Stability assessment of the Road Cut Slopes in the Xigeda mudstone considering long-term creep deterioration and suggestion for countermeasures: A case study of cut slopes along the Xichang–Panzhihua expressway

The Xigeda clay-rock strata exhibit typical characteristics of long-term creep deterioration and saturation softening, which is typical slide-prone stratum. Landslides are easily formed in Xigeda strata cut slope due to the continuous deterioration and stability reduction during the operation period, which poses great threats to operational safety. The reduction coefficients for the c and φ values due to long-term creep deterioration of Xigeda clay-rock are determined as 0.87 and 0.84 respectively. These values are derived from shear strength Parameters of slope excavation and sliding obtained through geological analysis, discrete element numerical simulation, and mutual verification involving the K2378 + 900 right-side landslide on the Xichang-Panzhihua Expressway. By conducting critical slip surface searches and stability calculations for 17 distinct Xigeda clay-rock slopes representing 5 different types, the average decrease of stability coefficient is found to be 0.184 when shear Parameters are reduced in accordance with creep deterioration within the range of 0.87～0.84. Consequently, targeted recommendations are proposed for key factors influencing the long-term stability of Xigeda clay-rock slopes, encomPassing safety coefficients, slope ratios, and reinforcement measures. It is demonstrated that employing a construction approach characterized by a gentler slope, wider platforms, and less intensive reinforcement is proved to be more conducive to the slope long-term stability. The research results provide important guidance and reference for highway construction and slope protection treatment within the Xigeda stratum area.