Early warning of slope instability will enable evacuation of vulnerable people and timely repair and maintenance of critical infrastructure. However, currently available warning systems are too expensive for wide-scale use or have technical limitations. The acoustic emission (AE) monitoring approach using active waveguides (i.e. a steel tube with granular backfill surround installed in a borehole through a slope), in conjunction with the Slope ALARMS AE measurement system, has the potential to be an affordable early warning system for slope instability. However, the challenge has been to develop strategies to interpret and quantify deformation behaviour from measured AE. The development of an approach to quantify slope deformation behaviour from measured AE will enable the AE monitoring system to provide early warning of slope instability through detecting, quantifying and communicating accelerations in slope movement. Field monitoring and full-scale physical modelling have been conducted to characterise the AE response from the system to both reactivated slope movements and first-time slope failure. Definitive field evidence has been obtained showing AE monitoring can measure slope movements and generated AE rates are proportional to slope displacement rates, which was confirmed through comparisons with both conventional inclinometer and continuous ShapeAccelArray deformation measurements. A field monitoring case study demonstrated that the AE approach can detect very slow slope movements of 0.075 mm/day. In addition, the concept of retrofitting inclinometer casings with active waveguides to convert the manually read instrument to a real-time monitoring system has been demonstrated using a field trial. Dynamic strain-controlled shear tests on active waveguide physical models demonstrated that AE monitoring can be used to quantify slope displacement rates, continuously and in real-time, with accuracy to within an order of magnitude. Large-scale first-time slope failure experiments allowed the AE response to slope failure to be characterised. AE was detected after shear deformations of less than a millimetre in previously un-sheared material, and AE rates increased proportionally with displacement rates as failure occurred. The AE rate-displacement rate relationship can be approximated as linear up to 100 mm/hour and shear surface deformations less than 10-20 mm. At greater velocities and larger deformations the gradient of the relationship progressively increases and is best represented using a polynomial. This is because complex pressure distributions develop along the active waveguide analogous to a laterally loaded pile, and the confining pressures increase. Variables that influence the AE rate-displacement rate relationship have been quantified using physical model experiments and empirical relationships. A framework has been developed to allow AE rate-displacement rate calibration relationships to be determined for any AE system installation. This provides a universal method that can be used by practitioners when installing AE systems, to calibrate them to deliver alarm statuses/warning levels that are related to slope displacement rates. Use of this framework has been demonstrated using a case study example, and decision making protocols have been suggested that use trends in alarms with time to trigger decisions, which could be to send an engineer to inspect the slope, manage traffic, or evacuate people.

Master of Science / Department of Civil Engineering / Dunja Peric / The main objective of this study was to experimentally investigate the Mohr-Coulomb strength parameters of masonry sand mixed with varying amounts of water and lignin. Lignin is a plant-derived biomass, which is a co-product of bio-fuel production. It exhibits binding qualities when mixed with water thus making it an ideal candidate for sustainable non-traditional sand stabilization. An experimental program was devised and carried out to quantify the compaction and early age stress-strain and dilatancy responses of sand-lignin mixes. The program included sieve analysis, Atterberg limit tests, standard Proctor tests, and direct shear tests. The experimental results were used to find the cohesion and the angle of internal friction of the tested material, therefore determining the influence of the amount of lignin and water on the strength of the samples. An extensive data analysis was subsequently completed to gain deeper understanding of the underlying strength gain mechanism. It was found that the normalized cohesion benefit due to lignin is controlled by two variables; water to lignin ratio and void ratio. The lignin and water create a paste, which provides particle bonding at the contacts of sand particles, thus increasing the stress-bearing cross sectional area. Increase in the portion of cross-sectional area occupied by water and lignin normalized by gravimetric lignin content, increases the normalized cohesion up to a point, while the cohesion per gravimetric lignin content decreases with the increasing area ratio. This in turn indicates that cohesion increases only up to 6% of lignin, beyond which it starts to decrease due to the presence of too much fine material within the pores. The presence of lignin in the pores consistently decreases the angle of internal friction. However, for all configurations with lignin tested herein, cohesion was larger than for dry sand, thus indicating strength benefits at low confining pressures or at normal stresses below the so-called limiting normal stress.

To minimize coastal land loss and create new land, dredged sediment has been in use in coastal Louisiana during the last several years. Engineering properties and material characteristics of dredged material are input parameters in several mathematical models used to predict the long-term hydrodynamic behavior of the coast. Therefore, proper characterization of the dredged material is of utmost importance in the correct design of coastal restoration and land creation projects. The sedimentation characteristics of the dredged material, among other factors, depends on the (a) grain size distribution of the dredged material, (b) salinity (fresh, brackish, or saltwater environment) of the composite slurry, and (c) concentration of the solid particles in the slurry. In this research, dredged sediments obtained from actual coastal restoration projects were characterized. Furthermore, the effects of grain size distribution, salinity and solid particle concentration on sedimentation characteristics have been evaluated.

There is a demand to reestablish a healthy coastal ecosystem by rebuilding wetlands with river diversion or dredged sediments in coastal Louisiana. Land building projects using dredged sediments from adjacent canals and river beds, can be used to protect the coastal properties and infrastructure systems from flood and storm surges. To predict the sediment’s long term behavior, math models require input parameters based on sediment engineering properties and material characteristics. Proper characterization is critical for accurate design of coastal restoration projects. The dredge material sedimentation characteristics and their effects on the settlement rate of suspended solid particles and underlying foundation soil depend, among other factors, on the grain size distribution of the dredged material, salinity of the composite slurry, and slurry solid particles concentration. This research evaluated the effects of grain size distribution, salinity, and initial solids concentration on the sedimentation characteristics of fine grained dredged sediments in Coastal Louisiana.

No description available.

Lunar soil, defined as the finest part of the lunar regolith which covers the entire surface of the Moon, has shown to have remarkable shear strength properties, highlighted by the clearly visible effects of soil cohesion. The main objective of this thesis is to unveil the physical explanations causing this unusual soil behaviour in a waterless, airless, lunar environment. Ultra-High Vacuum (UHV), in particular, is considered responsible for increasing the strength of surface energy forces due to lunar soil outgassing. In turn, the presence of surface energy forces, arising from van der Waals intermolecular forces, is thought to alter the mechanical properties of lunar soil. A particle-based microscopic approach by means of the Discrete Element Method (DEM) was utilised to investigate the effects of surface energy forces on the macroscopic soil be- haviour. A micro-mechanical contact model, based on the JKR theory, was selected to describe the inter-granular behaviour between lunar soil particles. Physical and geometrical parameters typical of lunar soil were employed. Several triaxial tests were run to identify a link, if any, between the microscopic surface energy parameter and the macroscopic soil cohesion, which was interpreted as a true soil cohesion. In addition, very low stress levels and high soil densities were simulated in order to take into account the low gravitational field and the high state of soil compaction caused by continuous meteorite impacts on the Moon. Results from triaxial tests were analysed at both the peak and critical state. It was found that in the ideal case of perfectly spherical grains, the presence of adhesion is a source of noticeable macroscopic soil cohesion. However, no influence was observed in terms of macroscopic friction angle. Furthermore, a brittle macroscopic soil behaviour was revealed, owing to the simulated inter-granular chemical bonds and the very low stress conditions applied. Finally, similar to the behaviour of cemented sands, very little cohesion was recorded at the critical state. Subsequently, particle shape effects were investigated by complementing the numerical model with a simple form of inter-particle rolling resistance. Simulations were also run with non-convex grains of increasing geometrical complexity in order to simulate more realistically the irregular shapes of lunar soil grains. In both cases, the interplay of surface energy forces with particle shape effects resulted in even higher shear strength, with predictions similar to the estimates of shear strength for real lunar soil. Once again, the peak strength was dominated by macroscopic cohesion which, on the other hand, was hardly observable at the critical state, confirming the tendency observed from spherical grains. Finally, the practical implications of the above findings were discussed in terms of bearing capacity, trafficability and slope stability on the lunar surface. In particular an analytical approach, based on the bearing capacity problem, was devised to study the performance of a rigid wheel rotating on a lunar terrain and operating under different dynamic conditions.

En av Sveriges största industrier är skogsindustrin. Att sköta stora skogsinnehav medför vissa svårigheter, t.ex. så kan i händelse av en storm kan delar av skogen bli vindfälld. Det är då viktigt att upptäcka och ta bort de fallna träden eftersom det annars kan leda till granbarkborrangrepp. En metod för att upptäcka den vindfällda skogen är att ta flygbilder över området, vilket kan bli både dyrt och tidsödande. Därför testas i denna studie detektering av stormfälld skog i Sentinel 2 bilder. Sentinel 2 har valts ut eftersom den har både en hög spatial- och temporal upplösning samt att bilderna är tillgängliga gratis. Tidigare studier på området har använt satellitbilder med en lägre spatial upplösning eller data från andra typer av fjärranalys. De flesta av dessa metoder är ganska komplexa eller väldigt specifika för ett särskilt fall. Metoden som tas fram i denna studie ska vara enkel att implementera även för personer utan någon djupare kunskap inom fjärranalys. Bilddifferens med olika index såsom NDVI, NDMI och GreenNDVI testas. Även oövervakad klassificering testas. Noggrannheten har utvärderats med två-stegs metoden med en noggrannhet på 85 % men även en konfusionsmatris tillämpas för att utvärdera noggrannheten av områden där ingen förändring inträffat. Bilddifferens med NDVI och GreenNDVI klarar två-stegs testet när ett statistiskt bestämt tröskelvärde används, NDVI får högst användarnoggrannhet. Felmatrisen visar dock att det finns många stormfällen i ytorna som blivit klassade som ingen förändring, den oövervakade klassificeringen får inte det problemet i samma utsträckning. Bilddifferens i NDVI med statistiskt bestämt tröskelvärde bedöms vara den mest effektiva metoden för att detektera stormfälld skog.

O jet grouting é uma das técnicas de tratamento de solos mais utilizadas em todo o mundo. Consiste em jatear uma calda de cimento a altíssima velocidade no subsolo, com ou sem a adição de água e/ou ar comprimido. Os fluidos são injetados através de minúsculos bicos posicionados na extremidade de uma composição especial de hastes, que giram à velocidade constante enquanto sobem lentamente em direção à superfície do terreno. O jato remove e mistura o solo, produzindo um corpo consolidado de formato aproximadamente cilíndrico (a coluna de jet grouting). Variando os parâmetros operacionais (pressão de bombeamento, quantidade e diâmetro dos bicos, velocidade de extração das hastes, relação água/cimento da calda) e em função do tipo de solo, podem ser obtidas colunas de diâmetros variáveis dentro de um amplo intervalo. Na busca do diâmetro desejado, a escolha dos parâmetros de tratamento é feita atualmente com base em regras empíricas nem sempre pertinentes, causando muitas vezes o fracasso do tratamento ou, ainda, tornando-o excessivamente oneroso. Esta tese de doutorado apresenta um método simplificado para a previsão do diâmetro das colunas de jet grouting (sistema monofluido). Conjugando a análise racional do fenômeno físico de interação jatosolo (Modoni et al., 2006) à facilidade de aplicação característica dos métodos empíricos, propõe-se uma ferramenta ágil para a escolha da combinação mais adequada dos parâmetros de tratamento. / Jet grouting is one of the most popular ground improvement techniques all over the world. The method is based on high-speed grouting of water-cement mixtures and/or other fluids (air, water) into the subsoil. The fluids are injected through small diameter nozzles placed on a grout pipe, which is continuously rotated at a constant rate and slowly raised towards the ground surface. The jet removes and mixes the soil, producing a cemented body of quasi-cylindrical shape (the jet grouting column). Varying the operational parameters (grout pressure, number and diameter of the nozzles, monitor lifting rate, water-cement ratio of the grout) and as a function of the soil type, columns of variable diameters can be obtained in a wide interval. Currently, in search of the required diameter, the choice of the operational parameters is done on the basis of empirical rules not always relevant, causing very often the failure of the treatment or making it excessively onerous. This thesis presents a simplificated method for the prediction of the column diameter (single fluid system). Conjugating the rational analysis of the physical phenomenon of jetsoil interaction (Modoni et al., 2006) to the typical easiness of empirical methods application, an agile tool is proposed for the choice of the most appropriate combination of the operational parameters.

Tradicionalmente, a análise de problemas da Engenharia Geotécnica esteve apoiada nos conceitos da Mecânica dos Solos, desenvolvida por Terzaghi, na Teoria da Elasticidade e nas teorias de análise limite. Este trabalho busca explorar uma abordagem que deveria ser mais utilizada neste tipo de problema, voltada à utilização de modelos constitutivos mais completos para a caracterização dos solos. Os aspectos teóricos e práticos deste tema são discutidos, dando destaque especial para sua implementação e seu desenvolvimento no âmbito do Método dos Elementos Finitos. Seguindo uma breve discussão sobre as principais características dos solos, os modelos constitutivos mais utilizados na Engenharia Geotécnica são apresentados. Em particular, os modelos Mohr-Coulomb e Cam-clay. Na seqüência são definidas as equações de Biot para o adensamento, objetivando sua utilização em um programa de elementos finitos, no caso o ADINA. Na segunda parte do trabalho, três estudos são realizados. O primeiro busca comparar os resultados obtidos por Nader (1993), para um solo siltoso submetido a diferentes trajetórias de tensão, com aqueles fornecidos pelos modelos Mohr–Coulomb e Cam-clay modificado, indicando os principais desvios encontrados. Na seqüência, analisa-se o problema de determinação do coeficiente N para obtenção da capacidade de carga do solo, no caso de sapatas corridas. Neste estudo, realizado através do ADINA, o modelo Mohr–Coulomb é utilizado, e a influência do ângulo de atrito (), do ângulo de dilatação () e da rugosidade da face inferior da sapata são pesquisadas. As dificuldades numéricas presentes quando a lei de fluxo é não associada são, também, discutidas. Finalmente, o problema de escavação de valas é discutido. O caráter evolutivo deste tipo de análise, o estudo do adensamento e a pesquisa da influência do coeficiente de empuxo em repouso (Ko) na resposta do problema são explorados. Neste caso, o modelo Cam-clay modificado é escolhido para realização de um conjunto de análises. A partir destes três estudos pode-se perceber a importância de utilizar modelos constitutivos mais representativos do comportamento dos solos, para reproduzir mais satisfatoriamente sua resposta. Neste trabalho cumpriu-se, também, o objetivo de confirmar a eficiência do ADINA como ferramenta computacional para resolução de problemas relevantes da Engenharia Geotécnica. / Traditionally, the solution of Geotechnical Engineering problems was supported by Soil Mechanics concepts, developed by Terzaghi, Elasticity Theory and the limit analysis theories. This work tries to explore an unusual approach, which concerns the use of complete constitutive models for soils description. Both theoretical and practical aspects of the theme are discussed, with special attention devoted to the Finite Element implementation and development. Following a brief discussion about soil characteristics, the constitutive models usually used on Geotechnical Engineering are presented. In particular, the Mohr-Coulomb and Cam-clay models are explored in details. The theoretical presentation is concluded by establishing the Biot equations for consolidation problems, observing its using on a finite element program, ADINA for instance. On the second part of the work, three studies are carried out. The first one tries to compare the triaxial response of a silty soil when subjected to different stress paths, described by Nader (1993), with the results achieved when the Mohr-Coulomb and the modified Cam-clay models are used, showing the main differences. After that, computations of the bearing-capacity factor N have been made in order to evaluate the bearing-capacity for strip foundations. On this study, also solved in ADINA, the Mohr-Coulomb model is used, and the friction angle (), dilation angle () and footing roughness effects on the response are investigated. It is also discussed the numerical difficulties observed when non-associative conditions are applied. Finally, the retaining wall problem is explored. The evolution aspect of the problem, the consolidation study and the pre-excavation earth pressure coefficient (Ko) effects are also discussed. On this case, the modified Cam-clay model is chosen for several analyses. From these three studies it was noticed that in order to reproduce satisfactorily soil response, it is fundamental to chose representative constitutive models of soil behaviour. Also, this work accomplished the aim of confirming ADINA as an efficient skill to relevant Geotechnical Engineering problems solution.

Geotechnical engineers are commonly faced with the need to perform ground improvement techniques to achieve the necessary bearing capacity for a project. Some of the most common techniques involve the excavation and replenishment of problematic geomaterial with one of better quality. Common projects, such as road embankments and retaining walls, also require the selection of backfill material. The guidelines for selecting backfill material are typically limited to complying with certain gradation bands, relative densities and allowable fines content. Round-grained silica sand, and beach sand from Boca Raton, FL, were used to generate a total of 16 binary granular mixtures containing different amounts of finer material, for which a series of direct shear tests were conducted. Based on the experimental results, it may be possible to provide an alternative criteria for selecting backfill material based on granulometric parameters and the amount of finer material. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection