Experimental Research On The Influence Of Scale Effect On The Compression Characteristics Of Rockfill Materials

Coarse-grained soil fillers are mostly used in filling projects such as earth-rock dams,roads,and ports because of their high shear strength,low cost,and small subsidence and deformation.Under high stress conditions of the dam,the material is prone to particle breakage,which changes the internal filling relationship and local strength,resulting in settlement deformation.The study on the compressibility and particle breakage of coarse-grained soils is usually done through indoor tests,which are limited by the sample size allowed by the indoor testing machine,and the on-site fillers need to be scaled before they can be used for indoor test research.Changes in sample size,scaling method,etc.will have an impact on the test results.Based on the post doctoral research project of Chongqing City,"study on constitutive model of rockfill material in critical state considering particle breakage under water level fluctuation(228512)".Stone materials are the research object,and indoor confined compression tests are carried out to study the compression and particle crushing characteristics of rockfill materials.The main research contents and results are as follows:(1)Through the dry confined compression test,the deformation of samples with different sample size,maximum particle size and scale method under different pressure levels is obtained.The coefficient of compressibility is selected as the index of compressibility,and the variation of the coefficient of compressibility with sample size,maximum particle size and scale method under different pressure conditions is revealed.In a certain range of vertical pressure,the relationship between compression coefficient and vertical stress is described by exponential function,and the relationship between relevant parameters and vertical stress is fitted.(2)By means of wetting and creep compression tests,the deformation of specimens with different scale methods under different pressure levels is obtained.Firstly,the relative wetting deformation of the specimen under different wetting stresses is calculated.The relationship between the relative wetting deformation and the vertical stress is described by power function,and the relationship between the relative parameters and the content of coarse particles is fitted.Secondly,the instantaneous deformation,compression and creep deformation of specimens with different scaling methods at 800 k Pa are calculated,and the variation trend of the percentage of instantaneous deformation in total deformation with the content of coarse particles is discussed.(3)Based on the screening test results of the specimens after the loading of the confined compression test,the influence of the specimen size,the maximum particle size of the specimen and the scaling method on the rockfill crushing is studied.Firstly,the concept of gradation equation is introduced into the solution of modified particle breakage rate,and the particle breakage of each experimental group is evaluated.The development of particle breakage rate with sample size,maximum particle size and scale method was studied.Taking the particle breakage rate as the intermediate variable,the power function relationship between the particle breakage rate and the vertical pressure and the linear relationship between the particle breakage rate and the compression coefficient are fitted,and an expression reflecting the compression coefficient and the vertical pressure is derived.(4)Based on the results of the side limit compression test,the existing lateral limit compression model is introduced,and a strength reduction parameter related to the grading curve is introduced to modify the original model,so that it can reflect the influence of the scale method and the maximum particle size of the sample on the compression of the sample.The empirical formula for calculating the reduction parameters is given.On the basis of the indoor test results,the compression curve of the original stage distribution under the dry condition is deduced,and a reduction factor related to the wetting and time of immersion is introduced respectively.Finally,the humidification and long-term deformation of the original grade distribution are calculated by using the indoor test results.