Dynamic mechanical properties and deterioration of red-sandstone subjected to repeated thermal shocks

• Impact tests are applied on sandstone free from or after thermal shock (TS) cycles.
• Physico-mechanical properties before or after different TS cycles are studied.
• Strain rate effects on mechanical behaviors of TS-damaged rock are analyzed.
• Decay models considering strain-rate effects are built to predict the degradation.
• Functions of decay-model-parameters versus strain rate are built through regression.

Rock engineering and stone constructions are always suffering recurrent thermal shock (TS) generated by sudden changes in temperature, and rock mechanical behaviors in projects usually involve responses to stress pulses or impact loads due to the widely existed blasting operation, mechanized construction and seismic oscillation. In this work, physical tests as well as static and dynamic mechanical experiments were carried out on red-sandstone free from and after 10, 20, 30, and 40 artificial TS cycles. TS-induced changes of physico-mechanical properties, including micromorphology, density, porosity, P-wave velocity, uniaxial compressive strength (UCS) and deformation modulus (Ed), illustrated the deterioration of sandstone after different TS cycles. Strengthening effects of strain rate on the dynamic mechanical properties of TS-weathered red-sandstone were analyzed. Considering the strain rate effect, deterioration models of dynamic UCS and Ed were built to predict the dynamic mechanical degradation of porous rock after repeated TS weathering. The model parameters, decay constant (λ) which indicated the mean relative integrity loss by the action of any single TS cycle, and half-life (N1/2) which measured the number of cycles necessary to reduce the integrity to half its value, were both expressed as functions of strain rate.