Study On Particle Breakage Behavior And Constitutive Model Of Coarse Granular Aggregates

The coarse granular aggregates are non-viscous admixture which composes by block stone,macadam(gravel),rock chips and rock powder etc.or by clay soil and abundant coarse granule.Coarse granular aggregates are applied widely in projects especially in rockfill dam and foundation engineerings,because of the engineering properties such as low compressibility,high shearing strength,high density,high hydraulic permeability,quick consolidation etc.In dam engineerings,the rockfill dam is optimization type of dam in hydropower construction in china,because of its excellent adaptability and economy.With the development of compacted rockfill technology and the construction of adjustive large reservoirs,the height of the rockfill dam increase quickly.For example,the height of the Shuibuya face rockfill dam is 233 meters;the height of the under-construction Nuozhadu core rockfill dam is 262 meters;the height of the Rumei core rockfill dam which plan to build in Sitsang lancing river is 315 meters.Compared with low dam,the stress level in high dam is greater,such as the 300 meters high rockfill dam is subjected to over 3MPa confining pressure.Through the previous experiments,we can fred that the index of particle breakage is up to 15%in shearing experiment that the confining pressure is 800KPa.So particle breakage has been a very importment phenomenon in high rockfill dam construction.In this paper,the research status of soil constitutive models which established by previous scholars is summed up and the advantages and disadvantages of the models are analysed.Through introducing the triaxial experiments and analysing the experimental results,the particle breakage in coarse granular aggregates triaxial shearing and the influence on mechanical properties of coarse granular aggregates by particle crushing are studied.At present,the coarse-grained soil constitutive models incorporating particle breakage are fewer.On the basis of the triaxial shearing experiments and the energy equation during shearing deformation,they have been developed incorporating the energy consumption due to particle breakage and the plastic flow rule is deduced.Adopt linear type yield locus and non-associated flow and hardening function derived from an undrained stress path to set up a constitutive model for coarse granular soil incorporating particle breakage.Finally,the model parameters are determined by using the modified swarm optimization fitting triaxial test curve.It is shown that the proposed model can realistically describe the strength and deformation characteristics of soils at every confining pressure.