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The relationship between stress and strength in granular soil differs under low confining pressure as compared to high confining pressure, which is of great importance for the geotechnical engineering. Numerical simulations using discrete element method (DEM) are conducted to model consolidated -drained triaxial compression tests, with the confining pressure o - c ranging from 1 to1000 kPa. From the analysis of the shear strength of granular soils under various confining pressures and void ratios, it is found that the peak stress ratio g p under a low o - c is significantly lower than that under the high o - c , particularly for samples with the same initial void ratio. As the confining pressure increases, g p for samples with the same initial void ratio increases up to 29 % under the low o - c while stabilizing under the high o - c . Conversely, g p for samples with the same void ratio after the consolidation can increase up to 13.5 % under the low o - c while declining under the high o - c . In addition, the critical confining pressure distinguishing the low and high confining pressures is about 200 kPa for dense samples with initial void ratio of 0.605 used in the study, and it increases as the sample void ratio increases. From the microscopic analysis, the variation of g p under the low o - c can be attributed to the enhanced anisotropy of normal contact force and contact normal under the low confining pressure. Finally, a modified Mohr -Coulomb failure criterion is proposed, which can determine the strength of granular soils under the low confining pressure with different void ratios. (c) 2024 Production and hosting by Elsevier B.V. on behalf of The Japanese Geotechnical Society. This is an open access article under the CC BYNC -ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

来源平台：SOILS AND FOUNDATIONS