The researchers studied how the density of sand-gravel materials affects their strength and deformation properties using triaxial tests. They found that as density increases, the strength of the samples also increases. Higher density leads to less axial strain during failure, especially at low confining pressures. Samples with greater density exhibit more dilatancy and less deformation. The stress level is significant during phase change. It is important to consider dilatancy when analyzing stress and strain in coarse-grained soil for high earth-rockfill dams.