Abstract: Argillaceous siltstone, a common hydrophilic rock in geotechnical engineering, experiences notable variations in its mechanical properties due to the influence of water and cyclic loading. Therefore, a systematic investigation into the mechanical behavior of argillaceous siltstone under cyclic loading in different wet-dry conditions is essential for guiding engineering design and improving disaster prediction accuracy. This study conducted triaxial cyclic loading tests on dry and saturated argillaceous siltstone samples collected from Shiyan, Hubei Province, varying the frequencies and confining pressures. The research involved a comparative analysis of the strength and deformation characteristics of dry and saturated specimens, examining the influence of frequency and confining pressure on their mechanical behavior. the mechanical mechanisms of argillaceous siltstone under cyclic loading were further elucidated from the perspective of energy. The findings indicate that, (1) saturated samples exhibit a substantial decrease in strength and modulus compared to dry samples, accompanied by a more pronounced movement of the hysteresis loop towards higher strain; (2) deformation of dry samples increases slightly with frequency, while the degradation of saturated samples is markedly accelerated at higher frequencies; (3) lower confining pressures can restrict crack development in saturated samples, but the excessive confining pressure accelerates their deterioration; (4) energy consumption rate and dissipated energy of dry samples under high frequency are lower than those under low frequency, while saturated samples display an increase in dissipated energy at higher frequencies, remaining relatively constant at low confining pressures and significantly increasing at high confining pressures; and (5) the failure mode of dry samples shifts towards conjugate shear damage as the confining pressure increases, whereas the angle of the failure surface in saturated samples also increases.

Key words: cyclic loading, frequency, confining pressure, argillaceous siltstone, saturation