Quantitative determination of the effect of temperature on mudstone decay during wet–dry cycles: A case study of ‘purple mudstone’ from south-western China

Abstract

Although temperature is considered a key factor influencing rock decay, little is known about the quantitative relationship between a rock's decay rate and temperature, which makes it difficult to quantitatively predict the rate of rock decay under varied temperature during wetting–drying cycle conditions. Thus, the aim of the present paper was to observe the decay rate of various purple mudstones and to develop a model with which to calculate their decay rates under varied temperature conditions. Three types of purple mudstone were sampled from the Tuodian group (J3t), Matoushan group (K2m) and Lufeng group (J1l), located in the Chuxiong district of Yunnan province, south-western China. All samples were manually cut into cubes of 50×50×50mm, before being subjected to 39 wetting–drying cycles in a 2mm sieve under artificial constant temperature, natural daily temperature variation and artificial temperature alternation (minimum and maximum) treatments in the laboratory. Decay rates were calculated by weighing the mass remaining in the sieve after each treatment cycle. The results showed that the decay rates of the tested rocks rose with an increase in temperature and temperature difference (maximum–minimum), with the rank order of decay rate being J3t>K2m>J1l. Quantitative analysis revealed rock decay rate to be significantly related to temperature by a power function, and exponentially related to temperature difference. Our results suggested that temperature difference has a stronger effect on purple mudstone decay than that of temperature magnitude during the wetting–drying processes.