DFI - PFSF Piling & Ground Improvement Conference 2022 Proceedings, (DFI and PFSF)
Modification in Current BRE Approach for Designing Pilling Rig Working Platforms on Soft Subgrades
Amir Shahkolahi and Jorg Klompmaker
In many cases, working platforms are located on weak soils, resulting in low bearing capacity, excessive settlements and even accidents. This requires the necessity to design a working platform. The design of such working platforms is often made based on practice and empirical methods. If the existing soil is not sufficiently strong to carry the loads of the piling rig, a design of the geogrid reinforced working platform is required to distribute the loads to an acceptable rate for the in-situ subgrade. The use of geogrid reinforcement can reduce the required thickness of the granular working platform. The current design approaches for both unreinforced and geogrid reinforced working platforms, such as BRE design approach, are very conservative and do not consider the real interaction and benefit of geogrid reinforcement. To overcome this limitation on current design methods, a modified approach for designing geogrid reinforced working platforms is developed based on large scale laboratory and field tests and Finite Element Modelling. Until now, the bearing capacity of soils, reinforced or not, have been calculated, but the real behavior of geosynthetic reinforcement was not clearly defined. In order to have a better knowledge of the real behavior of the geosynthetic reinforcement, to verify and improve the existing design methodology, an in-situ experimental test was performed. A geosynthetic-reinforced working platform was monitored in terms of stresses and strains and the results are presented in the paper. Further, a Finite Element (FE) numerical model was created and validated based on the in-situ results. Based on this model, the modified design approach for geogrid reinforced working platforms could be verified. The modification can result in 50% to 75% reduction in the thickness compared to an unreinforced working platform, and 35% to 70% reduction in the thickness compared to the current reinforced platform design approaches. The paper presents all the results (numerical and analytical) and the resulted conclusions. Local and international case studies are presented at the end.
|article #3845; publication #1076 (IC-2021)|