Given the durability of mudstone and the sensitivity of clay minerals to water (Liu et al., 2020), dry-wet cycling of the specimens was carried out to consider the water variation in the rock mass with seasonal and environmental temperature changes (Gokceoglu et al., 2000; Zhang and Gao, 2020). The samples were crushed into 2~5 mm grains, dried at 40°C for four days, sprayed with water (15% of the granule mass) and maintained in a sealed bucket for eight days. After each dry-wet cycle, granule samples were sieved to pass a 2 mm sifter to prepare coarse granules for next cycle. Sandstone grains were also tested to discuss the difference of weathering to lithology. The granule samples were labeled by cycle number, as shown in Fig. 2, where the samples before dry-wet cycling and after the 3rd and 6th dry-wet cycles were categorized into unweathered and weathered states, respectively.