An experimental and analytical study of various soil slopes in laboratory conditions

Thesis (Master)--Izmir Institute of Technology, Civil Engineering, Izmir, 2009Includes bibliographical references (leaves: 134-147)Text in English; Abstract: Turkish and Englishxviii, 147 leavesSlope stability is a significant subject of geotechnical engineering. Slope failures triggered by rainfall are causing considerable damage and loss of life every year throughout the world. Especially at dry seasons when the rainfall is scarce, the ground can develop considerable amount of suction and this improves the shear strength of the soil. In rainy season, when rainfall infiltrates into ground, suction decreases, while the shear strength also reduces, which may lead to slope instability. One of the principle objectives of this study is to represent the development of soil-water interaction modeling system (SWIMS) at IYTE. Using this system; effects of 3 different parameters, such as: initial water content, soil density, slope angle on modelling unsaturated slope stability were studied. Moreover, effects of infiltration on slope stability in shallow landslides, where it is assumed that the ground water tables are located at significant depths, were examined.In this thesis study, 12 main slope model experiments were completed in laboratory conditions, using Soil-Water Interaction Modelling System (SWIMS) by varying 3 different parameters. Result of studies shows that slope angle is the most important parameter affecting slope stability. Furthermore, parameters such as; soil density, degree of relative compaction of soil and initial water content affects slope stability, while these parameters also affect slope surface erosion and infiltration depths. In addition to experimental studies conducted in laboratory conditions with the 12 main slope model experiments, slope stability analyses to find FOS were performed by using Plaxis V9 (2D) finite element program (FEM), which uses shear strength reduction (SSR) technique and infiltration analyses using the Plaxflow module to model the rainwater infiltration into slope soil were performed. The FEM analyses show conforming results with the actual observations made using the tested soil model in laboratory conditions

Modelling the effects of soil variability on stability analysis of natural slopes in Durban.

Masters Degree. University of KwaZulu- Natal, Durban.Slope failure occurs due to various factors, one of the most significant being that of soil variability in a slope and associated geological threats such as unconsolidated soils, settlement, groundwater seepage and infiltration. The analysis of slope stability should incorporate and analyse the interactions between slope configuration, shear strength resistance, pore-water pressure and water conditions of a slope. This study focuses on the causal effects and slope stability of two natural slopes in Durban, KwaZulu-Natal. Large parts of the study area are underlain to great and varying depths by problem soils, namely the Berea Red Sands. These are dune soils, deposited by ancient wind activity, that are found parallel to the east coast of Durban. The Berea Red “sands” vary greatly in soil type ranging from fine grained sands to silts and clays. Those of looser consistency are known to undergo significant settlement under loading, and also with water interaction. The clay and silt varieties are known to exhibit heave under the same circumstances. In some cases, liquefaction of Berea sands may occur due to the loss of soil structure upon water introduction into the soil mass. The aim of this research is to formulate and compare the stability of the two slopes under different water conditions in the form of Factors of Safety and Probabilities of Failure, using RocScience© software. Site investigations were conducted to classify and collect soils, which were then put through rigorous laboratory testing. The results from testing were applied where possible to the modelling software and a host of important findings were made. The liquefaction potential of poorly graded, uniform Berea sands was observed first-hand on site, in the laboratory and again during slope stability analyses. As anticipated, the slope stability of both sites proved to increase reaching “optimum” conditions due to the positive effects of matric suction. Upon increasing water conditions further or saturating the slope, increasing incidences of failure and instability occurred due to the loss of matric suction and cohesion. This instability can also be attributed to the proven decrease in shear strength properties of the soil, cohesion and internal friction, leading to loss of shear strength in the slope. The positive effects of matric suction were further proven when the slope of Site A that considered matric suction (in the form of an air entry value), exhibited a slightly higher FOS and improved slope stability than the one without. The results and conclusions of this research project prove the importance of investigating a soils variability and the subsequent slope reaction under varying moisture conditions. These are key factors to consider prior to civil construction on problem soils, so as to mitigate major failures and the consequences thereof

Environmental and material controls on desiccation cracking in engineered clay embankments

PhD ThesisDesiccation cracking is a natural phenomenon commonly associated with drying of expansive soils. The role of cracks in surface permeability increase and overall deterioration of infrastructure slopes makes it a key factor in climate-related slope instability processes. Despite this significance, the controls on soil cracking in engineered slopes still represent a poorly understood area. In this study, soil cracking behaviour in clay embankments exposed to cyclic wetting and drying was investigated to improve understanding of this phenomenon for application in geotechnical practice. A complimentary field and laboratory study was undertaken, approaches commonly conducted in isolation in the literature. The field program involved direct investigation of natural crack development in a heavily instrumented, clay embankment (BIONICS, Newcastle University). Crack morphology parameters were quantified under engineering, meteorological and near surface soil hydrological conditions to understand how temporal change influences these. Laboratory experimentation was carried out on materials representative of typical embankment fills and construction methods in the UK in a bespoke climate control system. Time series photographs of the crack networks were analysed using image processing technique to compare their intensities across the experimental conditions. Syntheses of field and laboratory results show the influence of factors related to the embankment geometry (i.e. slope aspect, layer thickness), material properties (i.e. soil density and plasticity) and environmental condition (i.e. wetting and drying cycles) on the cracking behaviour in engineered clay slopes. The sensitivity of cracking intensity under given climate conditions critically relates to the rate of moisture loss and the material strength. Overall, this research presents how newly gained understanding of cracking can potentially impact upon improved construction techniques of engineered clay embankments and the susceptibility of historic embankments constructed to lower densities to climatic changes, including how drying/wetting cycles can exacerbate crack development.Akwa Ibom State University, TETFUN

Creep and plasticity parameter determination of sand-TDA mixtures for the purpose of constitutive modeling

L'objectif de cette étude est le développement d'une base de connaissances pour la conversion d'un déchet problématique en matériau de construction pour des projets de génie civil. Le phénomène de mécanisation des sociétés, la croissance rapide de la population, ainsi que le développement du réseau de transport terrestre par la construction des nouvelles routes et autoroutes ont entraîné une croissance sans cesse de l'industrie automobile à travers le monde et par conséquent l'accumulation de gros volumes de pneus usés. Chaque année, les Américains et les Canadiens éliminent en moyenne environ 300 millions de pneus (respectivement 250 et 30 millions de pneus), ce qui a accru les préoccupations environnementales liées à l'élimination de ces déchets non biodégradables et polluants. Par conséquent, la gestion des déchets de pneus nécessite des méthodes innovantes et efficaces d'élimination et de réutilisation des pneus. Un pneu est généralement composé de trois composants principaux, notamment le caoutchouc, le métal et le tissu. Le cycle de vie des pneus est généralement composé de cinq étapes principales : extraction, production, consommation, collecte des pneus usagés et enfin la gestion des déchets qui comprend les sites enfouissement et la récupération. Grâce à l'un des processus de récupération, les pneus usagés sont découpés en différentes formes et tailles appelées agrégats dérivés de pneus (ADP). Actuellement, des efforts considérables sont en cours au niveau mondial pour recycler les pneus usagés sous forme d'agrégats dérivés de pneus (ADP) à des fins d'ingénierie civile et géotechnique différentes. En tant que géo-matériau, les formes déchiquetées et granulées des pneus usés sont généralement mélangées avec du sable et / ou du limon pour former ce que l'on appelle communément des mélanges sol-ADP. En raison de leur faible poids, de leur bon drainage, de leurs propriétés d'isolation thermique satisfaisantes, de leur atténuation des vibrations, etc., les géo-matériaux d'ingénierie contenant du ADP sont devenus intéressants pour les ingénieurs concepteurs. Cependant, en raison de leur faible module d'élasticité, les mélanges ADP-sol présentent une compressibilité significative par rapport à celle des sols conventionnels. Spécifiquement, la compressibilité excessive des mélanges sol-ADP, qui est composé à la fois de la partie immédiate et celle dépendante du temps est extrêmement difficile à cerner dans les applications où de lourdes charges sus-jacentes sont appliquées. Afin de maximiser leur fiabilité et de minimiser la possibilité de ruptures, il est nécessaire d'avoir une compréhension précise du comportement mécanique (par exemple, élastique, plastique et fluage) des mélanges sol-ADP lorsqu'ils sont soumis à une charge. La présente étude comprend deux phases. Les phases consistent en un programme expérimental qui a été mené pour déterminer les paramètres essentiels d'élasticité, de plasticité et de fluage des mélanges granulés ADP-sable. Des simulations MEF ont ensuite été réalisées aux fins de la validation des résultats des essais. Les valeurs des paramètres obtenus grâce aux observations expérimentales ont été utilisées dans le développement de modèles de comportement qui sont proposés pour les comportements de fluage et de déformation plastique des mélanges sable-ADP. En ce qui concerne le fluage, les résultats indiquent une phase de fluage primaire qui est rapidement passée à une phase de fluage stationnaire secondaire, n'atteignant jamais la phase tertiaire. Il a également été observé que l'ampleur de la déformation de fluage est fortement affectée par la teneur en fraction volumique de l’ADP et la charge appliquée. Cette observation a conduit à l'adoption de la loi Norton-Bailey comme modèle constitutif possible du fluage des mélanges ADP-sable. En outre, un modèle complet de comportement sol-ADP doit également englober la plasticité. Ceci a été réalisé grâce au développement d'un modèle d'état critique, basé sur les paramètres de plasticité obtenus expérimentalement des tests triaxiaux. Les courbes de contrainte déviatorique en fonction de la déformation axiale obtenues avec le modèle d'état critique ont capturé la réponse élastoplastique non linéaire obtenue dans les essais. Les résultats ont indiqué que le niveau de résistance au cisaillement dépend fortement de l'angle de frottement à l'état critique qui à son tour dépend de la teneur en ADP. Pour les mélanges ADP-sable utilisés dans cette étude, l'effet de la teneur en ADP démontre un renforcement de la matrice de sable. Cependant, ce renforcement diminue à mesure que la teneur en ADP augmente.The aim of this study is the development of a knowledge base for the conversion of a problematic waste product into a construction material for civil engineering projects. The phenomenon of mechanization of the societies, rapidly growing population, and also the development of the land transportation network through the construction of the new roads and highways have resulted in an unceasingly growing of auto industry across the world and consequently accumulation of large volumes of scrap automobile tires. Every year Americans and Canadians together average disposal of approximately 300 million tires (respectively 250 and 30 million tires) which consequently has increased environmental concerns over the disposal of such non-biodegradable and pollutant waste materials. Hence, scrap tire management requires innovative and efficient methods of tire disposal and reuse. A tire is generally made from three main components including rubber, metal, and fabric. The tire life cycle is generally composed of five main stages including extraction, production, consumption, collection of used tires and finally waste management which is comprised of landfilling and recovery. Through one of the recovery processes, scrap tires are cut into different shapes and sizes called tire-derived aggregate (TDA). Presently, global extensive efforts are underway in order to recycle the waste tires in the form of tire-derived aggregate (TDA) for different civil and geotechnical engineering purposes. As a geomaterial, usually the shredded and granulated forms of scrap tires are mixed with sand and/or silt to form what is commonly referred to as soil-TDA mixtures. Due to their lightweight, good drainage, satisfactory thermal insulation properties, vibration mitigation, etc., engineered geomaterials containing TDA have become of interest to design engineers. However, due to their low elastic modulus, TDA-soil mixtures exhibit significant compressibility compared to that of conventional soils. Specifically, the excessive compressibility of soil-TDA mixtures which is composed of both immediate and time-dependent portions is extremely challenging in such applications wherein heavy overlying loads are applied. In order to maximize their reliability and to minimize the possibility of failures, it is necessary to have an accurate understanding on the mechanical behavior (e.g., elastic, plastic and creep) of the soil-TDA mixtures when subjected to loading. The present study consists of two phases. These phases consist of an experimental program that was conducted to determine the elastic, plastic, and creep parameters of TDA-sand granulated mixtures. FEM simulations were subsequently conducted for the purposes of test result validation. Values of the parameters obtained through the experimental observations were used in the development of constitutive models which are proposed for the creep and plastic deformation behaviors of the sand-TDA mixtures. In regard to creep, the results indicate a primary creep phase that rapidly transitioned into a secondary stationary creep phase, never attaining the tertiary phase. It has been also observed that the magnitude of the creep strain is strongly affected by the TDA volume fraction content and the applied load. This observation conducted the adoption of the Norton-Bailey law as a possible constitutive model for creep of TDA-sand mixtures. Furthermore, a complete model of soil-TDA behavior must also encompass plasticity. This was achieved through the development of a critical state model, based on the experimentally obtained plasticity parameters of triaxial tests. The calculated deviatoric stress versus axial strain curves obtained with the critical state model captured the non-linear elastoplastic response obtained in the tests. Results indicated that the level of the shear strength is highly dependent on the critical state friction angle which in turn depends on the TDA content. For the loose TDA-sand mixtures used in this study, the effect of the TDA content demonstrates a reinforcement of the sand matrix. However, this reinforcement diminishes as the TDA content increases

Numerical analysis of evapotranspiration and its influence on embankments

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Groundwater flow through the test dike constructed with dredged materials

Nella tesi si è studiato la filtrazione attraverso un corpo arginale sperimentale costruito nei pressi di Danzica, in Polonia. Si sono eseguite delle analisi agli elementi finiti per valutarne la stabilità in condizioni stazionarie e non e si sono, infine, confrontati i risultati ottenuti con quelli misurati in sito durante una campagna di indagine

DEVELOPMENT OF A DECISION-MAKING TOOL FOR PREDICTION OF RAINFALL-INDUCED LANDSLIDES

Landslides are frequently observed in mountainous places following prolonged periods of rain, frequently resulting in substantial topography changes. They pose a significant risk to human lives and the built environment globally, particularly in areas prone to excessive rainfall. While slope failures can occur because of human-caused factors such as slope loading or toe cutting for construction purposes, many failures occur because of rainfall penetrating an otherwise stable slope. A greater understanding of the characteristics and mechanics of landslides is consequently critical for geotechnical research, particularly in evaluating prospective mitigation strategies. The potential of slope failure is a primary consideration when assessing the risk associated with landslide movement. The current research seeks to develop a real-time decision-making tool for rainfall-induced landslides that enables users to compare governing parameters during intense rainfall, comprehend the in-situ stability condition, and therefore assure safety. The first section of the study employs a one-dimensional transient infiltration analytical solution (Yuan and Lu 2005) to evaluate seasonal variations in soil hydrologic behavior. The one-dimensional transient infiltration analytical solution enables better control and flexibility of the soil-water characteristic curve’s transient infiltration equations and fitting parameters. Due to the model\u27s ability to determine fitting parameters, it was possible to calibrate it using in-situ soil hydrologic behavior. The second section of the study will examine how a slope behaves under seasonal rainfall variation utilizing soil hydrologic and mechanical techniques. The case study is based on data collected from a true monitored slope. Two years of monitoring were conducted on the slope. Throughout this time, the place experienced seasonal drying and wetting. Field hydrologic and deformation sensors were installed during the monitoring period. A finite element program was used to generate the monitored slope utilizing in situ slope geometry and initial condition data. Following that, the hydrologic and deformation reactions of the soil were investigated. At two previously reported slope locations, behavioral analysis is conducted. The final section of the study proposes a model for projecting the sub-surface’s volumetric water content using observations of surface rainfall and evapotranspiration. Initially, the prediction model was created using the location of a previously reported site. The prediction model was validated and then tested in six distinct Kentucky locations. The six locations lacked in-situ measurements of soil hydrologic and geotechnical parameters. As a result, Soil Active and Passive Moisture (SMAP) and Web Soil Survey were used to collect soil hydrologic and geotechnical data for the test locations. Combining the data with SMAP\u27s soil hydrology data resulted in the establishment of a safety factor for the test sites. On increasing competitive advantage for member firms. Firm-level outcomes and inter-organizational relationship structures related to network involvement were investigated

Wadi Flash Floods

This open access book brings together research studies, developments, and application-related flash flood topics on wadi systems in arid regions. The major merit of this comprehensive book is its focus on research and technical papers as well as case study applications in different regions worldwide that cover many topics and answer several scientific questions. The book chapters comprehensively and significantly highlight different scientific research disciplines related to wadi flash floods, including climatology, hydrological models, new monitoring techniques, remote sensing techniques, field investigations, international collaboration projects, risk assessment and mitigation, sedimentation and sediment transport, and groundwater quality and quantity assessment and management. In this book, the contributing authors (engineers, researchers, and professionals) introduce their recent scientific findings to develop suitable, applicable, and innovative tools for forecasting, mitigation, and water management as well as society development under seven main research themes as follows: Part 1. Wadi Flash Flood Challenges and Strategies Part 2. Hydrometeorology and Climate Changes Part 3. Rainfall–Runoff Modeling and Approaches Part 4. Disaster Risk Reduction and Mitigation Part 5. Reservoir Sedimentation and Sediment Yield Part 6. Groundwater Management Part 7. Application and Case Studies The book includes selected high-quality papers from five series of the International Symposium on Flash Floods in Wadi Systems (ISFF) that were held in 2015, 2016, 2017, 2018, and 2020 in Japan, Egypt, Oman, Morocco, and Japan, respectively. These collections of chapters could provide valuable guidance and scientific content not only for academics, researchers, and students but also for decision-makers in the MENA region and worldwide