التحليل بطريقة الفروقات المنتهية لمنصة نقل الأحمال المدعمة بالجيوغريد فوق الدعائم الصلبة

Finite Difference Analysis of Geogrid Reinforced Load Transfer Platform Over Rigid Inclusions

Abstract

The construction of embankments and foundation systems over weak or compressible soils often requires advanced ground-improvement techniques to ensure stability and serviceability. Geosynthetic-Reinforced Load Transfer Platforms (GRLTP) combined with rigid inclusions have proven effective in redistributing vertical stresses and minimizing differential settlements. Nevertheless, a clear gap exists in previous research regarding the combined influence of applied vertical stress, trapdoor displacement magnitude, trapdoor geometry and arrangement, footing dimensions and location, and the inclusion of geosynthetic reinforcement on load transfer platforms under localized subsidence. Earlier studies rarely examined these factors simultaneously within a rigorous finite-difference framework.
This study addresses that gap by employing the finite difference method (FDM), implemented in FLAC3D, to perform an advanced three-dimensional numerical investigation of GRLTPs over rigid inclusions subjected to trapdoor-induced subsidence and surface loading. A suite of calibrated models explored the effects of displacement, trapdoor width and multiplicity, footing size and offset, and reinforcement depth and configuration. Validation against published laboratory trapdoor tests demonstrated good agreement, with a root mean square error (RMSE) about 3.18%, confirming the robustness of the models.
The results showed that soil arching mobilizes rapidly at relatively small displacements, effectively redirecting stresses toward adjacent supports. However, arch efficiency progressively degrades with continued displacement or under high surface loads, as vertical stresses re-concentrate above the yielding zones. Reinforcement was found to significantly enhance stability, with single geogrid layers positioned near the settlement plane achieving a Stress Reduction Ratio (SRR) of about 0.75 and TC–SE stress intersection about 70 kPa, corresponding to a good performance rating. Furthermore, multiple reinforcement layers provided even greater improvements, where double reinforcement achieved a 60% increase in performance compared to the single-layer baseline, raising the TC–SE intersection from 70 kPa to 110 kPa and yielding an excellent cost–benefit ratio. However, the addition of a third reinforcement layer resulted in only marginal gains, with poor cost–benefit efficiency.
The study further revealed that increasing the number of trapdoors fundamentally alters the load transfer mechanism. In double- and triple-trapdoor systems, intermediate supports subdivided the embankment into multiple interacting arching zones, reducing the direct load on trapdoors and enhancing stress uniformity across supports. Wider footings and increased offset from the trapdoor center further improved load transfer efficiency. Collectively, these findings provide a comprehensive understanding of LTP behavior under multi-trapdoor subsidence, offering refined insights for optimizing pile-supported embankment design.