Non-synchronous coordinated reduction method (NSCR) for slopes based on 3D geological modeling

Abstract Conventional slope stability analyses often rely on two-dimensional models, which neglect local geological heterogeneity and spatial distribution of materials. This simplification can lead to inaccuracies in evaluating slope safety. Additionally, traditional strength reduction methods (SRMs) uniformly reduce the parameters of rock and soil, failing to represent the actual degradation process during progressive failure. This study aims to improve the accuracy of slope stability analysis by developing a method that better captures the spatial variability of geological conditions and the nonsynchronous degradation of shear strength. A three-dimensional (3D) geological model was constructed to restore the actual stratigraphic structure of the slope. Based on the shear strength degradation mechanism, a nonsynchronous coordinated reduction (NSCR) method was proposed, incorporating advanced reduction steps ( n ) and a correlation factor ( λ ). This method simulates progressive slope failure more realistically. An engineering case study demonstrated that the 3D NSCR method obtained a safety factor of Fs = 1.265, which is very close to that of the most critical two-dimensional limit equilibrium method section (with a difference of about 1%), whereas the traditional SRM and the two-dimensional coordinated reduction method show relatively larger errors. The 3D analysis revealed the overall dangerous slip surface, providing enhanced insight into slope instability mechanisms. The proposed NSCR method, supported by 3D geological modeling, improves the accuracy of slope stability analysis by better representing progressive failure. It is a feasible and effective tool for engineering applications involving complex slope conditions.