Study on damage evaluation indexes and evolution models of rocks under freeze-thaw considering the effect of water saturations

Freeze-thaw action of rocks has caused many engineering geological disasters in cold regions. Estimation of the freeze-thaw damage degree and strengths loss of rocks are crucial for the prevention of freeze-thaw disasters. The main aim of this research is to investigate the influence of water saturation on the deterioration of rocks under freeze-thaw and find the best evaluation index. P-wave velocity, elastic modulus and porosity, as the widely used indexes, were adopted to define the freeze-thaw damage variables and predict the UCS loss under freeze-thaw. The change law of these three indexes shows that the critical water saturation for causing a considerable freeze-thaw damage of sandstones is approximately 60%∼80%. P-wave velocity is proved to be a competitive nondestructive parameter, which can be measured easily and correctly without any time-consuming mechanical test. In addition, P-wave velocity can be well used to predict strength loss of rocks under freeze-thaw by performing a statistical analysis of experimental data. It is suggested that the P-wave velocity may be the primary and best index to quantify the freeze-thaw damage degree of rocks with different water saturations comparison with the other two indexes. This study can provide a better understanding of the deterioration of physico-mechanical properties for unsaturated rocks and give a reference for the selection of freeze-thaw evaluation indexes.