The effect of matric suction on stress-strain relation and strength of three Alfisols

Abstract

Undisturbed cores taken from two depths (0–5 and 25–30 cm) from three Greek Alfisols (a Typic Haploxeralf, Ultic Palexeralf and Typic Rhodoxeralf) of high structural stability were equilibrated at 0.001, 0.01, 0.1, 1 and 100 MPa and tested for Young's modulus, unconfined compressive strength (UCS) and indirect tensile strength (ITS). The differences among soils and depths in clay content and mineralogy as well as in the concentration of cementing material was reflected in different values of Young's modulus, UCS and ITS. Within any given soil type, however, the measured properties were mainly determined by the effective stress. Young's modulus calculated using an extension of the effective stress theory suggested in this work was in reasonable agreement with measured values. Although theoretical UCS, calculated according to effective stress theory, provided a general indication of expected values, no relation was obtained between theoretical and measured ITS values. Very close linear relationships were obtained, however, between both measured UCS and ITS values and the product of matric suction and the degree of saturation. The UCS ITS ratio was variable and decreased with increasing matric suction.