Abstract
The scale effect is an unavoidable problem in the laboratory test of coarse-grained materials. By combining the self-developed cellular automaton program with laboratory experiments, a method of simulating the triaxial test of coarse-grained materials was proposed in this paper, and a triaxial test numerical specimen that can characterize the discontinuous, nonuniform, and heterogeneous characteristics of bulk geotechnical materials was established. The parallel grading method was adopted to create six grading curves for numerical simulation based on one in situ grading curve. The failure process and the scale effect on the strength and deformation of coarse-grained materials were analyzed and discussed. The results showed that under the same confining pressure, the peak stress and initial deformation modulus E i increased with the increase of the maximum particle size d max , while the degree of shear shrinkage and Poisson’s ration υ decreased. As the confining pressure increased, the scale effect of coarse-grained materials would be magnified. If particle breakage and migration were assumed to be neglected, the internal friction angle φ and d max would be roughly proportional, the cohesive force c fluctuated with the increase of d max , and the empirical relations between d max and c and φ were established, respectively, which provides a reference for estimating the actual shear strength parameters of coarse-grained materials on-site. The research results can provide a way of thinking for the study of the scale effect of coarse-grained materials and also have certain reference significance for inferring the strength parameters of the original-graded coarse-grained materials.
Highlights
Because of good engineering properties, coarse-grained materials are widely used as the primary filling materials for railway ballasts, reservoirs, and dams and are the main bulk geotechnical material piled up in the dumps of open-pit mines
As a granular loose geotechnical material, the strength of coarse-grained materials is affected by gradation composition, particle shape, and intergranular force, mineral composition of rock, and other factors [9], so even coarse-grained material subjected to multiple same laboratory tests has the same gradation composition, and the results may not be consistent
Taking the grid of the FLAC3D calculation model of the test piece as the evolution space of the software stochastic evolution program of heterogeneous materials (SEPOHMs), a grid in FLAC3D is a cellular space in SEPOHM, and the distribution of each particle group evolved by the software can be imported into the established FLAC3D model of the sample, and five numerical sample models for the triaxial compression test of coarse-grained materials with random and uneven distribution of particle groups are generated
Summary
Because of good engineering properties, coarse-grained materials are widely used as the primary filling materials for railway ballasts, reservoirs, and dams and are the main bulk geotechnical material piled up in the dumps of open-pit mines. Most of the numerical simulation of coarse-grained materials study the effect of gradation on the physical and mechanical properties based on the particle flow code software PFC [18, 19], but few studies on the scaling effect. Is method can effectively characterize the random and uneven distribution of particles in each group of coarse-grained materials and efficiently complete the simulation of the triaxial test of coarse-grained materials. It can eliminate the influence of the human factor on the test results during sample preparation. By analyzing the stress-strain curve of the tested coarse-grained material, some common understandings have been obtained, which make us better understand the mechanical behavior of the coarse-grained material during the triaxial test and can provide a certain reference for actual engineering
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