Dynamic mechanical property deterioration model of sandstone caused by freeze-thaw weathering

Abstract

In cold climate regions, rock engineering structures are subjected to repeated processes of freeze–thaw weathering and consequently the integrity of these structures will gradually deteriorate. The resulted reduction in rock strength makes the structures become increasingly more vulnerable to external loads, particularly to dynamic loads such as blasting or earthquakes, even when these loads are below the original designed capacity. In this work, the reductions in static and dynamic strengths of sandstones after they are treated with different number of freeze–thaw cycles were studied using conventional UCS experiments and impact tests with split Hopkinson pressure bar apparatus. Based on the experimental results, a decay model was used to describe the reduction of rock strength with the increasing number of freeze–thaw weathering cycles. For the prediction of the degradation of dynamic rock strength corresponding to freeze–thaw weathering, a model describing the dynamic increase factor for the dynamic rock strength corresponding to different strain rates and specimen sizes was proposed and its parameters are obtained by regression analysis of published experimental data. These two models were then combined into a unified model which can be used to describe the reduction in the dynamic strength of rocks when they are subjected to repeated freeze–thaw weathering processes. Though only tested on sandstones, the proposed unified model, with different parameters, is expected to be applicable to other types of rocks as long as the rocks undergo the same or similar damage mechanism when they are subjected to freeze–thaw weathering processes.