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A series of full-scale experiments was conducted to estimate lateral soil constraints on pipes buried in dense sandy slopes at different burial depths. The experimental data indicated that the soil force on the pipe increases with increase in the slope grade and burial depth ratio. The lateral soil force against relative pipe displacement response observed from the experiments is presented and compared to those arising from level ground conditions. The study was extended to larger burial depth ratios by simulating pipes under sloping ground conditions using a numerical (finite-element) model that was initially calibrated using the results from physical modelling. The findings from the study in terms of the variation of peak lateral soil restraint as a function of the slope grade and burial depth ratio are presented for consideration in pipeline design.

The bender element (BE) test has been widely used for the characterization of soil specimens to determine the dynamic or low-strain shear modulus. However, the actual behavior of the BE inside the soil specimen still remains unknown. The current ASTM standard does not consider the interference of P waves in BE measurements, which can lead to significant errors in the evaluation of shear wave velocities. In this paper, the BE motion inside different media is numerically studied through a coupled piezoelectric and solid mechanics finite element (FE) model. The numerical results are calibrated and compared with the real motion of the BE monitored using a high-frequency laser vibrometer. The proposed model successfully captured the measured motion of the BE in the air as well as transparent soils.More importantly, the proposed model provided a method for understating the interactions of P waves and S waves in a soil specimen. Simulated signals for an Ottawa sand specimen showed a good agreement with independent results from resonant column tests. The proposed piezoelectric-solid mechanics FE model can be used to study the soil-bender element interaction so that sound recommendations can be given to improve the interpretation of BE tests for different soils.

Horizontal directional drilling (HDD) is one of the popular pipeline trenchless construction techniques for sites where surface excavations and conventional trenching are not desirable. An integral part of the pipeline design and construction process is to perform stress analysis on the HDD overbends, which can be subjected to significant cross-sectional deformations due to stresses/strains imposed by thermal expansion and internal pressure. This paper proposes a novel approach to reduce the stress range in the HDD overbends using carbon fibre reinforced polymer (CFRP) wraps. Although this reinforcement technique is primarily used in the pipeline industry for repairing damaged pipes, there is a handful of recent studies that showed the promising effect of using CFRP reinforcement on undamaged pipe bends. A total of 259 finite element analyses are conducted with a different combination of pipe diameter to thickness ratio, CFRP length and thickness, fibre orientation, and internal pressure. An exploratory data analysis is then performed to demonstrate the impact of each variable on the maximum equivalent stresses imposed on the HDD overbend. The finite element results show that multi-directional fibre orientation leads to the highest reduction of peak equivalent stress on the HDD overbend. Besides, an increase in CFRP thickness results in a greater reduction of stresses on the HDD overbend. However, CFRP length does not have a noticeable effect on decreasing the stresses on the HDD overbend.

This paper aims to study the combined effects of incident wave angularity and geometrical characteristics on the seismic spectral response of curved valleys filled with alluvium. The parametric stu...

This paper examines the accuracy of a new elastic-thermoviscoplastic (E-TVP) constitutive model developed based on Critical State Soil Mechanics. The model can be used for simulating the temperature dependent, and strain-rate dependent behavior of clay soils. The study compares the E-TVP behavior of a single soil element with previously published thermo-mechanical experimental results performed on saturated clay specimens at different temperatures. Suggestions regarding unloading and reloading at constant temperatures as well as thermal consolidation under constant loads are presented. A modification for unloading-reloading adds a new criterion to the volumetric thermoviscoplastic strain rate formulation. A physics-based term is added to the current specific volume of the soil to include the viscous effect induced by temperature change. These modifications improve the convergence of laboratory data and simulated model responses. Comparisons of results from an earlier E-TVP model and the newly improved model provide evidence of improved predictive capabilities.

Microbially induced calcium carbonate precipitation (MICP) is a nature-based soil stabilization technique, which has been developed for the past 20 years. Nevertheless, the application of the MICP method for stabilization of clays has received less attention in the literature as it is necessary to boost its effect in various ways to ensure its efficiency. Simultaneous use of the MICP method with natural nanomaterials can be a way to enhance the performance of MICP. In this study, the effect of nano-CaCO3 and nano-SiO2 on enhancing the MICP processes in a kaolinite clay is investigated. The nanomaterials and bacteria and cementation solutions were added to the host soil with different percentages. A series of unconfined compressive strength (UCS) tests was conducted to study the effect of nano-enhanced bio-cementation on soil strength after different curing times. Furthermore, the microstructure of the treated soils was investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Raman spectroscopy, chemical decomposition and X-ray diffraction (XRD) analyses. It was observed that the amount of calcium carbonate and UCS increased in all nano-bio-treated samples with curing time. SEM images of the modified samples showed that the soil texture becomes flocculated with the addition of nano-SiO2 with the MICP method and calcium carbonate was formed in the voids between the clay minerals, which increased the strength of the soil. XRD analyses and Raman spectroscopy confirmed the presence of calcium carbonate in the soil texture.

Release of metal debris from a pair of gear teeth is a consequence of their contact. Any excessive metal debris can lead to the onset of fatigue and failure. This paper aims to derive a contact mec...

The ground is a natural grand system; it is composed of myriad constituents that aggregate to form several geologic and biogenic systems. These systems operate independently and interplay harmoniously via important networked structures over multiple spatial and temporal scales. This paper presents arguments and derivations couched by the authors, to first give a better understanding of these intertwined networked structures, and then to give an insight of why and how these can be imitated to develop a new generation of nature-symbiotic ground engineering techniques. The paper draws on numerous recent advances made by the authors, and others, in imitating forms (e.g. synthetic fibres that imitate plant roots), materials (e.g. living composite materials, or living soil that imitate fungi and microbes), generative processes (e.g. managed decomposition of construction rubble to mimic weathering of aragonites to calcites), and functions (e.g. recreating the self-healing, self-producing, and self-forming capacity of natural systems). Advances are reported in three categories of Materials, Models, and Methods (3Ms). A novel value-based appraisal tool is also presented, providing a means to vet the effectiveness of 3Ms as standalone units or in combinations.\ud \ud

A numerical analysis is carried out to study the behaviour of pipelines subjected to slow landslides at three at-risk landslide zones of Manitoba Pipeline Network. The pipeline’s longitudinal axis is parallel to the slow landslides at all three research sites. The ground displacements monitored for 5 years are imposed on the pipe using a special purpose pipe–soil interaction element (PSI element) using ABAQUS/Standard. The stiffness of PSI elements is defined based on soil–pipe interface properties according to a 2017 technical report from Pipeline Research Council International Inc. The results of the numerical analysis are compared with the instrumentation data to draw recommendations for future monitoring programs in slow landslide zones.

The study of wave propagation in biomimetic porous scaffold requires the inclusion of some complex physics such as the interaction of the ultrasonic wave with pore fluid, solid phase, and porous material. Also, due to viscous interactions between the pore fluid and skeletal frame, the dynamic tortuosity as a fractional function of frequency in the clinically relevant ultrasound frequency range is considered. The bone scaffold here is simulated using a porous slab whose two dimensions are infinite. The Biot-JKD theory used for wave propagation in porous media is conditioned with many physical parameters. Solving such governing equations for complex multi-physics problems is computationally expensive. Therefore, developing efficient tools and numerical methods to address multi-physics problems is appealing. Artificial Neural Network (ANN) can efficiently solve convoluted-parametric problems. The purpose of this research is to propose a physics-aware ANN to simulate wave propagation in bone scaffold filled with a viscous fluid. A set of data including porosity, viscosity, tortuosity, viscous characteristics length, Poisson’s ratio, and elastic modulus which are sensitive to the transmission and reflection signals are applied to the ANN as inputs and the reflection and transmission signals are obtained as outputs. The reflected and transmitted waves for different porosities are considered and the results show an excellent agreement with the proposed analytical theory and experimental data found in the literature.

A two-dimensional infinite length porous slab is employed to simulate biomimetic porous scaffold. The pores of slab are saturated with a relatively low and high viscous fluids such as air and bone marrow. Ultrasonic waves based on the Biot-JKD formulation travel through the porous slab and create viscous exchanges between the skeletal frame and the fluid. The Biot-JKD formulation focuses on the parameters, biomarkers of the biomimetic porous scaffold, which are sensitive to the transmission and reflection signals. These parameters include porosity, tortuosity, viscous characteristic length, Young’s modulus, and Poisson’s ratio. An artificial neural network (ANN) based on a set of the biomarkers is rendered to model the transmitted and reflected waves from the porous slab. The validation of the proposed analytical approach and released artificial neural network is evaluated by the pertinent literature. The output of the artificial neural network, the transmitted-reflected waves, is inversely applied to the analytical expression to estimate the biomarkers associated with bone regeneration. The results show that for a medium filled with a relatively high viscous fluid the longitudinal waves are more prone to estimate mechanical properties of the medium such as Young’s modulus and Poisson’s ratio while the transverse waves, in addition to longitudinal waves, are essential to estimate the physical properties of the medium including porosity, tortuosity, and viscous characteristic length. Furthermore, it is also concluded that for the medium filled with a relatively low viscous fluid such as air the longitudinal waves alone is able to estimate the biomarkers, which reduce significantly the computational efforts.

The adverse effects of climate warming on the built environment in (sub-)arctic regions are unprecedented and accelerating. The planning and design of climate-resilient northern infrastructure, as well as predicting deterioration of permafrost from climate model simulations, require characterizing permafrost sites accurately and efficiently. Here, we propose a novel algorithm for the analysis of surface waves to quantitatively estimate the physical and mechanical properties of a permafrost site. We show the existence of two types of Rayleigh waves (R1 and R2; R1 travels faster than R2). The R2 wave velocity is highly sensitive to the physical properties (e.g., unfrozen water content, ice content, and porosity) of active and frozen permafrost layers, while it is less sensitive to their mechanical properties (e.g., shear modulus and bulk modulus). The R1 wave velocity, on the other hand, depends strongly on the soil type and mechanical properties of permafrost or soil layers. In situ surface wave measurements revealed the experimental dispersion relations of both types of Rayleigh waves from which relevant properties of a permafrost site can be derived by means of our proposed hybrid inverse and multiphase poromechanical approach. Our study demonstrates the potential of surface wave techniques coupled with our proposed data-processing algorithm to characterize a permafrost site more accurately. Our proposed technique can be used in early detection and warning systems to monitor infrastructure impacted by permafrost-related geohazards and to detect the presence of layers vulnerable to permafrost carbon feedback and emission of greenhouse gases into the atmosphere.

In this paper, the transient acoustic wave propagation in a bone-like porous material saturated with a viscous fluid was investigated using Biot’s theory. Due to the interaction between the viscous fluid and solid skeleton, the damping behavior is proportional to a fractional power of frequency, i.e., the dynamic tortuosity was written in terms of the fractional power of frequency. Furthermore, to describe the viscous interaction of fluid and solid in the time domain, the fractional derivative was used. The fast and slow waves, which are the solutions to Biot’s equations, were described by fractional calculus in the time domain. The reflection and transmission operators were expressed in the Laplace domain and inverted into the time domain using Durbin’s numerical inversion. Once the numerical implementation was validated, the effects of porosity and viscosity on the stress, and reflected and transmitted waves were investigated. The results showed that by increasing the porosity the stress in a bone-like material filled with either air or bone marrow increases. The transmitted pressure decreases by increasing the porosity. The reflected pressure decreases for low viscous fluid when the porosity increases while it increases when the viscosity of the fluid is high. In addition, the results showed the importance of taking into account the fractional derivatives in the transient wave propagation in such porous materials.

Snow and ice accumulation induces hazardous driving conditions due to the effect of reduced friction on the road surface. A traditional chemical-based snow melting approach is not environmentally friendly and effective when the temperature is below − 3 . 9 ∘ C. Thermal snow melting techniques, such as hydronic heating system, can be an alternative to chemical-based methods. In this paper, a new approach is proposed for sizing the hydronic snow melting system. For this purpose, a transient heat transfer mechanism is considered. A complete energy balance equation including solar radiation, snowfall, and convective heat flux is used at a bridge surface. The Nelder-Mead algorithm is used to minimize the energy consumption used for snow melting by determining an optimum relation between the inlet temperature and flow rate. Since the performance of such systems depends significantly on the weather design, sensitivity analyses were performed to analyze the sensitivity of the optimum design to variations in air temperature, snowfall rate, wind speed and insulating methods. The results showed that the insulating methods and snowfall rate are the most dominant factors influencing the energy consumption of the hydronic heating system. The energy consumption rate is expected to increase by 29% without insulating the bottom and sides of a bridge deck. A 30% increase in snowfall rate leads to a rise in energy consumption by 35%. On the other hand, heat loss due to the variation in air temperature, wind speed, and solar radiation is not significant.

Snow melting systems using geothermal energy piles are a clean technology to overcome the problems of traditional chemical-based snow melting methods. This paper aims to study the feasibility of such systems in six major cities (Calgary, Edmonton, Montreal, Ottawa, Toronto and Winnipeg) in Canada. The amount of energy, as well as the inlet temperature of a hydronic system required to warm up and keep the surface temperature of a bridge slab unit above 0 °C during a typical snowfall were determined based on a transient energy balance at the slab surface and weather conditions for each city. The coefficient of performance (COP) of the heat pump for a bridge was then derived for each city based on its specific local geological conditions and heating demands. Also, the problems related to the ground thermal imbalance due to the operation of such systems were addressed. Finally, the economic feasibility study was performed to compare costs between a snow melting system for a bridge deck using geothermal energy piles and an electricity-based heating system. It was concluded that the snow melting system using geothermal energy piles is efficient and cost effective. However, the extent of efficiency and saving varies with implementation areas.

Frost action in soils can cause detrimental damage to buried utilities, such as water and gas pipes. One of the promising approaches to protect buried utilities against frost damage and reduce the excavation cost is to install thermal insulation over and around the pipe. This paper considers two different conductive heat transfer models, with and without the effect of soil pore-water phase change, as well as a heat and mass transfer model for freezing soils to investigate the effectiveness of insulation systems for frost protection of buried pipes. It was found that the latent heat released during the phase change significantly affects the heat transfer process and that the impact of phase change on insulation design should not be overlooked. Furthermore, by comparing numerical results to field measurement data, it is found that the mass transfer has an insignificant effect on the temperature and unfrozen water content distribution in the frost-susceptible foundation soil. A parametric study was carried out to assess the effects of different factors such as the backfill materials, geometry, total length, thickness of insulation, distance between pipe and insulation as well as the burial depth of pipe on the thermal performance of insulation. Finally, the Nelder-Mead algorithm was implemented to determine the optimum insulation design so that the overall cost is minimized while the pipe is protected from freezing.

Triclinic materials are categorized as anisotropic elastic materials with no existence of a symmetry plane. To characterize such materials, 21 elastic constants are required. The previous studies have not investigated triclinic materials due to a high number of material constants considered in the modelling. This paper presents a closed-form 3D piezoelectric model to investigate the free vibration of an arbitrary thick triclinic piezoelectric hollow cylinder. The piezoelectric cylinder is assumed to be infinitely long and short circuit boundary conditions are applied at the inner and outer surfaces of the shell. The natural frequencies of the cylinder are calculated using the transfer matrix approach along with the state space method. The effects of different anisotropic piezoelectric properties including orthotropic, monoclinic, and triclinic materials on the dispersion curve of natural frequencies are studied. The numerical results show that if the value of the axial wave number, the circumferential wave number, or natural frequency increase the resonant frequency of triclinic material deviates from other anisotropic materials such as orthotropic. Finally the validity of the proposed model is confirmed by comparing with simplified cases studied in the literature.

In this paper, the performance of a proposed geothermal energy pile system for the energy demand of an institutional building is investigated. The building studied in this research is situated in the Fort-Garry campus of the University of Manitoba in the southernmost portion of Winnipeg (MB) in Canada. In an urban area, underground temperatures are substantially higher than the surrounding rural areas due to the buildings heat leakage to their underneath ground. In this study, this heat loss is harvested through geothermal piles and rejected to the building for the HVAC system utilization. The underground thermal imbalance, which is the most common problem encountered while utilizing the geothermal energy in cold regions, is extensively studied. It is concluded that despite the heat leakage through the basement enclosure, thermal balance of the soil, in case of supporting the total energy demand of the building by geothermal piles, cannot be met. The application of some auxiliary heat sources is proposed. Finally, the amount of energy harvested from the ground is calculated by maintaining the thermal balance of the soil and preventing the freezing at the soil-pile interface which affects adversely the structural performance of geothermal piles.

Non-destructive testing (NDT) plays an important role in material inspection and characterization. In geotechnical engineering, the popular seismic NDT includes Spectral Analysis of Surface Wave (SASW), Multichannel Analysis of Surface Waves Method (MASW) and Continuous Surface Wave (CSW). A forward solver and a back-calculation algorithm are required to determine the soil stratigraphy and the properties of each soil layer. However, most of available forward solvers are limited to elastodynamic solutions in which the soil’s porous nature and water content and can’t be taken into consideration. In this paper, a poro-elastodynamic forward solver for seismic NDT is presented. The proposed solver provides an analytical solution for wave propagation in saturated soil media using the spectral element method. The P and S waves are decoupled through the Helmholtz decomposition. The P waves in solid skeleton and porewater are further decoupled through an Eigen decomposition technique. Such a solver can effectively determine the dispersion relation for a given structure, which can be further used for geophysical inversion application based on surface wave tests.

Geothermal heat pump (GHP) systems have recently gained popularity in providing heat to buildings. In this study, the short-term and long-term performance of closed-loop horizontal GHP systems in cold regions and the effectiveness of seasonal balancing were investigated. A period of 50 years was simulated to cover the life of a conventional system. A repeating block of heat exchangers at three depths was modeled in a series of 3D multi-physics finite element simulations. Two operation modes were defined, representing the non-balanced mode and the seasonal balancing through the injection of lake water in summer. The climate conditions at the ground surface were explicitly modeled by defining a temperature boundary condition. A novel AI framework was developed to generate the projections of ground surface temperatures from air temperature and other atmospheric variables. An artificial neural network was trained using the air and ground temperature measurements at the nearby weather station. Several training approaches were compared to minimize prediction errors. The model was then used to convert the air temperatures from downscaled outputs of the CanESM2 climate model into surface temperatures. Finite element models, representing the two operation modes under three climate change scenarios and various heat exchanger spacing, were simulated and verified by comparing the resulting ground temperatures with the local measurements. The outputs were processed into extraction power, thermal output, and carbon emissions. Results suggest that in order to attain a stable heat extraction throughout a year, heat exchangers should be placed at depths that are not affected by seasonal variations of surface conditions. Simulations revealed thermal depletion and its inverse correlation with heat exchanger spacing. The seasonal balancing operation approach showed enhancement in total thermal output by 55%. The system was found to be resilient when subjected to the major climate pathways. In a rough estimate based on the average carbon footprint of electricity production in Canada, a system with 100 heat exchangers was found to save up to 800 tons and 1300 tons of equivalent CO2 emissions over its life, under the non-balanced and balanced operation modes, respectively.

Energy piles are bi-functional structural elements that are used to support the structural loads of a building and to operate as a geo-heat exchanger for shallow geothermal energy systems. In urban areas, energy piles can eventually be used to harvest the heat loss through the basement enclosure and re-inject the energy to the building for the heating and cooling purposes. In spite of a higher thermal profile beneath the buildings due to energy loss through the below-grade envelope, an underground thermal imbalance may still occur due to the application of energy piles in cold regions. This paper aims to study the structural performance of an energy pile in cold regions considering the potential occurrence of thermal imbalance in the foundation soil through a Thermo-Mechanical (TM) analysis. This will be the first step of adoption of such a technology in Canadian cold climate. Results showed a safe margin between the pile settlement and the allowable settlement. However, the axial stress applied to the pile increased by 9% due to thermal loads. In addition, a maximum decrease of 9% in mobilized shaft friction along the pile-soil interface was recorded due to the thermal loads. To consider the energy piles as an alternative for buildings energy supply in cold regions, further considerations should be made to keep the mechanical response of the energy piles in the admissible range.

In the current industry practice guidelines, the soil restraints to assess the behaviour of pipelines subject to permanent ground displacements are numerically characterized using independent “soil springs”. These guidelines have been primarily generated by considering the typical configurations of buried pipelines in level ground. The assumption of level ground does not always hold true when assessing pipelines located on sloping ground in mountainous areas and riverbanks. This research presents the outcomes from a set of full-scale physical model tests conducted on a pipe buried in slopes. The results highlight the significance of the slope grade effects on soil-pipe interaction. The results are useful as input to modify soil springs accounting for the ground surface inclination.

Harvesting shallow geothermal energy for heating and cooling building spaces in winter and summer is considered environmentally friendly and renewable. Recently, geothermal energy piles have been used as heat exchanger elements in ground source heat pump systems to exchange heat with the ground underneath buildings for heating and cooling purposes. However, imposing thermal cycles on such piles may result in possible adverse effects on their structural and geotechnical performance. A comprehensive understanding of the behavior of geothermal energy piles is therefore vital for the successful applications of such systems. This paper aims to investigate the interaction between the soil and geothermal energy pile subjected to a combination of mechanical loading and thermal cycles. Coupled thermo-hydro-mechanical (THM) finite element analyses were carried out on a hypothetical geothermal energy pile using climatic and geological conditions in Winnipeg, Manitoba, Canada. Numerical results were presented in this paper in terms of pile head displacements, strains, and stresses developed in the pile, as well as shaft friction and effective radial stresses along the pile-soil interface. The effects of heating and cooling on the ultimate geotechnical pile capacity were also presented. Based on the numerical results, it was found that the thermo-mechanical loads have considerable effects on the geothermal energy pile responses.

The propagation of poroelastic waves in a soil specimen is dependent on the physical and mechanical properties of the soil. In the geotechnical practice, such properties are obtained through in-situ geotechnical testings or element soil testings in the laboratory. These methods require almost advanced equipment and both testing and sample preparation may be expensive and time-consuming. This paper aims to present an algorithm for a laboratory-scale ultrasonic non-destructive testing to determine the physical and mechanical properties of saturated soil samples based on the distribution of stress waves. The ultrasonic setup, in comparison to most conventional soil lab testing equipment, is low-cost and non-invasive such that it reduces the soil disturbance. For this purpose, a poro-elastodynamic forward solver and differential evolution global optimization algorithm were applied to characterize the porosity, density, and other mechanical properties for a soil column. The forward solver was developed based on a semi-analytical solution which does not require intensive computational efforts encountered in standard numerical techniques such as the finite element method. It was concluded that the proposed high-frequency ultrasonic technique characterizes effectively the saturated soil samples based on the output stress wave measured by the receiver. This development makes geotechnical investigations time-efficient and cost-effective, and as such more suited to applications in remote areas.

Typical subsurface investigation tools used on Earth are not applicable for subsurface exploration of the Moon and other extraterrestrial bodies due to payload limitations in space missions. Instead, light and compact subsonic projectile probes can be considered as an alternative subsurface investigation tool in such exploratory missions to overcome a host of challenges. Such probes can be launched from a lunar orbiter or lander to the surface of the Moon to provide the initial effective penetration from the impact. Here, we develop a model based on the spherical cavity expansion theory to predict the deceleration rate and final penetration depth of a rigid projectile probe into geological targets under the perpendicular subsonic impact. Two stress fields are assumed to propagate in the medium, plastic (near field) and elastic (far field), upon the impact. The stresses at the cavity wall are obtained by combining the Mohr–Coulomb failure criterion for the target failure (plastic region) considering two different assumptions for plastic wave propagation. Two field experiments are used to compare and assess the robustness of the proposed solutions in the subsonic range. Base on the simulation results and the experiments, it is concluded that the cavity expansion model considering the locked hydrostat assumption, with the modification here introduced for the volumetric strain, can provide us with a reasonable prediction of the projectile penetration, final penetration depth and the stresses on the probe. Thus, our proposed solution can be used as a benchmark for sophisticated and computationally-expensive numerical calculations.

This paper investigates topographic effects of rocky valleys with irregular topographic conditions subjected to vertically propagating SV waves of Ricker type using a boundary element code. Valleys with two intersecting slopes, [Formula: see text] and [Formula: see text], are modelled in order to study their combined effects on ground motion. Presented in the form of pseudo-acceleration response spectra, results of this work can be extended to similar topographies. The main findings are: (i) [Formula: see text] (the first slope angle) and [Formula: see text] (L is the half width of the valley and [Formula: see text] is its corresponding height) have amplifying effects, and [Formula: see text] (the second slope angle) has de-amplifying effects on the site response. (ii) [Formula: see text] has a straight effect on intensifying the effects of both [Formula: see text] and [Formula: see text]. (iii) The combined effects of slope angles have been found to be important in modifying the response so more than a single slope should be considered for seismic analysis. (iv) Engineers should use the maximum amplification of 2.4 in case of valleys with the first and second slope angles below [Formula: see text].

This study investigated the long-term effect of horizontal Ground-Source Heat Exchangers (GSHEs) on mitigating permafrost thaw settlement. In the conceptual system, a fan coil was used to chill the recirculating fluid in the linear High-Density Polyethylene (HDPE) ground loop system. A fully coupled thermo-hydro-mechanical finite element framework was employed to analyze multiphysics processes involved in the thaw settlement phenomenon. To investigate the sustainability of the system, a period of 50 years was simulated. Two operational modes were defined: one without and the other with HDPE. Different heat carrier velocities and inlet temperatures, and heat exchanger depths were examined to explore their effects on the thaw settlement rate. It was concluded that the proposed system can effectively alleviate the predicted permafrost thaw settlement over the study period. Moreover, the heat carrier temperature was found to have a prominent impact on the thaw settlement rate amongst other parameters.

Roadways over culverts experience severe distresses due to frost action in the subgrade. Thermal insulation placed near the culvert can reduce frost penetration in the soil surrounding the ...

Due to population growth and increasing energy demand all over the world, geothermal energy, which can be extracted from both deep and shallow geothermal resources, is widely applied in recent years. In the current paper, application of shallow geothermal energy using ground-source heat pump system is assessed and different elements of this system are introduced. Furthermore, different features of the geothermal energy pile, one of the most popular ground heat exchangers (GHEs) which serves two purposes of supporting the structural loads of buildings and providing heat to them, have been reviewed. Thermal imbalance, which is encountered during harness of geothermal energy, is discussed. Then, the potential solutions for alleviating this problem are reviewed. These solutions are divided into two major categories of GHE modification and application of auxiliary heating/cooling units. If feasibility of such solutions is justified, the underground thermal imbalance can be eliminated efficiently.

In this study, an elastoplastic contact model is developed for L1–L5 lumbar spine implants. Roughness effect is included to estimate energy loss which is an indication of wear and subsequently the issue of metal debris in body. A Gaussian function is assumed for the distribution of asperities. The contact surfaces of the implants are assumed to be spherical caps. Subsequently, a least-square approach is applied to obtain an approximate expression for the contact force using the data from integration over contact zone. The energy loss is calculated, next, which is due to plastic deformations of asperities. The numerical results indicate that for a given loading–unloading condition, the amount of energy dissipation increases in L1–L4 lumbar spine implants, while it decreases from L4 to L5 implants. The implants geometrical specifications are chosen to cover a wide range of patients' age. Finally, a closed-form expression is obtained for the plastic energy dissipation per cycle in terms of plasticity index for the lumbar spine L4, as the worst-case scenario. Such a function can serve as a very useful tool for implant designers and manufacturers.

In this paper, a semi-analytical elastodynamic forward solver was proposed for the Multichannel Analysis of Surface Waves (MASW) using the spectral element technique for the first time. A root finding method based on Brent's algorithm was proposed to accurately extract the dispersion curves. The trust region reflective method, an effective bound-supported least square algorithm, was applied, for the first time, for the inversion analysis of MASW data. In comparison to the commonly used neighborhood algorithm, the proposed solver converges rapidly; the Euclidean distance between the measured and numerically calculated dispersion curves are significantly reduced within only 300 runs of the forward solver in comparison to over 10,000 runs using the neighborhood algorithm. Several numerical case studies were performed to demonstrate the selection of initial guesses as well as the bounds of each optimization parameter. Also, a parametric study was performed to determine the effect of discontinuity in the soil stratigraphy on the dispersion curves. Finally, the integrated approach developed in this study was used to analyze the MASW data collected in a site in south Iceland. It was concluded that the proposed approach determines effectively and efficiently the soil stratigraphy as well as soil properties.

Extracting heat from a sewage pipe through a typical horizontal ground heat exchanger has recently been introduced as a renewable energy alternative to reduce fossil fuel usage. This paper presents a novel design for a ground heat exchanger that extracts heat from the surrounding soil and sewage within the pipe while simultaneously being carried to a wastewater treatment plant. This research focuses on the long-term efficiency of the system under transient conditions in a cold climate. A numerical model using COMSOL Multiphysics was developed to verify the sustainability of the system for over 25 years. The model used constant inlet fluid temperatures to evaluate heat transfer with convective pipe flow and conductive phase change within the soil. The results showed a maximum temperature change in the surrounding soil adjacent to the heat extraction system over 25 years was 0.10 °C during the heating season in Winnipeg, Manitoba. The distance at which the heat extraction system did not show an impact on temperature change of adjacent soil was determined at 4 m. Critical parameters in this evaluation were system depth, sewage level, and the high-density polyethylene pipe thermal properties. The sustainability of the system was not affected by the system depth due to thermal balancing between climatic, subsurface and sewage heat fluxes. Sustainable behavior was achieved at 50 % and 75 % of sewage pipe capacity. The effect on thermal performance from the high-density polyethylene pipe thermal properties was deemed insignificant.

In this paper, the effects of transverse acoustic waves in characterizing a bone-like, porous medium filled with a viscous fluid are analyzed for the first time. Scattering operators along with stress fields are derived by using the standard Biot-JKD model. A short duration acoustical pulse is applied to one side of a bone-like, porous medium so that both longitudinal and transverse waves travel through the intermediate medium which is filled with a viscous fluid. The reflection and transmission operators along with stresses in the medium are expressed in terms of these waves. The numerical implementation is validated for the longitudinal wave by comparison with the numerical simulation performed by Fellah, Chapelon, Berger, Lauriks, and Depollier (2004). The effects of the transverse waves on the reflection and transmission coefficients as well as the stress field are studied by considering different viscosities and porosities. It is shown that when the fluid viscosity in the medium is relatively high (such as bone marrow), the effect of the transverse wave dominates. However, this effect is negligible when the medium is filled with a relatively low viscous fluid (such as air). Furthermore, it is shown that the role of transverse waves in characterizing bone structures and bone loss is imperative since the acoustical response of such media at specific frequencies can be triggered only by considering the effects of transverse waves.

Harvesting geothermal energy through the use of thermo-active pile systems is an eco-friendly technique to provide HVAC energy demand of buildings. Mechanical behaviour of thermo-active piles is impacted by thermal cycles. Moreover, in urban areas, the temperature of the ground is higher than non-constructed areas due to the heat loss through the below-grade enclosure of buildings. This heat dissipation increases the thermal capacity of the soil and affects the mechanical response of the geothermal pile foundation subjected to thermo-mechanical loading. To investigate the effect of buildings heat loss on thermo-active piles, a numerical thermo-mechanical (TM) analysis was carried out on a proposed energy foundation system for an institutional building, the Stanley Pauley Engineering Building (SPEB) in the campus of the University of Manitoba, Winnipeg, Canada. The mechanical response of the geothermal piles to the thermal cycles with and without considering heat leakage through the basement of the SPEB is compared. Results showed that the cooling loads induced a maximum vertical pile head displacement of -1.18 mm. After 5 years operation of the system, the maximum vertical pile head displacement decreased to -1.05 mm for the case in which heat loss through the basement in considered in the models. In addition, the maximum axial load effective along the pile axis was 6% higher for the case that considers heat loss through the basement compared to the case without considering heat leakage through the building’s below-grade envelope.

The effects of freeze-thaw cycles on the thermal properties of foundation soils are often neglected in many building energy simulation programs. Consequently, there is a lack of research focused on the energy dissipation through the below-grade enclosure of buildings in cold regions, where freeze-thaw cycles occur in soils. This paper aims to investigate the energy performance of the below-grade envelope of an institutional building in cold regions by considering the effect of pore water phase change on the thermal properties and consequently the heat exchange between the basement structure and the surrounding soils. For this purpose, the energy loss through the below-grade envelope of the building was numerically studied using 3-D and 2-D analyses. Moreover, the importance of a promising insulation system for the basement of the building was investigated in this paper. The results showed that the energy loss through the below-grade enclosure of the building decreased by approximately 60% when the insulation layers were added to the basement walls and floor slab (i.e., a 230 mm thick insulation layer underneath the floor slab and a 125 mm thick insulation layer surrounding the basement walls). Although reduced, the below-grade heat losses were still significant. To mitigate that, an additional horizontal insulation layer was attached to the basement walls, which lowered the heat loss through the basement walls by 23%. In addition, it was concluded that the presence of a layer of backfill materials surrounding the basement walls that was initially designed for drainage purposes, decreased the basement heat loss by 16.5%. Finally, the results of the 3-D analysis were compared to an equivalent 2-D analysis. The results showed that the 2-D model predicted approximately 22% higher heat flux compared to the 3-D model.

Thermal stress induced in a buried pipeline due to temperature variation is of great concern in Canada due to its extreme cold winter and warm summer. Thermal stress decreases by increasing the pipe’s burial depth while the interaction forces due to ground displacement increase by increasing the burial depth. As a result, the optimum burial depth of a pipeline is of great importance to pipeline companies to minimize interactions between the pipeline and soil in case of temperature variations and ground displacements. Thermal stress is estimated from a heat transfer analysis considering the phase change in the soil using COMSOL. Soil-pipeline interaction based on 1984 ASCE Guidelines [1] is used for considering the effects of ground movements. The combined stress on the pipeline is estimated as a function of burial depth and is presented in a curve for design purposes. Numerical analysis by ABAQUS shows the adequacy of the presented curve.