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| Influence of water content on the physical and mechanical behaviour of argillaceous siltstone and some microscopic explanations |
| JIA Hailiang1，WANG Ting2，XIANG Wei3，TAN Long3，SHEN Yanjun1，YANG Gengshe1 |
(1. School of Architecture and Civil Engineering，Xi?an University of Science and Technology，Xi?an，Shaanxi 710054，China；
2. School of Highway，Chang?an University，Xi?an，Shaanxi 710064，China；3. Faculty of Engineering，China University of Geosciences(Wuhan)，Wuhan，Hubei 430074，China) |
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Abstract The strength of clay-bearing siltstone is strongly susceptible to the moisture and the moisture-induced decay of strength endangers seriously the safety of engineering constructions. The results of experiments on the full process saturation and dehydration of argillaceous siltstones were presented. During the dehydration stage，the sizes of rock samples and their P-wave velocities were monitored. The mechanical properties of the samples，especially the compressive and tensile strengths，were discussed at designated degrees of saturation. The results indicate that the shrinkage of rock samples has clearly four stages during the dehydration and that the maximum rate of size reduction lies in the range of degree of saturation 55%–40%. The P-wave velocities of rock samples decrease firstly and increase subsequently，and reach the minimum at the degree of saturation of 65% . With the increasing of the degree of saturation，both the strength and elastic moduli of rock samples drop. Over 60% of the strength loss(68.2% of compressive strength loss and 62.6% of tensile strength loss) occurs in the low saturation interval(below 40%). The tensile strength is more susceptible to the softening effect of water than the compressive strength. The microscopic mechanisms of the softening effect of pore water on argillaceous siltstone may be divided into two categories：one is the load-dependent mechanisms including the change of pore water pressure，flow of pore water，lubricating effect of bound water film and the Rhebinder effect；the other is the load-independent mechanisms including clay mineral hydration and dissolution of soluble minerals. Finally，the dominant mechanism of rock softening under different saturations is discussed.
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2018, Vol. 37 
