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.

Yes / Wave-induced seabed instability caused by the residual liquefaction of seabed may threaten the safety of an offshore foundation. Most previous studies have focused on the structure that sits on the seabed surface (e.g., breakwater and pipeline), a few studies investigate the structure embedded into the seabed (e.g. a mono-pile). In this study, by considering the inertial terms of pore fluid and soil skeleton, a three-dimensional (3D) integrated model for the wave-induced seabed residual response around a mono-pile is developed. The model is validated with five experimental tests available in the literature. The proposed model is then applied to investigate the spatial and temporal pattern of pore pressure accumulation as well as the 3D liquefaction zone around a mono-pile. The numerical simulation shows that the residual pore pressure in front of a pile is larger than that at the rear, and the seabed residual response would be underestimated if the inertial terms of pore fluid and soil skeleton are neglected. The result also shows that the maximum residual liquefaction depth will increase with the increase of the embedded depth of the pile. / This work was supported by the Fundamental Research Funds for the Central Universities [2017B15814], the International Postdoctoral Exchange Fellowship Program [20170014], National Science Foundation for Distinguished Young Scholars [Grant No. 51425901], Fundamental Research Funds for the Central Universities (2017B21514), Key Laboratory of Water-Sediment Sciences and Water Disaster Prevention of Hunan Province (2018SS02), Natural Science Foundation of Jiangsu Province [Grant No. BK20161509] and Open Foundation of State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University [Project No: 2016491011].

Yes / Most previous studies on seabed liquefaction around offshore pipelines focused on investigating the wave-induced pore pressure variation in sandy seabed, while limited studies have been conducted for silty seabed. In this study, laboratory experiments are conducted to investigate wave-induced pore pressure within silty bed around the buried or partially/fully backfilled pipeline. Results show that residual pore pressure is the dominant factor that causes the liquefaction in silty soil. For buried pipeline, liquefaction first occurs at the pipeline bottom, then propagates upwards and downwards vertically. Comparing with the buried pipeline, the liquefaction potential is reduced when the pipeline is placed in a trench. To protect pipeline from liquefaction, backfill is recommended. Experiments show that the residual pore pressure significantly decreases as backfill depth increases. Fully backfilled pipeline is the best choice for silty seabed. Furthermore, backfill material with coarser particle size than native soil provides better protection for pipeline. In this study, there is no residual pore pressure around the pipeline periphery for three backfill soils (d50 = 0.15 mm; 0.3 mm; and 0.5 mm) tested. Results indicate that for the range of this experimental study, d50 = 0.15 mm is the best backfill material that provides the most protection for the underneath pipeline. / National Postdoctoral Program for Innovative Talents granted by China Postdoctoral Science Foundation (Grant No. BX20190105) and the Fundamental Research Funds for the Central Universities (Grant No. B200202062).

Liquefaction-induced settlement can cause extensive damage to infrastructure. Quantifying the amount of settlement that may occur after an earthquake is crucial to seismic design. The Pacific Earthquake Engineering Research (PEER) Center developed performance-based earthquake engineering (PBEE) as a probabilistic framework to characterize the risks associated with a seismic event. When applied to liquefaction-induced settlement, the PBEE framework provides a more complete and accurate representation of liquefaction hazard than other more conventional evaluation methods. Performance-based engineering is not widely used in practice, however, due to its complexity. In an attempt to make performance-based engineering methods more accessible to engineers for routine projects, this thesis derives a simplified map-based procedure to evaluating performance-based post-liquefaction settlements. A simplified PBEE procedure is developed for the Cetin et al. (2009) and Ishihara and Yoshimine (1992) empirical post-liquefaction volumetric strain models. The simplified map-based procedure involves obtaining a hazard-targeted value of vertical strain for a reference soil layer which is then adjusted using site-specific soil parameters to assess the liquefaction-induced settlement hazard at a particular location. This thesis derives the equations needed to perform a simplified analysis. The simplified procedure presented herein is then validated in which 15 cities across the United States are analyzed using both the simplified procedure and the full performance-based procedure. The simplified procedure is shown to adequately estimate a full performance-based procedure for post-liquefaction settlement. This thesis also presents SPLIQ, a spreadsheet tool that streamlines the derived simplified procedure in a single, user-friendly program.

Finite element modeling of laminar shear box testing that consisted of loose sand treated with large diameter prefabricated vertical drains (PVDs), was performed. The objective of the modeling was to evaluate the reliability of the computer program FEQDrain for predicting excess pore pressure ratios (Ru) at sites treated with prefabricated drains. FEQDrain was found to be capable of successfully modeling measured excess pore pressure ratio time histories from the laminar shear box experiment, as long as an appropriate combination of €˜number of equivalent cycles and €˜shaking duration was chosen, and sensitive parameters were in the range of measured values. Hydraulic conductivity, soil compressibility, and cycles to liquefaction are sensitive parameters and govern the computed Ru values.Modeling shows that the loading rate in the laminar shear box (15 cycles at 2 Hz) likely induced higher Ru values than would be expected in a typical earthquake event with a longer duration. The longer duration allows the drains to dissipate pore pressures and prevent liquefaction. The number of equivalent cycles and duration of shaking combinations recommended for various moment magnitudes in the FEQDrain user manual predict lower, but similar Ru versus time curves. Thus, suggesting that PVDs would be equally effective for any size earthquake. However, drains are most effective at preventing liquefaction when earthquake ground motions are long and uniform, rather than short and intense.Results from models in this study compare favorably with those from computer modeling performed by Howell et al. (2014). The individual hydraulic conductivity and compressibility values were different they were somewhat compensating. Similar Ru values can be modeled with different combinations of these parameters.Based on computer analyses, wick drains and 2€ diameter PVDs were found to be relatively ineffective for preventing liquefaction. However, 3€ diameter PVDs are fairly effective but can be overwhelmed during intense shaking. In contrast, 4€ diameter and larger PVDs are significantly more effective.

This thesis derives the equations needed to perform a simplified analysis. The simplified procedure presented herein is then validated in which 15 cities across the United States are analyzed using both the simplified procedure and the full performance-based procedure. The simplified procedure is shown to adequately estimate a full performance-based procedure for post-liquefaction settlement. This thesis also presents SPLIQ, a spreadsheet tool that streamlines the derived simplified procedure in a single, user-friendly program. In an attempt to make performance-based engineering methods more accessible to engineers for routine projects, this thesis derives a simplified map-based procedure to evaluating performance-based post-liquefaction settlements. A simplified PBEE procedure is developed for the Cetin et al. (2009) and Ishihara and Yoshimine (1992) empirical post-liquefaction volumetric strain models. The simplified map-based procedure involves obtaining a hazard-targeted value of vertical strain for a reference soil layer which is then adjusted using site-specific soil parameters to assess the liquefaction-induced settlement hazard at a particular location. Liquefaction-induced settlement can cause extensive damage to infrastructure. Quantifying the amount of settlement that may occur after an earthquake is crucial to seismic design. The Pacific Earthquake Engineering Research (PEER) Center developed performance-based earthquake engineering (PBEE) as a probabilistic framework to characterize the risks associated with a seismic event. When applied to liquefaction-induced settlement, the PBEE framework provides a more complete and accurate representation of liquefaction hazard than other more conventional evaluation methods. Performance-based engineering is not widely used in practice, however, due to its complexity.

Finite element modeling of laminar shear box testing that consisted of loose sand treated with large diameter prefabricated vertical drains (PVDs), was performed. The objective of the modeling was to evaluate the reliability of the computer program FEQDrain for predicting excess pore pressure ratios (Ru) at sites treated with prefabricated drains. FEQDrain was found to be capable of successfully modeling measured excess pore pressure ratio time histories from the laminar shear box experiment, as long as an appropriate combination of ˜number of equivalent cycles and ˜shaking duration was chosen, and sensitive parameters were in the range of measured values. Hydraulic conductivity, soil compressibility, and cycles to liquefaction are sensitive parameters and govern the computed Ru values.Modeling shows that the loading rate in the laminar shear box (15 cycles at 2 Hz) likely induced higher Ru values than would be expected in a typical earthquake event with a longer duration. The longer duration allows the drains to dissipate pore pressures and prevent liquefaction. The number of equivalent cycles and duration of shaking combinations recommended for various moment magnitudes in the FEQDrain user manual predict lower, but similar Ru versus time curves. Thus, suggesting that PVDs would be equally effective for any size earthquake. However, drains are most effective at preventing liquefaction when earthquake ground motions are long and uniform, rather than short and intense.Results from models in this study compare favorably with those from computer modeling performed by Howell et al. (2014). The individual hydraulic conductivity and compressibility values were different they were somewhat compensating. Similar Ru values can be modeled with different combinations of these parameters.Based on computer analyses, wick drains and 2 diameter PVDs were found to be relatively ineffective for preventing liquefaction. However, 3 diameter PVDs are fairly effective but can be overwhelmed during intense shaking. In contrast, 4 diameter and larger PVDs are significantly more effective.

Earthquake-induced liquefaction can cause severe damage to infrastructure is a serious concern in civil engineering practice. Post-liquefaction settlement is one of the common effects of liquefaction. The ability to predict and quantify post-liquefaction free-field settlement is a crucial part of seismic design. Many approaches have been developed during the past 50 years to perform liquefaction hazard analysis. The performance-based earthquake engineering (PBEE) framework developed by the Pacific Earthquake Engineering Research (PEER) center is a probabilistic framework that can provide a more accurate and complete seismic hazard analysis than other traditional methods. However, the PBEE framework is not widely used in routine projects due to its complexity.Previous researches have been performed to develop simplified performance-based procedures that can combine the simplicity of a traditional method and the accuracy of the full performance-based method. Unfortunately, these simplified performance-based procedures are only available for SPT. With the increase use of CPT, there is a need to develop simplified performance-based procedures for CPT. This study develops simplified performance-based procedures for the assessment of post-liquefaction free-field settlement for CPT, using the Boulanger and Idriss (2014) and the Ku et al. (2012) triggering models. The Juang et al. (2013) model, which is a probabilistic version of the Ishihara and Yoshimine (1992) model, is used in this study to performance free-field settlement calculations. The simplified procedure is based on the idea of liquefaction reference parameter maps. Reference values obtained from these parameter maps are then adjusted, using correction equations, to site-specific conditions. This study presents the deviations of the correction equations for the simplified performance-based procedure. The simplified procedure will then be validated in which 18 cities across the United States are analyzed using both the simplified procedure and the full performance-based procedure. The simplified performance-based procedure is shown to reasonably estimate the results of the full performance-based procedure. Finally, a study is performed to compare the accuracy and consistency of the simplified performance-based and the conventional pseudo-probabilistic procedures. The simplified performance-based procedure is found to provide better approximations of the full performance-based procedure with more consistency and precision.

Dynamic Cone Penetration Tests for LiquefactionEvaluation of Gravelly SoilsMichael H. TalbotDepartment of Civil and Environmental Engineering, BYUDoctor of PhilosophyIn North American practice, the Becker Penetration Test (BPT) has become the primary field test used to measure penetration resistance of gravelly soils. However, this test is expensive and uncertainties exist regarding correlations and corrections for rod friction. As an alternative, the dynamic penetration test (DPT) developed in China has recently been correlated with liquefaction resistance in gravelly soils. The DPT equipment consists of a 74 mm diameter cone tip driven by a 120 kg hammer with a free fall height of 100 cm using 60 mm drill rod to reduce friction. The DPT is a very rugged, economical device, capable of penetrating dense gravel layers. During DPT field investigations following the 2008 Wenchuan earthquake in China, liquefaction resistance was correlated with DPT blow count.Dynamic Cone Penetration tests (DPT) tests were also performed adjacent to Becker Penetration test (BPT) sites at Pence Ranch, Whiskey Springs, and Larter Ranch in Idaho where gravel liquefaction was observed during the 1983 Mw6.9 Borah Peak earthquake. Companion DPT tests were performed using an automatic hammer at two energy levels, namely the energy specified in the original Chinese standard and the energy typical of SPT testing which would be easier to use in practice. Companion testing was undertaken to determine if the cone could be driven in gravelly soil with more standard drilling equipment available to geo-professionals. The second energy level also offers the potential to provide more resolution on the soil layering. PDA measurements were made to determine the energy transferred to the cone rods and the statistical variation in the energy transferred.Additionally, companion DPT tests were undertaken at the downstream toe of Millsite Dam near Ferron, Utah, where gravelly soils are predicted to liquefy in an earthquake. Two energy levels were used, one using an automatic hammer and the other a manual donut hammer. The blow counts from the BPT and DPT correlated reasonably well for gravels using the automatic hammer, but poor correlation was obtained with the donut hammer. Liquefaction resistance for the BPT and DPT soundings were also in reasonable agreement for gravel layers suggesting that the DPT can provide liquefaction hazard evaluations more economically than the BPT using direct correlations with field performance.Correlations suggest that the standard energy corrections developed for the SPT can be used for the DPT. In general, the liquefaction resistance from the BPT and DPT correlated reasonably well when using the 30% probability of liquefaction resistance curve developed for the DPT.Keywords: Michael H Talbot, liquefaction, Chinese dynamic penetration test, gravelly soils.

Efter det dammbrott som skedde vid Brumadinho i Brasilien under januari 2019, där hundratals människor miste sina liv, har frågor kring statisk liquefaction hos anrikningssand fått stort fokus inom gruvdammsindustrin.  Statisk liquefaction kan modelleras med den konstitutiva modellen NorSand, där NorSand-parametrarna kan utvärderas från triaxialförsök. I det här arbetet har ett laboratorieprogram bestående av siktning, sedimentationsanalys, korndensitet, ödometerförsök och triaxialförsök utförts och NorSand-parametrar utvärderats. Fokus ligger på genomförande av laboratorieförsök samt utvärdering av parametrar. Målet är att redogöra för olika osäkerheter som kan påverka resultatet för att på så sätt reda ut vilka de känsligaste faktorerna är, och identifiera vilka moment under utförandet som är särskilt kritiska. Totalt har fyra dränerade och sex odränerade triaxialförsök utförts. Baserat på dessa har NorSand-parametrar utvärderats grafiskt samt genom att matchning av modellerade triaxialförsök i PLAXIS Soiltest mot de utförda försöken. Samtliga utvärderade parametrar ligger inom förväntat spann baserat på litteratur. Flertalet kritiska moment har identifierats avseende genomförandet av triaxialförsök. Vid utvärdering av NorSand-parametrar är bestämningen av portal det klart mest kritiska. Nästan samtliga NorSand-parametrar relateras till de utvärderade portalen. Portalen kan i sin tur bestämmas på olika sätt med olika osäkerheter. För att kunna värdera resultatet är det viktigt att veta vilken metod som använts och hur de känsliga momenten hanterats. På grund av hur kritiskt det är med korrekta portal så kan det vara en bra idé att använda två metoder och sedan jämföra resultaten med hänsyn till deras osäkerheter.  Samtliga NorSand-parametrar förutom Poissons tal bygger på subjektiv tolkning. Antingen utvärderas parametrarna grafiskt baserat på linjer anpassade av individen, eller så matchas modellerade försök till de utförda och då är det upp till individen att balansera försöken mot varandra. För att minimera utrymmet för individuell tolkning är det viktigt att tillräckligt många försök utförs så att potentiella uteliggare kan identifieras. Det är också viktigt att kommande försök planeras för att täcka in de spänningar och portal där det saknas information. / After the tragic failure of the Brumadinho tailings facility in Brazil during January 2019, where hundreds of people lost their life, the question of static liquefaction has received a lot of focus in the tailings industry.  Static liquefaction can be modelled using the constitutive model NorSand, where the parameters are evaluated from triaxial tests. The focus of this work has been on laboratory work and evaluation of NorSand-parameters. The laboratory work consisted of sieving, sedimentation analysis, particle density, oedometer tests, and triaxial tests from which the NorSand-parameters were evaluated. The aim is to identify uncertainties during triaxial testing and evaluation of NorSand-parameters, from which critical factors can be determined. In total, six undrained and four drained triaxial tests have been performed.  Multiple critical factors have been identified during the execution of triaxial tests. In relation to the evaluation of NorSand-parameters, the determination of void ratios is the most significant. For the resulting values to be assessable, it is important to know which method was used and how uncertainties were managed. Because of how critical correct void ratios are, it might be a good idea for them to be determined and compared using different methods. All NorSand-parameters except one are based on a certain amount of subjective interpretation. The person conducting the evaluation either manually fits lines to the test data or tries to match modelled triaxial tests to the ones performed by balancing the tests against each other. To minimize the impact of the individual it is important to carry out enough tests for potential outliers to be identified. It is also of importance to plan upcoming tests to cover stresses and void ratios with lacking data.