Research on Stability of Covered Karst Foundation Under Vehicle Loads

Covered karst geological conditions pose significant geotechnical hazards in highway construction, including karst roof collapse, ground subsidence, and differential foundation settlement. This study investigates these risks through a numerical simulation analysis of a highway project in Yulin City. We systematically examined the influence mechanisms of vehicular loads on the stress distribution within the bedrock surrounding karst cavities and the resulting vertical and lateral displacement responses of the subgrade, considering various configurations of covered karst. An evaluation framework was developed based on the safety factor against instability and the subgrade deformation coefficient to quantitatively assess the stability of covered karst foundations. The results reveal distinct stress and displacement patterns. Tensile stress concentrations occur primarily at the roof and floor of the cavity, as well as at the upper corners of the cavity roof. Conversely, shear stress accumulates predominantly at the haunches (sidewalls) of the cavity. Crucially, both tensile and shear stresses exhibit a continuous increase with rising vehicular loads. Consequently, the stability safety factor demonstrates a corresponding decreasing trend. Displacement analysis shows a characteristic "horn-shaped" symmetric distribution of lateral displacement along the embankment centerline. Specifically, lateral displacement increases from the embankment toe towards the shoulder, reaching a peak near the shoulder, and subsequently decreases towards the centerline. Vertical displacement, however, displays a symmetric "concave basin-shaped" distribution along the centerline, with maximum values at the centerline itself and minima at the embankment toes. Both lateral and vertical displacements amplify significantly with increasing vehicular loads, leading to a synchronous rise in the subgrade deformation coefficient. Ultimately, the stability state of the covered karst foundation is comprehensively evaluated by analyzing the coupled variation patterns of these dual coefficients (safety factor and deformation coefficient). This research provides critical theoretical foundations and technical support for the planning, design, and construction of highway projects in covered karst regions.