NMR, MRI and AE Statistical Study of Damage due to a Low Number of Wetting–Drying Cycles in Sandstone from the Three Gorges Reservoir Area

Excerpt

Cyclic wetting–drying plays an important role in the deterioration of rock materials in many engineering fields, such as tunnelling, mining, and dam foundation construction (Wu et al. 2005; Wang et al. 2014). Typical examples of the effects of wetting–drying cycle can be found at the Three Gorges Reservoir (see Fig. 1), which is the world’s largest hydroelectric power facility. The average water level in the Three Gorges Reservoir fluctuates by approximately 30 m (from 145 to 175 m). Many studies have shown that the stability of the sandstone bank slope was reduced after reservoir impoundment due to the impact of wetting–drying cycles (Chai et al. 2009; Jiang et al. 2012). The total length of the bank slopes in the Three Gorges Reservoir is 5300 km, and approximately 10% (approximately 500 km) of these slopes have low stability. A low number of wetting–drying cycles would affect the mechanical properties of a reservoir. From just August 2008 (when the water level reached 175 m for the first time) to March 2011, geologic hazards in Three Gorges Reservoir increased more drastically than before. During this period, 378 geological hazards happened; the total volume of landsliding and collapse was approximately 320 million cubic metres, the total length of bank collapse was approximately 25.1 km, and 10,482 people were urgently moved out of the area. Therefore, it is necessary to study and evaluate the effects of a low number of wetting–drying cycles on sandstone in this area. …