Three-Dimensional Upper-Bound Plastic Limit Analysis and Experimental Validation of Karst Foundations: Bearing Capacity Assessment and Failure Mechanisms

Karst foundations, characterized by caves and weak interlayers, pose significant challenges in stability assessment. Traditional 2D methods fail to capture the complex spatial interactions governing load transfer and failure mechanisms. This study develops a 3D upper-bound plastic limit analysis approach that incorporates tetrahedral elements to model cave–interlayer interactions, overcoming the limitations of existing methods. Compared with conventional techniques, the proposed method improves accuracy in predicting ultimate bearing capacity and provides deeper insights into failure evolution. Large-scale model tests validate the numerical findings, confirming that 3D analysis more effectively accounts for anisotropic material behavior and load redistribution. The results highlight that optimizing load orientation and reducing vertical load components can significantly enhance foundation stability. This research offers a more reliable tool for geotechnical engineers to assess and mitigate risks in karst foundation design.