Under the complex geological structural stress of the Western Himalayan syntaxis, the widespread distribution of hard and brittle rocks (such as sandstone and limestone) makes them prone to the formation of conjugate joints, also known as X-joints. These joints create weak structural planes in the slope rock mass, and when combined with weak interlayers within the slope, they result in a complex dynamic response and hazard situation in this region, which is further exacerbated by frequent seismic activity. This poses a serious threat to the planning, construction, and safe operation of the Belt and Road Initiative. To study the slope vibration response and instability mechanisms under these conditions, we conducted a shaking table test using the Iymek avalanche as a case study and performed Hilbert–Huang Transform (HHT) analysis. We also compared the results of the shaking table test on slope models without X-joints but containing weak interlayers. The findings show that the presence of X-joints leads to an earlier onset of plastic failure in the slope. During the failure development, X-joints cause stress concentration and the diversification of stress redistribution paths, delaying energy release. Ultimately, the avalanche failure mode in the X-joint slopes is more dispersed compared to the landslide failure mode in the model without X-joints. At the toe of the slope beneath the weak interlayer, low-frequency seismic waves can cause a significant amplification of acceleration, and the weak interlayer is often the shear outlets of the slope. These findings provide new insights into the seismic failure evolution of jointed slopes with weak interlayers and offer practical references for seismic hazard mitigation in mountainous infrastructure.

Surface roughness is ubiquitous in hard rock discontinuities at different scales and plays a critical role in governing frictional behavior and rupture dynamics. In this study, triaxial shear tests were conducted on sawcut smooth fractures and tension-induced rough fractures to investigate frictional behavior, roughness evolution, and rupture dynamics with increasing shear cycles. The results demonstrate that rough fractures exhibit higher shear strength and more intense stick-slip behavior than smooth fractures, but show strength weakening and reduced stress drops with shear cycle. In contrast, smooth fractures display relatively stable strength and stress drops. These differences in frictional behavior are governed by roughness evolution. Although roughness decreases in both fracture types after shearing, rough fractures experience degradation nearly an order of magnitude greater than that of smooth fractures. The initial stick-slip event on rough fractures generates the largest stress drop and apparent breakdown work. In addition, analyses of stress drop and energy dissipation reveal that friction drops for different types of fracture are concentrated within the range of 0.01 to 0.3. These findings highlight the critical role of roughness evolution in fault stability and provide valuable insights for seismic hazard assessment in deep underground engineering.