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

Receive updates for this collection

Numerical modelling of surface subsidence associated with block cave mining using a finite element / discrete element approach

Peer reviewed: 
No, item is not peer reviewed.
Date created: 
2008
Abstract: 

Recent years have seen a major increase of interest in the block cave mining method which is characterized by extraction of a massive volume of rock usually accompanied by the formation of a significant surface depression above and in the vicinity of the mining operation. The ability to predict surface subsidence is important for mine planning, operational hazard assessment and evaluation of environmental and socio-economic impacts. Owing to problems of scale and lack of access, the fundamental understanding of the complex rock mass response leading to subsidence is limited as are current subsidence prediction capabilities. Through the use of an integrated FEM/DEM-DFN modelling technique this thesis presents a new approach to simulation of block caving induced surface subsidence allowing physically realistic simulation of subsidence development from caving initiation to final subsidence deformation. As part of the current research, a fundamental issue in modelling, the selection of representative equivalent continuum rock mass modelling parameters, is investigated and a procedure for calibration of modelling parameters devised. Utilizing a series of conceptual numerical experiments our fundamental understanding of the mechanisms and the role of the factors controlling block caving subsidence development is investigated. Valuable insights gained from this work are summarized in a preliminary subsidence classification and an influence assessment matrix of the governing factors. These are intended as an aid to engineering judgment for decision makers at the pre-feasibility and mine design stages. This study also addresses one of the most challenging problems in mining rock engineering - the interaction between block cave mining and a large overlying open pit, focusing on caving induced step-path failure initialization. Using a novel approach to modelling data analysis a clear link between caving propagation, step-path failure development within the slope, and the resultant surface subsidence is established. In addition, FEM/DEM-DFN modelling is applied to the preliminary analysis of the block caving triggered slope failure at Palabora open pit. This research represents a valuable contribution to block caving geomechanics and is a major step forward in the understanding of complex block caving subsidence phenomena, paving the way to more reliable assessment of caving induced subsidence deformations.

Document type: 
Thesis
File(s): 
Supervisor(s): 
D
Department: 
Dept. of Earth Sciences - Simon Fraser University
Thesis type: 
Thesis (Ph.D.)

Comparison of approaches for aquifer vulnerability mapping and recharge modelling at regional and local scales, Okanagan Basin, British Columbia

Date created: 
2008
Abstract: 

Aquifer vulnerability and direct recharge from precipitation were modelled in Okanagan Basin, British Columbia. The vulnerability study evaluated mapping approaches for regional and local scales using the DRASTIC method. Original rating tables provide sufficient detail for mapping at regional scales, where broad ranges of geologic material are present. However, modified rating tables improved spatial representation of input parameters at local scales, which is useful for local planning. Spatially-distributed recharge throughout the valley bottom was modelled using the HELP code. Average annual recharge is 65 mm/yr, with 109 mm/yr near Vernon, and 37 mm/yr near Oliver. The regional recharge map adequately captured the magnitude and distribution compared to a local map constructed using HELP (42 mm/yr); However, regional recharge results were higher compared to a local map constructed using the MIKE-SHE code (6 mm/yr). Compared to measured evapotranspiration data, HELP appears to under-estimate evapotranspiration, therefore over-estimating recharge within semi-arid regions.

Document type: 
Thesis
File(s): 
Supervisor(s): 
D
Department: 
Dept. of Earth Sciences - Simon Fraser University
Thesis type: 
Thesis (M.Sc.)

Well-cuttings based, sequence stratigraphic framework of the mixed siliciclastic-carbonate Lower Cretaceous sediments of the North Carolina coastal plain

Author: 
Date created: 
2008
Abstract: 

A lithology-based, sequence stratigraphic framework and depositional model for mixed siliciclastic-carbonate Lower Cretaceous sediments of the North Carolina coastal plain (southeastern U.S.) is proposed. Twenty-five lithofacies are recognized. Ten recurring facies associations are defined, and are merged into siliciclastic - and carbonate-dominated depositional profiles, comprising coastal plain to deep shelf depositional environments. Parasequences are recognized from the well data, and are grouped into parasequence sets indicating progressive progradational or retrogradational (highstand and transgressive systems tracts, respectively) stacking patterns. Lowstand deposits are not recognized, although they probably occur in more basinward positions lying to the east. Seismic reflectors guided correlations between wells, and typically coincided with key sequence stratigraphic surfaces. Three third-order sequences are defined, which are dominated by siliciclastic depositional processes. The late highstand deposits of Sequence 1, however, are carbonate rich. The low relative sea-level conditions during late highstand likely favoured climatic aridity, facilitating carbonate-dominated sedimentation.

Document type: 
Thesis
File(s): 
Supervisor(s): 
B
Department: 
Dept. of Earth Sciences - Simon Fraser University
Thesis type: 
Thesis (M.Sc.)

Quaternary alkaline and calc-alkaline basalts in southern British Columbia: mixed signals from mantle sources above the southern edge of the Juan de Fuca–Pacific slab window

Date created: 
2008
Abstract: 

Subaerial lava flows of the Quaternary valley lavas mark the end of Chilcotin Group intraplate volcanism in southern British Columbia. Two geographically defined units are recognized: the Quilchena and Lambly Creek lavas. Erupting intermittently from discrete centres, lava flowed into existing paleodrainages from 1.5 Ma (Lambly Creek) to 780–100 ka (Quilchena). Erosion removed most of the estimated 8.8– 21.1 km3 of lava. Internal features are well preserved, some indicative of flow inflation and transport direction. The lavas are alkaline to calc-alkaline basalts, trachy-basalts, basaltic andesites and trachy-basaltic andesites, with trace element characteristics similar to ocean island basalt and εNd values from +8.0 to +8.4. The magmas resulted from partial melting of garnetiferous asthenosphere that upwelled through the subducted Nootka Fault and thermally eroded Explorer and northern Juan de Fuca plates south of a slab window. Geochemical modelling indicates that the mantle source was heterogeneous, composed of variably enriched peridotite.

Document type: 
Thesis
File(s): 
Supervisor(s): 
D
Department: 
Dept. of Earth Sciences - Simon Fraser University
Thesis type: 
Thesis (M.Sc.)

Numerical modelling of brittle fracture and step-path failure: from laboratory to rock slope scale

Author: 
Date created: 
2008
Abstract: 

Recent research indicates that brittle fracture and step-path failure are important considerations in both natural high-mountain and engineered rock slopes. Newly developed techniques for field survey and numerical modeling of brittle fracture and step-path failure are presented in this research in an attempt to overcome many of the limitations of traditional approaches. Research primarily focuses on the simulation of brittle fracture and step-path failure at both the laboratory and large slope scale, and the application of LiDAR and digital-imaging techniques in the field characterization of brittle fracture. BEM, FEM, DEM(UDEC Voronoi) and hybrid FEM/DEM codes are all used in an attempt to realistically simulate laboratory step-path brittle fracture. The selected approaches are constrained through comparison of simulated fracture coalescence patterns with published physical model experiments. The combined utility of a diverse suite of data interpretation methods is shown to aid in the identification of fracture initiation and propagation. Simulation of brittle fracture propagation using both the hybrid FEM/DEM code and the FEM code PHASE2 is presented for a conceptual large open pit slope with the specific objective of investigating the relationship between intact rock bridge width and the potential for toe breakout. A major high mountain rock slope failure, the Randa rockslide, is used to demonstrate the potential of the hybrid code in modelling the influence of discontinuity persistence and step-path failure on progressive rock slope instability. The importance of characterizing three dimensional step-path failure modes in the field and the subsequent simulation using a three dimensional distinct element code are illustrated. A variety of block movement modes (i.e. translation, rotation, buckling and toppling) are shown to be highly sensitive to joint orientation, joint spacing, the assumed joint friction angle, and acting boundary constraints. The insights gained from this research provide a major contribution toward understanding of the limitations and advantages of varying numerical approaches in the simulation of brittle fractures and step-path failure. It is hoped that by examining the process of brittle fracture and step-path failure using state-of-the-art numerical codes and field characterization methods, this thesis, will provide a foundation for improved hazard assessment and rock slope design.

Document type: 
Thesis
File(s): 
Supervisor(s): 
D
Department: 
Dept. of Earth Sciences - Simon Fraser University
Thesis type: 
Thesis (Ph.D.)

Quartet Mountain Lamprophyres and crustal xenoliths: new insights into the Mesoproterozoic metamorphic history of northwestern Laurentia

Date created: 
2008
Abstract: 

The Quartet Mountain Lamprophyres are Early Cambrian ultramafic dykes that crosscut Proterozoic sedimentary strata in the Wernecke Mountains, east-central Yukon. They were derived from low-degree partial melting of a light REE-enriched garnetiferous upper mantle and have near-chondritic Nd530 values of -1.5 to 1.9. The lamprophyres co ntain xenoliths derived from the crust and upper mantle. SHRIMP U-Pb isotopic analysis of zircon from five xenoliths identified ages of metamorphism, at 1.60 Ga, 1.27 Ga and 1.15 Ga. The 1.60 and 1.27 Ga events were likely caused by nearby, documented events of metasomatism and magmatism. The 1.15 Ga metamorphism correlates with scattered igneous and metamorphic ages from the northern and central North American Cordillera, the Grenville orogen and the Sibao orogen of South China. The 1.15 Ga event in northwestern Cordillera is thought to reflect crustal heating in an extensional regime generated by the oblique convergence of the Yangtze Craton with western Laurentia.

Document type: 
Thesis
File(s): 
Supervisor(s): 
D
Department: 
Dept. of Earth Sciences - Simon Fraser University
Thesis type: 
Thesis (M.Sc.)

Quaternary geology of the Zama City area, northwestern Alberta

Date created: 
2008
Abstract: 

Geologic studies in the Moody Creek (84M/02) map area were undertaken to map surficial geology, establish glacial history, and classify materials geotechnically. Surficial geology mapping was completed in 2006. The stratigraphy is represented by 6 units: glaciolacustrine; till; englacial/subglacial gravels; retreat glaciolacustrine; readvance till; alluvium; and peat. The Laurentide Ice Sheet advanced over shale be drock and glaciolacustrine sediments, resulting in clay-silt tills with high plasticities. During the last glacial maximum, ice flow was west-southwestward, and during deglaciation ice flow was westward. During deglaciation, regional drainage was blocked by the retreating ice margin, forming Glacial Lake Hay. Glaciolacustrine sediments occur below 410 m, and shorelines occur at 340 m. Iceberg scours are observed between 340 and 400 m. A late glacial readvance covered most of the area flooded by Glacial Lake Hay. Aggregate is in short supply, and the sole active pit in the study area exploits sub-till gravel.

Document type: 
Thesis
File(s): 
Supervisor(s): 
B
Department: 
Dept. of Earth Sciences - Simon Fraser University
Thesis type: 
Thesis (M.Sc.)

Integrated Ichnology, sedimentology and stratigraphy of the Lower Falher member, Spirit River formation, northeastern British Columbia and central Alberta

Date created: 
2008
Abstract: 

The lower Falher Member comprises facies successions of wave- and storm-dominated delta complexes and strandplain settings. Both are characterized by interbedded, moderately burrowed mudstones and sandstones, passing into heterolithic intervals dominated by sporadically burrowed, stacked sandy tempestites. These pass upwards into current ripples and trough cross-stratification, capped by low-angle planar-stratified sandstones, pebbly sandstones and conglomerates. Prodeltaic intervals contain syneresis cracks, organic-rich mudstone drapes of fluid-mud origin, current and combined flow ripples, soft-sediment deformation, and carbonaceous detritus. Trace fossil suites are typified by reduced diversities and abundances of ichnogenera, lowered bioturbation intensities (BI 0-2), and a paucity of suspension-feeding structures in the tempestites. Offshore deposits contain rare fluid-mud drapes, and greater bioturbation intensities (BI 0-5), increased ichnogenera diversities, and the presence of suspension-feeding structures in sandy tempestites. These facies characteristics may be useful in identifying other deposits in the Western Interior Seaway, which have been interpreted as wave- and storm-dominated shorelines.

Document type: 
Thesis
File(s): 
Supervisor(s): 
J
Department: 
Dept. of Earth Sciences - Simon Fraser University
Thesis type: 
Thesis (M.Sc.)

Amplitude Variation with Offset and Lam? Parameter Analysis of Sediments at the Toe of the Cascadia Accretionary Prism

Date created: 
2003
Abstract: 

The Cascadia convergent margin lies off the west coast of North America where the Juan de Fuca oceanic plate is being subducted beneath the North American continental plate. West of Vancouver Island a large accretionary wedge has evolved as sediments have been scraped off the subducting oceanic plate and welded on to overriding North American plate. At the toe of the accretionary complex, sediments are squeezed by tectonic forces leading to decreases in porosity and expulsion of pore fluids. Expelled fluids migrate to other layers where they may become trapped and can lead to 'over pressuring' of layers. Porosity and pore pressure variations within sediments lead to changes in elastic properties such as hp, pp, Poisson's ratio and Up. Changes in these properties affect the angle dependent P-wave reflectivity of a reflector bounding the base or top of a layer. By fitting a linearised approximation to the Zoeppritz equations to P-wave reflection amplitude variation with offset (AVO) data it is possible to extract changes in elastic properties within layers, and thus infer regional changes in porosity and pore pressures. Extracted reflectivities and inverted elastic impedances (and thus hp and pp) are highly dependent on the available background P- and S-wave velocity information. Currently S-wave velocities are unknown and can only be estimated approximately; thus, extracted values are not quantitatively accurate, and only qualitative interpretations can be made. A 2-D seismic reflection line was processed to extract P and S-wave reflectivities from Pwave AVO. These reflectivities were subsequently inverted for kp and pp. These values show that porosities in the Juan de Fuca basin decrease approaching the deformation front. A package of sediments towards the base of the basin sediments is highly fractured. This package has a low pp relative to surrounding sediments. At the top of this layer a thin bed of extremely low pp is evident. This layer appears not to be decreasing in porosity at the same rate as surrounding layers. This thin bed shows evidence of having high pore fluid pressures and may act as a trap for fluids escaping the fractured layer below.

Document type: 
Thesis
File(s): 
Department: 
Theses (Dept. of Earth Sciences) / Simon Fraser University
Thesis type: 
Thesis (M.Sc. (Earth Sciences))