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.