Open Theses and Dissertations
Permanent URI for this collection
This collection is the result of a joint project between the Faculty of Graduate Studies and Libraries and Cultural Resources which provides Graduate students with the opportunity to archive their thesis with University Archives in our digital repository.
If you are a Graduate student submitting your final thesis to PRISM, please ensure you have read and submitted all required documents: http://grad.ucalgary.ca/current/thesis
If you require assistance submitting your thesis please contact thesis@ucalgary.ca
The electronic theses and dissertations on this site are for the personal use of students, scholars and the public. Any commercial use, publication or lending of them in libraries is strictly prohibited.
Browse
Browsing Open Theses and Dissertations by Department "Civil Engineering"
Now showing 1 - 20 of 154
Results Per Page
Sort Options
- ItemOpen AccessA contribution to risk-based inspection and maintenance planning for deteriorating pipelines and pressure vessels(2017) Haladuick, Shane; Dann, Markus R; Maes, Marc; Achari, Gopal; Egberts, Philip; Huang, QindanEngineering systems are subject to deterioration processes, such as corrosion and fatigue, which reduce the resistance to failure. If failure occurs, it can have large social, economic, and environmental consequences. To mitigate this risk, regular inspections and maintenance are performed. To minimize the overall cost of operating the system, it is important to optimize the inspection and maintenance plan. Lifecycle risk-based inspection and maintenance planning, which involves determining the expected total cost of operating a system over its lifecycle, is the most established method of determining the optimal inspection and maintenance plan. However, lifecycle risk-based inspection and maintenance planning for complex engineering systems with many components requires a detailed analysis that can be computationally demanding; therefore, simplifications and assumptions are commonly used in the literature. The objective of this dissertation is to expand the state of knowledge in risk-based inspection and maintenance planning for pipelines and pressure vessels, removing many common assumptions and simplifications. Some aspects of the research specifically target pipelines or pressure vessels, while others are generic to any engineering system. Specifically regarding pressure vessels, a simple methodology is presented to determine the optimal maintenance time for a pressure vessel with an unexpectedly severe defect. This methodology is then expanded to account for the dependent failure events in pressure vessels with multiple defects and failure modes. For pipelines, a risk-based maintenance methodology is developed to decide whether it is better to continuously repair defects in a pipeline or to replace entire pipeline sections. This methodology also examines the impact of an uncertain lifecycle on risk-based maintenance planning. For general engineering systems, the use of heuristic algorithms in improving the computational efficiency of solving risk-based inspection and maintenance optimization problems is examined. Finally, a methodology is developed to perform risk-based inspection planning for the next inspection type, without requiring a lifecycle analysis. This study aids system operators in determining the optimal inspection and maintenance plan. It also provides methodology to perform risk-based inspection and maintenance planning in a computationally efficient or simpler manner, to make the techniques more practically applicable.
- ItemOpen AccessA Decision Support System for Efficient Utilization of Overdesign as a Fast Tracking Technique in Modular Steel Pipe Racks(2012-12-12) Khoramshahi, Fereshteh; Ruwanpura, JanakaAbstract To effectively address today’s aggressive schedule demands in the oil and gas industry, engineering and construction activities are usually overlapped to some extent to attain schedule compression. Overdesign is one of the techniques used in a project’s engineering phase to reduce the information dependency between activities, which results in overlapping. When there is insufficient design information, designers usually adopt more conservative assumptions in their designs than would normally be the case. This overdesign means successor activities can start and progress well ahead of and long before accurate details can be determined. Although this helps to reduce the overall schedule, it is not a risk-free process on its own. One of the major concerns in overdesign is the lack of design optimization, which will be directly translated to extra costs and increased materials wastage. Likewise, the assumptions made might not be conservative enough, necessitating rework. A review of the overdesign literature pointed to a lack of explicit research about overdesign as a schedule compression technique. This research study was designed in a way to address some of the gaps in the current overdesign literature. The purpose of the research presented in this thesis was to develop a decision support system for choosing the best opportunities to apply overdesign in oil and gas projects that provide the greatest schedule compression for the least incremental cost. The scope of the research is limited to the modular steel pipe racks. A mixed methods approach was taken to conduct this research. The purpose of the qualitative part was to build the overdesign conceptual framework, which further formed the basis for formulating the overdesign time-cost trade-off problem. This helped model the overdesign problem using stochastic decision tree principles. The entire process laid the foundation for developing the decision support system. The quantitative part of the research involved gathering real project information, which was used to relate the degree of conservativeness of the assumptions in overdesign to the probability of rework associated with any overdesign decision. This research provides contributions in four distinct categories: theoretical, literature, methodological and finally industry contribution.
- ItemOpen AccessA Methodology for Estimating Greenhouse Gas Emissions from Heavy Duty Diesel Trucks Used for Road Transportation in the Construction Sector(2014-05-23) Amiri, Mona; Sadeghpour, FarnazA large growth in the number of Heavy Duty Diesel Vehicles (HDDVs) is one of the main causes that Greenhouse Gas (GHG) emissions from the road transportation experienced a significant increase since 1990. With 97.5% of the total fleet used for delivery being HDDVs, these vehicles play an important role in Canada’s freight transportation. Latest statistics show that 17% of the heavy trucks operate in the construction sector. The objective of this study is to develop a methodology to estimate emissions from a single HDDV used in construction road transportation. The developed methodology showed -14% difference with on-road measurements, which suggests a reasonable accuracy in comparison with similar methods in the literature. This methodology can be used to address increasing GHG emissions from road transportation through implementing behavioural changes such as route planning and load factor management. It can also be also used by the construction suppliers to track and control their share of GHG emissions.
- ItemOpen AccessA Model for Project Governance in Delivery of Oil and Gas Projects in Alberta(2015-05-12) Hussain, Tariq; Jergeas, George“Effective project governance, within corporate governance framework, has become a serious concern for organizations” (Crawford, Cooke-Davies, 2005). Findings of the research revealed various levels of understanding of project governance and a range of governance structures in practice within oil and gas owner organizations in Alberta. The new project governance model recommends oil and gas owners of Alberta reorganize their project governance structures, improve their policies and procedures, develop tools that support project governance, make it mandatory for project personnel to follow governance procedures, improve the governance role of Project Management Office (PMO), do audits for compliance, keep processes updated, and use lessons learned. The results of the focus group survey, conducted to validate the new governance model, revealed an overall agreement from industry professionals. The researcher concludes that the new governance model applied proficiently will help oil and gas owner organizations of Alberta improve governance and oversight.
- ItemOpen AccessA New Design and Environment Evaluation Approach for Managed Lanes on a Freeway Facility(2015-02-25) Ansari Esfeh, Mohammad; Kattan, LinaIn this thesis, a new design and environmental evaluation of the managed lane is presented. HOV/HOT lane is an efficient transportation strategy aims to mitigate the congestion by tolling freeway. In the first part of this study, a dynamic toll pricing approach was taken to minimize the total passenger travel time of the tolled freeway. The model was tested using a PARAMICS microsimulation model on a section of the Deerfoot Trail in Calgary, Alberta. The environmental impact of the proposed model is determined using PARAMICS Monitor. In the second part of this study, the long-term impacts of deploying transportation strategies on greenhouse gas (GHG) emission is evaluated. While previous studies relied only on simulation results, this study uses Leontief’s input-output (I-O) model to capture the large-scale environmental impacts of transportation strategies. The I-O model was utilized to assess the impacts of improvements on the induced demand and evaluate the environmental impact of transportation strategy. The transportation strategies effects were estimated in terms of congestion reduction savings, to identify the industries that would be affected. The environmental impact in terms of changes in GHG emissions was conducted for all affected industries. A case study was also conducted on HOV/HOT lane deployment in Deerfoot Trail described in the first part. A sensitivity analysis was conducted for the level of GHG emission savings enhanced by transportation strategies for Calgary and Edmonton, which are two major Alberta cities that are similar in size, population and congestion level to compare the results. The results of the study show that the traditional approaches that focus on simply evaluating the short-term impacts of these strategies considerably overestimate the reduction of GHG emissions. Another major finding of this study is that deploying transportation strategies that would result in the same reduction in congestion levels is shown to result in significantly different long-term impacts on GHG emissions of the two examined cities. This is mainly attributed to the difference in the structure of the economic and industrial sectors in the two cities.
- ItemOpen AccessA New Shear Test Method for Mortar Bed Joints(2013-04-30) Popal, Rashid; Lissel, ShelleyFrom a review of existing test methods devised to determine the shear strength of a mortar joint, it was concluded that among the existing methods, the triplet test is the simplest to perform and the Hofmann & Stöckl test provides the best results in terms of uniform stresses. The advantages of these two tests were combined in a new shear test method designed, constructed, and utilized in this research. In the new test method, simple equipment is used to subject a couplet to a time-dependent horizontal load as well as to a level of normal compression stress. The couplet is placed between two rubber sheets, two steel plates, and two roller rails to accommodate the unevenness of the surface of the bricks, to allow smooth movement of the rollers, and to minimize the friction between the couplet and the vertical support planes, respectively. The results of the experimental investigation show that the developed test method produces uniform shear stress as in the Hofmann & Stöckl test and is as simple to perform as the triplet test.
- ItemOpen AccessA Novel Urine Evaporation and Collection System for Dry Toilets(2015-04-28) Bethune, David; Chu, AngusA Urine Evaporation System (UES) that evaporates human urine and collects the nutrient-rich dry product from a urine-diverting dry toilet at backcountry or rural locations was designed and tested in the laboratory and field. The UES consists of vertically stacked plastic cafeteria-style trays with a thin layer of sand on the bottom of each tray. The trays provide an evaporation surface and allow collection of the solid product remaining after evaporation. The sand prevents the solid product from sticking to the bottom of the trays. The trays are held on tracks cut into the inside of a wood or Plexiglas box. The initial laboratory experiment (Chapter 2) consisted of evaporating urine supplied at a constant rate by a peristaltic pump. The evaporation process produced a dark, highly saline, brine solution before drying to a solid product. The solid product had low odour and was mostly comprised of K, Na, Cl, P and N. About 90% of the ammonia was lost during the evaporation process (primarily by volatilization). In the second laboratory experiment (Chapter 3), the UES was improved to enhance airflow across the surface of each tray by constructing a wooden box with a fan. Five litres per day (output of approx. 4 persons per day) was input to the UES at the same time each day until the first trays were entirely full of solid product (65 days). During the experiment, increasingly oxidizing conditions were measured in the evaporating urine brine. The solid products in the stack of trays had a physical and chemical zonation characterized by leaching of solids in the upper trays and accumulation in the lower trays. The majority of N remained in the stable, organic form associated with organic carbon and approximately 35% of the ammonia nitrogen was lost due to volatilization. Oxidizing conditions favoured more stable mineralized forms of nitrogen and sulphur. A prototype passive field UES was designed and constructed and field-tested in a semi-arid temperate climate (Chapter 4). The UES consisted of a Plexiglas® box vented by a black metal chimney. The average evaporation rate over the study period was 3.2 L/day (0.66 mm) with monthly amounts of 117 L (24.3 mm) for August and 76 L (15.8 mm) for September. A multiple-regression analysis indicates that continuously running of the UES from April 1 to Oct 31 (when daytime temperatures in Calgary are consistently above freezing) would have evaporated a total of almost 1000 L (204 mm) of municipal water. A multiple-regression analysis indicated that the evaporation rate could be explained by changes in air temperature, wind speed and incoming solar radiation. The UES design and operation can be optimized according to the user’s desire to maximize evaporation, minimize O&M, minimize costs or maximize fertilizer collection.
- ItemOpen AccessA Theoretical Framework for Implementing Convertible Contracts in Oil and Gas Projects(2016) Moazzami Goudarzi, Mohammad; Ruwanpura, Janaka; Jergeas, George; Hettiaratchi, Patrick; Lozon, Jim; Gates, Ian; Al-Hussein, MohamedConventional forms of contract cannot address the dynamic and unpredictable environment of fast-track projects in the oil and gas industry. Using a single contract type such as cost reimbursable or lump sum for the whole project life cycle shifts the project risks to the owner or the contractor inequitably. Convertible contracts have been used in some oil and gas projects as an alternate contracting strategy to optimize risk taking/rewarding between contracting parties. Through this study, it was discovered that there is a significant gap in academic studies addressing the most challenging issues in managing convertible contracts. This identified gap led the researcher to design the research questions regarding the conversion time, estimation strategy, potential risks, and contractual relationships in convertible contracts. Accordingly, by addressing the research questions, this research aimed to develop a theoretical framework for implementing convertible contracts in oil and gas projects. Since the research questions were quite interpretive and investigative and the main objective of this study was to develop a theoretical framework, a grounded theory study was chosen as the main qualitative research design. Interview was the major instrument to collect the required data and information, and an in-depth review of documents was conducted. The collected data were analyzed through open coding, axial coding, selective coding, and theoretical integration to develop the main deliverable of the study, a theoretical framework, which consists of four main modules: conversion process, estimating strategy, potential risks, and collaborative strategy. To optimize the conversion process in convertible contracts, Module One provides important factors that influence deciding the conversion points, practical recommendations to enhance the conversion process, and possible conversion strategies in application of convertible contracts. Module Two presents an effective way to estimate a more accurate and reliable lump sum price at the time of conversion. The third module presents the potential risks in applying convertible contracts in oil and gas projects and appropriate strategies to mitigate the impact of cost risks in estimating the lump sum price. The fourth module proposes organizing a project collaboration centre with focus on critical activities/decisions before and after conversion.
- ItemOpen AccessAccuracy Assessment of Ultra-Wideband for a Site Safety Monitoring System(2016) Andolfo, Carlo; Sadeghpour, Farnaz; Dann, Markus; Jergeas, George Farage; O'Keefe, Kyle Patrick GordonConstruction has one of the highest rates of accidents among all industries worldwide. In Canada, 22% of workplace fatalities are recorded in the construction industry. An analysis conducted in this study showed that one of the main causes of accidents on construction sites is workers’ lack of awareness of proximity of danger. The objective of this study is to develop a Site Safety Monitoring System that helps improve safety on construction sites by providing safety status of workers in real-time. The system is composed of an available UWB Real-Time Locating System that estimates workers’ location on the site, and a Detection Model that detects when workers are in the proximity of danger using the provided location estimations. Laboratory experiments are conducted to measure the accuracy of UWB in tracking workers, and to examine the reliability of the model in detecting unsafe situations.
- ItemOpen AccessAccuracy Assessment of UWB for Locating Resources on Construction Sites(2013-01-30) Maalek, Reza; Sadeghpour, FarnazContinuous construction site monitoring and resource tracking can assist in ensuring workers’ safety, efficient materials handling and inventory tracking, timely use of resources, and theft prevention. Traditionally, on site data are collected manually, which is an error-prone, costly and time consuming task, particularly in large scale projects. Automated tracking can improve the management of construction projects through effective site monitoring. Based on the comparative evaluation of remote sensing technologies applicable to tracking conducted in this dissertation, Ultra-Wide Band (UWB) technology is shown to be efficient under dynamic characteristics and the harsh environment of construction sites. The use of UWB tracking systems for construction site applications has attracted the attention of researchers in recent years. However, to enable an effective application, it is important to establish the accuracy of its location estimation and its performance under suboptimal conditions of construction sites, which has not been systematically addressed in previous studies. Expanding on previous research, this dissertation presents a systematic approach towards assessing the accuracy of UWB Real-time Location Estimation System (RTLS) in both static and dynamic modes under conditions that can commonly occur on construction sites. A number of variables affecting the performance of the UWB technology in construction sites were identified that have not been addressed or conclusively treated previously; namely: the presence of metal objects that reflect UWB signals; best signals being blocked by other objects; tracking metal objects; removing the timing cables; tracking multiple tags simultaneously; decreased number of receivers; tracking resources with increasing velocities; tracking multiple tags to identify the orientation of the resource and tracking static and dynamic resources simultaneously. Series of experiments were conducted in which the impact of each condition was simulated by changing a variable. Each experiment was designed to reflect a scenario that commonly occurs on indoor construction sites. The experiments were carried out in two different environments, a laboratory and an active workshop. The accuracy and the relative error of location estimations were calculated for each experiment and the effects of influential variables were quantified. In this context, representative correlations were established between the accuracy and different influential variables. For all the experiments carried out here, more than 96% of the measurements in both 2D and 3D achieved an accuracy of less than 1 metre. On the basis of the results achieved in this work, recommendations have been provided for effective utilisation of the UWB technology in detecting objects and resources on construction sites. The findings of this research are essential to assess the feasibility of using UWB RTLS for different construction site applications, such as material handling and safety management.
- ItemOpen AccessAccuracy Assessment of UWB RTLS for Tracking Resources on Construction Sites(2015-07-24) Esmaeilnejad, Seyedshahab; Sadeghpour, FarnazThe evolution of positioning technologies such as Ultra-Wide Band (UWB) has created an opportunity to improve the construction in various aspects. Enhanced situational awareness can be used to improve the level of safety and productivity of the construction. Providing information about situational awareness of static and moving objects on a construction site is feasible with applying positioning awareness. In order to apply positioning methods and technologies efficiently, they should be evaluated and assessed in different situations. The positioning performance changes when the dynamic parameters such as speed changes. In this study, two experiments are designed and carried out on the dynamic performance of UWB positioning. The result of the experiments and the evaluation of the results are stated in details.
- ItemOpen AccessAdvanced Failure Analysis in Geomaterials: Application to Reservoir Geomechanics(2017) Gong, Xu; Wan, Richard; Hicher, Pierre-Yves; Coombe, Dennis; Sudak, Les Jozef; Priest, Jeffrey; Wong, Ron Chik-KwongThe manifestation of failure in geomaterials and its proper analysis are constitutive aspects that geotechnical engineers are faced with routinely in design. In most instances, geostructures are examined at the ultimate plastic state where failure is deemed to occur along a slip surface where plastic deformations localize. This plasticity condition is classically analyzed with the Mohr-Coulomb failure criterion. However, other forms of failure also exist where the localization of deformations is totally absent such as in the case of static liquefaction. This distinct mode has been coined as ‘diffuse failure’ which has the peculiarity of occurring at stress levels well below the plastic limit, thus rendering a classic Mohr-Coulomb analysis insufficient. Hence, the signature of failure in geomaterials seems to be directly related to two principal modes by which it is manifested: one with localized slips, and another variant where deformations are diffused without any localization phenomena. In order to address the many subtle features of failure, a clear mathematical representation of the underlying physical phenomena is needed. In this thesis, failure is considered as an instability of homogeneous deformations, and as such the observed failuremode is a direct result of the underlying constitutive equations admitting bifurcations in solutions for the material response. Different failure criteria are derived, serving as failure indicators which signal the various modes that emerge during loading history following a certain hierarchy. To translate theory into engineering practice, the thesis endeavors to apply the above mathematical aspects of failure in the study of geomaterials undergoing multiphasic flow and thermal transport such as in the extraction of heavy oil from an oilsand reservoir in Alberta, Canada. Governing equations describing the physics of all phases (solid, water, gas and oil) involved are formulated within mixture theory using continuum mechanics principles. A special computational strategy is adopted to solve efficiently the coupled system of equations using both finite elements and finite differences. Finally, the developed computational model is tested in the context of an actual oil field case study implicating steam injection and oil production in an oilsand reservoir in Alberta, Canada. To close the loop, attention is obviously focused on material failure concepts developed in the first part of the thesis. Geomechanical properties that enter the computational model are obtained from a separate comprehensive laboratory testing of shales and oilsands at high temperature and pressure.
- ItemOpen AccessAdvanced Oxidative Processes for Treatment of Emerging Contaminants in Water(2016) Mehrabani-Zeinabad, Mitra; Achari, Gopal; Langford, Cooper; Bergerson, Joule; Tay, Joo-Hwa Andrew; Ponnurangam, Sathish; Surampalli, RaoIn this research, degradation of emerging contaminants in municipal and industrial wastewater was studied by using a variety of advanced oxidation processes. Bisphenol A (BPA) and bisphenol S (BPS) were selected as candidate emerging contaminants in municipal wastewater and sulfolane as a candidate for industrial wastewater. Degradation kinetics of different oxidation processes in spiked water and contaminated wastewater/groundwater were investigated in batch as well as in a flow-through photo-reactor. Degradation of BPA and BPS in spiked water and post-secondary treated wastewater was studied using UVC, UVC/H2O2, O3 and UVA/O3 in a batch photo-reactor. The effective parameters of each process were identified and their impacts on degradation rates were further investigated. Based on the results obtained, the fate of BPA and BPS in municipal wastewater as they move through the UV disinfection unit of a local wastewater treatment plant in Calgary, Canada, was evaluated. It was found that only 1% of BPA and 6% of BPS were degraded in the disinfection unit. However, should 0.042 M H2O2 be added to the wastewater stream entering the disinfection unit, 56% of BPA and 47% of BPS can be degraded. By implementation of O3 and UVA/O3 processes, degradation levels could exceed 95%. Several oxidative methods were used to degrade sulfolane in spiked water and contaminated groundwater in a batch photo-reactor. These include UVA and UVC irradiation with suitable photoactive oxidants, including O3, H2O2, TiO2-based photocatalysis and their combinations. A synergistic effect was observed in the combination of H2O2 and O3 photolysis. The highest rate of sulfolane loss was attributed to UVC/O3/H2O2, UVC/H2O2 and UVC/O3 processes. Finally, the science established in the batch experiments for degradation of the candidate emerging contaminants in municipal and industrial wastewater was further developed into a technology for treating BPS and sulfolane in a flow-through photo-reactor with recirculation. It was found that the most effective process in terms of overall mineralization of BPS and sulfolane in post-secondary treated wastewater and contaminated groundwater, respectively, is the UVC/O3/H2O2 process. The effective parameters were identified and optimized for each of the emerging contaminants.
- ItemOpen AccessAge of Soils: A Measure of Creep History(2017) Guo, Junwei; Wong, Ron Chik-Kwong; Wan, Richard; Priest, Jeffrey; Sudak, LesTime-dependent behaviors of soils are critical for engineering design. Results of one-dimensional (1-D) constant rate of strain (CRS) tests on clays show that there is an existence of unique relationship between current stress and strain state for a given constant strain rate, irrespective to previous stress-strain-time history. In the present study, this relationship is employed to estimate the creep rate during the CRS test. It is found that the creep rate is consistently related to distance from current stress-strain state to the instant compression line, which is the creep void ratio or creep history, termed age of soils. Based on the creep rate as a function of creep strain or age of soils, the stress relaxation rate function is derived through the correspondence principle. Age contours are iso-creep rate lines defining the creep rate field in stress-strain space. Creep Balanced State equation states that CRS path will converge to a iso-creep rate line. This equation is used to determine the CRS path and quantify the rate effect on preconsolidation pressure. Age- and pressure-dependent secondary compression coefficients are incorporated in the above framework.
- ItemOpen AccessAn Assessment Tool for Measuring and Enhancing Innovation in Construction Projects(2018-02) Alhomadi, Ahmad Awaduallah; Jergeas, George Farage; Ruwanpura, Janaka; Lozon, JimInnovation is essential to maintaining competitiveness, improving performance, increasing national economic growth, and contributing to a knowledge-based economy. The construction industry is one of the leading economic contributors in today’s societies. However, the industry is fragmented, diverse, and challenged with a constantly changing business environment and increasing complexity and sophistication. By investing in innovations, the industry seeks to promote performance and sustain competitiveness. The construction industry is mainly project-based, and project level innovation plays a key role in enhancing the performance of project-based companies. The main objective of this research, therefore, was to holistically investigate the factors influencing innovation processes and their diffusion outputs in the construction project context and develop an assessment tool that can help firms measure and benchmark innovation levels on construction projects. A multiphase mixed methods design was conducted, where the different phases interrelate to address the main research objective. The research design encompassed three main sequential phases. The first phase involved the collection and analysis of qualitative data using semi-structured interviews and an exploratory survey. This was followed by a development phase of translating the qualitative findings into a quantitative questionnaire instrument. Then the quantitative phase involved administering the developed instrument to a representative sample in Canada to measure the extent of innovation within the construction projects. The analysis of the quantitative data entailed several statistical procedures, particularly, exploratory factor analysis, scales reliability analysis, and multiple regression analysis. As a result, factor influencing innovation process and their outputs were examined, their prevalence within the context of construction projects was measured, and key factors and their relationships were identified. A construction project innovation assessment tool (CPIAT) was developed based on a synthesis of the results from the previous phases with 13 rigorous innovation indicators. Furthermore, the CPIAT was applied on two different construction projects and showed consistency and efficiency in meaningfully benchmarking construction projects’ innovation.
- ItemOpen AccessAn Effective Stress Equation for Unsaturated Granular Media in Pendular Regime(2014-04-28) Khosravani, Sarah; Wan, RichardThe mechanical behaviour of a wet granular material is investigated through a micromechanical analysis of force transport between interacting particles with a given packing and distribution of capillary liquid bridges. A single effective stress tensor, characterizing the tensorial contribution of the matric suction and encapsulating evolving liquid bridges, packing, interfaces, and water saturation, is derived micromechanically. The physical significance of the effective stress parameter (χ) as originally introduced in Bishop’s equation is examined and it turns out that Bishop’s equation is incomplete. More interestingly, an additional parameter that accounts for surface tension forces arising from the so-called contractile skin emerges in the newly proposed effective stress equation. Therefore, a so-called capillary stress is introduced which is shown to have two contributions: one emanating from suction between particles due to air-water pressure difference, and the second arising from surface tension forces along the contours between particles and water menisci. It turns out that the capillary stress is anisotropic in nature as dictated by the spatial distribution of water menisci, particle packing and degree of saturation, and thus engenders a meniscus based shear strength that increases with the anisotropy of the particle packing and the degree of saturation. The newly proposed effective stress equation is analyzed with respect to packing, liquid bridge distribution and strength issues. Finally, discrete element modelling is used to verify the micromechanical aspects of the proposed effective stress equation.
- ItemOpen AccessAn Evaluation of Different Risk Ranking Systems for Contaminated Sites(2014-01-27) Sha, Huimei; Achari, Gopal; Langford, CooperRisk ranking systems for contaminated sites have been developed by different jurisdictions with similar purpose, but it is not clear whether they provide results that are comparable. The United States’ Preliminary Assessment (PA) system, Sweden’s Methods for Inventories of Contaminated Sites (MICS) and New Zealand’s Risk Screening System (RSS) methods are assessed in this thesis. These methods were compared with each other and with the Canada’s National Classification System for Contaminated Sites (NCSCS) as well as a preliminary quantitative risk assessment (PQRA) method. The objectives were to determine if all these systems can yield similar recommendations regarding further actions, and to assess if there are acceptable correlations between the different methods. The study concludes that the PA, MICS and NCSCS methods can achieve similar conclusions, although there is a certain degree of inconsistency that is present; the RSS system can distinguish the very high and very low risk sites and; acceptable correlations exists among the these methods except for between PA and PQRA.
- ItemOpen AccessAn experimental study on time-dependent behaviour of reconstituted clayey soils in 1D and triaxial compression(2018-09-26) Wickrama Kaluthota Hewage, Rajitha Eranga Wickramage; Wong, Ron; Hayley, Jocelyn; Wan, Richard; Maini, Brij; Siddiqua, SumiAccurate assessment of the safe performance of geotechnical structures against the time-dependent strength-deformation behaviour of soils relies on the knowledge acquired from laboratory and field experiments. Therefore, the focus of this research is to experimentally investigate the role of stress history, soil properties and loading system in the time-dependent strength-deformation behaviour of reconstituted clayey soils. The experimental program consists of oedometer and triaxial compression tests on compacted lightly overconsolidated natural soils (high plastic Regina clay and low plastic Calgary till) as well as on artificial soil mixtures made by mixing pure kaolinite or bentonite with crushed Opal, silt or Calgary till. Results of multiple-stage oedometer tests show that vertical stress level, clay content, size of the coarse particle, coarse particle type, clay type, and liquid limit affect the secondary compression behaviour of oils. Results of constant rate of strain tests in oedometer and triaxial conditions show that at a given strain level, faster strain rates always result in a higher effective vertical stress or deviatoric stress value for high plastic Regina clay. Thus, the behaviour is considered as isotach. However, low plastic Calgary till shows isotach behaviour only under overconsolidated or unsaturated conditions. Further, strain rate effect on shear strength is found to increase with liquid limit, OCR value, matric suction, and absolute magnitude of strain rate. In both oedometer and triaxial conditions, the ratio between relaxed stress at any time and the stress level at the beginning of the relaxation test is found to be linear with the logarithm of time after an initial time period. These linear segments are approximately parallel for stress relaxation tests conducted within or closer to the NC region/post-peak region of the stress-strain curve a soil. The gradient of these parallel segments is found to be independent of the soil structure and confining pressure but depends on the test condition and degree of saturation. Intercepts of fitted lines to these parallel segments can be used to correlate strain rate, stress relaxation behaviour and pre-consolidation pressure. Keywords: Time-dependent, secondary compression, stress relaxation, shear strength, isotach
- ItemOpen AccessAn Instrumented Spatial Linkage to Measure In-Vivo Kinematics and Motion Reproduction with a Robotic Test System(2014-05-14) Rosvold, Joshua; Shrive, NigelDetermination of the mechanical environment of the knee joint is essential in order to understand the normal and pathological states of the tissues in that joint, mechanisms of injuries, and in developing and evaluating surgical interventions. A 6 degree of freedom Instrumented Spatial Linkage (ISL) was developed to record ovine stifle joint kinematics during normal treadmill gait, and reproduce those same motions in-vitro on a robotic testing platform in order to provide an in-vitro environment in which to examine the effects of in-vivo displacement on the soft tissues of the joint. The ISL was designed to provide increased accuracy, reduced processing time, and ease of use when compared to traditional motion capture methods. The ISL was evaluated dynamically to ensure that accurate results were maintained. The ISL and robotic test platform allow determination of the loads on the four major ligaments and the two menisci in the joint. Structural loads for 4 animals were determined for 20 representative strides beginning at hoof strike. Results showed similar loading patterns between animals but with some quantitative differences. With respect to the gait cycle beginning at hoof strike, the PCL reached a peak load just after hoof strike (5%) followed by rapid unloading. The ACL was loaded immediately thereafter with a peak at about 10% of gait. The MCL tended to follow the PCL but with a much reduced force magnitude. The LCL was largely unloaded throughout, suggesting that this ligament must play a more prominent role in other motions. For three of the four animals the average meniscal load was nearly even between the lateral and medial menisci, the fourth animal carried an average of 46.9 N more load in the lateral meniscus. Linear correlations between joint structures and kinematics were attempted but no strong correlations existed. Additionally, ligament length was also shown to be a poor predictor of ACL load. A method is proposed whereby an Artificial Neural Network can be constructed as to accurately predict ACL load given relative joint position and orientation. This study shows for the first time the loads experienced by all 4 major ligaments of the knee, and the minimum loads in the menisci in response to in-vivo motions. The load in each structure has been shown throughout gait and future studies can look at a variety of different motions and loading situations.
- ItemOpen AccessAn Integrated Framework for Worker Planning and Supervision in Construction(2016) Siriwardana, Chandana Sameera Attygala; Ruwanpura, Janaka; Hewage, Kasun; Jergeas, George; Lozon, JamesConstruction is a highly labour-intensive industry; therefore, the planning of worker crews is vital to achieving quality, cost, schedule and productivity targets. However, current construction practices do not initiate worker planning during the early stages of construction, nor do they pay attention to the full life cycle of the project. These pitfalls lead to worker demotivation and performance and productivity losses. Comprehensive worker performance measurement evaluation criteria the Construction Worker Performance Index (CWPI) was developed. A pilot study was carried out to test the applicability and validity of the conceptual framework. After conducting an analytic hierarchy process (AHP) analysis, relative weights for the technical skills assessment framework of Borcherding et al. (2001) were refined; and, the technical skills assessment framework was expanded by adding more sub-attributes to make it suitable for assessing construction workers of Alberta, Canada. The CWPI worker performance measurement formula was finalized using two rounds of surveys based on Delphi survey principles. A worker grading scheme was developed that classifies workers beyond current conventional worker planning, which is based only on skill levels. A cohesion measurement framework was developed based the guidelines provided Carron et al. (1985) and Widmeyer et al. (1985). By integrating different aspects related to worker planning, an overall worker planning framework was created to cover the full life cycle of a construction project. The applicability of the developed framework was field-tested on a construction site in Alberta, Canada. The CWPI and cohesion values of 114 construction workers were measured and documented. Nine construction worker crews (further divided in to twenty sub-groups) were observed, and the structures of the worker crews were studied. Characteristics of high and low performing worker crews were identified, and relationships between factors were investigated. Management level perspective about the developed framework was obtained through a survey conducted among 28 building industry practitioners. Relationships among the factors of the framework were investigated using a correlation analysis. A regression analysis was conducted to determine the causality between input factors and the cohesion level of worker crews. Finally, the limitations of the research were identified, and recommendations for future research were provided.