This book describes a study that was done to evaluate the fluid mechanics and geomechanical properties of unconsolidated sands under changing in- situ stress conditions. A series of "confined compressive" tests were run, under both increasing and decreasing mean stress conditions. Sand samples with different grain size distribution and initial porosity were used. During the triaxial compression test, the samples were isotropically loaded to the required confining stress. Then the axial stress was increased while the radial stress was kept constant. In another test, called "radial extension", the samples were first isotropically loaded to a specific stress after which the radial stress was reduced while the axial stress was kept constant. During these tests, axial and radial stresses, axial and volumetric strains and, permeability were determined.