Effects of sand sizes on engineering properties of tropical sand matrix soil

This paper presents an experimental study focusing on the effects of various sizes of sand on the engineering properties of tropical sand matrix soils, particularly the undrained shear strength. Static triaxial tests on reconstituted samples of sand with 0, 10, 20, 30, and 40% of low plasticity fines content by weight were carried out using GDS ELDYN® triaxial machine. The tests were performed on tropical specimens of three different sizes of sand (coarse, medium, and fine sand) which were mixed with kaolin as the fines content. Samples were tested at 15% relative density under two effective confining pressures of 100 kPa and 200 kPa, respectively. From the results of Consolidated Undrained Triaxial tests, the Critical State Line of the sand matrix soils with different sizes of sand had been developed. Based on the results from stress path diagram, the critical state parameters of sand matrix soils, represented by the critical stress ratio, M, are found to range from 1.41 to 1.35 for coarse, 1.38 to 1.29 for medium, and 1.30 to 1.25 for fine sand matrix soils. The maximum particle density was achieved at lower values of fines content for medium and fine sand matrix soils compared to coarse sand matrix soil. The sand size affects the maximum and minimum void ratio of sand matrix soils. At the same fines content, the void ratio of sand matrix soils increased as the sand size decreased