angleφ,were tested by direct shear test on the ZJ equipment.The result indicated that if the dry density keeps constantly,the two strength parameters would decrease with the moisture content and if the moisture content keeps constantly,the two strength parameters would increase with the dry density.By studying the data using the Excel,it was concluded that the natural logarithm of the cohesive strength C with the relationship of the dry density and the moisture content could be described by a linear function,respectively.The natural logarithm of the internal frictional angleφwith the relationship of dry density and content water could also be described by a linear function, respectively.A multi-parameter simulation of compaction process was carried out according to the FEA model.The results showed that the optimized parameter should be as followings,the vibration frequency 24 Hz,the vibration amplitude 1.6 mm,clockwise start-oscillation.After the third compaction pass,the settlment of that working condition was 3.3 mm and the y-stress under the drum was 0.0835 MPa at the depth of 15 cm.At present,the overlap zone was confirmed maily through experience.A new method was put forward in this paper according to the stress distribution along the width direction of the vibration drum.The experimental investigation showed that the new method was better than the experience method.After the twelfth compacting pass,the compactness of speading was homogeneous along the width of the road.The extreme difference compactness was 0.6%. The negative power function,a=k·r^-β,was used to describe the attenuation of y-stress along the depth of soil resonably.The results indicated that rolling velocity and the compactness state were the very important factors to affect the stress distribution regularities of soil.During the construction of roadbed,it was helpful to increase the compaction efficiency by improving the rolling velocity with the increasing compaction pass.