Microscale Characterization of Energy Dissipation Mechanisms During Liquefaction

This study utilizes the discrete element method (DEM) to present a microscopic energy monitoring approach to characterize energy dissipation mechanisms in seismically loaded soils. Numerical simulations were conducted on saturated deposits of granular particles subjected to seismic excitations, modeled using a transient fully-coupled continuum-fluid discrete-particle model. The onset of liquefaction is illustrated through macroscopic and microscopic response patterns. An in-depth look at the individual microscale energy components both before and after the onset of liquefaction is presented. Prior to liquefaction, energy is dissipated mainly through inter-particle sliding (friction energy), but after liquefaction particle-to-particle impact damping also plays a major role in dissipating energy

DEM Simulation of Liquefaction-Induced Lateral Spreading

This paper reports the results of a model-based simulation of 1g shake table tests of sloping saturated granular deposits subjected to seismic excitations. The simulation technique utilizes a transient fully-coupled continuum fluid discrete particle model of the watersaturated soil. The fluid (water) phase is idealized at a macroscale using an Eulerian averaged form of Navier-Stokes equations. The solid particles are modeled at the microscale as an assemblage of discrete spheres using the discrete element method. The interphase momentum transfer is accounted for using an established relationship. Numerical simulations were conducted to investigate the liquefaction induced lateral spreading of a mild-sloped semi-infinite deposit subjected to a dynamic base excitation. The employed model reproduced a number of response patterns observed in the 1g experiment. In addition, the simulation results captured the initiation of sliding at failure planes, the propagation of liquefaction front and associated large strain localization, and the redistribution of void space during shaking

Numerical Modeling of the Effect of Desaturation on Liquefaction Hazard Mitigation

Earthquake-induced liquefaction is always a concern when the soil near the surface of a site is composed of relatively loose saturated sand. One of liquefaction mitigation methods is to induce gas bubbles into the deposit to reduce the degree of saturation. A coupled pore-scale model is presented herein to investigate liquefaction resistance of desaturated granular materials. The multiphase fluid, which mimics the behavior of air and water, is modeled using the multiphase single component lattice Boltzmann method. The solid phase is modeled using the discrete element method. The coupled framework was utilized to study the behavior of a soil deposit with the different degrees of saturation of 100%, 92%, and 82% during an earthquake loading. Based on the results of the simulations performed, liquefaction occurred in the fully saturated granular deposit and was not observed anywhere at depth in the desaturated deposits. It has also been found that reducing the saturation level from 100% to 92% significantly affects behavior. In desaturated deposits, higher average coordination number, lower pore pressure buildup, and slower effective stress decay were observed compared to fully saturated deposits. However, it turned out that a further reduction in the degree of saturation from 92% to 82% does not have a significant impact on the calculated parameters

Actinomycetes from the Red Sea Sponge Coscinoderma mathewsi: Isolation, Diversity, and Potential for Bioactive Compounds Discovery

The diversity of actinomycetes associated with the marine sponge Coscinoderma mathewsi collected from Hurghada (Egypt) was studied. Twenty-three actinomycetes were separated and identified based on the 16S rDNA gene sequence analysis. Out of them, three isolates were classified as novel species of the genera Micromonospora, Nocardia, and Gordonia. Genome sequencing of actinomycete strains has revealed many silent biosynthetic gene clusters and has shown their exceptional capacity for the production of secondary metabolites, not observed under classical cultivation conditions. Therefore, the effect of mycolic-acid-containing bacteria or mycolic acid on the biosynthesis of cryptic natural products was investigated. Sponge-derived actinomycete Micromonospora sp. UA17 was co-cultured using liquid fermentation with two mycolic acid-containing actinomycetes (Gordonia sp. UA19 and Nocardia sp. UA 23), or supplemented with pure mycolic acid. LC-HRESIMS data were analyzed to compare natural production across all crude extracts. Micromonospora sp. UA17 was rich with isotetracenone, indolocarbazole, and anthracycline analogs. Some co-culture extracts showed metabolites such as a chlorocardicin, neocopiamycin A, and chicamycin B that were not found in the respective monocultures, suggesting a mycolic acid effect on the induction of cryptic natural product biosynthetic pathways. The antibacterial, antifungal, and antiparasitic activities for the different cultures extracts were also tested

Lessons Learned from a Game-Based Learning Intervention in Civil Engineering

The aim of our project is to create a scalable and sustainable educational model of mixed reality gaming in civil engineering education that provides practical experiences, develops engineering judgment competency, and engages a diverse student audience. Specifically, we have been building a game-based learning module focused on experiencing the field testing technique cone-penetration testing (CPT). As part of the module, students start a virtual internship at a fictional engineering company. After being briefed through a lecture on CPT, they enter a 3D (game) environment where they conduct CPTs. Students analyze CPT data extracted from the environment and submit a report. To assess student experience of this module, we collected pre/post surveys, game data (including in-game assessments), and student/faculty interviews. In this paper, we report the findings of implementing this CPT module in the initial three years of the project (2016-2019) at five institutions. Overall, we find that students are engaged, especially women and students from historically marginalized communities, increase their knowledge and confidence in the subject matter, and find the module valuable to gain much-needed (field) experience. More recently, we find that the game-based learning intervention seems resilient and, in fact, a solid solution to the disturbances caused by the pandemic, with many students providing positive remarks about being able to experience hands-on learning, which is key to quality engineering education and difficult to achieve through online education. Opportunities for improvement exist regarding access to technology, as well as the instructional design. While we demonstrate the scalability of this approach across multiple institutions and classrooms, open questions remain on how to transform institutions to embed game-based learning not as an intervention but as a key part of the curriculum.This presentation is published as Harteveld, C., & Bennett, V., & Zastavker, Y. V., & El Shamy,, U., & Tiwari, B., & De,, A., & Wirth, X., & Wen, K., & Saftner, D. A., & Ajmera, B., & Brandenberg, S., & Kennicutt, A. R., & Congress, S. S. C., & Tessari, A., & Omidvar, M., & Cabas, A. (2023, June), Lessons Learned from a Game-Based Learning Intervention in Civil Engineering Paper presented at 2023 ASEE Annual Conference & Exposition, Baltimore , Maryland. https://strategy.asee.org/43423. Posted with permission. © 2023 American Society for Engineering Education. Other scholars may excerpt or quote from these materials with the same citation. When excerpting or quoting from Conference Proceedings, authors should, in addition to noting the ASEE copyright, list all the original authors and their institutions and name the host city of the conference.<br