Water-Weakening Effects on the Strength of Hard Rocks at Different Loading Rates: An Experimental Study

Excerpt

Water is one of the most important environmental factors affecting rock mechanical properties, because most rock masses in engineering practice are in the moist or saturated state (Fig. 1). Previous studies have concluded that the uniaxial compressive strength (UCS) of rock is generally reduced to various degrees in the presence of water (Shakoor and Barefield 2009; Eunhye et al. 2017). Furthermore, several mechanisms related to water-weakening effects have been revealed through numerous experiments, including (a) clay mineral softening (Van Eeckhout 1976; Erguler and Ulusay 2009), (b) stress corrosion (Brantut et al. 2014), (c) pore water pressure (Atkinson 1984; Zhou et al. 2016; Huang et al. 2019), and (d) friction-weakening effects (Baud et al. 2000). Among them, clay mineral softening arises in rocks containing clay mineral (as its name implies), and stress corrosion often occurs in siliceous rocks (Atkinson et al. 1981; Masuda 2001). It should be noted that, the effects mentioned above are usually combined, and there is no generally accepted explanation due to the great differences in rock types as well as in loading conditions. Therefore, it is challenging to detangle the contribution of a specific mechanism and describe the extent of its effect.

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