Thesis (Ph. D.)--University of Canterbury, 2006. / Typescript (photocopy). Four maps in pocket. Includes bibliographical references (leaves 224-243). Also available via the World Wide Web.

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

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

A compreensão dos condicionantes deflagradores de movimentos de massa é importante na medida em que a partir do entendimento desses é possível prevenir ou mitigar desastres naturais em determinada região. No caso do município de Baixo Guandu-ES, mais de 1200 cicatrizes de deslizamentos foram fotointerpretadas e posteriormente checadas em trabalhos de campo. Segundo informações da Defesa Civil Municipal a deflagração desses eventos se deu, majoritariamente, em 25 de dezembro de 2013 durante uma forte precipitação, causada por um corredor de umidade que estacionou sobre a região pela ação de uma Zona de Convergência do Atlântico Sul. Cerca de 77% das cicatrizes mapeadas estão em encostas com declividade não superiores a 30º. Até o dia 23 de dezembro, apesar do acumulado de chuva de mais de 600 milímetros, nenhum ou pouco evento de movimentações de massa haviam ocorrido no município. As análises mostraram que a região com maior quantidade de cicatrizes observada é coincidente com a área onde o acumulado de chuva entre os dias 23/12/2013 e 24/12/2013 (dois dias antes de ocorrer os deslizamentos) foi de mais de 120 milímetros. Dentre as condicionantes estudadas, o principal agente deflagrador para os movimentos de massa que atingiram região de Baixo Guandu-ES foi a chuva de dois dias antes dos eventos, onde o solo já se encontrava quase saturado e as forças atuantes estavam praticamente iguais as forças de resistentes do maciço. / The knowledge of the triggering factors of mass movements is important for the prevention and mitigation of natural disasters in a particular region. In the case of the municipality of Baixo Guandu-ES, more than 1200 sliding scars were photointerpreted and later assessed in field work. According to information shared by the Municipal Civil Defense Office, the outbreak of these events had occurred mainly on December 25, 2013 during a heavy rainfall, caused by a humidity corridor that parked over the region by the action of a South Atlantic Convergence Zone. About 77% of the scars mapped are located on slopes not exceeding 30º. Until December 23, despite accumulated rain of more than 600 millimeters, no mass movement event had occurred in the city. Data revealed that the region with the highest number of scars coincides with the area where the accumulated rainfall between 12/23/2013 and 12/24/2013 (two days before landslides) was more than 120 mm. Among the potential variables studied, the main deflagrating agent for the mass movements that reached the Baixo Guandu-ES region was the rainfall of two days before the events; since the soil was already almost saturated and the driving forces were practically equal to the resistance forces.

More than 1100 debris flows were mobilized from shallow landslides during a rainstorm from 9 to 13 September 2013 in the Colorado Front Range, with the vast majority initiating on sparsely vegetated, south facing terrain. To investigate the physical processes responsible for the observed aspect control, we made measurements of soil properties on a densely forested north facing hillslope and a grassland-dominated south facing hillslope in the Colorado Front Range and performed numerical modeling of transient changes in soil pore water pressure throughout the rainstorm. Using the numerical model, we quantitatively assessed interactions among vegetation, rainfall interception, subsurface hydrology, and slope stability. Results suggest that apparent cohesion supplied by roots was responsible for the observed connection between debris flow initiation and slope aspect. Results suggest that future climate-driven modifications to forest structure could substantially influence landslide hazards throughout the Front Range and similar water-limited environments where vegetation communities may be more susceptible to small variations in climate.

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No description available.

Understanding the deformation mechanisms and the impact forces generated by landslides on structures is essential for risk assessment and improving the design of mitigation measures. This thesis studies the effect of different basal sliding characteristics of biplanar compound landslides on the post-failure mechanics and the interaction with rigid structures. The Material Point Method (MPM), an advanced numerical tool capable of simulating large deformations, captures the whole instability and the impact process. A simple geometry of a biplanar compound landslide is considered with two different types of biplanar slope transitions along the basal surface – sharp transition (or "kink" geometry) and curved transition (with different radii). A comprehensive parametric study with more than 280 simulations is performed to analyze the landslide post-failure behavior in terms of the radii of transition, the basal friction angle, the distance to the rigid wall, the roughness of the rigid wall, and the scale of the landslide. The results are presented in terms of maximum impact force on the rigid wall and final runout (in the absence of the wall). Results show that the basal characteristics impact the landslide kinetics and energy dissipations, which in turn, influence the impact forces on the rigid wall as well as the final runout of the landslide. The basal friction amplifies the influence of slope geometry on maximum impact forces. In addition, the maximum impact force from numerical results is compared with the predictions from existing semi-empirical approaches. Finally, a preliminary empirical framework is proposed to incorporate the effects of basal sliding characteristics of compound landslides into predicting impact forces on retaining walls. / Master of Science / Landslides and slope failures are a major problem in the geotechnical field that causes significant damage to lives and infrastructure worldwide. It, therefore, becomes essential to understand the mechanisms and the deformation patterns from the standpoint of assessing the impact on infrastructure near the landslide. This thesis studies the effects of the geometry of compound landslides on the maximum impact forces exerted on a rigid structure at a given distance from the landslide. It uses the Material Point Method (MPM), a numerical method that simulates problems involving large deformations. MPM allows the study of the entire instability process from failure initiation to final runout and impact against barriers. Several theoretical models of generic landslides of different radii of slope transition, friction on the sliding surface, and different distances from the wall are presented to study the effects of these parameters on the maximum impact force exerted on the wall. Along with this, the effects of the scale of a landslide on the impact forces are also analyzed. Based on the results, an empirical framework is proposed to help calculate maximum impact forces on a vertical rigid wall while incorporating the basal failure surface characteristics.

This MSc thesis reprocessed seismic data collected at a site near the Gota River in 2011, focusing on two lines. The two seismic lines ran through a landslide scar zone for a total length of 1 km, both of which used dynamite as the seismic source. The thesis used a standard seismic processing tool for this purpose, with the main processes including static corrections, bandpass filtering, velocity analysis, NMO corrections, stack, and migration. Analysis of the resulting images reveals a coarse-grained layer near the surface, which is in contact with the quick clays overlying them. Bedrock is close to the surface at high elevations and reaches a depth of 90 m under the landslide scar. The reflections are discontinuous at some locations. The first breaks were inverted using tomography methods and the resulting inversion models was correlated with the reflection images. Analysis of the subsurface topography suggests a situation where the quick-clay landslide hazard may be present, the specifics of which need to be combined with other geological and geotechnical investigations and scenario buildings. The high-resolution reflection seismic imaging method has a great promise for quick-clay landslide studies.

Landslides are a massive problem within the Appalachians causing large amounts of damage, and even loss of life. Urban development on the hill slope further destabilizes slope and accelerates failure. The objective of this project is to examine the slope stability condition at an urban community in eastern Tennessee and assess the relative risk in the area. The first step included a digital survey of the area by collecting all available soil, geology, elevation, watershed, slope, drainage condition, stream, and building footprint data. This data was collected from a multitude of sources including but not limited to the United States Geological Survey (USGS), Environmental Systems Research Institute (ESRI) and Tennessee State Government resources. After this a process of field verification was required to confirm the validity of acquired digital data. This field verification process included four separate trips that aimed to access the extent of damage, slope condition, bedrock geology, and soil information. The data collected from the previous digital survey and field verification trips were used to prepare a landslide hazard prediction map using Weighted Overlay method in ArcGIS Pro software. To validate the accuracy of the hazard map, an unmanned aircraft system (UAS) drone survey will be completed in April 2023. A final Slope Stability Hazard Map will be produced for the urban community and the report will be shared with the community members. The result indicated that both the soil and geology reports were spatially inaccurate as the entirety of urban development was constructed on Sevier Shale Formation, whereas Knox Formation appears on the map. The slope and hill shade information were correct including the identification of a road that was uncompleted that undercut a steep slope. After our first survey the maps were combined and weighted in a “Weighted Overlay map” with slope, curvature, and stream data to make a map that showed likely areas of risk. The study area contains multiple areas with high slope instability risk. These areas are steep slopes as high as 51° and weathered shale with a lack of vegetation that has been undercut by a roadway that was unfinished. Other areas of high concern with clear evidence of slope sliding are present with the movement of supportive foundation beams. Signs of cracking and sliding have been spotted within the road leading to some of the housing complexes. This information will then be compared to a UAS drone survey to create a final Slope Stability Hazard Map. The urban community can plant vegetation, divert storm water, keep the slope dry, and reduce overburden pressure on the slopes to reduce further movement. Costly engineering structures like slope anchors, soil nails, and retaining walls are possible solutions and could help to support the steep and overburdened slopes.