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Cyclic interactions between rocks and water have general significance and are particularly relevant to engineering failures and geohazards. A comprehensive investigation of the multi-scale deterioration effects and mechanisms of cyclic wetting-drying on rocks can contribute to better engineering applications, but the probabilistic characterization of rock mass properties under cyclic wetting-drying remains a problem due to the difficult-to-test parameters and limited data. Numerous experiments on rock samples of argillaceous siltstone subjected to cyclic wetting-drying of Yangtze River water demonstrate progressive alteration of rock properties on multiple scales, including changes in mineralogy, grain structure, computed tomography, microporosity, and complexity of micropores, with calcite and albite being the most active minerals. The uniaxial compression strength and indirect tensile strength decrease exponentially with the cyclic number, while the Young's modulus increases. Considering the probabilistic characteristics of the geological strength index, the probabilistic mechanical properties of rock mass of studied argillaceous siltstone are then estimated through the generalized Hoek-Brown criterion. The results indicate that the uniaxial compression strength and indirect tensile strength of rock mass both follow lognormal distributions, while the Young's modulus follows a skewed distribution. Long-term strength parameters of rock and rock mass can also be determined as they exhibit exponential trends with the cyclic number. During the cyclic wetting-drying process, the water-rock interactions produce progressive changes in mineral compositions, microstructures, and micropores; with the accumulation of variations of physical properties, defects grow and develop into weak zones, thus the mechanical properties of argillaceous siltstone are significantly weakened. Investigations of the wetting-drying effects on the geological strength index and probabilistic characteristics of rock sample properties are recommended to accurately evaluate rock mass properties affected by cyclic wetting-drying. • Argillaceous siltstone is treated by cyclic wetting-drying of Yangtze River water. • Dissolution of calcite and albite results in the synergistic evolution of rock properties. • Micropores with a diameter greater than 100 μm become predominant. • Probabilistic properties of rock mass strength under cyclic wetting-drying are evaluated. • Long-term strength of the rock mass is evaluated through the exponential fitting. [ABSTRACT FROM AUTHOR]

Most soft interlayers tend to be key factors affecting rock slope stability due to their low strengths. A series of ring shear tests is conducted on reconstituted overconsolidated soft interlayers to investigate the influences of remolded water content and normal stress on shear behavior under drained conditions. The soft interlayer raw samples taken from a potential landslide site in China are first remolded into overconsolidated samples with different water contents but the same dry density and further drained under different normal stresses. The peak strength, residual strength, corresponding shear displacement of the soft interlayers and the loss rate of water content are positively correlated with water content and normal stress. Transformation of strain softening to strain hardening occurs for samples under higher normal stresses. Variations in water contents have notable effects on the shear strengths. Meanwhile, displacements, fragmentations and orientations of samples differ, showing strain softening and hardening behaviors of soft interlayers. • Stress-strain characteristics of soft interlayers are systematically investigated. • Ring shear test is utilized successfully for shear behavior studying. • Variation in compaction moisture content has an obvious effect on shear strength. • Shear behaviors are closely related to the microstructure of soft interlayers. [ABSTRACT FROM AUTHOR]

The construction of the huge Three Gorges reservoir affected a large region, and the resultant geological and environmental impacts have caused global concern. The remarkable, 30-m annual fluctuation in the reservoir water level poses a significant threat to slope stability in this area. Four hundred sixty-two landslides were identified in the Zigui basin using historical records, satellite images, field investigations and unmanned aerial vehicle (UAV) observations, enabling the construction of a complete landslide database and distribution map. Three failure modes of landslides in the Zigui basin are used to illustrate the major factors that govern reservoir-induced landslides. The results show that (1) > 99% of identified landslides occur on slopes angle <47°, while >80% occur at elevations below 600 m; (2) Jurassic Niejiashan Formation is highly prone to landslides; (3) Low reservoir levels of 145 m to 155 m greatly reduce slope stability. Based on the information entropy method that use the conditional probability of different influencing factors and principal component analysis as inputs, the relative contributions of various influencing factors are quantified and a landslide susceptibility map was drawn. This susceptibility map helps define the countermeasures that will best reduce fatalities and property losses for areas having different landslide conditions and susceptibilities. • Database of 462 reservoir-induced landslides in Zigui basin, TGR was created. • Identifying failure modes and quantifying contributions of influential factors. • Conditional probability and information entropy model yields landslide susceptibility. • Susceptibility map, failure modes, and strategies suppressing the slope instability. [ABSTRACT FROM AUTHOR]