Civil and Environmental Engineering Commons^™

Functionalizing Three-Dimensional Superhydrophobic Materials, Li He

Doctoral Dissertations

Traditional bulk superhydrophobic materials are usually characterized by high porosity, low fracture toughness, and extremely low strength due to the low surface energy on the internal surface. Therefore, it is very challenging to achieve a bulk superhydrophobic material with high strength and mechanical durability. This dissertation presents an experimental study of strengthening a superhydrophobic siloxane using carbon-based nanomaterials, emphasizes the effects of microscale dispersion and macroscale distribution of reinforcing graphene on the uniformity and strength of the composite, studies the impact factors on the water adsorption for hydrophilic and hydrophobic materials, and applies chemical modification modify the surface of clay …

Experimental Investigation Of Clay Aggregate And Granular Biofilm Behavior, Tao Jiang

Doctoral Dissertations

Clay minerals are a class of phyllosilicates as the major solid constituents in cohesive fine-grained soils (e.g., clays). Owing to their tiny size (i.e., < 2 μm), high aspect ratio, and active surface properties that inherit from the geological process, clay minerals can extensively interact with other suspended matter (e.g., exoployemers, microorganisms) and dissolved ions via the process of flocculation and aggregation, resulting in the formation of larger, porous cohesive particulate aggregates or flocs. Such a complex mechanism of microscale particle interaction generates significant challenges for understanding the bulk clay behavior as a particulate system. In order to better characterize the flocculation and aggregation of clay minerals under various stimuli and to understand the underlying mechanism of particle interactions, particle/aggregate size kinetics of flocculated suspensions of illite, a representative 2:1 clay mineral abundant in marine soils, are studied with varied ionic strength induced by monovalent salt (NaCl), pH, and hydrodynamic shearing in the first phase of this research. Furthermore, a new statistical data binning method termed “bin size index” (BSI) was employed to determine the probability density function (PDF) distributions of flocculated illite suspensions. The statistical results demonstrate that the size kinetics of flocculated illite suspensions is chiefly controlled by the face-to-face and edge-to-face interparticle interactions under the mutual effects of ionic strength and pH, while the hydrodynamic shearing has minimal effects on the variation of particle size groups. In the second phase of this research, the mechanics of clay aggregates are studied using an innovative measurement technique and analytical approach. Individual clay minerals prepared with different mineralogy and salinities are tested via unconfined compression, which shows that the increasing ionic strength can improve the strength and stiffness of clay aggregates, which are further affected by the mineralogical compositions and dominant microfabric in different water chemistry. In the final phase of this research, a collaborative study with an environmental engineer on an NSF CAREER project was conducted to investigate the mechanical behavior of macroscale, light-induced oxygenic granules (biofilm aggregates) using the same technique and analytics developed for the individual clay aggregates. The findings are expected to provide reference values to subsequent studies and engineering practices associated with the water treatment process.

Big Data Nanoindentation: Concepts, Principles And Applications To Cemented Materials, Yucheng Li

Doctoral Dissertations

The exploration of oil/gas in the petroleum industry presents a lot of issues both during and after the drilling process, such as wellbore stability, formation clogging, and cementation. Understanding the chemo-mechanical alterations caused by drilling activities to the surrounding formations has been a crucial part of a successful drilling operation. However, as multi-phases, multi-scales, heterogeneous composites, the mechanical properties of rock can vary significantly with its diverse constituent minerals (e.g., quartz, feldspar, and clay minerals) and sometimes hard to be characterized due to the availability of rock samples (i.e., cylindrical core samples are arduous to acquired especially at deep formations). …

Influence Of Foundation Damping On Offshore Wind Turbine Monopile Design Loads, Wystan Carswell, Sanjay R. Arwade, Jörgen Johansson, Don J. Degroot

Publications

The dynamic behavior of offshore wind turbines (OWTs) must be designed considering stochastic load amplitudes and frequencies from waves and mechanical loads associated with the spinning rotor during power production. The proximity of the OWT natural frequency to excitation frequencies combined with low damping necessitates a thorough analysis of sources of damping; of these sources of damping, least is known about the contributions of damping from soil-structure interaction (foundation damping). This paper studies the influence of foundation damping on cyclic load demand for monopile-supported OWTs considering the design situations of power production, emergency shutdown, and parked conditions. The NREL 5 …

Density State And Shear Behavior Of Granular Soils With Influence Of Particle Size Distribution, Yibing Deng

Doctoral Dissertations

Heterogeneous granular soils are ubiquitous in nature and man-made deposits. Heterogeneity of soil is characterized by its particle size distribution (or fines content for gap-graded soils). The particle size distribution of soil is the main factor that affects its mechanical properties. However, in soil mechanics, the influence of particle size distribution on mechanical properties is only considered in an empirical manner. There are few analytical methods that can explicitly account for the effect of particle size distribution. In this study, there are two purposes: 1) to develop a particle packing theory for modeling the effect of particle size distribution on …

Multiscale Investigation Of Thixotropy In Soft Clays, Jing Peng

Doctoral Dissertations

Fine-grained clay particles of <2 >µm in size are ubiquitous in soils and sedimentary rocks. Due to their platy shape, high aspect ratio, and surface charges, clay particles play a dominant role in controlling the mechanical properties of those fine-grained geomaterials such as soft clays and shales. In physics and engineering, some materials show that the strength and stiffness increases with time even if the boundary conditions remain unchanged (e.g., no change in pressure, temperature, or composition), and such a phenomenon is called thixotropy. It is generally agreed that the principle of thixotropy of wet clays is complex. For a closed, …

Breaking Wave Hazard Estimation Model For The U.S. Atlantic Coast, Spencer T. Hallowell

Publications

As offshore wind development is in its infancy along the U.S. Atlantic Coast challenges arise due to the effects of strong storms such as hurricanes. Breaking waves on offshore structures induced by hurricanes are of particular concern to offshore structures due to high magnitude impulse loads caused by wave slamming. Prediction of breaking wave hazards is important in offshore design for load cases using long mean return periods of environmental conditions. A breaking wave hazard estimation model (BWHEM) is introduced that provides a means for assessing breaking hazard at long mean return periods over a large domain along the U.S. …

Characterization Of A Natural Clayey Silt And The Effects Of Sample Disturbance On Soil Behavior And Engineering Properties, Øyvind Blaker

Doctoral Dissertations

Silts are considered a challenging material to deal with in geotechnical engineering design practice and there has been limited research on determining the engineering parameters of silts either by in situ or laboratory testing. This thesis presents results of an extensive research program that investigated the in situ and laboratory behavior of a low plasticity silt deposit at the Norwegian National Geotechnical Test Site at Halden, Norway. Results from multiple in situ tests including: piezocone, pore pressure dissipation, in situ pore pressure measurements, field vane, self-boring pressuremeter and screw plate load tests were synthesized to characterize the Halden silt. Soil …

Synthesis And Characterization Of Geopolymers Cast And Cured In Saline Water And The Potential Application In Construction Engineering, Xiaonan Ge

Doctoral Dissertations

The characteristics of underwater cast and cured geopolymers were experimentally studied to understand the interactions between geopolymer slurry and curing saline water and pertinent effects on its strength development. Geopolymers were synthesized from a mixture of Class C fly ash and metakaolin, and the influences of two different Si/Al molar ratios (1.78 and 2.00) and four different Na/Al (0.67, 0.80, 0.84, and 1.00) molar ratios were investigated, respectively. The geopolymer slurry was prepared and then cast into porous molds, followed by immediately submerged into 0, 15, and 35 ppt saline solutions (prepared with commercial seasalts) for 28-days’ curing in ambient …

Nanoindentation Characterization Of Elastic Properties Of Shales And Swelling Clay Minerals, Shengmin Luo

Doctoral Dissertations

Oil and gas shales are a class of multiscale, multiphase, hybrid inorganic-organic sedimentary rocks that consist of a generally uniform, preferentially oriented clay matrix with randomly embedded silt and sand particles as solid inclusions. A thorough understanding of the mechanical properties of shales is crucial for the exploration and production of oil and gas in the unconventional shale reservoirs, but it can be a challenging task due to their nature of compositional heterogeneity and microstructural anisotropy. In efforts to better characterize the mechanical properties of shales across different length scales and to fundamentally understand the laws of upscaling from individual …

A Multiline Anchor Concept For Floating Offshore Wind Turbines, Casey Fontana

Doctoral Dissertations

Floating offshore wind turbines (FOWTs) hold great potential for the renewable energy industry, but capital costs remain high. In efforts to increase FOWT substructure efficiency and reduce costs, this thesis investigates a novel multiline anchor concept in which FOWTs share anchors instead of being moored separately. The goal of this thesis is to evaluate the force dynamics, design, and potential cost reduction of the system. Anchor forces are simulated using the NREL 5 MW reference turbine and OC4-DeepCwind semisubmersible platform, and multiline anchor force is computed as the vector sum of the contributing mooring line tensions. The use of a …

Application Of Ground Penetrating Radar For Use In Thermal Conductivity Site Investigations, Aaron J. Rubin

Doctoral Dissertations

Measurement of soil thermal conductivity in-situ is important for many practical geotechnical and civil engineering applications. However, for a variety of reasons it can be difficult to measure in-situ. A novel method to estimate the thermal conductivity of sands based on electrical relative permittivity (dielectric constant) measurements and GPR data is presented. First, an analytical model to estimate thermal conductivity of soils was developed and validated using a database of thermal conductivity measurements. The new thermal conductivity model was then compared to existing models using a larger database of new and pervious thermal conductivity measurements conducted on a wide range …

Performance Of Concrete Tunnel Systems Subject To Fault Displacement, Michael Morano

Masters Theses

A Finite Element Analysis (FEA) investigation of concrete tunnel systems traversing seismic faults is carried out to determine how to effectively mitigate the stresses induced in the liner when subject to fault displacement. A parametric study of various fault parameters, both in the damage zone and competent rock, is carried out to determine the site conditions which induce the most stress on the tunnel liner system. Results indicate that friction angle, cohesion, and elastic modulus of fault zones have varying effects on the stresses induced on the liner. The width of damage zone and expected displacements are also investigated and …

Evaluation Of New Methods For Determining The Minimum And Maximum Index Densities Of Sand, Hossein Ganji

Geotechnical Engineering Masters Projects

This thesis presents the results of a laboratory testing program that evaluated the applicability of a new-established method for determining minimum and maximum dry density values by Norwegian Geotechnical Institute (NGI). Seven fine to medium grained cohesionless sand batches with different inclusion of fines content were selected for a series of testing programs in compliance with American Society for Testing and Materials (ASTM) and NGI recommendations. All three methods of ASTM D4254 – 16 and method 1B of ASTM D4253 – 16 were applied for minimum and maximum dry density determination, respectively. The results compared with the NGI minimum and …

Evaluation Of Helical Piles As Anchors For Floating Offshore Wind Turbine Foundation Systems, Martha Shannon Harris

Geotechnical Engineering Masters Projects

The development of floating offshore wind energy is essential for growth of the renewable energy industry, and to decrease the reliance on fossil fuels and emission of greenhouse gasses. Advances in ease of construction and installation of turbines can make the floating offshore wind industry more marketable and feasible on a large scale; this can in part be achieved by innovation in foundation anchoring systems.

This thesis presents an evaluation of helical pile foundations for offshore deep-water application as anchors for floating offshore wind systems with catenary mooring lines in clay and sandy soils. This research outlines the influence of …

Experimental Investigation Of Hydraulic Fracturing Fluid On Shale And Soil, Zhenning Yang

Doctoral Dissertations

Mitigation and prevention of shale-formation damage caused by hydraulic-fracturing fluid/rock interactions play an important role in well-production stability and subsequent refracturing design. This study presents three experimental investigations on the interaction of water/shale, fluid/clay, and fluid/shale. A series of experiments were designed to investigate fluid/shale interactions: hydrophilic to hydrophobic alteration through chemical-vapor deposition, nanoindentation testing on shale sample, geotechnical laboratory experiments on contaminated clay, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscope (SEM) on shale sample. A clay-matrix-based data-screening criterion is proposed for nanoindentation. The continuous-stiffness-measurment (CSM) method is proved to have better definition and characterization of …

Compressibility And Normalized Undrained Shear Behavior Of Soft Coastal Fine-Grained Soils, Arash Pirouzi

Doctoral Dissertations

This thesis investigates empirical correlations between consolidation design parameters and index properties of soft fine-grained soils from coastal Louisiana region, normalized undrained shear behavior of high liquid limit organic fine-grained coastal soils, and consolidation behavior of fine-grained soils. The first phase of this research consisted of studying a database of site investigation data from 15 marsh creation projects across the coastal Louisiana region. The database includes a wide variety of fine-grained soils ranging from low-plasticity inorganic clays and silts to high-plasticity organic clays and silts with a large range of water content and liquid limit. Most of the empirical correlations …

Evaluation Of The Erodibility Of Soft Clays And The Influence Of Biopolymers, Pamela Judge

Doctoral Dissertations

Erosion of silts and clays is less well understood than erosion of sands. Further, current and anticipated climate change impacts along coastlines compel consideration of new approaches to coastal protection measures; seawalls and breakwaters designs now include natural and nature-based measures. The first research topic consists of the Adaptive Gradients Framework which was a theoretically-informed facilitation tool. The framework was intended to aid a collaborative and interdisciplinary decision-making process to encourage inclusion of natural and nature-based measures in coastal protection planning and design. This research is the culmination of a series of workshops and fieldtrips executed by the Sustainable Adaptive …

Modeling Deformation Behavior And Strength Characteristics Of Sand-Silt Mixtures: A Micromechanical Approach, Mehrashk Meidani

Doctoral Dissertations

This dissertation is comprised of six chapters. In the first chapter the motivation of this research, which was modeling the deformation behavior and strength characteristics of soils under internal erosion, is briefly explained. In the second chapter a micromechanis-based stress-strain model developed for prediction of sand-silt mixtures behavior is presented. The components of the micromechanics-based model are described and undrained behavior of six different types of sand-silt mixtures is predicted for several samples with different fines contents. The need for a more comprehensive compression model for sand-silt mixtures is identified at the end of this chapter. This desired compression model …

An Experimental Investigation Of The Influence Of Sampling On The Behavior Of Intermediate Soils, William Lukas

Doctoral Dissertations

Laboratory tests were performed in order to determine the effects of tube sampling disturbance on intermediate soils. Synthetic soils composed of Kaolin clay and silica silt, a reconstituted natural silt, and block sample specimens of a sensitive marine clay were tested. Tube sampling disturbance was simulated in a triaxial stress path system with bender element using the Ideal Sampling Approach prior to reconsolidation and undrained shear. ISA strain cycles of ±0.5, ±1 and ±3% were used to represent progressively greater degrees of disturbance. The influence of overconsolidation ratio (OCR) was explored by testing at OCRs of 1, 1.8, 3.6 and …

Influence Of Reconsolidation Procedure On Small Strain Shear Modulus And Undrained Shear Behavior Of Silts Subjected To Tube Sampling Disturbance, Shreya Pandey

Geotechnical Engineering Masters Projects

This thesis presents results of a laboratory testing program that studied the effects of laboratory simulated tube sampling disturbance on the undrained shear strength behavior of reconstituted low plasticity silts at overconsolidation ratios of 1.0 and 3.6. The three test soils consisted of two different mixtures of kaolin clay and silica silt and a reconstituted natural Dedham silt. Triaxial tests with bender elements were conducted on the reconstituted samples using the Ideal Sampling Approach (ISA) followed by post-ISA reconsolidation and undrained shear. The specimens were subjected to ± 1% and ± 3% ISA axial strain cycles. Changes in shear wave …

Evaluating The Influence Of Breakdown Fouling And Moisture Content On Mechanical And Electromagnetic Properties Of Ballasted Railroad Track, Hamed Faghihi Kashani

Doctoral Dissertations

A complete study was performed to develop correlations between electromagnetic and mechanical properties of ballast. These correlations can be used to predict the deformation properties of ballast and also its dynamic behavior under heavy axle load in different fouling and moisture conditions by GPR survey. By developing this technique and performing similar tests on different types of ballast and fouling materials, a criterion can be developed to detect the railroad high risk areas and predict the engineering properties of ballast by GPR surveys. This study was performed on granite ballast and breakdown fouling and has three phases: performing GPR survey …

Aging And Property Changes Of Clay Around Driven Piles, Hasian R. Zapata

Geotechnical Engineering Masters Projects

The purpose of this research was to determine how soil disturbance caused by the installation of piles (of differing types and geometries) in clay affect the short and long-term capacity of piles. Several types of piles were installed in lightly overconsolidated clay at three different test sites in Amherst, Massachusetts. Before and after pile installation, an in-situ testing program consisting of field vane shear tests was carried out around piles installed at one of the three testing sites. Undrained shear strength and water content profiles allowed for an approximate determination of changes in the behavior of the clay surrounding some …

Soil-Structure Modeling And Design Considerations For Offshore Wind Turbine Monopile Foundations, Wystan Carswell

Doctoral Dissertations

Offshore wind turbine (OWT) support structures account for 20-25% of the capital cost for offshore wind installations, making it essential to optimize the design of the tower, substructure, and foundation to the extent possible. This dissertation focuses on monopile foundations, as the vast majority (approximately 75%) of currently installed OWTs are supported by monopile structures. The objective of this dissertation is to provide information on the behavior of monopile support structures to better substantiate design and planning decisions and to provide a basis for reducing the structural material costs. In pursuit of these objectives, research is presented on the topics …

Fracture Toughness Assessment Of Shales By Nanoindentation, Yunqui Liu

Geotechnical Engineering Masters Projects

Nanoindentation has been reported as an effective tool for realizing the strength and stiffness (modulus of elasticity) of different materials including thin film materials, cementitious composites and rock or clay mineral materials. However, to the best of the authors’ knowledge, nanoscale fracture of shale materials has rarely been examined. Fracture toughness property of shale has been typically studied by observing crack growth of notched macroscale specimens subjected to flexural or tension loads. This research discusses the possible characterization of fracture toughness of shale using contact mechanics at the nanoscale. The analysis method is based on two traditional fracture toughness measurement …

The Effect Of Immediate Saline Water Curing On The Strength, Composition, And Microstructure Of Geopolymer Cement, Lindsay Duran

Geotechnical Engineering Masters Projects

The low durability and low resistance of ordinary Portland cement led to an investigation into the viability of geopolymer cement as an alternative to well cement for soil improvement in saline environments and well cement in offshore drilling and carbon sequestration projects. This thesis presents the results of a laboratory investigation into the effect of immediate saline water curing on the strength, composition, and microstructure of geopolymer cement. The experimental program began with preliminary work in designing adequate geopolymer cement and developing a curing environment that simulates offshore or underground conditions and facilitates immediate curing of cement specimens. Pure geopolymer …

Investigation Of Installation Torque And Torque-To-Capacity Relationship Of Screw-Piles And Helical Anchors, Mark Ruberti

Geotechnical Engineering Masters Projects

Installation torque has been used in the design of helical anchors (Screw-Piles) since the late 1960s. KT factors released by the manufacturer relating ultimate capacity of Screw-Piles to installation torque allow engineers to calculate a design installation torque which is necessary to achieve the design capacity in the field. These KT factors have been based on shaft geometry alone (Hoyt and Clemence 1989). Recent full-scale uplift tests in both clay and sand have shown that the traditional methods of analysis for estimating uplift capacity based on microscale tests are not representative of macroscale behavior. A soil wedge does not fully …

Study Of Minimum Void Ratio For Soils With A Range Of Grain-Size Distributions, Zhenning Yang

Geotechnical Engineering Masters Projects

Minimum void ratio or maximum packing density is an important soil property in geotechnical engineering. It apply to volume change tendency control, fluid conductivity control and particles movement.

Previous researchers have attempted to predict maximum packing density by empirical/graphic method, rock correction method, alpha method. Based on the concepts of F. de Larrard in concrete mixture research, we have developed a mathematic model that can predict the minimum void ratio for soils with a wide range of particle size.

Probability density function-lognormal distribution was tested and used to provide a reasonable representation for soils with a range of grain-size distribution. …

Hydrogeologic Characterization Of A Till Mantled Leaky Fractured Bedrock Aquifer, William Lukas

Geotechnical Engineering Masters Projects

In glaciated areas till can serve as a leaky aquitard for fractured bedrock aquifers. The characterization of a leaky till mantled fractured bedrock aquifer is presented. Multiple high resolution data sets were collected in response to unprecedented changes in the hydraulic head at a research site in eastern Massachusetts. Local scale aquifer and aquitard hydraulic conductivity, transmissivity and storativity values are determined through the analysis of purge recovery tests using Ostendorf and DeGroot (2010) and Cooper et al (1967) theories. The local scale parameters are in turn used to determine large scale aquifer transmissivity and storativity through an analysis of …

Probabilistic Analysis Of Offshore Wind Turbine Soil-Structure Interaction, Wystan Carswell

Masters Theses 1911 - February 2014

A literature review of current design and analysis methods for offshore wind turbine (OWT) foundations is presented, focusing primarily on the monopile foundation. Laterally loaded monopile foundations are typically designed using the American Petroleum Institute (API) p-y method for offshore oil platforms, which presents several issues when extended to OWTs, mostly with respect to the large pile diameters required and the effect of cyclic loading from wind and waves. Although remedies have been proposed, none have been incorporated into current design standards. Foundations must be uniquely designed for each wind farm due to extreme dependence on site characteristics. The uncertainty …