Abstract: During testing low impedance materials such as clay by conventional split Hopkinson pressure bar (SHPB), the transmission strain pulse is always too weak to be collected correctly. In addition, the clay specimen will not deform homogeneously during the test, which makes it impossible to get valid data. To overcome these problems, the quartz transducer technique and the controlled loading pulse were introduced to test the unsaturated clay specimen with different moisture contents under different loading rates. Besides, the stress equilibrium in the specimen was monitored by quartz transducer mounted at the two end faces of the specimen. The results indicate that the compressive response of the unsaturated clay is sensitive to moisture content and strain rate, which the axial compressive strength decrease with the increase of moisture content, but increase with the increase of strain rate. Furthermore, the relationship of the axial compressive strength with the moisture content, and the normalized axial compressive strength with the strain rate are given respectively. The fitting curves are better consistent with the experimental data.

Key words: unsaturated clay, split Hopkinson pressure bar(SHPB), quartz crystal