Drained and undrained triaxial tests were performed to study effects of sand density on behavior at high pressures in compression and extension. Initial relative densities of 30, 60, and 90% and confining pressures from 0.25 to 60 MPa were used. Isotropic compression curves merge at high pressures resulting in a single compression curve and similar sand response during shearing, independent of initial relative density. Failure envelopes merge at high pressures, and shear strength continues to increase linearly with confining pressure. Total stress interpretation shows that sand at high pressures behaves as normally consolidated clay.