Discrete Element Simulation Study On Vibration Compaction Process Of Rock-fill Roadbed

With the development of highway foundation construction in China,the high-grade highway projects are extending from the eastern to the Midwest.The construction is becoming more and more popular on high level road in mountain areas.Deep-cut of roadbed and tunnel construction produces a large number of waste rocks.In addition,large amounts of the waste rocks accumulated in perennial mining in some mine areas such as Tong guan in Shaanxi.It is urgent to make rational utilization of it.These waste rocks occupy farmland,obstruct mountains and rivers,and destroy the environment.And the paving of rock-fill roadbed can turn it into a treasure.Thereby improving local environment and saving resources,it has double benefits of the social and economic.However,the research on the compaction process,dense status and mechanism of fill roadbed is not mature.This restricts its extension and development.On the one hand,the finite element method uses a continuous and homogeneous theory.This method cannot simulate the "dispersion" and "movement" characteristics of gravel packing.On the other hand,the acquisition workload of the experimental data is large.And the variability is also large,the processing method is limited.In view of this,the discrete element method is used to simulate the compaction process of rock-fill roadbed.It provides analysis methods and suggestions for the research on compaction technique of rock-fill roadbed.The working contents are as follows.Firstly,the composition and classification method of rock-fill roadbed were introduced.The difference between the stone filled with soil and earth stone roadbed were compared and analyzed.The characteristics of rock-fill roadbed were clarified.The compaction principle and methods of existing compaction equipment were inducted.And the factors affecting compaction of rock-fill roadbed were analyzed.At the same time,the calculation principle and method of discrete element were described.Then the simulation constitutive model was analyzed.The feasibility that the discrete element method simulated the compaction of rock-fill roadbed was proved theoretically.Secondly,three rigid particle models were established by using the multiple spherical coordinate displacement migration method.Its shape is spherical,prism and flat.The contact parameters were virtual calibrated using file batch processing.On this basis,the compaction process of the roadbed was simulated.It analyzed the changes in stress field,velocity field and porosity during compaction process.And the effect of particle shape on compaction characteristics was analyzed.The effectiveness of the discrete element simulation method was verified combined with the porosity of on-site pits.Thirdly,it considered the possibility that the rock material filler may crush during the compaction construction.And it compiled granular substitution program through EDEM application programming interface.The rock fragments can be produced by die casting shaping method.These rock fragments are bonded to different shapes by small particles.It provides a model support for the simulation that compaction process of fill roadbed.Finally,based on the constitutive model of based on the Hertz-Mindlin with bonding which generates 20 percent of the rock fragments.And the compaction process simulation is carried out.Analyze the factors that affects the compaction such as vibration frequency,excitation force and particle breakage.Comparing with the compaction simulation results of all rigid particles,the simulation compaction process with partially rock fragments is closer to the practical.According to the measured porosity data at the construction site,it can be seen that the simulation results are difference of only 0.89 percent than those measured on site.And the trend is the same.It is proved that the discrete element method used in this paper is accurate and reliable for simulating the compaction process of rock-fill roadbed.