Department of Civil Engineering Faculty Publications

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    Simulations of Landslide Wave Generation and Propagation Using the Particle Finite Element Method
    (Wiley, 2020-06-03) Mulligan, Ryan P.; Franci, A.; Celigueta, M. A.; Take, W. Andy
    In this study, the impulse waves generated by highly mobile slides in large-scale flume experiments are reproduced numerically with the Particle Finite Element Method (PFEM). The numerical technique combines a Lagrangian finite element solution with an efficient remeshing algorithm and is capable of accurately tracking the evolving fluid free-surface and velocity distribution in highly unsteady flows. The slide material is water, which represents an avalanche or debris flow with high mobility, and the reservoir depth is varied, thereby achieving a range of different near-field wave conditions from breaking waves to near-solitary waves. In situ experimental observations of fluid velocity and water surface levels are obtained using high-speed digital cameras, acoustic sensors, and capacitance wave probes, and the data are used to analyze the accuracy of the PFEM predictions. The two-dimensional numerical model shows the capability of holistically reproducing the entire problem from landslide motion, to impact with water, to wave generation, propagation, and runup. Very good agreement with the experimental observations are obtained, in terms of landslide velocity and thickness, wave time series, maximum wave amplitude, wave speed, and wave shape. In a broad perspective, the results demonstrate the potential of this numerical method for predicting outcomes of interacting multi-hazard scenarios, such as landslides triggered by loss of slope stability and the generation of tsunami.
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    Tidal Dynamics in Palaeo-Seas In Response to Changes in Physiography, Tidal Forcing and Bed Shear Stress
    (Wiley, 2022-01-25) Zuchuat, Valentin; Steel, Elisabeth; Mulligan, Ryan P.; Collins, Daniel S.; Green, J. A. Matthias
    Simulating hydrodynamic conditions in palaeo-ocean basins is needed to better understand the effects of tidal forcing on the sedimentary record. When combined with sedimentary analyses, hydrodynamic modelling can help inform complex temporal and spatial variability in the sediment distribution of tide-dominated palaeo-ocean basins. Herein, palaeotidal modelling of the epicontinental Upper Jurassic (160 Ma, lower Oxfordian) Sundance and Curtis seas of North America reveals possible regional-scale variations in tidal dynamics in response to changes in ocean tidal forcing, physiographic configuration and bottom drag coefficient. A numerical model forced with an M2 tidal constituent at the open boundary shows that the magnitude and location of tidal amplification, and the variability in current velocity and bed shear stress in the basin, were controlled by palaeophysiography. Numerical results obtained using a depth of 600 m at the ocean boundary of the system enable the prediction of major facies trends observed in the lower Curtis Formation. The simulation results also highlight that certain palaeophysiographic configurations can either permit or prevent tidal resonance, leading to an overall amplification or dampening of tides across the basin. Furthermore, some palaeophysiographic configurations generated additional tidal harmonics in specific parts of the basins. Consequently, similar sedimentary successions can emerge from a variety of relative sea-level scenarios, and a variety of sedimentary successions may be deposited in different parts of the basin in any given relative sea-level scenario. These results suggest that the interpretation of sedimentary successions deposited in strongly tide-influenced basins should consider changes in tidal dynamics in response to changing sea level and basin physiography.
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    Local and Remote Storm Surge Contributions to Total Water Levels in the Gulf of St. Lawrence During Hurricane Fiona.
    (Wiley, 2023-07-28) Mulligan, Ryan P.; Swatridge, L.; Cantelon, J. A.; Kurylyk, B. L.; George, E.; Houser, C.
    Post-tropical Hurricane Fiona generated a large storm surge that resulted in pronounced flooding and coastal erosion in Atlantic Canada in September 2022. In this study we apply a regional barotropic storm surge model in the Gulf of St. Lawrence, a semi-enclosed sea, to demonstrate a method of evaluating different contributions to the total water levels. These include the surge generated over the ocean, the surge generated by the cyclonic winds over the gulf, and the tides. The results indicate that the highest storm surge occurred in the southeastern region, a combination of locally and remotely generated components. The surge that entered from the ocean was greater than the surge generated over the gulf; however, these were not in phase. To investigate the case where the local and remote surges are coincident, we shift the wind field relative to the timing of the boundary conditions and find the near “perfect storm” with significantly higher storm surge elevations. These findings highlight the importance of basin morphology and storm conditions in controlling the interactions of surge components, and this approach can be applied to simulate a range of storm-driven hazard outcomes for future extreme events.
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    2D and 3D Numerical Modelling of Exposed Steel Base Plate Connections under Cyclic Loading
    (Canadian Science Publishing, 2022-04-04) Singh, Gursarbjot; Woods, Joshua
    The degree of fixity at the base of steel gravity columns with exposed base plate connections is often assumed in analysis and design. However, past experiments have shown these connections do provide lateral stiffness and strength that could contribute to the load carrying capacity of a structure. The goal of this study is to develop a numerical modelling approach for exposed steel base plate connections that can capture their nonlinear cyclic behaviour, including their stiffness, strength, and energy dissipation capacity. Two modelling approaches are proposed, one that is suitable for detailed study of connection behaviour and another comparatively simple approach that can be used in nonlinear time-history analysis of a structure. Results from the two methodologies are compared with experimental data from the literature and the results show that both approaches can capture the nonlinear cyclic response of the studied connections. Limitations of the proposed modelling approach are also discussed.
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    17-Year Elevated Temperature Study of HDPE Geomembrane Longevity in Air, Water and Leachate
    (ICE Publishing, 2018-10-17) Ewais, Amr; Rowe, R. Kerry; Rimal, Santosh; Sangam, Henri P.
    A 17-year investigation of a geomembrane (GMB) aged at 55, 70 and 85°C in air, water and leachate is reported. At test termination, the mechanical properties had only reached nominal failure in leachate and water at 70 and 85°C. Consistent with a previous study, there is a significant reduction in stress crack resistance (SCR) before there is clear evidence of oxidative degradation; this is attributed to the morphological changes due to disentanglement of entangled polymer chains. The effect of this apparent morphological change on SCR appeared to be greatest for the GMB when immersed in water and leachate at 70°C, although it is evident for all fluids at all three test temperatures. Using the most conservative estimates, the time to nominal failure (tNF, time to 50% of the initial or specified property value) in leachate, water and air (no UV exposure) ranged from >13, 18 and 170 years at 60°C to 660, 1500, and 1700 years, respectively, at 20°C. Assuming minimal tensile strains in the GMB, the time to nominal failure of this GMB in a composite liner is likely estimated to vary from >50 years at 60°C to >550 years at 35°C and > 1100 years at 20°C.