Inversion of slab-base interface stiffness based on an improved Thomson-Haskell method and its impact on dynamic response of rigid pavements

Slab–base bonding degradation reduces shear transfer and alters rigid-pavement response under traffic loading. An inverse framework based on the improved Thomson–Haskell method identifies interfacial tangential stiffness (K t ) from Rayleigh-wave dispersion data. It combines a high-frequency-stable transfer-matrix formulation with an asymptotically equivalent thin-layer interface representation. The identified stiffness is incorporated into a finite-element model under moving vertical loads with and without braking traction. The stress amplification factor (SAF) and normalised fatigue life are evaluated relative to the fully bonded reference. Within the investigated range, decreasing stiffness increases slab-bottom tensile stress, interfacial slip, and surface deflection, while reducing normalised fatigue life. The nonlinear response indicates evolution from shear-coupled to slip-dominated behaviour. For the investigated configuration and loading, three response regimes are provisionally distinguished: relatively stable, transition, and weakly bonded. Braking traction intensifies interfacial shear effects, shifting the response from reciprocating slip to forward-biased, shear-driven slip at low stiffness. A supplementary three-slab analysis also shows increasing near-joint stress, slab–base slip, and mid-panel stress as the interface degrades. These findings link interface stiffness degradation to dynamic response and fatigue indicators, supporting performance assessment of rigid pavements with deteriorated slab–base bonding.