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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. [ABSTRACT FROM AUTHOR]

Carbonaceous mudstone is a common embankment material with the characteristics of water softening and water disintegration, which often causes the instability of embankments. This paper presents an experimental work on the disintegration characteristics and mechanisms of carbonaceous mudstone under the combined action of load and cyclic drying–wetting. Disintegration tests were conducted by a novel instrument. Afterward, the evolution of disintegration parameters [i.e., coefficient of uniformity (Cu), coefficient of curvature (Cc), disintegration rate (DRE), disintegration ratio (Dr), and fractal dimension (D)] during the disintegration process was studied. Finally, the gray relational theory was used to evaluate the impact of disintegration characteristics on the degree of stability of carbonaceous mudstone. The results show that the large particles decrease in number and the small particles increase in number with increasing drying–wetting cycles. Moreover, the DREs of carbonaceous mudstone are very high with final values larger than 10% in all cases. Generally, the larger the load is, the higher the DRE is, while the lower the Dr is. The D increases with the increase of load and number of cycles. The results of gray relation analysis show that the variation in the Dr is the best parameter for characterizing the disintegration of carbonaceous mudstone. The Dr of carbonaceous mudstone decreases with increasing number of drying–wetting cycles under different loads, which can provide a useful reference for the stability analysis and engineering practice of carbonaceous mudstone embankments. [ABSTRACT FROM AUTHOR]