Numerical simulation of deformation performance of Waba Dam

Mona El Mosallamy, Tareq Salloum, Peter Hassan, Jinyuan Liu

In the proceedings of: GeoRegina 2014: 67th Canadian Geotechnical Conference

Session: Infrastructure

ABSTRACT: simulation of deformation performance of Waba Dam Mona El Mosallamy Department of Civil Engineering, Ryerson University, Toronto, Canada Tareq Salloum, Peter Hassan Ontario Power Generation, Niagara-on-the-Lake, Canada Jinyuan Liu Department of Civil Engineering, Ryerson University, Toronto, Canada ABSTRACT Waba Dam is a zoned earth fill structure that was constructed on a deep deposit of a soft and sensitive marine clay. This marine clay is characterized by its low shear strength and a large void ratio. To accommodate expected settlement, the dam was designed with an upwards camber and over the last 32 years, the dam and its foundation have settled over 1.5 m (5 ft). Piezometric readings indicated that the excess pore water pressure in the foundation has not yet fully dissipated. Therefore, to ensure the continuous and safe operation of the dam it remains prudent to predict the deformation performance and check whether any adverse behaviour is likely to develop during its life span. Deformation performance is simulated using a two-dimensional finite difference program, FLAC. FLAC is used in this study to simulate the deformation behaviour of the dam due to its consolidation and the associated lateral deformation. The predicted deformations and pore water pressure are in general agreement with those measured in the field. RÉSUMÉ. Waba barrage est une structure de remplissage de terre zonée qui a été construit sur un chiffon doux, argile marine sensible profonde, caractérisée par une faible résistance au cisaillement et grande colonie de consolidation. Au cours des quatre dernières décennies, le barrage et sa fondation sont installés plus de 1,5 m (4,92 pi). Lectures piézométriques ont indiqué que la pression de l'eau interstitielle dans la fondation en excès n'a pas encore complètement dissipée après une longue période de temps. Par conséquent, pour assurer le fonctionnement continu de sécurité du barrage, il reste prudent de prévoir la performance de déformation et vérifier si tout comportement indésirable est susceptible de développer au cours de sa durée de vie. Performances de déformation est simulé en utilisant un programme fini de différence à deux dimensions FLAC. de simuler numériquement le comportement en déformation du barrage en raison de sa consolidation et la déformation latérale associée. Le règlement; déformation latérale; et la pression de l'eau interstitielle mesurée sur le terrain sont en général d'accord avec ceux prédits numériquement. 1 INTRODUCTION Marine clay deposits are widely spread along coastal regions all over the world (Lei et al. 2011). Construction of buildings, roads, and embankments over these soft deposits is always associated with stability and settlement problems. Marine clays are normally deposited in saline water environments. Due to the presence of polarized cations on the clay particles, there remains a tendency for the particles to settle and develop into a flocculated fabric. These clays develop their strength from this flocculated structure and the attractive forces between neighboring particles. Any reduction in the electrolyte concentration in the pore water, i.e. leaching of salts, tends to increase both the soil sensitivity and the repulsion forces between particles. Therefore, any physical disturbance will cause the pore water to be released and the soil structure to be broken, which will lead to progressive settlements or failures in the clay (Penner et al.1978). Canadian marine clays are typically covered by mantle of sand or weathered clay (Gadd 1960). Canadian marine clays exist throughout the Ottawa and St. Lawrence River valleys, extending southward to the lower regions of Lake Ontario and northward to the drainage basin of St. John Lake in Quebec (Karrow 1961). Settlement of Waba Dam due to consolidation of underlying soft marine clay was identified during the design stage. The dam was designed with an upward camber to accommodate settlement. In order to monitor the long-term behaviour and ensure the safety of the dam, an extensive instrumentation program has been implemented and monitored since its construction. Monitoring data shows the dam has already settled over 1.5 m (5 ft) beneath its maximum section and has widened with a lateral deformation of 0.3 m (1 ft) over 32 years of service (Salloum et al. 2009). The data also shows that consolidation of the foundation soils is still in progress, as anticipated during the design stage, resulting in a lower crest level. In this paper, the long-term deformation behaviour of Waba Dam is investigated using a two-dimensional finite difference program, FLAC. Based on these finite difference analyses, a comparison is performed between numerical predictions and field measurements, including settlement; lateral deformation; and pore water pressures.

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Mona El Mosallamy; Tareq Salloum; Peter Hassan; Jinyuan Liu (2014) Numerical simulation of deformation performance of Waba Dam in GEO2014. Ottawa, Ontario: Canadian Geotechnical Society.

@article{GeoRegina14Paper334,author = Mona El Mosallamy; Tareq Salloum; Peter Hassan; Jinyuan Liu,title = Numerical simulation of deformation performance of Waba Dam,year = 2014}