The effects of fines content on the monotonic triaxial testing of cohesionless soils for evaluation of in situ stat

The influence of fines content on the undrained monotonic response of sand has been reported by Been and Jeffries (1985) and Hird and Hassona (1990). Pitman (1994) illustrated the influence of various types of fines on the undrained monotonic response of Ottawa sand at one stress level. A test methodology developed by Sasitharan (1994) was used to determine the steady state lines for Ottawa sand with from 0 to 20 percent Kaolinite fines content. This involved monotonic triaxial compression testing of various sand/fines mixtures at varying levels of isotropic consolidation. The triaxial test results indicated a rotation and shift in the steady state line as fines increased. The slope of the steady state line increased with added fines as did the slope of the isotropic consolidation line. The sample compressibility increased as fines were added. The shift in steady state line was noted with the addition of as little as 5% fines. Been and Jeffries (1985) showed a shift with as little as 2% fines addition.;Sasitharan (1994) and Cunning (1994) used bender element technology to measure shear wave velocity in triaxial samples. The shear wave measurements, and corresponding state conditions were used to develop a framework for estimating the in-situ state of Ottawa sand with varying fines content. A single relationship between shear wave velocity and void ratio was found to describe reasonably well both compressible and incompressible sands, with and without fines content. The undrained shear strength at steady state may be determined for both contractive and dilative conditions.