Soil liquefaction has caused major damage to pile foundations in many previous earthquakes. Pile foundations are relatively vulnerable to lateral loads such as those from earthquake shaking; during liquefaction this vulnerability is particularly pronounced due to a loss of strength and stiffness in the liquefied soil. In this research seismic assessment methods for piles in liquefied soil are studied; a simplified approach and a detailed dynamic analysis are applied to a case study of a bridge founded on pile foundations in liquefiable soils. The likely effects of liquefaction, lateral spreading and soil-structure interaction on the bridge during a predicted future earthquake are examined. In the simplified approach, a pseudo-static beam-spring method is used; this analysis can be performed using common site investigation data such as SPT blow count, yet it captures the basic mechanism of pile behaviour. However, the phenomenon of soil liquefaction is complex and predictions of the seismic response are subject to a high level of aleatoric uncertainty. Therefore in the simplified analysis the key input parameters are varied parametrically to identify key features of the response. The effects of varying key parameters are evaluated and summarised to provide guidance to designers on the choice of these parameters. The advanced analysis was based on the effective stress principle and used an advanced constitutive model for soil based on a state concept interpretation of sand behaviour. The analysis results give detailed information on the free field ground response, soil-structure interaction and pile performance. The modelling technique is described in detail to provide guidance on the practical application of the effective stress methodology and to illustrate its advantages and disadvantages when compared to simplified analysis. Finally, a two-layer finite element modelling technique was developed to overcome the limitations conventional two-dimensional (2-D) models have when modelling three-dimensional (3-D) effects. The technique, where two 2-D finite element meshes are overlapped and linked by appropriate boundary conditions, was successful in modelling 3-D characteristics of both deep-soil-mixing walls for liquefaction remediation and pile groups in laterally spreading soil. In both cases the new two-layer model was able to model features of the response that conventional one-layer models cannot; for cases where such aspects are important to the overall response of the foundation, this method is an alternative to the exhaustive demands of full 3-D analysis.

A technique was developed for analyzing and developing mechanical properties for porous geomaterials subjected to the high pressures encountered in penetration and blast-type loadings. A finite element (FE) code was developed to verify laboratory test results or to predict unavailable laboratory test data for porous media loaded to multikilobar stress levels. This FE program eliminates a deficiency in the process of analyzing and developing mechanical properties for porous geomaterials by furnishing an advanced analysis tool to the engineer providing properties to material modelers or ground shock calculators. The FE code simulates quasi-static, axisymmetric, laboratory mechanical property tests, i.e., the laboratory tests are analyzed as boundary value problems. The code calculates strains, total and effective stresses, and pore fluid pressures for fully- and partially-saturated porous media. The time dependent flow of the pore fluid is also calculated. An elastic-plastic strain-hardening cap model calculates the time-independent skeletal responses of the porous solids. This enables the code to model nonlinear irreversible stress-strain behavior and shear-induced volume changes. Fluid and solid compressibilities were incorporated into the code, and partially-saturated materials were simulated with a "homogenized" compressible pore fluid. Solutions for several verification problems are given as proof that the program works correctly, and numerical simulations of limestone behavior under drained and undrained boundary conditions are also presented. / Ph. D.

Subglacial processes that control the water pressure and flow determine the large-scale behavior of the overlying ice by regulating basal resistance. We implement a model in which a steady-state subglacial conduit system is surrounded by fully saturated porous media. We investigate branching in this system at fixed angles of 15 degrees, 30 degrees and 45 degrees to the direction of ice flow and further assess these systems by calculating the hydraulic potential gradient to determine conduit flow path. We solve our governing equations for porous media flow and allow ice infiltration of the pore space to occur at a critical effective stress N infiltration. For low values of N infiltration, ice infiltration of sediment allows these conduits to follow their original paths. Where insufficient ice infiltration occurs, the conduit path instead lies parallel to the direction of ice flow. Our results speak to the importance of incorporating small-scale processes into models of subglacial hydrologic networks.

Internal instability of a widely graded cohesionless soil refers to a phenomenon in which its finer particles migrate within the void network of its coarser particles, as a result of seepage flow. Onset of internal instability of a soil is governed by a combination of geometric and hydromechanical constraints. Much concern exists for embankment dams and levees built using soils with a potential for internal instability. Migration of finer particles to a boundary where they can exit, by washing out, may cause erosion or piping failure and, occasionally, induce collapse of these soil structures. There is a need, in professional practice, to better understand the phenomenon and to develop improved methods to evaluate the susceptibility of a soil. A series of permeameter tests was performed on six widely-graded cohesionless materials. The objectives are to assess the geometric indices proposed for evaluation of susceptibility, and examine hydromechanical factors influence the onset of internal instability. A modified slurry mixing technique, with discrete deposition, was found satisfactory for reconstitution of the homogeneous saturated test specimens. The onset of internal instability was founded to be triggered by a combination of effective stress and hydraulic gradient. The finding yields a hydromechanical envelope, unique for a particular gradation shape, at which internal instability initiated. Three commonly used geometric criteria were comprehensively evaluated with reference to these experimental data and also a database compiled from the literature. The relative conservatism of each criterion was examined and a modified semi-empirical geometric rule then proposed based on the capillary tube model. A theoretical framework for plotting the hydromechanical envelope was established based on an extension of the α concept of Skempton and Brogan, and subsequently verified by test data. Finally, a novel unified approach was proposed to assess the onset of internal instability, based on combining geometric and hydromechanical indices of a soil.

Internal instability of a widely graded cohesionless soil refers to a phenomenon in which its finer particles migrate within the void network of its coarser particles, as a result of seepage flow. Onset of internal instability of a soil is governed by a combination of geometric and hydromechanical constraints. Much concern exists for embankment dams and levees built using soils with a potential for internal instability. Migration of finer particles to a boundary where they can exit, by washing out, may cause erosion or piping failure and, occasionally, induce collapse of these soil structures. There is a need, in professional practice, to better understand the phenomenon and to develop improved methods to evaluate the susceptibility of a soil. A series of permeameter tests was performed on six widely-graded cohesionless materials. The objectives are to assess the geometric indices proposed for evaluation of susceptibility, and examine hydromechanical factors influence the onset of internal instability. A modified slurry mixing technique, with discrete deposition, was found satisfactory for reconstitution of the homogeneous saturated test specimens. The onset of internal instability was founded to be triggered by a combination of effective stress and hydraulic gradient. The finding yields a hydromechanical envelope, unique for a particular gradation shape, at which internal instability initiated. Three commonly used geometric criteria were comprehensively evaluated with reference to these experimental data and also a database compiled from the literature. The relative conservatism of each criterion was examined and a modified semi-empirical geometric rule then proposed based on the capillary tube model. A theoretical framework for plotting the hydromechanical envelope was established based on an extension of the α concept of Skempton and Brogan, and subsequently verified by test data. Finally, a novel unified approach was proposed to assess the onset of internal instability, based on combining geometric and hydromechanical indices of a soil.

Internal instability of a widely graded cohesionless soil refers to a phenomenon in which its finer particles migrate within the void network of its coarser particles, as a result of seepage flow. Onset of internal instability of a soil is governed by a combination of geometric and hydromechanical constraints. Much concern exists for embankment dams and levees built using soils with a potential for internal instability. Migration of finer particles to a boundary where they can exit, by washing out, may cause erosion or piping failure and, occasionally, induce collapse of these soil structures. There is a need, in professional practice, to better understand the phenomenon and to develop improved methods to evaluate the susceptibility of a soil. A series of permeameter tests was performed on six widely-graded cohesionless materials. The objectives are to assess the geometric indices proposed for evaluation of susceptibility, and examine hydromechanical factors influence the onset of internal instability. A modified slurry mixing technique, with discrete deposition, was found satisfactory for reconstitution of the homogeneous saturated test specimens. The onset of internal instability was founded to be triggered by a combination of effective stress and hydraulic gradient. The finding yields a hydromechanical envelope, unique for a particular gradation shape, at which internal instability initiated. Three commonly used geometric criteria were comprehensively evaluated with reference to these experimental data and also a database compiled from the literature. The relative conservatism of each criterion was examined and a modified semi-empirical geometric rule then proposed based on the capillary tube model. A theoretical framework for plotting the hydromechanical envelope was established based on an extension of the α concept of Skempton and Brogan, and subsequently verified by test data. Finally, a novel unified approach was proposed to assess the onset of internal instability, based on combining geometric and hydromechanical indices of a soil. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

The main goal of this research is to evaluate the behavior of earth pressure profiles in unsaturated soils under transient flow. In the first part, an empirical correlation is proposed to obtain the fitting parameters of Brooks and Corey’s soil-water retention model from Fredlund and Xing’s model. The retention models and the proposed equivalency between the models were assessed for 601 soil samples from the unsaturated soils hydraulic database (UNSODA). In the second part, a coupled one-dimensional hydro-mechanical model is introduced and is implemented into Rankine’s earth-pressure model to represent active and passive earth pressure profiles in unsaturated soils under transient flow. A realistic coupling process of infiltration and deformation in the porous medium is established based on the variation in permeability along with deformation in the soil body. The results showed that ignoring the hydro-mechanical coupling effect can lead to underestimation of earth pressure values, especially for fine-grained soils.

Fractures are the main flow channels in naturally fractured reservoirs. Therefore the fracture permeability is a critical parameter to production optimization and reservoir management. Fluid pressure reduction caused by production induces an increase in effective stress in naturally fractured reservoirs. The change of effective stress induces fracture deformation and changes fracture aperture and permeability, which in turn influences the production. Coupled interactions exist in the fractured reservoir: (i) fluid pressure change induces matrix deformation and stress change; (ii) matrix deformation induces fluid volume change and fluid pressure change; (iii) fracture deformation induces the change of pore pressure and stress in the whole field (the influence disappears at infinity); (iv) the change of pore pressure and stress at any point has an influence on the fracture and induces fracture deformation. To model accurately the influence of pressure reduction on the fracture permeability change in naturally fractured reservoirs, all of these coupled processes need to be considered. Therefore, in this dissertation a fully coupled approach is developed to model the influence of production on fracture aperture and permeability by combining a finite difference method to solve the fluid flow in fractures, a fully coupled displacement discontinuity method to build the global relation of fracture deformation, and the Barton-Bandis model of fracture deformation to build the local relation of fracture deformation. The fully coupled approach is applied to simulate the fracture permeability change in naturally fracture reservoir under isotropic in situ stress conditions and high anisotropic in situ stress conditions, respectively. Under isotropic stress conditions, the fracture aperture and permeability decrease with pressure reduction caused by production, and the magnitude of the decrease is dependent on the initial effective in situ stress. Under highly anisotropic stress, the fracture permeability can be enhanced by production because of shear dilation. The enhancement of fracture permeability will benefit to the production of oil and gas.

Master of Science / Department of Geology / Brice LaCroix / Abdelmoneam Raef / South-central Kansas has experienced an increase in seismic activity within the Proterozoic basement over the past 10 years. In 2009, Oklahoma seismic stations recorded 50 earthquakes statewide, a 200% increase from 2008. Oklahoma Geological Survey (OGS) seismograph stations recorded 1,028 in 2010, an increase of over 2000% from 2009. Between 2000-2012, Kansas experienced only 12 earthquakes statewide. Beginning in September 2013, clusters of seismic events in south-central Kansas began to increase. In 2015 alone, Kansas seismograph stations recorded 448 earthquakes, of which 166 resulted in a magnitude 2.0 or greater. Since 2013, United States Geological Survey (USGS) seismograph stations have recorded over 12,000 earthquakes within Kansas and Oklahoma. Pore fluid pressure increases associated with recent high-rate wastewater injection into the dolomitic Arbuckle disposal zone are hypothesized as cause of reactivation of the faulted study region’s Proterozoic basement. Although the magnitude of fluid-pressure change required for reactivation of these faults is likely low given failure equilibrium conditions in the midcontinent, heterogeneities (i.e. permeability, porosity, fluid pressure) in the basement could allow for a range of fluid pressure changes associated with injection. This research aims to quantify the fluid pressure changes responsible for fault reactivation of the Proterozoic basement. To address this issue, we use 97 earthquake focal mechanisms and over 12,000 seismic events, from the USGS catalog, within an area encompassing ~ 4,000 km². Focal mechanism data was utilized to determine the regional stress field present within the study region. Nodal plane data extracted from the focal mechanisms was crucial to identifying lineaments within the underlying basement complex. A 3D seismic dataset covering the Wellington and Anson Bates Fields in north central Sumner County, Kansas was utilized for enhanced structural delineation of an interpreted faultnetwork affecting the Mississippian and Arbuckle Groups, to investigate whether it impacts the underlying granitic basement and its complex network of potentially interconnected fault planes. Smoothed similarity and spectral whitening analyses were applied to the dataset to improve depth of investigation and uncover fault lineaments masked by seismic attenuation due to increasing depth. An interpreted network of fault planes at depths of 3.5 km was uncovered beneath Wellington Field. The lineaments are well aligned with known structural features present within the Proterozoic basement, the Central Kansas Uplift and the Nemaha Ridge-Humboldt fault zone.

[pt] Este trabalho apresenta os resultados da aplicação de análises probabilísticas na avaliação da estabilidade de taludes, com base no caso da ruptura de um quebra-mar construído sobre argila mole no Terminal Portuário de Sergipe, em outubro de 1989. Realizou-se uma análise estatística das características geotécnicas dos materiais presentes na obra, enfatizando a variabilidade inerente dos dados. Nas análises probabilísticas, foram adotados três métodos: FOSM, Estimativas Pontuais e Simulação de Monte Carlo. São apresentados os conceitos básicos de confiabilidade e probabilidade de ruptura e as hipóteses e etapas de cálculo consideradas em cada método. Discutem-se brevemente os diferentes métodos de equilíbrio limite utilizados para superfícies poligonais de ruptura. Três cenários foram estudados, em relação aos procedimentos adotados: análises em tensões totais, com a resistência da argila mole obtida por ensaios de campo e laboratório; análises em tensões efetivas, com o ângulo de atrito da argila oriundo de ensaios triaxiais, e análises em tensões efetivas, com o ângulo de atrito da argila obtido de retroanálise da ruptura ocorrida na obra. Observou-se que para os três cenários os valores de probabilidades de ruptura foram, respectivamentem, da ordem de: 1/70, 1/2100 e 1/30. Além disso, ao considerar as metodologias de cálculo probabilístico por FOSM e Estimativas Pontuais, os resultados foram mais conservadores em relação a Simulação de Monte Carlo. / [en] This work aims at applying available methods of probabilistic analysis for assessing the stability of a breakwater built on soft clay at the Sergipe Terminal, gathering information on the existent materials in the field and a statistical analysis of the geotechnical parameters, emphasizing the inherent variability as part of the research. Three probabilistic techniques of analysis have been used: FOSM, Point Estimates and Monte Carlo Simulation. The hypotheses, calculation steps and basic concepts of reliability index and probability of failure are presented, with brief discussions on the different limit equilibrium procedures used for polygonal surfaces. Three scenarios were studied, regarding the soft clay parameters: total stress analysis, considering undrained loading, effective stress analysis with effective friction angle from triaxial tests, and effective stress analysis with effective friction angle from back analysis of a previous failure. For the three scenarios, the probability of failure values were, respectively around: 1/70, 1/2100 and 1/30. Besides this, when using the FOSM and Point Estimates probabilistic techniques, the results proved to be more conservative, in comparison to Monte Carlo Simulation.