Laboratory weathering experiment on sandstone of Niche of
Sakyamuni Entering Nirvana at Dazu Rock Carvings, China
Jingke Zhang1, Zhen Li1, Li
Li2, Jianhui Liu2, Dun
Liu1, Mingshen Shao2
1Key Laboratory of Mechanics on Environment and
Disaster in Western China, and School of Civil Engineering and
Mechanics, Lanzhou University, Lanzhou, Gansu 730000, China
2Chinese Academy of Cultural Heritage, Beijing 100029,
China
*Corresponding author: Zhen Li, School of Civil Engineering and
Mechanics, Lanzhou University, Lanzhou, Gansu 730000, China. E-mail:
zhli2017@lzu.edu.cn
2.0 Abstract
The sandstone of
Niche
of Sakyamuni Entering Nirvana statues at Dazu Rock Carvings in China has
been experiencing surface weathering for an extensive period of time. To
understand the weathering effects of the local environment, three
experiments were set up, including dry-wet cycle, freeze-thaw cycle and
acid rain cycle. In this study, the mass, surface hardness, P-wave
velocity, surface microstructure, were applied to explore the sandstone
weathering degree over multiple cycles (for a total of 50 periods, 350
days). Various devices (e.g., X-ray diffraction (XRD), scanning electron
microscope (SEM)) were adopted to analyze the sandstone weathering
mechanism. The experimental results indicate that the main sandstone
deterioration is granular disintegration. For all experiments, the
variation in mass decayed exponentially with the periods; while the
variation in surface hardness and P-wave velocity decayed as a power
function with the periods. The rankings of influencing environmental
factors of sandstone weathering follow this order: acid rain cycle,
freeze-thaw cycle, and dry-wet cycle. More generally, the water-rock
interaction (WRI) occurs from the surface to the inner structure of the
sandstone. Granular disintegration is driven by (1) the dissolution of
calcite, alteration of feldspar, and water swelling and drying shrinkage
of smectite; and (2) the widening inter-granular micro-cracks. The
findings could provide useful insights for the protection of the studied
statues.