This project addresses the topic of evaluating water movement inside a hillslope using a combination of conventional and advanced geophysical techniques. While slope dynamics have been widely studied, ground water movement in hills is still poorly understood. A combination of piezometers, ground-penetrating radar (GPR), and electrical resistivity (ER) surveys were used in an effort to monitor fluctuations in the subsurface water level in a reengineered slope near Keokuk, Iowa. This information, integrated with rainfall data, formed a picture of rainfall-groundwater response dynamics. There were two hypotheses: 1) that the depth and fluctuation of the water table could be accurately sensed using a combination of monitoring wells, ground-penetrating radar and resistivity surveys; and 2) that the integration of data from the instrumentation array and the geophysical surveys would enable the characterization of water movement in the slope in response to rainfall events. This project also sought to evaluate the utility and limitations of using these techniques in landslide and hydrology studies, advance our understanding of hillslope hydrology, and improve our capacity to better determine when slope failure may occur. Results from monitoring wells, stratigraphy, and resistivity surveys at the study site indicated the presence of a buried swale, channelizing subsurface storm flow and creating variations in groundwater. Although there was some success in defining hydrologic characteristics and response of the slope using this integrated approach, it was determined that GPR was ultimately not well suited to this site. However, the use of GPR as part of an integrated approach to study hillslope hydrology still appears to hold potential, and future work to further evaluate the applicability and potential of this approach would be warranted.

Made available in DSpace on 2014-06-11T19:26:15Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-04Bitstream added on 2014-06-13T18:29:47Z : No. of bitstreams: 1 benessiuti_mf_me_bauru.pdf: 4336666 bytes, checksum: b38250d3f308f9ca935e1e148d3fa7a0 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A região das nascentes do ribeirão Guaratinguetá, localizada no contraforte da Serra da Mantiqueira, Vale do Paraíba, tem sido intensamente modificada por ações antrópicas criando condições que favorecem os movimentos de massa, princiapalmente devido à supressão da mata nativa. Estas ações, somada ao aumento a intensidade de chuvas sobre uma complexa geologia da região, têm potencializado os escorregamentos translacionais, de modo que foram registradas mais de 40 ocorrências, nas chuvas do final de 2008 e início de 2009. Neste contexto, as proposta desta dissertação é de identificar os mecanismos que geram essas instabilidades através da avaliação das características geotécnicas de dois escorregamentos característicos na bacia do ribeirão Guaratinguetá. Para isso, as atividades envolveram ensaios de laboratório e de campo. No laboratório foram realizados ensaios para a caracterização completa das amostras, ensaios de sucção, para determinação das curvas características, e ensaios de cisalhamento direto, para determinação dos parâmetros de resistência. No campo, foram determinadas as propriedades hidráulicas através do permeâmetro de Guelph e a resistência à penetração dos horizontes utilizando o Penetrômetro Dinâmico de Cone. O estudo dos possíveis processos de identificação de instabilidade foi realizado a partir de retro-análises dos dois escorregamentos estudados, através do software SLOPE/W, da GeoSlope, e de simulações de cenários, através do modelo matemático Shalstab. Nestas análises, foram consideradas diferentes hipóteses relativas à presença de água no subsolo, onde foram verificados os respectivos fatores de segurança. Os resultados das retro-análises indicam coerência entre as superfícies previstas e observadas no campo, para a condição de solo saturado acima da superfície de ruptura e solo na umidade residual... / The land degradation process as consequences of deforestation and farming activities at the northem part of the Guaratinguetá creek watershed, Paraíba Valley, is compromising the environmental balance of the region traduced by increase in the numbers of shallow landslides occurring during rain seasons. In summer 2009, more than 40 shallow landslides occurred during an intense rainfall with serious consequence for the local population. In this context, the purpose of this dissertation is to understand the mechanism that triggered the soil movement based on geotechnical investigation of two landslides in the Guaratinguetá creek watershed. The geotechnical profiles of two landslides and the hydraulic parameters were determined by field tests using Dynamic Cone Penetrometer and Guelph Permeameter. In laboratory, physical and mechanical soil properties were determined. The shear strength parameters were obtained by direct shear tests on undisturbed speciments for three initial gravimetric water contents (residual, natural and saturated). The instability process was inferrred by back-analysing these two landslides using the SLOPE/W, GeoSlope, and simulating scenarios using SHALSTAB model. These analyses took into account the physical properties and the shear strength parameters of the solis for different water contents. The predicted slip surfaces were in agreement with the observed ones when the analyses considered the soil parameters above the slip surface as saturated and the soil parameters below the slip surface as in residual water content condition. The susceptibility map using SHALSTAB were then carried out for the soil parameters for satured condition. The influence of the vegetation (root strength) was inserted in the analyses by a scale factor based onn Algebra Map Technique. The validation of the applied methodology was verified by crossing the predicted unstable... (Complete abstract click electronic access below)

Debris flows are a known hazard in southern California where growing numbers of people are moving into the urban-wildland interface, threatening lives and property. A common location to see a debris flow head scarp is the upper one-third to one-half of an unburned slope at or near the head of a first-order catchment, particularly in areas of relatively shallow soils overlying bedrock. Unburned, relatively steep slopes with gently rounded shoulders and thin soil over bedrock in southern California were investigated to determine if there is a position on these types of slopes where near-surface water levels and the associated pore pressures are relatively and consistently higher during and after rainfall events than the rest of the slope, resulting in an area of preferential shallow slope failure and debris flow initiation. It was hypothesized that this position, if it exists, would be on the upper one-third to one-half of the slope near a change from a shallower slope to a steeper slope (the slope shoulder). It was further hypothesized that elevated subsurface pore pressures at this location would contribute to it being an area of preferential shallow slope failure. The near-surface water levels at two field sites in southern California were monitored for three field seasons. In the laboratory, a meso-scale simulator was constructed and used to replicate field conditions using an adjustable artificial slope and simulated rainfall. The field research showed that areas of higher water levels can exist on the upper one-third to one-half of hillslopes meeting the designated criteria. The laboratory simulations showed elevated water levels in the same general area as the field data. Laboratory simulations also suggested that this is an area of preferential shallow slope failure. The angle of the slope influenced how long a slope took to fail and how much water was needed to do so, with gentler slopes requiring more time and approximately double the amount of water than steeper slopes.

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Orientador: George de Paula Bernardes / Banca: Eduardo Dell'Avanzi / Banca: Heraldo Luiz Giacheti / Resumo: A região das nascentes do ribeirão Guaratinguetá, localizada no contraforte da Serra da Mantiqueira, Vale do Paraíba, tem sido intensamente modificada por ações antrópicas criando condições que favorecem os movimentos de massa, princiapalmente devido à supressão da mata nativa. Estas ações, somada ao aumento a intensidade de chuvas sobre uma complexa geologia da região, têm potencializado os escorregamentos translacionais, de modo que foram registradas mais de 40 ocorrências, nas chuvas do final de 2008 e início de 2009. Neste contexto, as proposta desta dissertação é de identificar os mecanismos que geram essas instabilidades através da avaliação das características geotécnicas de dois escorregamentos característicos na bacia do ribeirão Guaratinguetá. Para isso, as atividades envolveram ensaios de laboratório e de campo. No laboratório foram realizados ensaios para a caracterização completa das amostras, ensaios de sucção, para determinação das curvas características, e ensaios de cisalhamento direto, para determinação dos parâmetros de resistência. No campo, foram determinadas as propriedades hidráulicas através do permeâmetro de Guelph e a resistência à penetração dos horizontes utilizando o Penetrômetro Dinâmico de Cone. O estudo dos possíveis processos de identificação de instabilidade foi realizado a partir de retro-análises dos dois escorregamentos estudados, através do software SLOPE/W, da GeoSlope, e de simulações de cenários, através do modelo matemático Shalstab. Nestas análises, foram consideradas diferentes hipóteses relativas à presença de água no subsolo, onde foram verificados os respectivos fatores de segurança. Os resultados das retro-análises indicam coerência entre as superfícies previstas e observadas no campo, para a condição de solo saturado acima da superfície de ruptura e solo na umidade residual... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The land degradation process as consequences of deforestation and farming activities at the northem part of the Guaratinguetá creek watershed, Paraíba Valley, is compromising the environmental balance of the region traduced by increase in the numbers of shallow landslides occurring during rain seasons. In summer 2009, more than 40 shallow landslides occurred during an intense rainfall with serious consequence for the local population. In this context, the purpose of this dissertation is to understand the mechanism that triggered the soil movement based on geotechnical investigation of two landslides in the Guaratinguetá creek watershed. The geotechnical profiles of two landslides and the hydraulic parameters were determined by field tests using Dynamic Cone Penetrometer and Guelph Permeameter. In laboratory, physical and mechanical soil properties were determined. The shear strength parameters were obtained by direct shear tests on undisturbed speciments for three initial gravimetric water contents (residual, natural and saturated). The instability process was inferrred by back-analysing these two landslides using the SLOPE/W, GeoSlope, and simulating scenarios using SHALSTAB model. These analyses took into account the physical properties and the shear strength parameters of the solis for different water contents. The predicted slip surfaces were in agreement with the observed ones when the analyses considered the soil parameters above the slip surface as saturated and the soil parameters below the slip surface as in residual water content condition. The susceptibility map using SHALSTAB were then carried out for the soil parameters for satured condition. The influence of the vegetation (root strength) was inserted in the analyses by a scale factor based onn Algebra Map Technique. The validation of the applied methodology was verified by crossing the predicted unstable... (Complete abstract click electronic access below) / Mestre

Submarine slope failure releases sediments; it is an important mechanism that changes the Earth surface morphology and builds sedimentary records. I study the mechanics of submarine slope failure in sediment that dilates under shear (dilative slope failure). Dilation drops pore pressure and increases the strength of the deposit during slope failure. Dilation should be common in the clean sand and silty sand deposits on the continental shelf, making it an important mechanism in transferring sand and silt into deep sea. Flume experiments show there are two types of dilative slope failure: pure breaching and dual-mode slope failure. Pure breaching is a style of retrogressive subaqueous slope failure characterized by a relatively slow (mm/s) and steady retreat of a near vertical failure front. The retreating rate, or the erosion rate, of breaching is proportional to the coefficient of consolidation of the deposit due to an equilibrium between pore pressure drop from erosion and pore pressure dissipation. The equilibrium creates a steady state pore pressure that is less than hydrostatic and is able to keep the deposit stable during pure breaching. Dual-mode slope failure is a combination of breaching and episodic sliding; during sliding a triangular wedge of sediment falls and causes the failure front to step back at a speed much faster than that from the breaching period. The pore pressure fluctuates periodically in dual-mode slope failure. Pore pressure rises during breaching period, weakens the deposit and leads to sliding when the deposit is unstable. Sliding drops the pore pressure, stabilizes the deposit and resumes breaching. The frequency of sliding is proportional to the coefficient of consolidation of the deposit because dissipation of pore pressure causes sliding. Numerical model results show that more dilation or higher friction angle in the deposit leads to pure breaching while less dilation or lower friction angle leads to dual-mode slope failure. As a consequence, pure breaching is limited to thinner deposits and deposits have higher relative density. / text

Failure mechanisms in large scale open pit slopes are more complex than could be considered through conventional slope design methods. Pit slope behaviour must be predicted accurately, because for very deep open pits, a small change of slope angle can have serious technical and economic consequences. Failure of hard rock slopes often involves both failure along naturally existing weakness planes and failure of intact rock. Without an advanced understanding of combined rock slope failure mechanisms, the validity of commonly applied methods of large scale slope analysis is questionable. The problem was investigated by means of a toolbox approach, in which a wide range of slope stability analysis methods were used and compared to address specific problems arising during slope design optimisation of the Cadia Hill Open Pit, NSW. In particular, numerical modelling is an advanced tool to obtain insight into potential failure mechanisms and to assist the slope design process. The distinct element method was employed to simulate complex rock slope failure, including fracture extension, progressive step-path failure and brittle failure propagation, which were previously often considered unimportant or too difficult to model. A new, failure-scale-dependent concept for the categorisation of slope failures with six categories ranging from 0 (stable) to 5 (overall slope failure) was suggested to assist risk-based slope design. Parametric slope modelling was conducted to determine the interrelationship between proposed categories and critical slope/discontinuity parameters. Initiation and progression of complex slope failure were simulated and described, which resulted in an advanced understanding of combined slope failure mechanisms and the important role of rock bridges in large scale slope stability. A graphical presentation of the suggested slope failure categories demonstrated their interrelationship to varied slope/discontinuity parameters. Although large scale slope analyses will always involve data-limited systems, this investigation shows that comprehensive, conceptual modelling of slope failure mechanisms can deliver a significantly improved insight into slope behaviour, so that associated slope failure risks can be judged with more confidence. The consideration of combined slope failure mechanisms in the analysis of large scale open pit slopes is essential if slope behaviour is to be realistically modelled.

Failure mechanisms in large scale open pit slopes are more complex than could be considered through conventional slope design methods. Pit slope behaviour must be predicted accurately, because for very deep open pits, a small change of slope angle can have serious technical and economic consequences. Failure of hard rock slopes often involves both failure along naturally existing weakness planes and failure of intact rock. Without an advanced understanding of combined rock slope failure mechanisms, the validity of commonly applied methods of large scale slope analysis is questionable. The problem was investigated by means of a toolbox approach, in which a wide range of slope stability analysis methods were used and compared to address specific problems arising during slope design optimisation of the Cadia Hill Open Pit, NSW. In particular, numerical modelling is an advanced tool to obtain insight into potential failure mechanisms and to assist the slope design process. The distinct element method was employed to simulate complex rock slope failure, including fracture extension, progressive step-path failure and brittle failure propagation, which were previously often considered unimportant or too difficult to model. A new, failure-scale-dependent concept for the categorisation of slope failures with six categories ranging from 0 (stable) to 5 (overall slope failure) was suggested to assist risk-based slope design. Parametric slope modelling was conducted to determine the interrelationship between proposed categories and critical slope/discontinuity parameters. Initiation and progression of complex slope failure were simulated and described, which resulted in an advanced understanding of combined slope failure mechanisms and the important role of rock bridges in large scale slope stability. A graphical presentation of the suggested slope failure categories demonstrated their interrelationship to varied slope/discontinuity parameters. Although large scale slope analyses will always involve data-limited systems, this investigation shows that comprehensive, conceptual modelling of slope failure mechanisms can deliver a significantly improved insight into slope behaviour, so that associated slope failure risks can be judged with more confidence. The consideration of combined slope failure mechanisms in the analysis of large scale open pit slopes is essential if slope behaviour is to be realistically modelled.

Mines have an inherent risk of geotechnical failure in both rock excavations and tailings storage facilities. Geotechnical failure occurs when there is a combination of exceptionally large forces acting on a structure and/or low material strength resulting in the structure not withstanding a designed service load. The excavation of rocks can cause unintended rock mass movements. If the movement is monitored promptly, accidents, loss of ore reserves and equipment, loss of lives, and closure of the mine can be prevented. Mining companies routinely use deformation monitoring to manage the geotechnical risk associated with the mining process. The aim of this dissertation is to review the geotechnical risk management process to optimize the geotechnical risk management analysis. In order to perform a proper analysis of slope instability, understanding the importance as well as the limitations of any monitoring system is crucial. Due to the potential threat associated with slope stability, it has become the top priority in all risk management programs to predict the time of slope failure. Datasets from monitoring systems are used to perform slope failure analysis. Innovations in slope monitoring equipment in the recent years have made it possible to scan a broad rock face in a short period with sub-millimetric accuracy. Instruments like Slope Stability Radars (SSR) provide the quantitative data that is commonly used to perform risk management analysis. However, it is challenging to find a method that can provide an accurate time of failure predictions. Many studies in the recent past have attempted to predict the time of slope failure using the Inverse Velocity (IV) method, and to analyze the probability of a failure with the fuzzy neural networks. Various method investigated in this dissertation include: Minimum Inverse Velocity (MIV), Maximum Velocity (MV), Log Velocity (LV), Log Inverse Velocity (LIV), Spline Regression (SR) and Machine Learning (ML). Based on the results of these studies, the ML method has the highest rate of success in predicting the time of slope failures. The predictions provided by the ML showed ~86% improvement in the results in comparison to the traditional IV method and ~72% improvement when compared with the MIV method. The MIV method also performed well with ~75% improvement in the results in comparison to the traditional IV method. Overall, both the new proposed methods, ML and MIV, outperformed the traditional inverse velocity technique used for predicting slope failure.

In most civil engineering projects, the risk of slope failure has to be considered for allexcavations performed until the project is completed. The risk is founded in the uncertaintiesof the geotechnical properties of the soil that the excavations are performed in. With the riskof slope failure follows the risk towards the project budget, delays versus time plan andinjures to those involved in the excavation. To prevent the aforementioned risks the SwedishGeotechnical Society, SGF, have written a report that presents a structured way to performrisk management within geotechnical projects.By performing an excavation that simulates one that would be excavated for installing pipeswithin clay, measurement have been performed on wooden sticks that has reflex tape. Thewooden sticks were placed on the head and the toe of the excavated slope, with the intentionto capture the movement of a beginning slope failure. This was performed by using theobservational method for the risk treatment in the risk management process for theexcavation. The results of the measurements in the slope toe indicates a beginning of a slopefailure. However, due to the large spread of measured results on the excavation head theresults could not be used as information for risk treatment.