Experimental Study On The Mechanical Properties Of Rockfill Material Under Different Loading Stress Paths

Rockfill material has the advantages of high strength,small deformation,good compactness and good material nearby,at present,it has been widely used in the construction of embankment,airport,foundation,dam and so on.In the southwest of China,there is a large water flow gap,which is rich in hydropower resources,because of the traffic inconvenience,much land and few people,it is suitable to use of local materials to build earth dam.Most of the rockfill materials come from blasting and excavating,it has the characteristics of large particle size,better particle grading and particle breakage,because of these characteristics of rockfill materials,the stress and deformation of the rockfill dam has been paid more and more attention.At present,research on the characteristics of stress deformation and the mechanical parameters of rockfill is mainly concentrated on the constant ?3,little research on the variation of material parameters under complex stress paths.Hower,the actual stress paths of dam during filling and storage is a complex loading process,whether there are differences between different stress path's particle breakage and conventional stress path's particle breakage have little research,so the effect of the stress paths on the particle breakage remains to be further studied.Moreover,the dilatancy equation of rockfill is mainly obtained by the conventional triaxial test,however,it is unclear whether these dilatancy equations can reflect the dilatancy law of rockfill under different stress paths.Therefore,carry out the mechanical properties of rockfill materials under different loading stress paths,study of the Particle breakage and stress dilatancy rule,it has important theoretical and engineering significance to accurately analyze the safety of high earth rockfill dam and its impervious body.this paper has carried out the following work:(1)Four kinds of different stress path tests of the saturated rock samples of a high rockfill dam were carried out by means of high pressure and stress path's triaxial apparatus,study the influence of stress path on the stress and deformation of rockfill.The result show that: the influence of stress paths on the relationship between peak strength and confining pressure is not significant.(2)After the experiment,the rockfill material has been screened accurately and obtain the particle breakage rate under different stress paths tests,it is found that there is a consistent relationship between particle breakage rate and plastic work under different stress paths.(3)Tests with four different stress paths,including constant confining pressure ?3,constant axial stress ?1,constant mean effective stress p,and constant principal stress ratio Kc are conducted to study the influence of stress paths on the dilatancy.The results show that: At present,the dilatancy equation related to the stress state and the state can be used to reflect the dilatancy law of rockfill under the single stress path,but it cannot well describe the dilatancy relationship under different stress paths,At present,the dilatancy equation can not effectively describe the dilatancy law which depend on the stress increment direction.It is found that there is an approximate linear relationship between the slope parameter and the intercept parameter with the stress increment direction,so,a modified dilatancy equation is proposed and its rationality is verified.