Characterization of Volumetric Crack Rate and Its Influence on Unconfined Compressive Strength of Red Clay

Abstract

Desiccation cracking is a common phenomenon for red clay due to alternating wet and dry weathers. The presence of cracks definitely affects the strength of the soil; however, characterizing the development of desiccation cracks inside the soil has been a challenge. The purpose of this study was to propose a method to quantify the volumetric crack rate (VCR) of red clay and investigate the influence of VCR on the unconfined compressive strength (UCS) of red clay. First, the relationship between wave speed and VCR was quantified by a prefabricated crack method to obtain the equivalent VCR (EVCR). Then, the EVCR was compared with the surface crack rate (SCR) to determine the reliability of the method. Finally, unconfined compression tests were carried out to explore the relationship between EVCR and UCS. The results show that the relationship between the prefabricated VCR and wave velocity can be described by a logarithmic equation. The calculated VCR by this equation is linearly correlated to the SCR of red clay, indicating that the logarithmic equation is effective to quantify the VCR of red clay caused by wet and dry cycles. The UCS and residual strength of red clay containing cracks reduce following an exponential function with increasing EVCR. Gray relational analysis showed that the correlation between UCS and EVCR is better than that between UCS and SCR, suggesting that it is more reliable to express the crack rate by EVCR when studying the UCS of red clay.