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.