Abstract: Dynamic compression tests were carried out to investigate dynamic properties of artificial frozen sand under active confining pressure. In the experiments, a variable cross-section split Hopkinson pressure bar (SHPB) apparatus with a diameter of 50 mm was employed. Frozen sand was sampled from -94.52 m level at a coalmine in Jining, Shandong province, and the ratio of length to diameter of the cylindrical frozen sand specimen was 0.5. The influence of confining pressure and strain rate on dynamic properties for artificial frozen sand was analyzed as well. The results show that under uniaxial loading condition, the stress-strain curve can be divided into four stages, i.e., elastic stage, plastic stage, viscous stage and failure stage. Moreover, the corresponding failure mode is brittle. However, under confining pressure, the plastic stage has been extended, there is no viscous stage and crack failure occurred. Dynamic compressive strength of artificial frozen sand under confining pressure is greater than that under uniaxial loading condition, and increases with the increase of confining pressure. When the strain rate is 220 s-1 and the temperature is -15 ℃, under the confining pressures of 0.5 MPa, 1.0 MPa, 1.5 MPa and 2.0 MPa, dynamic compressive strengths are 1.19, 1.40, 1.58 and 1.81 times that under uniaxial loading condition, respectively. Strain convergence phenomenon occurs under different confining pressure conditions, and the convergence position tends to uniaxial loading condition. The dynamic compressive strength increased with the increase of strain rate.

Key words: frozen soil mechanics, frozen sand, split Hopkinson pressure bar (SHPB), confining pressure, strain rate