Prediction of small-strain elastic stiffness of natural and artificial soft rocks subjected to freeze-thaw cycles

The deterioration of soft rocks caused by freeze - thaw (F-T) climatic cycles results in huge structural and financial loss for foundation systems placed on soft rocks prone to F-T actions. In this study, cement-treated sand (CTS) and natural soft shale were subjected to unconfined compression and splitting tensile strength tests for evaluation of unconfined compressive strength (UCS, q u ), initial small-strain Young’s modulus ( E o ) using linear displacement transducers (LDT) up to a small strain of 0.001%, and secant elastic modulus ( E 50 ) using linear variable differential transducers (LVDTs) up to a large strain of 6% before and after reproduced laboratory weathering (RLW) cycles (–20 °C–110 °C). The results showed that eight F-T cycles caused a reduction in q u , E 50 and E o , which was 8.6, 15.1, and 14.5 times for the CTS, and 2.2, 3.5, and 5.3 times for the natural shale, respectively. The tensile strength of the CTS and natural rock samples exhibited a degradation of 5.4 times (after the 8th RLW cycle) and 2.7 times (after the 15th RLW cycle), respectively. Novel correlations have been developed to predict E o (response) from the parameters q u and E 50 (predictors) using MATLAB software's curve fitter. The findings of this study will assist in the design of foundations in soft rocks subjected to freezing and thawing. The analysis of variance (ANOVA) indicated 95% confidence in data health for the design of retaining walls, building foundations, excavation in soft rock, large-diameter borehole stability, and transportation tunnels in rocks for an operational strain range of 0.1%–0.01% (using LVDT) and a reference strain of less than 0.001% (using LDT).