On February 8, 2025, a catastrophic landslide occurred in Jinping Village, Junlian County, Sichuan Province, resulting in severe casualties and significant property losses. Field investigations, laboratory tests, and historical image analysis indicated that the landslide was caused by progressive weakening of the strength of the rock mass under long-term dry–wet cycles. The sliding body consisted of interbedded sandstone and mudstone, forming a typical hard-over-soft lithological structure, with well-developed joints and high permeability. After 5 cycles, particles larger than 40 mm completely disintegrated, whereas after 20 cycles, the fraction of particles smaller than 5 mm increased from 0.035% to 31.268%, indicating significant granular refinement. The slake durability index I d > 10 mm decreased to 0.573 after 20 cycles, quantitatively demonstrating the pronounced weakening of silty mudstone under dry–wet cycles. Field investigations revealed the presence of water-rich zones formed by the superposition of highly permeable layers and aquicludes. In this case, groundwater accumulation increased pore water pressure and reduced shear strength. While daily rainfall in the 24 h before the event was minimal (0.3 mm), sustained precipitation in the preceding month (85.4 mm) had maintained elevated pore pressures. Combined with long-term dry–wet cycles, these conditions progressively weakened the slope and pushed it into a near-critical state. This study highlights the pivotal role of dry–wet cycles in landslides evolution in mountainous regions and provides theoretical insights for early identification and disaster prevention in areas with seasonal climatic variability.
JIA et al. (Sat,) studied this question.