Influence of non-uniform distribution of fine soil on mechanical properties of coarse-grained soil

In order to study the influence of non-uniform distribution of fine soil on mechanical properties of coarse-grained soil under freeze-thaw cycles, triaxial shear tests are conducted on different specimens with different distributions of fine soil undergoing different freeze-thaw cycles and confining pressures. The variation trends of position of the largest dilatancy, stress-strain behavior, initial yield strength, initial yield strain, static strength, initial yield strain and failure strain are investigated. The test results show that the position of the largest dilatancy rises with height of specimens when the fine soil mass in the upper two layers of specimens increases under the same non-uniform distribution between fine and coarse-grained particles, and the rising speed becomes faster with the increase of freeze-thaw cycles. More non-uniform distribution between fine and coarse-grained particles and higher accumulation degree of coarse-grained particles let specimens have higher brittleness, which makes degree of strain-softening more obvious. Increasing freeze-thaw cycles decreases strain-softening difference of three specimens with different fine soil masses in their upper two layers, and makes composite structure of fine and coarse-grained particles more stable. The difference of the initial yield strength or the static strength caused by the non-uniform distribution of fine soil under the same confining pressure is respectively reduced by the increase of freeze-thaw cycles. The more non-uniform the distribution between fine and coarse-grained particles, the greater the initial yield strength or static strength. The ratio of the static strength to the initial yield strength under confining pressure of 100 kPa changes unstably the freeze-thaw cycles, and that under 300 kPa changes stably with freeze-thaw cycles. The non-uniform distribution of fine soil is the most significant influence factor for the initial yield strain and failure strain, but the confining pressure has a more obvious influence on the failure strain than on the initial yield strain. The non-uniform distribution of fine soil has a more
significant influence on the initial yield strain than on the failure strain.