[pt] Apresenta-se, neste trabalho, resultados de um extenso estudo experimental de laboratório, cujos objetivos eram: obter informações do comportamento tensão-deformação em condições não drenadas, e verificar a susceptibilidade à liquefação de um resíduo oriundo da lavra do itabirito silicoso da Mina de Fernandinho, que situa-se no Quadrilátero Ferrífero (Minas Gerais ), região com grande concentração de minério de ferro. Para realizar o estudo de susceptibilidade à liquefação do resíduo, foi necessário projetar e construir um equipamento que é constituído de: uma célual triaxial, servo-motores, válvulas para regulagem de pressão, um microcomputador AT486, conversor D/A, um sistema de aquisição de dados da National Instruments e alguns acessórios que foram desenvolvidos para facilitar a execução dos ensaios. Durante a fase de projeto e montagem deste equipamento foi implementado um programa na linguagem de programação C para gerenciar os ensaios. Este equipamento possibilitou a execução dos ensaios triaxiais cíclicos e monotônicos com trajetórias de tensões servo controladas. Na primeira fase deste estudo foram realizados ensaios de caracterização completa, análise mineralógica e de microscopia eletrônica. Após a caracterização física do material, passou-se ao estudo do comportamento tensão- deformação e resistência com a execução de ensaios triaxiais. Nesta fase foram executados ensaios monotônicos e cíclicos em corpos de prova adensados isotropicamente e anisotropicamente. Com as análises dos resultados e entendimento do comportamento tensão deformação deste material em condições de laboratório, concluiu-se que este é susceptível à liquefação devido ao comportamento colapsível e desenvolvimento elevado de poropressões. Finalmente, propõe-se uma nova metodologia experimental para estudar os mecanismos que levam o solo a desenvolver o fenômeno de liquefação, tendo em vista que as metodologias apresentadas na literatura corrente não são adequadas para estudar este fenômeno. / [en] This work presents results of na experimental research programme executed in the laboratory at PUC-Rio, Brazil. The aim of this research was investigated the stress-strain behaviour and the evaluation of the susceptibility of fine grained tailing material from Fernandinho Mine to liquefaction. This mine is at Quadrilatero Ferrífero (Minas Gerais - Brazil), region with one of the largest sources of iron ore in Brazil.In order to study the susceptibility to liquefaction of tailing material an servocontrolled triaxial device was developed. This device were composed by: triaxial cell, servo-motors,pressure regulators, microcomputer, one digital analogy convert of, one analogy digital convert developed in the laboratory at PUC-Rio and other accessories. During the development of the device, one software to control all the trajetories was implemented. Using this device some cyclic and monotonic triaxial tests were carried out.Complete characterization, mineralogical and eletronic microscope analysis were carried out in the preliminary steps of this research. After this, an extensive programme of triaxial tests were carried out in order to determine the failure envelope, stress-strain behaviour and liquifiction resitance of the tailing material.A colapsive behavior of the tested material was observed at small strain and stress conditions. Another important observation was the high level of poropressure development,suggesting that this material is susceptible to liquefaction in special conditions.Finally, based on the test results, a new methodology is proposed to investigate soils when submitted to undrained conditions.

An experimental study on the effect of fuel mixing on the products resulting from hydrothermal liquefaction (HTL) was conducted. The feedstocks used were kraft lignin (KL), GROT (GT) and microalgae cultivated in wastewater (MA). Three sets of mixtures were prepared, each containing two types of feedstocks with a 1:1 ratio: KLGT, MAKL, and MAGT. The experiments were performed using a pilot-scale continuous HTL-system. Elemental analysis CHNO and thermogravimetric analysis were used to determine the ultimate and proximate composition of the samples. Scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS) was used to further analyse the elemental distribution on the hydrochars’ surface. The co-liquefaction effect (CE) was evaluated by comparing the experimental results found for the mixtures with the theoretical values calculated as the average of the respective pure components. The results showed that the yield of light oil was not significantly affected for any mixture. However, the mixtures containing KL showed a lower yield of heavy oil than the predicted value, while a higher yield was found for MAGT. All heavy oils had higher carbon content than expected from the predicted values. Every mixture had a significantly larger yield of hydrochar than what was expected. The increased yield of hydrochar for KLGT was insufficient to compensate for the loss of heavy oil and thus the overall product yield was decrease showing antagonistic interactions in the mixture. The hydrochar from MAGT had the highest ash content, and upon closer inspection with SEM/EDS it showed a much larger phosphorus content than any other hydrochar, even compared to the predicted value. This suggests that an interaction between MA and GROT causes the hydrochar to bind more contaminants and enables it to collect more ash than what would have been achieved from liquefying the components individually. Thus, MAGT showed synergetic effects overall, MAKL had increased carbon recovery but at the cost of heavy oil yield making in a poor choice for HTL, and KLGT showed antagonistic effects in the form of lower yield of biocrude and overall recovery of products. The study highlights that co-liquefaction can potentially have a larger impact on the hydrochar than it does on the biocrude, and that evaluation of hydrochar should be included when examining co-liquefaction

Cemented paste backfill (CPB) is a novel technology developed in the past few decades to better manage mining wastes (such as tailings) in environmentally friendly way. It has received prominent interest in the mining industry around the world. In this technology, up to 60% of the total amount of tailings is reused and converted into cemented construction material that can be used for secondary support in underground mine openings (stopes) and to maximize the recovery of ore from pillars. CPB is an engineered mixture of tailings, water, and hydraulic binder (such as cement), that is mixed in the paste plant and delivered into the mine stopes either by gravity or pumping. During and after placing it into the mine stopes, the performance of CPB mainly depends on the role of the hydraulic binder, which increases the mechanical strength of the mixture through the process of cement hydration. Similar to other fine-grained soils undergoing cementations, CPB’s behavior is affected by several conditions or factors, such as cement hydration progress (curing time), chemistry of pore water, mixing and curing temperature, and filling strategy. Also, it has been found that fresh CPB placed in the mine stopes can be susceptible to many geotechnical issues, such as liquefaction under ground shaking conditions. Liquefaction-induced failure of CPB structure may cause injuries and fatalities, as well as significant environmental and economic damages. Many researches studied the effect of the aforementioned conditions on the static mechanical behavior of CPB. Other researches have evaluated the liquefaction behavior of natural soils and tailings (without cement) during cyclic loadings using shaking table test technique. Only few studies investigated the CPB liquefaction during dynamic loading events using the triaxial tests. Yet, there are currently no studies that addressed the liquefaction behavior of CPB under the previous conditions by using the shaking table technique. In this Ph.D. study, a series of shaking table tests were conducted on fresh CPB samples (75 cm × 75 cm ×70 cm), which were mixed and poured into a flexible laminar shear box (that was designed and build for the purpose of this research). Some of these shaking table tests were performed at different maturity ages of 2.5 hrs, 4.0 hrs, and 10.0 hrs, to investigate the effect of cement hydration progress on the liquefaction potential of CPB. Another set of tests were conducted to assess the effect of the chemistry (sulphate content) of the pore-water on the cyclic response of fresh CPB by exposing cyclic loads on couple of CPB models that contain different concertation of sulphate ions of 0.0 ppm and 5000 ppm. Moreover, as part of this study, series of shaking table test was conducted on CPB samples that were prepared and cured at different temperatures of 20oC and 35oC, to evaluate the effect of temperature of the cyclic behavior of CPB. Furthermore, the effect of filling strategy on the cyclic behavior of fresh CPB was assessed by conducting set of shaking tables tests on CPB models that were prepared at different filling strategies of continuous filling, and sequential or discontinuous (layered) filling. The results obtained show that CPB has different cyclic behavior and performance under these different conditions. It is observed that the progress of cement hydration (longer curing time) enhances the liquefaction resistance of CPB, while the presence of sulphate ions diminishes it. It is also found that CPB mixed and cured in low temperature is more prone to liquefaction than those prepared at higher temperatures. Moreover, the obtained results show that adopting the discontinuous (layered) filling strategy will improve the liquefaction resistance of CPB. The finding presented in this thesis will contribute to efficient, cost effective and safer design of CPB structures in the mine areas, and will help in minimizing the risks of liquefaction-induced failure of CPB structures.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 160-167. / by Mark David Bucknam. / M.S.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18241号 / 工博第3833号 / 新制||工||1587(附属図書館) / 31099 / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 木村 亮, 教授 三村 衛, 准教授 木元 小百合 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Deep foundations constructed in liquefiable soils require specialized design. The design engineer of such foundations must consider the effects of liquefaction on the foundation and overlying structure, such as excessive settlement, loss of skin friction at the soil-pile interface, and the development of downdrag on the pile. Controlled blasting was employed to liquefy a loose, saturated sand in order to test the liquefaction prevention capabilities of full-scale, vertical composite earthquake (EQ) drains and to investigate the development of downdrag on full-scale test piles. Blasting produced liquefaction at a test site without EQ drains which eventually resulted in 270 mm of settlement. Liquefaction caused the skin friction on the test pile to decrease to zero immediately following blasting. As pore pressures dissipated and the sand settled, negative skin friction developed, with a maximum magnitude of about onehalf of the positive skin friction. Blasting also produced liquefaction at a site with drains but the settlement was reduced to 225 mm, a decrease of 17% relative to the untreated site. Nevertheless, the dissipation rate dramatically increased. Skin friction did not decrease to zero in the liquefied sand and negative skin friction increased to a value equal to the positive skin friction in the liquefied layer. The computer software, FEQDrain, was utilized to develop a calibrated model of the soil profile using pore pressure and settlement data measured during blast testing. This model was then used to simulate drainage systems with smaller drain spacing and larger drain diameter. Results indicated that pore pressures and settlement could be limited to levels acceptable for many applications. However, development of downdrag on deep foundations would not likely be prevented. EQ drains provide an attractive method of liquefaction mitigation. Furthermore, liquefaction can cause significant amount of downdrag on pile foundations which should be accounted for in deep foundation design.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第23484号 / 工博第4896号 / 新制||工||1765(附属図書館) / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 渦岡 良介, 教授 木村 亮, 准教授 澤村 康生 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

Characterization and assessment of liquefaction potential of gravelly soil in a reliable cost-effective manner has always been a great challenge for the geotechnical engineers. The typical laboratory investigation techniques have proven to be ineffective for characterizing gravelly soil due to the cost and difficulty of extracting undisturbed sample from gravelly deposits. The traditional in-situ tests like SPT or CPT are not very suitable for gravelly soil because of interference with large size gravel particles which can artificially increase the penetration resistance. The Becker Penetration Test, well known for gravelly soil characterization, is cost-prohibitive for routine projects and is not available in most of the world. The Chinese dynamic cone penetration test (DPT) with a larger diameter probe compared to the SPT or CPT, can be economically performed with conventional drilling equipment. Besides the penetration testing, in-situ measurement of shear wave velocity (Vs) is another alternative of characterizing gravel liquefaction. Probabilistic liquefaction triggering curves were developed by performing both DPT and shear wave velocity test at the Chengdu Plain of China where massive gravel liquefaction took place during 2008 Wenchuan earthquake. These curves have significant uncertainty as they were developed from a single event database. As a part of this study, both DPT and Vs tests have been performed at various sites around the world where gravelly soil did or did not liquefy in various past earthquakes. These newly collected data have been added to the existing Chinese dataset to form a large database on gravel liquefaction case histories for both DPT and Vs. Based on this larger database, new magnitude dependent probabilistic liquefaction triggering procedures have been developed for both DPT and Vs. The larger database has significantly improved the triggering curves by reducing the spread and constraining the curves at both the higher and lower end. New Magnitude Scaling Factor (MSF) curves have been developed for both DPT and Vs which were found to be consistent with existing MSF curves. Further, an instructive comparison has been drawn between the performance of CPT and newly developed DPT triggering procedure the liquefaction potential of gravelly deposits CentrePort in Wellington. Results showed that both DPT and CPT performed reasonably well in liquefaction assessment of the gravelly fill. However, the CPT-based CRR profiles contain intermittent spikes due to the interaction with gravel particles whereas the DPT resistance appear to be relatively smooth. Similar comparison has been presented between the DPT and BPT in performing liquefaction assessment of gravelly soil at the Borah Peak sites in Idaho. It is found that both DPT and BPT successfully evaluate the liquefaction potential of the loose critical layers but the medium dense to dense layers are identified as non-liquefiable by the DPT whereas the same deposits are identified as liquefiable by the BPT. Lastly, an investigation has been carried out to observe the effect of hydraulic conductivity and in-situ drainage on the liquefaction triggering in gravelly soils based on field data along with a group of numerical analyses. It is found that the hydraulic conductivity of gravelly soil reduces with sand content which eventually may cause liquefaction during earthquake shaking. Low permeability cap layer may also impede the drainage path to generate excess pore pressure to trigger liquefaction in the gravelly strata.

Assessment of post-liquefaction residual strength is needed for the development of empirically-based, predictive correlations for earthquake engineering design. Previous practice commonly assigned negligible strengths to liquefied materials for engineering analysis, producing overly-conservative designs. Increasingly available case history data, and improved analytical tools have allowed for more accurate and less overly-conservative estimation of soil residual strength, improving empirical predictive models. This study provides a new case history to the limited suite of (approximately 30) liquefaction failure case histories available for post-liquefaction in-situ strength predictive correlations. This case history documents the Las Palmas gold mine tailings dam failure, resulting from seismic-induced liquefaction during the moment magnitude 8.8 February 27, 2010 Maule, Chile earthquake; the sixth largest since 1900. Forensic analysis provides reasonably well-constrained values of 1) back-calculated representative post-liquefaction residual strength, 2) representative penetration resistance, and 3) representative vertical effective stress along the suspected liquefied failure surface. This study employs the incremental momentum method to incorporate momentum effects of a moving soil mass. The incremental momentum method requires a series of cross sections animating the geometry of failure progression from initiation to termination, converging on the observed final geometry. Using interpreted soil strength characteristics, an iterative procedure approximates the back-calculated value of post-liquefaction residual strength. Findings of this case history plot well with existing empirical deterministic regression charts and are in general agreement with previous, related efforts. Results yield representative, well-constrained values of: 1) post-liquefaction residual strength ≈ 173 psf, 2) penetration resistance of N1,60,CS ≈ 5 and N1,60 ≈ 2.5, and 3) vertical effective stress ≈ 4,300 lb/ft2, or ≈ 2.0 atm.

Designing products and processes is a fundamental aspect of engineering that significantly impacts society and the world. Chemical process design aims to create more efficient and sustainable production processes that consume fewer resources and emit less pollution. Mathematical models that accurately describe process behavior are necessary to make informed and responsible decisions. However, as processes become more complex, purely symbolic formulations may be inadequate, and simulations using tailored computer code become necessary. The decision‐making process in optimal design requires a procedure for choosing the best option while complying with the system’s constraints, for which task optimization approaches are well suited. This doctoral thesis focuses on black‐box optimization problems that arise when using process simulators in optimal process design tasks and assesses the potential of derivative‐free, metaheuristics, and surrogate‐based optimization approaches. The optimal design of natural gas liquefaction processes is the case study of this research. To overcome numerical issues from black‐box problems, the first work of this doctoral thesis consisted of using the globally convergent Nelder‐Mead simplex method to the optimal process design problem. The second work introduced surrogate models to assist the search towards the global optimum of the black‐box problem and an adaptive sampling scheme comprising the optimization of an acquisition function with metaheuristics. Kriging as surrogate models to the simulation‐optimization problems are computationally cheaper and effective predictors suitable for global search. The third work aims to overcome the limitations of acquisition function optimization and the use of metaheuristics. The proposed comprehensive mathematical notation of the surrogate optimization problem was readily implementable in algebraic modeling language software. The presented framework includes kriging models of the objective and constraint functions, an adaptive sampling procedure, a heuristic for stopping criteria, and a readily solvable surrogate optimization problem with mathematical programming. The success of the surrogate‐based optimization framework relies on the kriging models’ prediction accuracy regarding the underlying, simulation‐based functions. The fourth publication extends the previous work to multi‐objective black‐box optimization problems. It applies the ε constraint method to transform the multi‐objective surrogate optimization problem into a sequence of single‐objective ones. The ε‐constrained surrogate optimization problems are implemented automatically in algebraic modeling language software and solved using a gradient‐based, state‐of‐the‐art solver. The fifth publication is application-driven and focuses on identifying the most suitable mixed‐refrigerant refrigeration technology for natural gas liquefaction in terms of energy consumption and costs. The study investigates five natural gas liquefaction processes using particle swarm optimization and concludes that there are flaws in the expected relationships between process complexity, energy consumption, and total annualized costs. In conclusion, the research conducted in this doctoral thesis demonstrates the importance and capabilities of using optimization to process simulators. The work presented here highlights the potential of surrogate‐based optimization approaches to significantly reduce the computational cost and guide the search in black‐box optimization problems with chemical process simulators embedded. Overall, this doctoral thesis contributes to developing optimization strategies for complex chemical processes that are essential for addressing some of the current most pressing environmental and social challenges. The methods and insights presented in this work can help engineers and scientists design more sustainable and efficient processes, contributing to a better future for all.