Experimental Research And Meso-simulation Of Rockfill Material Shrinkage Effect

Rockfill is a commonly used dam construction material for earth-rock dam projects.With the continuous increase in the construction height of earth-rock dams,its construction technology and construction requirements continue to increase,which also puts forward higher requirements for key indicators such as the strength and deformation of rockfills..The maximum particle size of the rockfill materials used at the construction site of the earth-rock dam has exceeded 1000mm.At present,the maximum diameter of the domestic triaxial instrument is 1000mm,and the maximum particle size of the rockfill materials in the laboratory test is 200mm.Therefore,it is necessary to consider shrinking the particles beyond the particle size range.In order to meet the requirements of indoor tests,the difference between the scaled test results and the mechanical properties of the rockfill at the construction site is a key concern for engineering safety.Through the super-large triaxial and large-scale triaxial shear tests on the rockfill,the strength and deformation characteristics of the rockfill after being scaled down,and the parameters of the Duncan Zhang E-B model are discussed.The particle flow software PFC is used to truly reproduce the indoor triaxial.The test process revealed the impact of particle crushing position,crushing form and particle crushing on dilatancy of rockfill materials during the shearing process.(1)The sample size of the main rockfill area of a rockfill dam is?500×1000mm(the maximum test particle size is 100mm)and?300×700mm(the maximum test particle size is 60mm)super large triaxial and large triaxial After the shear test,the cohesion C of the super large triaxial test and the large triaxial test are 201.1 and199.5 k Pa,and the internal friction angle?is 39.7°and 40.4°.Compared with the large triaxial,the rockfill The super-large triaxial test results are all low,but mainly the internal friction angle,which has little effect on the cohesion.(2)After sorting out the parameters of the Duncan Zhang E-B model of the two sets of experiments,it is found that the elastic modulus parameters K of the large triaxial and the super large triaxial are 1294.1 and 1106.8,respectively,and the bulk modulus parametersK_b are 545.9 and 498.8 respectively,that is,the large triaxial Duncan-The tensile modulus parameter K and the bulk modulus parameterK_b are16.92%and 9.44%larger than those of the super-large triaxial respectively.The analysis also found that the initial deformation modulus of the large three-axis and the super-large three-axis are in a power function relationship,and the Poisson's ratio is in a quadratic polynomial relationship.(3)The particle flow PFC software was used to establish a sample containing a cluster of flexible particles,and the ultra-large triaxial and large triaxial meso-numerical triaxial shear tests were carried out respectively.In the process of adjusting the meso-parameters,it is found that the greater the normal stiffness and tangential stiffness of the particles,the greater the initial elastic modulus;the peak stress increases with the increase of the friction coefficient;the normal connection force of the particle clusters and The greater the tangential connection force,the less likely to break the particle clusters;the stiffness ratio of the particles is related to the dilatancy of the sample,and the smaller the stiffness ratio,the more likely the sample is to undergo dilatation.(4)The particle crushing at several special strain moments when the confining pressure of the super-large triaxial and the large-scale triaxial is 3000k Pa are respectively counted.It is found that the particle crushing rate is low at the initial stage of loading,and a large amount of particle crushing begins to occur at the strain moment before the peak of deviatoric stress.And the rapid increase in particle fragmentation subsequently revealed the obvious internal mechanism of the particle fragmentation phenomenon of rockfill materials in ultra-high earth-rock dams under high confining pressure.(5)The types and distribution of particle crushing in the two sets of numerical tests were counted separately.It was found that most of the particle crushing in the two sets of tests was caused by shearing.Observing the distribution of crushed particles,it was found that the amount of particle crushing was larger The position is basically the same as that of the shear zone,and the distribution is roughly X-shaped.