The Undrained Shear Behavior of Reinforced Clayey Sand

Undrained instability in sandy soil containing fine particles such as liquefaction has remained a troublesome challenge in geotechnical research. Soil reinforcement could be taken as an approach to enhance its engineering properties like shear strength, cohesion, and bearing capacity. The present paper aims to evaluate the capability of geotextile reinforcement in improving undrained shear strength and diminishing undrained brittleness of loose clayey sands. A series of consolidated undrained triaxial tests were carried out on clayey sands containing 0, 5, 10, 15, 20 and 30% fines content (F.C.) under 100, 150 and 200 kPa confining pressures. To investigate the effect of geotextile reinforcement, experiments were performed in three reinforcement arrangements. The results indicate that geotextile reinforcement increases the steady state shear strength and decreases liquefaction potential and softening behavior. Geotextile reinforcement leads to decrease brittleness index of clayey sand specimens. It can also be pointed out that the presence of clay fines changes the dilative behavior of clean sand to contraction, and consequently reduces its undrained shear strength. Also, it is found that by increasing the clay content up to 10%, the undrained shear strength of reinforced and unreinforced clayey sand are decreased and brittleness index increased. With further rises in clay content, the undrained shear strength increases and brittleness behavior decreases.