Abstract:
As part of the expansion of Liquification Facilities at the existing LNG terminal on Porcupine Cove south of Providence, RI, site grades had to be raised approximately 15 ft. along the shoreline. The site is underlain by as much as 60 ft. of organic silt and peat which created significant challenges for both the slope stability and vertical stability of the new fill. Thornton Tomasetti utilized the hundreds of timber piles, some almost 80 years old, that had been left in place from former structures along the shoreline. These piles would be supplemented by a limit number of new, driven, precast, prestressed concrete piles where holes existed in the coverage of existing piles. Together, the existing and new piles supported the weight of the new fill required to raise the site above the storm level. New structures where then supported on independent drilled in micropiles. The talk will discuss our analysis of the system using finite element modelling, requirements by the client for redundancy in the event of deterioration of the existing timber piles and field verification of the timber pile condition.
The presentation will also discuss the design of the reinforced earth slope and erosion protection facing selected for the construction. The reinforced earth allowed a relatively steep face while also providing load transfer over the existing piles supporting the new fill. Geogrids with a welded wire basket facing were used for the initial construction. A second Rip Rap facing was then added for storm and wave protection. Again, finite element modeling was used for this complete soil-structure interaction evaluation. The reuse of the existing timber piles, confirmed by extensive field verification, proved to have both economic and construction schedule savings that benefited the project as well as meeting the requirements for resiliency, sustainability and beneficial reuse of existing infrastructure.