Influence of Unstable Soil Movement on Pile-Founded Concrete Floodwalls and a Resulting Design Methodology

• Main Author: Varuso, Richard James
• Other Authors: Dutrow, Barbara
• Format: Others
• Language: en
• Published: LSU 2010
• Subjects: Civil & Environmental Engineering
• Online Access: http://etd.lsu.edu/docs/available/etd-04192010-093617/

Efforts are underway in the New Orleans area to raise the elevations of its levee system to combat the effects of hurricane storm surge. When complete, the majority of the system will be comprised of a combination of levees, sheet pile I-Walls, floodgates, and pile-supported concrete floodwalls, commonly referred to as T-Walls. Given the magnitude of the hydrostatic forces associated with storm surge, global instability is failure mechanism that must be considered in the design of T-Walls. In the past, it was assumed that these forces would be resisted by the T-Walls sheet pile cut-off wall. Recent literature review and numerical modeling indicate that these forces will be absorbed by the support piles in lieu of the sheet pile wall. This study will test this hypothesis through combined experimental and numerical models. Geotechnical centrifuge models were utilized to study a prototype floodwall indicative of T-Walls designed for the HSDRRS. The models aimed to: (1) determine if the vertical hydrostatic forces cause an instable foundation, (2) how the forces associated with an unstable foundation would be resisted by the T-Wall sub-structure , and (3) assess the impact of spacing of the support piles. By conducting centrifuge models with no piles, with only support piles, and with both support piles and a sheet pile wall, the centrifuge models showed that the unbalanced forces associated with flood side hydrostatic forces could be resisted by the support piles and that the sheet pile wall only needs be designed for seepage or piping concerns. Results of these centrifuge models were corroborated by 3D finite element analyses (FEA) utilizing the software program PLAXIS 3D FOUNDATION. In this dissertation, a new methodology for the design of pile-supported T-Walls was developed that considers both classical forces and unbalanced forces associated with an unstable foundation. The design methodology is based on findings from studies related to passive loading of piles, geotechnical centrifuge model tests conducted at the Rensselaer Polytechnic Institute, and 3D FEA models. The end result was the development of a concise design methodology that results in cost effective and technically accurate T-Wall designs part of the HSDRRS.