4th Geotechnical Symposium, Adana, Turkey, 1 - 02 December 2011, pp.1-11
This is a case study of the stability of a wastewater lagoon dike subject to rapid drawdown. A coupled analysis of transient water flow into the dike due to external water level changes and the mechanical response of the dike to the associated pore water poressure changes was undertaken using two finite element analysis codes that communicate with each other, i.e., PLAXFLOW and PLAXIS. The numerical sumilations included initial conditions, raising of the dike height, rapid raising of water level due to discharges into the lagoon, sustained water level, and eventual drawdown by pumping water from the lagoon. Safety factor was calculated for all of these stages established by the owner. Classical limit equilibrium analyses, with their limiting assumptions, indicated potential failure during the imposed water level history. More realistic simulations, made possible by the coupled numarical analyses, indicated safe conditions at all stages enabling the owner to avoid costly dike reinforcement options.