A geração de resíduos provocada pela atividade mineradora é revestida de considerável preocupação ambiental, tanto em função da área envolvida no depósito deste material, quanto pelos impactos causados por eventuais rupturas que possam a ocorrer nestes reservatórios. O método de disposição de resíduos, frequentemente utilizado pelas mineradoras, consiste no bombeamento do material por via úmida até os reservatórios de alteamento contidos através de diques ou barragens. Este processo pode tornar estas áreas suscetíveis à ocorrência de rupturas causadas por liquefação do material. Quando este tipo de evento acontece, tem-se um aumento repentino da poropressão, com consequente redução da resistência ao cisalhamento. A verificação do potencial de liquefação de resíduos de mineração é, portanto, imprescindível à prevenção de impactos ambientais, além de colaborar na execução de projetos geotécnicos mais seguros e econômicos. Neste trabalho são analisados três reservatórios distintos, sendo um composto por resíduo de mineração de ouro e os outros dois por resíduo de mineração de bauxita. Os resultados de ensaios realizados em campo (SCPTU/CPTU e SDMT) são utilizados na avaliação geotécnica dos resíduos, buscando-se verificar a compatibilidade com avaliações já realizadas através de ensaios de laboratório. O potencial de liquefação estática dos materiais é observado em laboratório para baixos níveis de tensões, demonstrando que os resíduos são suscetíveis à liquefação estática. Este comportamento é verificado também na interpretação de ensaios de campo, interpretados através de correlações de natureza semiempírica baseadas na combinação de uma medida representativa de pequenas deformações (módulo cisalhante) combinado a uma medida obtida à grandes deformações (resistência à penetração) que, combinadas, permitem a determinação do parâmetro de estado do material. A primeira proposta consistiu na definição de uma fronteira entre materiais de comportamento contrátil e dilatante no espaço G0/qc versus p’/pa. Esta proposta apresentou uma resposta adequada, entretanto, a concentração de todos os pontos referentes aos resíduos analisados, possivelmente suscetíveis ao fenômeno de liquefação estática, numa mesma região gráfica, somente foi possível no espaço G0/qc versus qc1. Neste espaço a separação entre materiais de comportamento dilatante e contrátil foi possível com a inserção de uma fronteira empírica. Este estudo demonstrou a boa sensibilidade dos parâmetros G0 e qc ao fenômeno de liquefação estática. A suscetibilidade à liquefação cíclica dos resíduos de mineração de ouro e bauxita também foi verificada através de correlações com resultados de ensaios de campo. Esta análise indicou a possibilidade de ocorrência do fenômeno para os mais baixos níveis de magnitude de sismo atuante. / Waste generation caused by mining activity emerges as an environmental concern, both because of the large area involved in deposits of this material, as well as the possible impacts caused by occasional failures that may occur in these deposits. The method of waste disposal, often used by mining companies, consists by pumping wet material in sequence until completion of the reservoirs contained by dikes or dams. This process makes these areas susceptible to the occurrence of the liquefaction failures. When this type of event happens there is a sudden increase in pore pressure with consequent reduction shear strength, which can result is risk of containment structures. Therefore, verification of liquefaction potential of these materials is essential in the prevention of environmental impacts. The present work analyzes three different reservoirs, one consisting of gold mining tailings and the other two of bauxite mining tailings. The results of field tests (SCPTU/ CPTU and SDMT) are used in geotechnical evaluation of tailings in order to verify the compatibility with evaluations already carried out through laboratory tests. The static liquefaction potential observed in laboratory at low levels of stresses is consistent with field assessment from in situ tests. Semiempirical correlations based on field tests are based on small strain measurements (shear modulus) combined with large strain measurements (penetration resistance), that are used to defined the state parameter of the material. The first proposal consisted in defining a boundary between materials of contractive and dilatant behavior in space G0/qc versus p’/pa. The proposal presented an appropriate response, however, the concentration of all analyzed points, possibly susceptible to static liquefaction phenomenon, in the same graphical region was only possible in space G0/qc versus qc1. In this space the separation between materials of contractive and dilatant behavior was possible with the inclusion of an empirical boundary. This study demonstrated the good sensitivity of the parameters G0 and qc to the static liquefaction phenomenon. The cyclic liquefaction susceptibility of the gold and bauxite mining tailings was also verified by correlation with field tests results. This analyzes indicated the possibility of occurrence of the phenomenon to the lowest levels of earthquake magnitude.

The 2010, moment magnitude 8.8 earthquake that occurred near Maule, Chile caused major damages to several piers in the Port of Coronel located approximately 160 kilometers (100 miles) to the South of the earthquake epicenter. One of the piers, the North Pier, experienced significant lateral spreading that was caused from liquefaction of the soils at the approach zone of the pier. Damages from lateral spreading and liquefaction effects consisted of sheet pile welding ruptures of the cross-support beams, stiffener buckling, pile displacements, pile rotations, and pier deck displacement. Researchers analyzed the North Pier after the earthquake and documented in detail the damage caused by lateral spread displacements. This study introduces a simplified performance-based procedure called the "Simplified Modeling Procedure" that is used for the analysis of piles supporting a pier that are exposed to lateral spread displacements. The procedure uses the software LPILE, a common program for analyzing a single pile under lateral loading conditions, to evaluate a more complex multi-pile pier design. Instead of analyzing each of the piles in a given pier individually, the procedure utilizes what is known as a "Super Pile" approach to combine several piles into a single representative pile during the analysis. To ensure displacement compatibility between each "Super Pile" in the analysis, the "Super Piles" are assumed to be fully connected at the top of each "Super Pile" to the pier deck. The Simplified Modeling Procedure is developed and tested using the case study history of the North Pier from the Port of Coronel during the 2010 Maule earthquake. The Simplified Modeling Procedure incorporates p-y springs with a lateral push-over analysis. This approach allows the analysis to be performed in a matter of seconds and allows the user to more easily draw the needed correlations between the rows of piles. This procedure helps identify that different rows of piles either contribute to the movement of the pier or contribute to the bracing of the pier. The procedure ultimately predicts the anticipated pier deck deflection by determining when all the pile rows and their respective shear forces are in equilibrium. The Simplified Modeling Procedure predicted that the North Pier experienced deflections between approximately 0.31 meters (1.01 feet) and 0.38 meters (1.26 feet). The predicted deflections and rotations determined using the procedure were determined to be a relatively close representation of the observations made during the post-earthquake reconnaissance observations.

Deep foundations like auger-cast piles and drilled shafts frequently extend through liquefiable sand layers and bear on non-liquefiable layers at depth. When liquefaction occurs, the skin friction on the shaft decreases to zero, and then increases again as the pore water pressure dissipates and the layer begins to settle, or compact. As the effective stress increases and the liquefiable layer settles, along with the overlaying layers, negative skin from the soil acts on the shaft. To investigate the loss of skin friction and the development of negative skin friction, soil-induced load was measured in three instrumented, full-scale auger-cast piles after blast-induced liquefaction at a site near Christchurch, New Zealand. The test piles were installed to depths of 8.5 m, 12 m, and 14 m to investigate the influence of pile depth on response to liquefaction. The 8.5 m pile terminated within the liquefied layer while the 12 m and 14 m piles penetrated the liquefied sand and were supported on denser sands. Following the first blast, where no load was applied to the piles, liquefaction developed throughout a 9-m thick layer. As the liquefied sand reconsolidated, the sand settled about 30 mm (0.3% volumetric strain) while pile settlements were limited to a range of 14 to 21 mm (0.54 to 0.84 in). Because the ground settled relative to the piles, negative skin friction developed with a magnitude equal to about 50% of the positive skin friction measured in a static pile load test. Following the second blast, where significant load was applied to the piles, liquefaction developed throughout a 6-m thick layer. During reconsolidation, the liquefied sand settled a maximum of 80 mm (1.1% volumetric strain) while pile settlements ranged from 71 to 104 mm (2.8 to 4.1 in). The reduced side friction in the liquefied sand led to full mobilization of side friction and end-bearing resistance for all test piles below the liquefied layer and significant pile settlement. Because the piles generally settled relative to the surrounding ground, positive skin friction developed as the liquefied sand reconsolidated. Once again, skin friction during reconsolidation of the liquefied sand was equal to about 50% of the positive skin friction obtained from a static load test before liquefaction.

Liquefaction-induced settlements can cause a large economic toll on a region, from severe infrastructural damage, after an earthquake occurs. The ability to predict, and design for, these settlements is crucial to prevent extensive damage. However, the inherent uncertainty involved in predicting seismic events and hazards makes calculating accurate settlement estimations difficult. Currently there are several seismic hazard analysis methods, however, the performance-based earthquake engineering (PBEE) method is becoming the most promising. The PBEE framework was presented by the Pacific Earthquake Engineering Research (PEER) Center. The PEER PBEE framework is a more comprehensive seismic analysis than any past seismic hazard analysis methods because it thoroughly incorporates probability theory into all aspects of post-liquefaction settlement estimation. One settlement estimation method, used with two liquefaction triggering methods, is incorporated into the PEER framework to create a new PBEE (i.e., fully-probabilistic) post-liquefaction estimation procedure for the cone penetration test (CPT). A seismic hazard analysis tool, called CPTLiquefY, was created for this study to perform the probabilistic calculations mentioned above. Liquefaction-induced settlement predictions are computed for current design methods and the created fully-probabilistic procedure for 20 CPT files at 10 cities of varying levels of seismicity. A comparison of these results indicate that conventional design methods are adequate for areas of low seismicity and low seismic events, but may significantly under-predict seismic hazard for areas and earthquake events of mid to high seismicity.

Liquefaction-induced settlement can cause significant damage to structures and infrastructure in the wake of a seismic event. Predicting settlement is an essential component of a comprehensive seismic design. The inherent uncertainty associated with seismic events makes the accurate prediction of settlement difficult. While several methods of assessing seismic hazards exist, perhaps the most promising is performance-based earthquake engineering, a framework presented by the Pacific Earthquake Engineering Research (PEER) Center. The PEER framework incorporates probability theory to generate a comprehensive seismic hazard analysis. Two settlement estimation methods are incorporated into the PEER framework to create a fully probabilistic settlement estimation procedure. A seismic hazard analysis tool known as PBLiquefY was updated to include the fully probabilistic method described above. The goal of the additions to PBLiquefY is to facilitate the development of a simplified performance-based procedure for the prediction of liquefaction-induced free-field settlements. Settlement estimations are computed using conventional deterministic methods and the fully probabilistic procedure for five theoretical soil profiles in 10 cities of varying seismicity levels. A comparison of these results suggests that deterministic methods are adequate when considering events of low seismicity but may result in a considerable under-estimation of seismic hazard when considering events of mid to high seismicity.

Uncertainty in the global energy market and negative environmental impacts associated with fossil fuels has led to renewed interest in alternative fuels. The scalability of new technologies and production pathways are critically being evaluated through economic feasibility studies and environmental impact assessments. This work investigated the conversion of agricultural wast, delactosed whey permeate (delac), with yeast fermentation for the generation of biofuel via hydrothermal liquefaction (HTL). The feasibility of the process was demonstrated at laboratory scale with data leveraged to validate systems models used to perform industrial-scale economic and environmental impact analyses. Results showed a minimum fuel selling point of $4.56 per gasoline gallon equivalent (CGE), a net energy ratio (NER), defined as energy required to process biofuel divided by energy in the biofuel produced, of 0.81 and greenhouse gas (GHG) emissions of 30.03 g CO2-eq MJ-1. High Production costs can be attributed to operational temperatures of HTL while the high lipid yields of the yeast counter these heating demands, resulting in a favorable NER. The operating conditions of both fermentation and HTL contributed to the majority of GHG emissions. Further discussion focuses on optimization of the process, on the metrics of TEA and LCA and the evaluation of the process, on the metrics of TEA and LCA, and the evaluation of the process through a sensitivity analysis that highlights areas for directed research to improve commercial feasibility.

Effective-stress nonlinear dynamic analyses (NDA) were performed for piles in liquefiable sloped ground to assess how inertia and liquefaction-induced lateral spreading combine in long-duration vs. short-duration earthquakes. A parametric study was performed using input motions from subduction and crustal earthquakes covering a wide range of earthquake durations. The NDA results were used to evaluate the accuracy of the equivalent static analysis (ESA) recommended by Caltrans/ODOT for estimating pile demands. Finally, the NDA results were used to develop new ESA methods to combine inertial and lateral spreading loads for estimating elastic and inelastic pile demands. The NDA results showed that pile demands increase in liquefied conditions compared to nonliquefied conditions due to the interaction of inertia (from superstructure) and kinematics (from liquefaction-induced lateral spreading). Comparing pile demands estimated from ESA recommended by Caltrans/ODOT with those computed from NDA showed that the guidelines by Caltrans/ODOT (100% kinematic combined with 50% inertia) slightly underestimates demands for subduction earthquakes with long durations. A revised ESA method was developed to extend the application of the Caltrans/ODOT method to subduction earthquakes. The inertia multiplier was back-calculated from the NDA results and new multipliers were proposed: 100% Kinematic + 60% Inertia for crustal earthquakes and 100% Kinematic + 75% Inertia for subduction earthquakes. The proposed ESA compared reasonably well against the NDA results for elastic piles. The revised method also made it possible to estimate demands in piles that performed well in the dynamic analyses but could not be analyzed using Caltrans/ODOT method (i.e. inelastic piles that remained below Fult on the liq pushover curve). However, it was observed that the pile demands became unpredictable for cases where the pile head displacement exceeded the displacement corresponding to the ultimate pushover force in liquefied conditions. Nonlinear dynamic analysis is required for these cases to adequately estimate pile demands.

A liquefação hidrotermal (HTL) é uma tecnologia muito utilizada para a conversão de diversos tipos de biomassa em Bio-óleo bruto; contudo, enquanto tal combustível é produzido uma fase aquosa (PHWW), rica em matéria orgânica e alguns compostos tóxicos, também é gerada, podendo ocasionar severos impactos ambientais negativos. O objetivo da presente pesquisa foi aplicar dois bio-adsorventes: in natura (BAA) e ativado quimicamente (BAAA), derivados da casca de amendoim, como pré-tratamentos da PHWW afim de melhorar sua biodegradabilidade anaeróbia. O carvão ativado granular (GAC) foi utilizado como adsorvente modelo para comparação. Os processos de adsorção foram otimizados com a utilização de desenhos compostos centrais rotacionais (DCCR), no quais as variáveis independentes foram: pH do adsorvato, temperatura e quantidade de (bio) adsorvente no meio. A porcentagem de remoção de DQO e do íon amônio foram as variáveis dependentes. Isotermas de adsorção foram obtidas em ensaios em batelada. Após realizado o estudo do processo de adsorção, o potencial metanogênico dos efluentes pré-tratados e do efluente in natura foi determinado. Esses ensaios foram conduzidos com três concentrações de PHWW (6,5%, 13% e 26%), com dois ensaios controle, um negativo e outro positivo. A pressão nos frascos reatores foi monitorada diariamente e a determinação da composição do biogás produzido foi realizada por cromatografia gasosa uma vez por semana. Os resultados para a processo adsortivo foram encorajadores, uma vez que cada bio-adsorvente testado foi otimizado para diferentes variáveis resposta: BAA (NH4+) e BAAA (DQO). Os ensaios anaeróbios mostraram que uma maior taxa de produção metanogênica, dos efluentes pré-tratados, pode estar ligada à modificação química da superfície nas cascas de amendoim. Foi possível concluir que a bio-adsorção se perfila como uma alternativa sustentável para o pré-tratamento de efluentes advindos da HTL de cianobactérias. / Hydrothermal liquefaction (HTL) is a technology widely used for the conversion of several types of biomass to bio-crude oil; however, while such a fuel is produced an aqueous phase (PHWW), rich in organic matter and some toxic compounds, is also generated and can cause severe negative environmental impacts. The objective of the present research was to apply two bio-adsorbents: peanut bio-adsorbent (PB) and activated peanut bio-adsorbent (APB), as pre-treatments of PHWW to improve their anaerobic biodegradability. Granular activated carbon (GAC) was used as an absorbent model for comparison. The adsorption process was optimized with the use of central rotational composite designs (DCCR), in which the independent variables were: pH of the adsorbate, temperature and amount of (bio) adsorbent in the medium. The percentage of COD removal and ammonium ion were the dependent variables. After the study of the adsorption process, the methanogenic potential of the pretreated effluents and raw PHWW was determined. These trials were conducted with three concentrations of PHWW (6.5%, 13% and 26%), with two control trials, one negative and one positive. The pressure in the reactor flasks was monitored daily and the composition of the biogas produced was determined by gas chromatography once a week. The results for the adsorption process were encouraging, and ach bio-adsorbent tested was optimized for different response variables: PB (NH4+) and APB (COD). The anaerobic assays showed that a higher rate of methanogenic production of pretreated effluents may be linked to the chemical modification of the surface in the peanut shells. It was possible to conclude that the bio adsorption is outlined as a sustainable alternative for the pretreatment of effluents coming from HTL.

No description available.

Modern mines require systems that quickly deliver backfill to support the rock mass surrounding underground openings. Cemented Paste Backfill (CPB) is one such backfilling method, but concerns have been raised about CPB’s liquefaction susceptibility especially when the material has just been placed, and if it is exposed to earthquakes or large mining induced seismic events. Conventional geotechnical earthquake engineering for surface structures is now relatively advanced and well accepted, and so the objective of this thesis is to consider how that framework might be extended to assess the liquefaction potential of CPB. Seismic records were analyzed for earthquakes and for large mining induced events. Important seismological trends were consistent for rockbursts and earthquakes when the signals were recorded at distances as proximate as one kilometre, suggesting that the conventional earthquake engineering approach might plausibly be adapted for such design situations. For production blasts and for more proximate locations to rockbursts, much higher frequencies dominate and therefore new design methods may be required. Monotonic triaxial tests conducted on normally consolidated uncemented mine tailings demonstrated that the material is initially contractive up to a phase transition point, beyond which dilation occurs. Most importantly the material never exhibits unstable strain softening behaviour in compression, and only temporary or limited liquefaction in extension. The addition of 3% binder results in initial sample void ratios that are even higher than their uncemented counterparts, and yet the material friction is slightly enhanced when tested at 4 hours cure. These results suggest that the flow liquefaction phenomenon commonly associate with undrained loose sand fills will not occur with paste backfill. Cyclic triaxial test results analyzed in terms of number of cycles to failure for a given cyclic stress ratio exhibited a trend consistent with previous tests on similar materials. However, the addition of 3% binder and testing at 4 hours cure resulted in an order of magnitude larger number of cycles to failure – a surprising and dramatic increase, suggesting good resistance of the material to cyclic mobility. Future research is recommended to build on these results and develop more robust methods for liquefaction assessment of CPB.