Abstract:

To study the mechanical characteristics of frozen silt of Qinghai-Tibet, the triaxial compression and the loading and unloading tests were performed at temperatures of -2 °C, -4 °C, and -6 °C under the confining pressures of 1.0-14.0 MPa. The stress-strain curve, strength and other mechanical characteristics of frozen silt were obtained. Results indicate that the stress–strain curves could be divided into three stages: the linear elastic stage, the plastic stage, and the strain-softening stage. When ? 3 <3.0 MPa, the strain-softening stage appeared and mitigated as the increase of confining pressure; when ? 3 increased to 14.0 MPa, the strain-softening stage would appear again. The strength and elastic modulus of frozen silt increased with increase of confining pressure; then decreased with further increase of confining pressures. The volume of frozen silt reduced with the increase of axial strain at first; then expanded with further increase of axial strain under low confining pressures; however, the volume only reduced under high confining pressures. The plastic volumetric strain dissipated energies increased to a peak value with increase of volume under low confining pressures, then decreased with decreasing in plastic volumetric strain for dilatation; but the plastic volumetric strain dissipated energies increased with increasing plastic volumetric strain all the time under high confining pressures. The plastic shear strain dissipated energies increased with increase of plastic shear strain; and the plastic shear strain has a good parabolic relationship with the dissipated energy.

Key words: frozen silt, compressive strength, stress-strain curve, triaxial compression