To investigate the dynamic mechanical response and damage evolution behavior of ice-rich frozen clay, split Hopkinson pressure bar (SHPB) tests were performed on frozen clay specimens with initial moisture contents of 20%-1,000% under different temperatures, strain rates, and stress states. The stress-strain curves, dynamic strength, peak strain, absorbed energy density, failure mode, and failure progress were studied. The experimental results revealed the following: (1) in the radial-free state, the stress-strain curve of frozen clay with initial moisture contents ranging from 20% to 85% and 1,000% could be divided into three stages: elasticity, plasticity, and failure. In addition, a double peak phenomenon occurs in the stress-strain curves within the initial moisture content range of 120%-480%. (2) In the radial-free state, as the initial moisture content increased, the dynamic strength first increased to a maximum value, then decreased to a minimum value less than the dynamic strength of ice, and eventually increased marginally to the dynamic strength of ice. However, the variation in dynamic peak strain with initial moisture content followed a decrease-increase-decrease three-stage pattern. (3) In the passive confining pressure state, the initial moisture content of frozen soil determined its sensitivity to the confining pressure. (4) The high-speed camera test results indicated that the failure of the ice-rich frozen clay was mainly caused by tensile cracks. The degree of failure of the frozen clay specimens became more evident as the moisture content and strain rate increased. In the passive confining pressure state, the ice-rich frozen clay specimens remained intact except for a small amount of edge peeling.

To investigate the effect of oyster shell powder (OSP) on the static and dynamic properties of expansive soil, the mechanical properties of modified soil were obtained. Taking Ningming expansive soil as the research object, triaxial shear test, dynamic triaxial test and scanning electron microscope test were carried out on plain soil and 9 % expansive soil modified by oyster shell powder (ESMO). The results show that compared with plain soil, the effective cohesion of modified expansive soil with d(osp) < 1 mm (ESMO (d(osp) < 1 mm)) and d(osp) < 0.075 mm (ESMO (d(osp) < 0.075 mm)) is increased by 15.4 % and 32.8 %, respectively. Under cyclic loading, compared with plain soil, the plastic strain stability value of ESMO (d(osp)<0.075 mm) is reduced by 40.2 %, the pore water pressure stability value is reduced, and the stiffness is increased. The dynamic mechanical properties of ESMO (d(osp)<1 mm) showed the opposite trend. Through microscopic experimental analysis, the main reasons for this phenomenon are the particle size distribution, bonding form, and cementation of the two. The results can provide a theoretical basis for the practical application of ESMO and the establishment of constitutive model.

The icy lunar regolith (ILR) in the permanently shadowed regions (PSRs) of the lunar poles is an important lunar water resource for humans, which can be efficiently explored in situ by using a high-speed kinetic penetrator. The dynamic mechanical properties of ILR need priority research since they are related to the ballistics and overload of the penetrator. Based on ILR occurrence form and microscopic composition analyses, four types of ILR simulant (ILRS) specimens with typical water contents are prepared in the present study according to the principle of similar mineral composition and physical state. The dynamic mechanical properties of the ILRS specimens are investigated by combining the results of split Hopkinson pressure bar (SHPB), quasi-static unconfined compression, and variable angle shear (VAS) tests. The results show that the loading strain rates alter the microcrack number and expansion rate of the specimens, which in turn significantly affects their damage mode, dynamic uniaxial compressive strength (DUCS) and toughness ratio. Finally, based on the relationship between stress and strain in the SHPB tests, the damage properties of the ILRS under dynamic loading are analyzed, and a segmental constitutive model is provided by combining it with the Drucker-Prager strength theory. The research results could form the basis for subsequent penetrator structure design and ballistic prediction.