Effect of Reservoir Construction on Weathering Characteristics of the Cliff at Bingling Temple Grottoes

Bingling Temple Grottoes, in northwest China, is one of the World Heritage Sites. Water is considered as one of the main factors causing grottoes weathering. After the Liujiaxia Reservoir was constructed in 1974, the water level rises and humidity increases, leading to the accumulation of river water and atmospheric precipitation at the bottom, which directly affects the weathering of cliffs. Simultaneously, the construction of reservoir also results in the enhanced precipitation in the area, which indirectly affects the weathering of upper area. In this study, three typical cliff bodies were selected to investigate these direct and indirect effects. The values of wave velocity, surface hardness and rebound were tested in the area affected by different factors respectively. The test data were analysed by Kruskal–Wallis test. The results show that the degree of weathering of the top area (indirectly affected by the reservoir: increased precipitation and humidity) is the lowest. The degree of weathering of the bottom rock (directly affected by the reservoir: water soak) is in between. The highest degree of weathering was found in the middle area affected by combined effects of precipitation, humidity and capillary water from the bottom. The data between the three layers of each profile are statistically significant, suggesting that microenvironment changes induced by reservoir construction do affect cliff weathering to varying degrees.