Newby Island Landfill Liquefaction Mitigation (7 Phases Total)

The landfill, surrounded by a perimeter levee, is on soft estuarine soils. The proposed waste fill thickness of 87 m (285 ft) is relatively high, as is the M7. Specific site assessments have shown that the stability of the landfill-subgrade system is affected by several potentially liquefiable sand lenses beneath the site. Raito used in situ cement deep soil mixing (CDSM) throughout the levee to address the expected excessive seismic displacements in the underlying liquefiable layers. The design and construction of these mitigation measures involved evaluations of slope stability and seismic deformation using a de-coupled approach based on limit equilibrium and Newmark principles.