Experimental and DEM analyses of factors affecting the structural degradation rate of structured clays

The structural degradation rate (ξ) of structured clays was investigated through laboratory experiments and discrete element method (DEM) simulations. One-dimensional and isotropic compression tests were conducted to examine the effects of bonding strength, initial void ratio, clay type, and pore structure. DEM analyses further evaluated the micromechanical influences of bonding strength (bond shear cohesion and radius multiplier), initial void ratio, and loading mode. A normalized bond parameter (Bs) was introduced, whose initial magnitude reflects structural strength and whose reduction rate characterizes structural degradation. Experimental results show that ξ increases with bonding strength, as indicated by higher cement content and longer curing time. Specimens with larger initial void ratios exhibit higher ξ due to the presence of more compressible pores. Under similar conditions, the tested kaolin structured clay shows a slightly lower ξ than the tested Tianjin structured clay, while specimens prepared by the compaction method—with larger pores—display higher ξ than those prepared by the consolidation or pressing methods. DEM results confirm that stronger bonding increases the yield stress and initial Bs but accelerates its reduction with strain, whereas looser structures undergo faster bond breakage. Compared with isotropic compression, one-dimensional loading induces additional deviatoric strain, leading to more extensive bond failure. These findings provide guidance for determining degradation parameters and improving the prediction of deformation and stability in structured clays.