5.4 Sample preparation
Fig. 4 shows the detailed conditions of the geological body of Niche of Sakyamuni Entering Nirvana. It is divided (from top to bottom) into four strata, i.e., Layer A, Layer B, Layer C, and Layer D. Layer A and Layer B have similar compositions which are composed of medium-to fine-grained feldspar quartz sandstone. Layer A has the horizontal bedding structure and its bedding is developed, while Layer B has both cross-bedded and horizontal bedding structures and its bedding is not developed. There is a thin mudstone interlayer between Layer A and Layer B. Layer C is composed of fine-grained feldspar quartz sandstone which has horizontal bedding structure. Finally, Layer D consists of greyish brown silty mudstone (Zhang et al., 2018). In current study, the sandstone samples were collected from Layer A (called LA) and Layer B (called LB), which are in the core of the same layer of Niche of Sakyamuni Entering Nirvana. All core samples were of same orientation, and they were prepared as cylinders with a diameter of 50 mm and a height of 50 mm. The samples for each experiment are shown in Table 2.