Earth Sciences - Theses, Dissertations, and other Required Graduate Degree Essays

Receive updates for this collection

Contemporary subsidence and settlement of the Fraser River delta inferred from SqueeSAR(TM)-type InSAR data

Author: 
Date created: 
2014-12-02
Abstract: 

The Fraser River delta in southwestern British Columbia formed over the past 10 000 years and currently supports a population of about 250 000 people. This research focuses on the urbanized and rapidly expanding Richmond area of the Fraser River delta. Dyking, which began in the early 1900s, has prevented flooding and sediment deposition, with the result that the delta plain is subsiding at an average rate of 1-2 mm/a due to the slow, natural consolidation of thick Holocene sediment. Localized higher rates of subsidence stem from anthropogenic sources, notably the application of loads in construction. InSAR data was used to relate load-induced settlement to geology and the spatial and temporal pattern of urbanization. All displacement rates 10 mm/a or more are associated with industrial or large commercial structures. Similar amounts of total settlement are observed from similar sized loads, yet rates of settlement differ, indicating that while load is important in determining total settlement, lithology is as important as load in determining rates of settlement. Holocene sediments underlying the delta are water-saturated, porous, fine sand, silty sand, silt. They are compressible to considerable depth and can experience significant settlement when subjected to structural loads, dewatering, or seismic shaking. No relationship between subsidence rate and surface geology was observed, although surface settlements are generally removed prior to construction. There is an insufficient amount of subsurface data to disentangle lithology and sediment thickness effects. A weak relationship between Holocene thickness and displacement rate has been observed for commercial sized buildings in eastern Richmond with an increase of 0.95 mm/a in the displacement rate for every 100 m of sediment thickness. A weak logarithmic relationship was also observed for the entire RADARSAT dataset.

Document type: 
Thesis
Senior supervisor: 
John Clague
Department: 
Science:
Thesis type: 
(Thesis) M.Sc.

Applications of Uncertainty Theory to Rock Mechanics and Geotechnical Mine Design

Author: 
Date created: 
2015-01-07
Abstract: 

Uncertainty analysis remains at the forefront of geotechnical design, due to the predictive nature of the applied discipline. Designs must be analysed within a reliability-based framework, such that inherent risks are demonstrated to decision makers. This research explores this paradigm in three important areas of geotechnical design; namely, continuum, Discrete Fracture Network (DFN) and discontinuum modelling. Continuum modelling examined the negative effects of ignoring spatial heterogeneity on model prediction. This was conducted through the stochastic modelling of spatial heterogeneities found within a large open pit mine slope. DFN analysis introduced a novel approach to fracture generation to solve issues associated with the incorporation of traditional DFNs into geomechanical simulation models. Finally, discontinuum modelling explored the inherent mesh dependencies that exist in UDEC grain boundary models (UDEC-GBM). Conclusions suggest that a transition is required from deterministic to uncertainty based design practices within the geotechnical discipline.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Doug Stead
Department: 
Science:
Thesis type: 
(Thesis) M.Sc.

Characterizing Groundwater - Surface Water Interactions within a Mountain to Ocean Watershed, Lake Cowichan, British Columbia

Author: 
Date created: 
2014-11-19
Abstract: 

Watersheds located within a mountain to coast physiographic setting have been described as having a highly inter-connected surface water and groundwater environment. The quantification of groundwater-surface water interactions at the watershed scale requires upscaling. This study uses MIKE SHE, a coupled numerical model, to explore the seasonally and spatially dynamic nature of these interactions in the Cowichan Watershed on Vancouver Island, British Columbia, Canada. The hydrostratigraphy of the watershed is constructed using several datasets, including electrical resistivity tomography data. The calibrated model simulates a transition of the Cowichan River from mostly gaining within the valley, to losing stream near the coast where groundwater extraction is focused. Losing and gaining sections correlate with geological substrate. Recharge across the watershed accounts for 17% of precipitation. Climate change is projected to lessen snowpack accumulation in the high alpine and alter timing of snowmelt, resulting in higher spring river discharge and lower summer flows.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Diana M. Allen
Dirk Kirste
Department: 
Science:
Thesis type: 
(Thesis) M.Sc.

Risk to water security on small islands: a numerical modeling approach

Date created: 
2014-12-08
Abstract: 

The aim of this research is to characterise risk to water security for small islands. This is achieved by modeling the spatial and temporal impact from major stressors affecting water resources on small islands, and then evaluating the risk to water security through an integrated assessment framework. Numerical density-dependent flow and transport modeling is used to evaluate the response of the freshwater lens on Andros Island in The Bahamas to various climate change and human stressors including: sea level rise, changes in recharge, and increased pumping. SEAWAT models showed a reduction of freshwater lens volume by up to 24% under projected sea level rise and reduced recharge. The response time of the freshwater lens increased with stressor magnitude, resulting in a longer lens adjustment period. In addition, greater upconing was observed for pumping scenarios simulated under projected climate change conditions than under current conditions. The impact of a 2004 storm overwash event on Andros Island was simulated using HydroGeosphere. Results show that potable water is restored one month sooner when timely remedial actions are implemented; however, if delayed by four days or more, there is no improvement in recovery time. To extend the research more broadly, simulations of overwash for various island types observed worldwide were conducted. Dominant factors affecting freshwater lens response include vadose zone thickness and geologic heterogeneity, such as low or high permeability zones, whereas the dominant factor affecting freshwater lens recovery is recharge rate. A framework to characterise risk to water security was developed specific to an island hydrogeological setting. A freshwater lens susceptibility map was generated using the results of the numerical modeling. Hazard threats from climate change and human stressors (derived from numerical modeling and a land-use survey) were overlaid on the susceptibility map to represent vulnerability. Combining vulnerability with loss (or consequence) yielded a risk to water security map. High risk areas are largely concentrated within the developed areas near high chemical hazard activities, as well as along portions of the coastline. These maps were provided to local partners to inform water management policies and raise awareness about factors impacting water security.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Diana Allen
Department: 
Science:
Thesis type: 
(Thesis) Ph.D.

Architecture and Facies Analysis of Allomember F, Upper Cretaceous Horseshoe Canyon Formation, Drumheller, Alberta

Date created: 
2014-09-25
Abstract: 

Mixed-influence, marginal-marine deposits are typified by complex heterogeneous architectures that are challenging to model in the subsurface. Utilization of modern and outcrop analogs can serve to mitigate these limitations. Marginal-marine successions of the Horseshoe Canyon Fm near Drumheller, Alberta are well exposed in laterally continuous outcrops for 15 km down depositional dip and 3.5 km along depositional strike. This study uses 30 outcrop sections from Allomember F along the Red Deer River and Willow Creek and 4 subsurface cores to classify the deposits in terms of facies and to identify element complexes (EC). Depositional environments are interpreted to record a variety of marginal-marine, paralic, and coastal environments that include: wave-dominated, fluvial-influenced, tide-affected deltaic deposits (FA1); tidal-fluvial channels (FA2); wave-dominated, tide-influenced, fluvial-affected shoreface (FA3); and, delta plain/terrestrial deposits (FA4). The deposits are characterized using the WAVE Classification scheme. Using this process-based approach, FA1 is subdivided and categorized into two element complexes, namely a Fw (t) lobe complex and a Wf (t) mouthbar complex. FA2 is designated as a Ft channelized complex. FA3 is categorized as a Wtf beach complex. FA4 can be subdivided into multiple element complexes representing terrestrial deposits. Overall, the paleoshoreline forms a Wtf or Wft Element Complex Assemblage.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Dr. James MacEachern
Department: 
Science:
Thesis type: 
(Thesis) M.Sc.

Application of Photogrammetry to Estimates of Mine Pillar Damage and Strength

Author: 
Date created: 
2014-07-24
Abstract: 

The use of terrestrial photogrammetry for characterizing changes and damage in rock masses was investigated. Repeat photogrammetry surveys of hard rock pillars were conducted and compared to calculate material loss and damage. Damage measured from photogrammetry was then compared to stresses predicted by Displacement Discontinuity modelling and was found to agree well with current empirical damage-stress relationships. Observed damage profiles were also input into Boundary Element models to correlate predicted stress concentrations with locations of observed damage. Modelled stress concentration locations and magnitudes agreed well with observed damage locations and stress magnitudes from the literature, respectively. Geological structures were characterized from photogrammetry models and used to generate Discrete Fracture Networks, which in turn provided inputs for Distinct Element numerical models. The observed damage was then used to calibrate numerical models which, pending additional calibration, can be used to improve understanding of pillar strength.

Document type: 
Thesis
Senior supervisor: 
Douglas Stead
Davide Elmo
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.

Groundwater characterization and modelling in natural and open pit rock slopes

Date created: 
2014-05-29
Abstract: 

The stability of rock slopes is often compromised by the presence of groundwater in the discontinuities within the rock mass. Discontinuities form the major pathways for groundwater flow and result in seepage zones along slopes. The hydrogeological characterization of fractures is, hence, an important task in rock slope investigations. Nevertheless, most current techniques require direct access to the rock slope, which can often be severely limited due to access, safety and the limited coverage of survey methods. In an attempt to both complement and overcome existing limitations of current methods, the present research makes use of remote sensing techniques to implement a window mapping approach to allow for the collection of structural and seepage information over a wide spatial area. Photogrammetry, ground based LiDAR and Infrared Thermography (IRT) are discussed. Research is also undertaken investigating continuum, discontinuum (distinct element model) and lattice-spring scheme modelling applied to assess the effect of groundwater on large open pit rock slope stability. Fluid flow within a fractured rock mass occurs as a coupled process where the flow field is influenced by the stress field and changes in stress resulting in changes in pore water pressures within the rock mass. The key findings gathered through this research highlight the importance of considering the use of coupled field and state-of-the-art remote sensing techniques in the characterization of seepage areas on high engineered and natural rock slopes. Similarly, numerical codes provided meaningful ways to account for the effect of incorporating groundwater in slope stability analysis. The continuum code, Phase 2, is shown to be suitable for simulating non-fracture controlled slope analysis. Nevertheless, limitations exist when groundwater flow is mainly affected and controlled by the fractures defining the rock mass. The conventional UDEC code is shown to be useful at providing information on the effect of the inclusion of pore water pressures, UDEC-Voronoi/Trigon is demonstrated to be an innovative and meaningful technique to account for the development of stress-induced brittle fracturing. The newly developed lattice-spring Slope Model is proven to be a useful means to assess the role of groundwater conditions on slope instability.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Doug Stead
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.

Three dimensional strain distribution and deformation temperature interpreted from quartz microstructures and petrofabrics in the Okanagan Valley shear zone, southern Canadian Cordillera

Date created: 
2014-07-18
Abstract: 

The Eocene Okanagan Valley shear zone (OVsz) is a ~1-1.5 km thick, <30° west-dipping, extensional ductile to brittle detachment that facilitated exhumation of the southwestern Shuswap metamorphic complex in the southern Canadian Cordillera. A predominantly top-to-the-WNW sense of shear is confirmed by meso- and micro-shear-sense indicators. Quartz a-axis patterns obtained from crystallographic preferred analysis suggest general plane strain conditions with some constriction in the upper 150m of the shear zone. Deformation temperatures derived from recrystallization mechanisms and crystallographic orientations of quartz progressively increase from ~280 to >650 ° down the exposed structural section. The observed telescoping of isotherms in the immediate footwall of the OVsz is interpreted to be the result of detachment-parallel penetrative general shear flow in predominantly plane strain deformation during progressive exhumation. This thesis discusses the possible processes that could have been responsible for this intense compression of isotherms in the immediate footwall of the OVsz.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Dan Gibson
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.

The Hydrogeology of Salt Spring Island, British Columbia

Date created: 
2014-08-06
Abstract: 

Groundwater on Salt Spring Island, British Columbia, flows through fractures in sedimentary and igneous rock aquifers. Recharge is dominantly by rainfall infiltration. At a local scale, groundwater discharges into lakes and streams; regional flow is toward the coast where the groundwater discharges to the ocean. Groundwater evolves from a Na-Cl rainwater to a Ca-HCO3 type through calcite dissolution. Cation exchange (Ca exchanges for Na) is a dominant process in the sedimentary rocks (but not in the igneous rocks), resulting in a Na-HCO3 type water. Mixing with a Cl-rich end-member is also a dominant process in both rock types. Some wells near the coast are known to be impacted by saltwater intrusion. Despite the differences in scale for testing, and rock type, pumping and tidal response tests yield similar averages across the Gulf Islands. Transmissivity is estimated on the order of 10-5 to 10-4 m2/s and hydraulic conductivity on the order of 10-7 to 10-6 m/s. Using Visual MODFLOW, a steady-state fresh groundwater simulation for the Swan Point area generated a representative flow system and established a reasonable range for the aquifer properties. A tidally-forced transient model simulated the tidal response and further constrained the aquifer properties. Next, a density-dependent flow and transport model was constructed in SEAWAT to simulate the current position of the saltwater interface, which was found to be near vertical at the coast. The lack of a wedge likely reflects the relatively steep topography at this site and suggests that submarine groundwater discharge may occur. However, the small model domain and imposed boundary conditions may over-estimate the amount of inflowing water. The SEAWAT model was then used to determine the sensitivity of the aquifer to climate change, encompassing an increase in mean annual recharge by ~1.5 % and SLR of 1.17 m by the end of this century, as well as pumping. Model results showed no significant impacts to the salinity distribution or saltwater wedge geometry at this particular site due to the steep topography. Areas with less steep topography may have greater impacts and merit further research.

Document type: 
Thesis
File(s): 
Senior supervisor: 
Diana Allen
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) M.Sc.

Characterisation of large catastrophic landslides using an integrated field, remote sensing and numerical modelling approach

Date created: 
2014-04-09
Abstract: 

I apply a forensic, multidisciplinary approach that integrates engineering geology field investigations, engineering geomorphology mapping, long-range terrestrial photogrammetry, and a numerical modelling toolbox to two large rock slope failures to study their causes, initiation, kinematics, and dynamics. I demonstrate the significance of endogenic and exogenic processes, both separately and in concert, in contributing to landscape evolution and conditioning slopes for failure, and use geomorphological and geological observations to validate numerical models. The 1963 Vajont Slide in northeast Italy involved a 270-million-m3 carbonate-dominated mass that slid into the newly created Vajont Reservoir, displacing water that overtopped the Vajont Dam and killed 1910 people. Based on literature, maps and imagery, I propose that the landslide was the last phase of slow, deep-seated slope deformation that began after the valley was deglaciated in the Pleistocene. Field and air photograph observations and stream profiles provide the context of Vajont Slide. The first long-range terrestrial digital photogrammetry models of the landslide aid in characterising the failure scar. Analysis of the failure scar emphasises the complexity of the failure surface due to faults and interference between two tectonic fold generations, influencing failure behaviour. Observations of the pre- and post-failure slope and interpretation of numerical simulations suggest a complex three-dimensional active-passive wedge- sliding mechanism, with two main landslide blocks and five sub-blocks in the west block, separated by secondary shear surfaces. The 1959 Madison Canyon Slide in Montana, USA, was triggered by an M = 7.5 earthquake. A 20-million-m3 rock mass descended from the ridge crest, killing 24 people and blocking Madison River to create Earthquake Lake. Marble at the toe of the slope acted as a buttress for weaker schist and gneiss upslope until the earthquake undermined its integrity and triggered failure. Rock mass characterisation, long-range terrestrial digital photogrammetry, and kinematic analysis indicate that the lateral, rear, and basal release surfaces formed a hexahedral wedge-biplanar failure. Dynamic numerical modelling suggests topographic and damage amplification due to ridge geometry and pre-existing tension cracks. Analysis of the case studies highlights the complexity of large, catastrophic rock slope failures, their causes, and their evolution from incipient failure to disaster.

Document type: 
Thesis
Senior supervisor: 
Doug Stead
John J. Clague
Department: 
Science: Department of Earth Sciences
Thesis type: 
(Thesis) Ph.D.