Responses of frozen, fine-grained soils due to multiple packets of cyclic stress with variable amplitude and an empirical prediction model

Abstract

A suite of stress-controlled cyclic triaxial tests were performed on frozen fine-grained soils to assess the characteristics of the accumulated and cyclic behaviours under packets of cyclic stress with variable-amplitude. The influence of cyclic stress sequences is highlighted, and the results of the variable-amplitude cyclic tests indicate that the applied cyclic stress amplitude sequence is of significant importance regarding the final accumulated deformations. A step change is observed in the accumulated strain when the applied cyclic stress amplitude is beyond that of the previous stress package, while a decreasing level of cyclic stress below the previous loading package results in slight additional strain accumulation. The results of these tests also indicate that the cyclic stiffness is dependent on both the past accumulated strain and the current cyclic stress amplitude. For frozen soil, a higher past accumulated strain and lower cyclic stress levels yield a higher cyclic stiffness. An empirical approach for representing the response of frozen fine-grained soils under multiple packets of cyclic loading are proposed and then verified by the test data. The results show that the proposed empirical model is able to extract and predict the accumulated and cyclic behaviours under multiple packets of cyclic loading.

Experimental investigation on mechanical properties of coal samples under different freeze–thaw cycles

“…Sometimes the compressive strength of coal can be improved due to the additional reinforcement produced by ice crystals at the beginning of freezing time (Ritchie and Davison, 1968;Scherer et al, 2001). In the actual mining process of open-pit coal mines, the coupling disturbances of various factors such as excavation, blasting, mechanical vibration have a great effect on the stability of the slope, which further causes safety risks of coal mining (Deb et al, 2011;Li et al, 2020Li et al, , 2021Liu et al, 2020). Therefore, it is significant and meaningful to study the influence of F-T cycles on the mechanical properties of coal.…”

“…Wei et al (2019) revealed coal damage and cracking characteristics due to liquid nitrogen freeze-thaw by conducting nuclear magnetic resonance (NMR) tests. Yang et al (2020) focused on induced pore structural alterations due to cryogenic treatment and their effects on gas sorption and diffusion behaviors. Chen et al (2018) studied the microwave effect on the physical and mechanical properties of coal samples, and the causes of coal samples influenced by microwave based on Fourier Transform Infrared Spectroscopy (FTIR).…”