• Cui S. (Supervisors: Maghoul P.), 2023. Health Monitoring of (Geo)structures Using Stress Wave-Based Non-Invasive Techniques, Polytechnique Montréal, Montreal (QC), Canada. [Link]

During the service life of structures or geostructures, anomalies may appear. If these anomalies cannot be detected earlier, they may cause structural failure or serviceability issues. Therefore, (geo)structure health monitoring has become an important tool to evaluate the integrity and functionality of (geo)structures in construction and rehabilitation programs. Non-destructive testing (NDT) is a crucial component in engineering, construction, and geophysical applications. Because of its non-invasive nature and lower cost, NDT has been widely applied for structural health monitoring, quality control, geotechnical investigation, and material characterization of different types of infrastructure. The aim of this dissertation is to use NDT approaches based on stress waves to monitor the health of (geo)structures at two levels. The first level involves the characterization of the mechanical and geometric properties to monitor the structure’s macroscopic health, while the second level involves damage identification to monitor the structure’s microscopic health. An unknown pile and a beam structure are the application for general health monitoring and damage localization, respectively. Novel physics-based signal interpretation methods are proposed for pile foundation characterization based on the guided wave theory. The guided wave is the elastic wave propagating in a finite medium. The characterization of geometric and mechanical properties is of great significance for the evaluation and reuse of unknown foundations. The geometric property, such as the pile length can be used as a parameter to estimate the scour level and bearing capacity. The mechanical properties of the pile such as the longitudinal wave velocity and shear wave velocity can be used to evaluate the health condition or integrity of the pile. In a cylindrical pile, there are two modes of guided wave: the longitudinal and flexural modes. The longitudinal mode appears if the impact is placed on the pile top surface, and the flexural mode corresponds to a test configuration in which the impact is applied on the lateral side of the pile. The spectral element method can be used to obtain the dispersion relation, i.e. the relation between the phase velocity and the frequency, which is then used for pile length and pile properties characterization. For pile length estimation, first, the dispersion relation and the phase difference of the responses collected by at least two sensors located on the lateral side are combined to show the relationship between the phase difference and the wavenumber. By periodic analysis of this relationship, the pile length can be estimated. Second, the pile length can also be estimated by one sensor for data acquisition. The relationship between the wavenumber and the normalized magnitude can be obtained by combing the dispersion relation and the normalized magnitude. Then by periodic analysis of this relationship, the pile length can be estimated. In these two methods using the longitudinal mode of guided waves, the sensor can be placed on the lateral side and the top surface. The third method is to characterize the pile length using the flexural mode and an inversion method. The dispersion relation based on the flexural mode is used as the forward model, and then the experimental dispersion relation can be extracted by the resonant analysis of the signal collected on the lateral side of the test pile. An optimization algorithm based on the genetic algorithm is used to inversely estimate the pile length and physical properties, including shear wave velocity, longitudinal wave velocity and density, simultaneously.

  • Afsharipour M.H. (Supervisor: Maghoul P.), 2023. Small Modular Reactors for Energy Transition in Northern Canada: Thermal Modeling and Some Geotechnical Considerations, Polytechnique Montréal, Montreal (QC), Canada. [Link]

Remote northern communities in Canada face energy challenges due to their reliance on fossil fuels. Small modular reactors (SMRs) show promise as a sustainable solution to this issue, as they can reduce greenhouse gas emissions and promote sustainable development. However, SMRs require specific structural and geotechnical design paradigms for implementation and operation in permafrost regions, which are adversely affected by climate change and permafrost degradation. This study presents the potential of SMRs for sustainable energy production in the northern context. We provide an overview of SMRs and highlight their position in Canada’s energy transition in northern regions. Additionally, we discuss the challenges associated with the thermal design and implementation of SMRs in northern regions in the context of climate change. Our study presents two case studies, regarding hypothetical SMR sites at Salluit (QC) and Inuvik (NWT) and predicts the ground temperature profile at the end of the 21st century. This study contributes to the growing body of literature on SMRs in permafrost regions and highlights the need for further research and policy development to support their adoption. To present the ideas and results to stakeholders, the results of the study are brought to the Industry 4.0 context by developing an Augmented Reality (AR) and Virtual Reality (VR) platform to enhance the presentation and communication of research concepts. A detailed step-by-step process for creating 3D representations of the concepts, including texturing, UV mapping, animation, and export and publishing techniques, is introduced. For this purpose, two powerful 3D modeling and animation software programs, Autodesk Maya and Blender, are employed. In Autodesk Maya, a representation of the change in active layer depth as a result of climate change is presented, while Blender is utilized to create a minimal SMR model and its thermal effect on the ground. These avatars, along with several other pedagogical models, are then uploaded to Sketchfab, a popular publishing website that supports AR/VR formats. We also explore the potential for establishing a virtual laboratory for geotechnical engineering, highlighting the transformative possibilities it offers in terms of practical learning experiences and educational accessibility.


  • Katebi M. (Supervisors: Maghoul P. & Wijewickreme D.), 2021. Evaluation of pipeline performance subjected to slope instabilities, University of Manitoba, Winnipeg (MB), Canada. [Link]

The horizontal soil-pipe interaction in slopes is characterized in this research program for inclusion in pipeline guidelines. For this purpose, a series of full-scale experiments were conducted at the Advanced Soil-Pipe Interaction Research (ASPIRe™) testing facility at the University of British Columbia, Vancouver, BC, Canada. The experimental data indicated that the soil load is an increasing function of the slope grade for soil springs inside the landslide boundaries and a decreasing function of the slope grade for soil springs outside the landslide boundaries. The lateral force-displacement responses of pipes installed below sloping ground were presented and compared to those arising from the level ground condition. The experimental results suggest that the values of the horizontal bearing capacity factor can be two-fold higher than those estimated using pipeline guidelines. A finite element model was calibrated against the experimental data and was implemented in an extensive parametric study to extend the results to deep embedment conditions for loose, medium, and dense sands. The horizontal bearing capacity factors are presented in dimensionless graphs as a function of the slope grade and pipe burial depth, which can be used in pipeline guidelines as a benchmark for the design.

Non-destructive testing (NDT) plays an important role in the engineering, construction, and geophysical fields. The application of NDT in civil engineering is broad from quality control, structural health monitoring of infrastructure, geophysical and geotechnical field investigation and material characterization to detection of underground anomaly, among others. One of the frequently used NDT techniques for the characterization of geomaterials is based on the propagation of stress waves generated by an excitation source. However, the existing signal interpretation methods still predominantly rely on empirical relations or subjective judgements that are insufficient for the characterization of multiphase complex geomaterials. This research aims to develop novel physics-based signal interpretation methods to characterize physical and mechanical properties of multiphase geomaterials in both field and laboratory investigation scales. Several hybrid inverse and poromechanical models are developed to characterize dry, saturated, and frozen geomaterials subject to stress waves. First, a highly-efficient semi-analytical elastodynamic forward solver was proposed for the Multichannel Analysis of Surface Waves using the spectral element technique to determine effectively and efficiently the soil stratigraphy as well as soil properties. Next, a coupled piezoelectric and solid mechanics model is proposed to study the real response of the bender element (BE) and its interaction with soil samples in the BE test. A comprehensive laboratory investigation is also performed to better understand the response of the BEs inside different soil types. Then, a two-phase poromechanics-based signal interpretation model is developed for laboratory-scale ultrasonic testing to determine the physical and mechanical properties of saturated soil samples based on the distribution of stress waves. Subsequently, a three-phase poromechanical transfer function model is developed using the spectral element technique for pore-scale characterizations of permafrost samples. Furthermore, a comprehensive ultrasonic testing program is conducted to determine the properties of permafrost samples (e.g., ice content, unfrozen water content, porosity, soil type, and mechanical properties) reconstituted in the laboratory. Thereafter, a hybrid inverse and three-phase poromechanical approach is proposed for in-situ characterization of permafrost sites using surface wave techniques. Finally, the GeoNDT software developed to provide physics-based solutions for the interpretation of NDT measurements used in geotechnical and geophysical applications is presented.

  • Hodaei M. (Supervisor: Maghoul P. & Popplewell N.), 2021. Biomechanical modeling of acoustic wave propagation through bone-like porous materials using the Biot-JKD theory, University of Manitoba, Winnipeg (MB), Canada. [Link]

Osteoporosis is a degenerating disease which may cause a bone to break eventually. A way of monitoring the situation is to employ X-ray Absorptiometry (XA) to assess if a difference has happened in bone’s mineral density. XA tests have been widely used as a bone density test for the hip and spine, which can be a predictor of the likelihood of future breaks in other bones. Bone density in other bones such as the lower arm, wrist, finger, or heel can be measured through peripheral tests, also called screening tests, such as quantitative ultrasound (QUS). The results of screening tests for osteoporosis diagnosis are much less accurate and cannot be compared with the results of an XA test. One of the reasons for the limitations of QUS techniques in diagnosing bone loss is the lack of understanding of the mechanism of ultrasound wave propagation through a porous, complex bone structure. Despite these issues, some features of the QUS technique make it yet very appealing for bone loss detection. For instance, QUS packages are smaller and portable in comparison to bulky MRI or X-ray techniques. Also, they are relatively cheap, do not utilize harmful radiations, and are recognized as a non-invasive technique. This research aims to pave the way to understanding the biomechanical behavior of bonelike porous materials, i.e. cancellous bones, subject to different types of acoustical waves; and characterizing the cancellous bone’s biomechanical parameters for bone loss diagnosis using inverse problem.

  • Fatollahzadeh A. (Supervisor: Maghoul P.), 2021. Long-term efficiency of horizontal closed-loop geothermal heat exchangers for stabilization of permafrost beneath a Subarctic lagoon, University of Manitoba, Winnipeg (MB), Canada. [Link]

Wastewater treatment lagoons are practical and cost-effective systems for small municipalities to reduce nutrient and oxygen release into the environment. However, as they disrupt the natural soil temperatures, they initiate permafrost degradation and cause foundation instability and safety concerns in subarctic regions. In this thesis, the long-term effects of closed-loop horizontal geothermal heat exchangers (GHEs) on the stabilization of permafrost below a wastewater lagoon in northern Canada were studied. This research examined three different geometrical and operational parameters including pipe spacing, heat carrier inlet velocity, and temperature which have the potential to impact the GHE performance in preserving ice-rich permafrost. Thaw settlement was addressed in this context. Also, a machine-learning algorithm was employed to predict unavailable future lagoon temperature based on the currently available weather data. The thesis concludes that the GHE with high-density polyethylene pipes can effectively mitigate and postpone the predicted permafrost thawing under a lagoon. However, under the projected climatic scenario, the GHE system even with every different selected operational parameter fails to eliminate thawing over its lifetime of 50 years. The heat exchangers’ operational parameters substantially affect the permafrost thaw depth. Among all three studied parameters, the heat exchanger fluid temperature is the most influential parameter while the fluid inlet velocity only makes small differences in the thaw depth and thaw settlement.


  • Saaly M. (Supervisor: Maghoul P.), 2019. Energy and structural performance of thermoactive piles in cold regions, University of Manitoba, Winnipeg (MB), Canada. [Link]

The objective of this thesis was to develop and apply thermal and thermo-mechanical analyses to evaluate the structural and energy efficiency of a Geothermal Energy Pile Foundation System in cold regions. Such systems were used to re-harvest the buildings energy loss through their below-grade enclosures for providing heating and cooling energy demand. To investigate the energy performance of the below-grade envelope of a building in cold regions, a thermal analysis was carried out for an institutional building, the Stanley-Pauley Engineering Building (SPEB) located in the campus of the University of Manitoba. Knowing the amount of the annual heat dissipation from the sub-grade enclosure of the building to the ground, soil temperature increase was calculated. To efficiently harness the leaked heat from the basement, a geothermal energy system was proposed to be integrated to the foundation of the SPEB and the energy efficiency of such a system was assessed. In addition to the energy efficiency of the proposed system, the thermo-mechanical response of the proposed thermo-active foundation to the applied thermal and mechanical loads was also evaluated. Results showed that 8% of the annual energy consumption of the SPEB in terms of space heating was leaked into the ground. This energy loss increased the temperature of the soil underneath the building. Using the geothermal energy foundation system, the lost energy was aimed to be re-harvested. Results showed that the thermoactive foundation system could supply 4-15% of the building heating demand during Nov-Apr and 7-41% of the building cooling demand during May-Oct. It should be noted that application of such foundation system necessitated larger factor of safety effective on the allowable load.

  • Anongphouth A. (Supervisor: Maghoul P.), 2019. Investigating the performance of geothermal energy piles using coupled thermo-hydro-mechanical finite element analyses, University of Manitoba, Winnipeg (MB), Canada. [Link]

Harvesting shallow geothermal energy by means of energy piles coupled with ground source heat pump systems for heating and cooling buildings has increased in recent years. However, the structural integrity of such systems subjected to thermo-mechanical loads or heating-cooling cycles should be studied. Therefore, a comprehensive understanding of their structural and geotechnical performances is vital for successful applications. This thesis aims to investigate the responses of concrete energy piles subjected to thermal and thermo-mechanical loads using fully coupled thermo-hydro-mechanical (THM) finite element analyses. The axisymmetric models were carried out for two case studies of full-scale energy pile tests. Two hypothetical energy piles in Winnipeg were also analyzed to study their performances by considering local geological and climatic conditions. In general, it was found that the THM numerical models could capture considerably well the behavior of energy piles during cooling and heating cycles in comparison with the field data published in the literature. The thermo-mechanical loads did have significant effects on pile responses. From sensitivity analyses, it was found that there were considerable effects of the thermal expansion of concrete and soil stiffness on the thermo-mechanical pile responses. The pile head restrained conditions also affected the behavior of energy piles with stronger effects in the upper part of the pile near the pile head. From the simulations of the energy piles in Winnipeg, settlements of the pile head kept on increasing with increasing numbers of thermal cycles (ratcheting settlement phenomena). It was also found that the ultimate geotechnical pile capacities generally increased when the pile was heated but reduced when cooled.


  • Bobko K. (Supervisor: Maghoul P.), 2018. Energy efficiency of below-grade envelope of the Stanley-Pauley engineering building in Winnipeg, University of Manitoba, Winnipeg (MB), Canada. [Link]

Energy performance of basement structure of Stanley Pauley Engineering Building of the University of Manitoba is studied. A total of eighteen soil samples were collected at different locations and depths based on the geological profile of the ground. Thermal properties of the collected soil samples were obtained in the Geotechnical Engineering Lab using a KD2-Pro device by Decagon. Heat losses are predicted for the below-grade envelope by considering thermal properties of soil and building materials. For that purpose, a numerical model was created based on construction drawings using COMSOL Multiphysics software. The applied approach includes the calculation of heat loss due to heat transfer through conductive mechanism, also it considers phase change of water during freezing/thawing cycles. Different alternatives for heat preservation are suggested and compared in terms of economic effectiveness.

  • Liu H. (Supervisor: Maghoul P.), 2018. Numerical modeling in geotechnical engineering with applications in cold regions, University of Manitoba, Winnipeg (MB), Canada. [Link]

The objective of this thesis is to apply thermal analysis, coupled thermo-hydraulic analysis, and fully coupled thermo-hydro-mechanical analysis developed in this research to different engineering designs in cold regions. The applications vary from Geothermal Snow-Melting System Design to Structural and Thermal Integrity of Buried Infrastructure in cold regions. A feasibility study of geothermal energy pile based snow melting system was performed for six major cities in Canada. The coefficient of performance (COP) of heat pump is derived and the number of geothermal piles are determined for each city based on its specific local geological condition and heating demand. Also, the structural and thermal integrity of buried infrastructure were studied by performing an optimum design of rigid plastic foam insulations to protect buried utilities against frost damage and reduce the excavation cost. Furthermore, the effect of frost heave on the structural integrity of pavement structure and culverts are assessed.


  • Maghoul P. (Supervisors: Gatmiri B. & Duhamel D.), 2010. Solutions fondamentales en Géo-Poro-Mécanique multiphasique pour l’analyse des effets de site sismiques, Ecole des Ponts ParisTech, UR Navier, Paris, France. [Link]

The purpose of this dissertation is to develop a boundary element method (BEM) for multiphase porous media. Nowadays, the application of the BEM for solving problems of unsaturated porous media is still limited, because no fundamental solution exists in the published literature, neither in the frequency nor time domain. This fact rises from the complexity of the coupled partial differential equations governing the behaviour of such media. The developments of the BEM for the unsaturated soils carried out during this thesis are based on the thermo-hydro-mechanical (THHM) and hydro-mechanical (HHM) models presented in the first part of this dissertation. These phenomenological models are presented based on the experimental observations and with respect to the poromechanics theory within the framework of the suction-based mathematical model presented by Gatmiri (1997) and Gatmiri et al. (1998). After having presented the THHM and HHM models, for the first time, one establishes the boundary integral equations (BIE) and the associated fundamental solutions for the unsaturated porous media subjected to quasi-static loading for both isothermal (2D in the Laplace transform domain) and non-isothermal (2D and 3D in Laplace transform and time domains) cases. Also, the boundary integral equations as well as the fundamental solutions (2D and 3D in the Laplace transform domain) are obtained for the fully coupled dynamic model of unsaturated soils. In the next step, the boundary element formulations (BEM) based on the convolution quadrature method (CQM) regarding the saturated and unsaturated porous media subjected to isothermal quasi-static and dynamic loadings are implemented via the computer code HYBRID. Having integrated the BEM formulations for the wave propagation, as well as the consolidation problems in the saturated and unsaturated porous media, it seems that now the first boundary element code is obtained that can model the various problems in dry, saturated and unsaturated soils. Once the code is verified and validated, parametric studies on seismic site effects are carried out. The aim is to achieve a simple criterion directly usable by engineers, combining the topographical and geological characteristics of the soil, to predict the amplification of acceleration response spectra in sedimentary as well as hollow valleys.


  • Maghoul P. (Supervisor: Gatmiri B. & Arson C.), 2007. Numerical study (BEM/FEM coupling model) of the combined effects of topography and geology on the seismic response of sedimentary valleys (2D Site Effects), Ecole des Ponts ParisTech, UR Navier, Paris, France. [Link]

Un effet de site se manifeste par la modification de la réponse d’un sol soumis à une sollicitation sismique par rapport à un cas dit de référence. Les codes de dimensionnement parasismiques actuels reposent sur des calculs issus de modèles unidimensionnels. Cette méthode permet de mesurer l’influence de la nature et de l’épaisseur de la couche sédimentaire sur la propagation verticale des ondes de volume. Cependant, ces résultats ne concordent pas avec les estimations fournies par des modélisations bidimensionnelles ou tridimensionnelles. Lorsque le contraste d’impédance entre le sédiment et le substratum ou la profondeur de la vallée alluviale augmente, la résonance verticale 1D des ondes de volume et la propagation latérale des ondes de surface tendent à intervenir simultanément (Bard et Bouchon, 1985). En bureau d’étude, on utilise les courbes de ‘Spectre de réponse’. Mais malheureusement, les règlements d’ingénierie ne comportent pas de solution complète tenant compte de l’influence des conditions topographiques et géologiques sur le mouvement sismique et sur le contenu fréquentiel. Ce travail vise à caractériser et à quantifier les effets de site dans des configurations bidimensionnelles, dans le domaine spectral. Il s’agit de prendre en compte les influences combinées de la topographie et de la géologie sur la réponse sismique de vallées alluviales.