Data Preparation for Validation Study of Hazus Canada Flood Model

As our climate changes, the occurrence of extreme weather events and heavier rainfall becomes more common. This change in weather patterns and precipitation results in a greater number of recorded flood events and a larger magnitude of flood events. Canadian municipalities are therefore facing a pressing demand to perform hazard assessments to identify communities at risk and measure potential economic and societal losses due to flood events. Federal Emergency Management Agency (FEMA) developed a standardized tool, Hazus-MH, for loss estimation from natural disasters for use in the US. Recently, Hazus has been adapted for use in Canada. This paper introduces the Hazus flood loss assessment model and the adaption and development required for the Canadian Hazus release. Furthermore, the steps followed with respect to data acquisition and preparation of the required exposure and hazard input data and attribute translation methodology to conform to Hazus classifications for the pilot study in Fredericton, NB, are presented. A subsequent paper will report the flood model results and compare them to actual expenditures from the 2008 flood in Fredericton to verify the validity of the model, depth damage curves, and parameters employed

Containment Lining Solutions and Hydrodynamic Stability of Tailings Dam

The study investigates the impact of reservoir lining on the hydrodynamic stability of a tailings dam. A 3D coupled fluid-solid finite element model was used for detailed seepage analyses based on conventional flow-net and steady seepage conditions. Pore pressure, stationary seepage velocities, static liquefaction and the ratio between manifested and critical hydraulic gradients were predicted under three different lining conditions. The highest potential for internal erosion and heave was observed in the lined reservoir and starter dam scenario. Although there are environmental benefits, the incorporation of liners in dam design requires a comprehensive engineering assessment of the negative hydrodynamic effects

Probabilistic approach for seismic microzonation integrating 3D geological and geotechnical uncertainty

A novel probabilistic methodology for regional seismic site characterization is proposed and applied to a region with highly heterogeneous surficial geology and varying soil sediment thickness and stiffness. The method combines various sources of geological and geotechnical uncertainties to develop a three-dimensional (3D) shear-wave velocity (Vs) model and evaluate the associated uncertainties. A 3D geological model of the unconsolidated deposits was developed using geostatistical interpolation and simulation methods. Sequential indicator simulations produced a quantitative geologic model that explicitly quantified geological uncertainties based on the likelihood of specific soil types occurring. In situ measurements and multivariate statistical analysis allowed the development of empirical correlations between Vs, geotechnical parameters, depth, and soil types. The resulting 3D Vs values were estimated on the basis of Vs-depth correlations and the probability of occurrence of each soil type. In this approach, the propagated uncertainty was also quantified by considering the combined variance. Seismic microzonation mapping was then conducted by transforming the 3D Vs model into two-dimensional (2D) maps that represent the spatial distributions of the time-averaged shear-wave velocity of the top 30 m (Vs,30) and the fundamental site period (T0), along with their respective uncertainties using Monte Carlo simulations. The results indicate that microzonation maps and their uncertainties are influenced by the thickness, occurrence probability, and geotechnical properties of soils. The proposed method can be used to assess the probabilistic seismic risk at local and regional scales in areas with geologically and geotechnically complex soil properties

Investigating Multilayer Aquifer Dynamics by Combining Geochemistry, Isotopes and Hydrogeological Context Analysis

ABSTRACT: Geochemical tracers have the potential to provide valuable insights for constructing conceptual models of groundwater flow, especially in complex geological contexts. Nevertheless, the reliability of tracer interpretation hinges on its integration into a robust geological framework. In our research, we concentrated on delineating the groundwater flow dynamics in the Innisfil Creek watershed, located in Ontario, Canada. We amalgamated extensive hydrogeological data derived from a comprehensive 3D geological model with the analysis of 61 groundwater samples, encompassing major ions, stable water isotopes, tritium, and radiocarbon. By seamlessly incorporating regional physiographic characteristics, flow pathways, and confinement attributes, we bolstered the efficiency of these tracers, resulting in several notable findings. Firstly, we identified prominent recharge and discharge zones within the watershed. Secondly, we observed the coexistence of relatively shallow and fast-flowing paths with deeper, slower-flowing channels, responsible for transporting groundwater from ancient glacial events. Thirdly, we determined that cation exchange stands as the predominant mechanism governing the geochemical evolution of contemporary water as it migrates toward confined aquifers situated at the base of the Quaternary sequence. Fourthly, we provided evidence of the mixing of modern, low-mineralized water originating from unconfined aquifer units with deep, highly mineralized water within soil–bedrock interface aquifers. These findings not only contribute significantly to the development a conceptual flow model for the sustainable management of groundwater in the Innisfil watershed, but also offer practical insights that hold relevance for analogous geological complexities encountered in other regions

Quantifying exposure of linear infrastructures to earthquake-triggered transverse landslides in permafrost thawing slopes

The seismic shaking can cause slope instability in otherwise relatively stable permafrost terrains. In addition, rapid ice melting in low-permeability fine-grained soils can lead to excess pore water pressure build up and cause instability in slopes even at small angles. This study addresses the active layer detachment (ALD) slope instability hazard and develops a systematic risk assessment framework for existing and future linear infrastructures such as energy pipelines, bridges and roads traversing permafrost regions. Mild slopes, with average gradient of 7째, are considered in this study as the most representative of actual field conditions. The potential for earthquake-triggered ALD is analytically quantified. State-of-the-art Canadian North ALD morphological statistics are combined with seismic slope stability analyses to determine: (i) the probability of linear infrastructure exposure to permanent ground deformations (PGD) caused by ALD, and (ii) the extent of the potential PGD that the linear infrastructure may be subjected to. Monte Carlo technique is applied to simulate and assess the sensitivity of the model to parameters such as earthquake magnitude and source-to-site distance. The findings from this study can be used to evaluate the vulnerability of linear infrastructures exposed to the ALD hazard.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Development of empirical CPTu-Vs correlations for post-glacial sediments in Southern Quebec, Canada, in consideration of soil type and geological setting

The correlation of shear wave velocity (Vs) with piezocone penetration test (CPTu) parameters is investigated in post-glacial sediments along the St. Lawrence and Saguenay rivers, Southern Quebec, Canada. The compiled database includes 991 CPTu-Vs measurements at 40 sites. The objectives are to examine the applicability of existing CPTu-Vs correlations, identify the main CPTu parameters and develop specific CPTu-Vs correlations that account for the effects of soil type (sandy or clayey) and geological setting (Champlain or Laflamme sea sediments). Results reveal that the application of existing correlations is biased in varying degrees, denoting a need for site-specific correlations for the study area. Multivariate regression analyses confirm the importance of cone tip resistance and depth as Vs predictors assisted by normalised pore pressure and soil behaviour type index. Consideration of soil type and geological setting helps reduce uncertainties in CPTu-Vs correlations for fine-grained soils

Seismic microzonation of a region with complex surficial geology based on different site classification approaches

A seismic microzonation study was conducted to refine the seismic hazard model for the city of Saguenay, Canada. The Quaternary geology underlying Saguenay shows complex glacial and post-glacial stratigraphy with a number of buried valleys filled with fluvioglacial and glaciomarine sediments. High impedance contrast between rock formations and surficial sediments is prone to seismic amplification. To evaluate their applicability, advantages and limitations in capturing the geological specificity of the study area, four site classification methods were applied: the current National Building Code of Canada (NBCC) and Eurocode 8, both mainly based on the average shear-wave velocity for the surficial sediments (VS,avg) and for the top 30 m (VS,30); a method based on the fundamental site period (T0); and a hybrid method based on the combination of VS,30, T0 and VS,avg. The study specifically aimed to evaluate the importance of the site classification parameters on the resulting microzonation maps. VS,30 is capable to present the geological and geotechnical site conditions, however, the results may be further improved by considering Vs,avg in shallow and T0 in thick layers of soil sediments as secondary parameters. The T0 method gives also satisfactory results with T0 showing a better correlation to Vs,30 than to Vs,avg. The versatile hybrid method may be challenging to apply in certain cases with its nine different site categories and parameters

3D probabilistic modelling and uncertainty analysis of glacial and post-glacial deposits of the City of Saguenay, Canada

Knowledge of the stratigraphic architecture and geotechnical properties of surficial soil sediments is essential for geotechnical risk assessment. In the Saguenay study area, the Quaternary deposits consist of a basal till layer and heterogeneous post-glacial deposits. Considering the stratigraphic setting and soil type heterogeneity, a multistep stochastic methodology is developed for 3D geological modelling and quantification of the associated uncertainties. This methodology is adopted for regional studies and involves geostatistical interpolation and simulation methods. Empirical Bayesian kriging (EBK) is applied to generate the bedrock topography map and determine the thickness of the till sediments and their uncertainties. The locally varying mean and variance of the EBK method enable accounting for data complexity and moderate nonstationarity. Sequential indicator simulation is then performed to determine the occurrence probability of the discontinuous post-glacial sediments (clay, sand and gravel) on top of the basal till layer. The individual thickness maps of the discontinuous soil layers and uncertainties are generated in a probabilistic manner. The proposed stochastic framework is suitable for heterogeneous soil deposits characterised with complex surface and subsurface datasets

Experimental and analytical study of seismic site response of discontinuous permafrost

Seismic site response of discontinuous permafrost is discussed. The presence of frozen portions in soil deposits can significantly affect their dynamic response due to stiffer conditions characterized by higher shear wave velocities compared to unfrozen soils. Both experimental and numerical investigations were conducted to examine the problem. The experimental program included a series of 1g shaking table tests on small-scale models. Nonlinear numerical analyses were performed employing the FLAC software. The numerical model was verified using the obtained experimental results. Parametric simulations were then conducted using the verified model in order to study the variations of the free-field spectral accelerations (on top of the frozen and unfrozen soil blocks) with the scheme of frozen/unfrozen soil, and to determine the key parameters and their effects on the seismic site response. The results showed that spectral accelerations were generally higher in frozen soils than in unfrozen soils. It was found that the shear wave velocity of the frozen soil, the assumed geometry of the blocks and their spacing have significant impact on the site response.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Eigenvalue solution for arch dams: ADAD-IZIIS Software

3D earthquake analyses of complex engineering structures such as arch dams are based on the determination of a range of eigenvalues and associated eigenvectors. Despite the variety of practical numerical eigensolutions available in the literature, the method of subspace iteration was found to offer time efficient and accurate eigenvalue solutions appropriate for large systems with high degrees of freedom. This paper presents the theoretical principles of the well known subspace iteration method implemented in the existing ADAD-IZIIS software for finite-element analyses of arch dams