Conference Proceedings and Presentations
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PresentationDevelopment and Preliminary Field Testing of Cyclic Borehole Shear Soil Test Device(American Society of Civil Engineers, 2024-02-22)To help advance capabilities for measuring the in situ cyclic response of soils at chosen depths under controlled cyclic loading, a new prototype cyclic borehole shear test (CBST) device was developed in this study. Based on the monotonic BST device, the new CBST applies controlled normal and cyclic shear stresses to soil through serrated steel plates in contact with the wall of a 3-in. diameter borehole, while measuring the displacement of the shear plates as well as the shear stresses applied to the soil. Pore pressure is measured using a sintered porous disk embedded in one shear plate and hydraulically connected to a pressure transducer. Using the hardware and software control programs developed in this study, the capability of the prototype CBST device to measure the monotonic shear strength of soil is demonstrated, and preliminary results on the measured in situ soil behavior under cyclic loading conditions are presented.
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PresentationEffect of Temperature on the Shear Strength of Fine-Grained Permafrost Soils(American Society of Civil Engineers, 2024-02-22)Warming of the climate adversely impacts the permafrost by causing a degradation in the shear strength, especially in regions of discontinuous permafrost. This is triggered by an increase in the temperature of the permafrost resulting in an increase in the unfrozen water content and a weakening of underlying materials. Thus, infrastructure built in such regions will be prone to damage and failure. This study investigates the shear strength of fine-grained soils as a function of temperature. For this purpose, a temperature-controlled direct shear device was developed to conduct direct shear experiments at desired temperatures between −10°C and +4°C. The temperature-controlled direct shear device circulates chilled glycol within the device to prepare specimens with uniformly distributed ice contents at various vertical stresses. The results showed that shear strength decreased with an increase in temperature. This reduction in strength was also dependent on the vertical stress and shearing rate. At low temperatures, the samples were seen exhibiting dilative behavior, while contractive behavior was observed in the samples tested at temperatures greater than −2℃. Finally, the peak shear strength of the soil mass decreased with a decrease in the shearing rate.
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PresentationGeotechnical Engineering Curriculum Modules for High School Math and Science Classes(American Society of Civil Engineers, 2024-02-22)High school science and math classes can often seem irrelevant to the everyday lives of students leading to difficulties in engaging students in these topics. Moreover, limited opportunities for hands-on learning can further perpetuate perceptions of subject matter difficulty and result in limited exposure to available career paths. By incorporating hands-on curriculum modules in geotechnical engineering, it is possible to overcome these issues while providing students with real-world applications making the material more engaging and meaningful. This paper presents two curriculum modules developed as part of the National Science Foundation-funded Research Experiences for Teachers (RET) site at North Dakota State University. These modules—one for a high school science class and one for a high school math class—were developed with the aim of promoting science, technology, engineering, and mathematics education (STEM), while inspiring students to consider careers in geotechnical engineering. The lessons are designed to align with the Next Generation Science Standards and include hands-on activities along with real-world applications to enhance student understanding of the subject matter. The effectiveness of these modules was evaluated through formative and summative assessment and student surveys. The results indicate that the modules can effectively engage students in geotechnical engineering by connecting the math and science concepts from their classes and increase their interest in STEM fields. These curriculum modules are a valuable resource for high school math and science teachers looking to integrate engineering into their classes.
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PresentationParametric Study of the Effect of Slope Geometry, Soil Properties, and Rainfall Characteristics on the Stability and Deformation of Slope Failures(American Society of Civil Engineers, 2024-02-22)Climate change is causing changes in precipitation patterns around the world with some regions experiencing increased rainfall. This increase in rainfall can result in increased instability and landslide risks, especially in those areas with steep slopes and poor soil conditions. For example, the Pacific Northwest has seen an increase in the frequency of landslides in recent years as a result of more intense and frequent rainfall events. In this study, numerical models, developed in SIGMA/W of GeoStudio, were calibrated and validated using the results from a series of experimental models constructed in a Plexiglas container. These experiments were conducted on models with varying slope inclinations, void ratios, and rainfall intensities. The numerical models were then used to study the impact of slope geometry, soil properties, and rainfall characteristics on deformation of real-scale slope failures. In particular, the models were also used to evaluate the seepage velocity of the infiltrating water as well as the deformation affecting the stability of the slope. Seepage velocity was found to increase with an increase in the void ratio and rainfall intensity as well as duration. The time required for the slope to saturate was found to increase with an increase in the void ratio for a constant slope inclination and rainfall intensity. The swell of the slope was found to remain constant with an increase in the rainfall intensity.
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PresentationLaboratory Assessment for Utilizing Eggshell Waste on Iowa Soil Stabilization(American Society of Civil Engineers, 2024-02-22)Iowa has become the number one state in America in egg production in the past several years. Consequently, large amounts of eggshells are generated as unused wastes. Eggshell is made almost entirely of calcium carbonate crystals. Due to the rich calcium in eggshells, it has the great potential to be used as a calcium-based stabilizer material. However, such benefits of eggshells have not been evaluated and practiced in Iowa yet. This study aims to assess the beneficial use of Iowa eggshells as bio-based cementitious materials in stabilizing Iowa subgrade soils. Eggshells were ground into eggshell powder (ESP) through a coffee grinder. The testing results indicated that ESP treatment could elevate the plasticity of soil as well as the strength. The optimum content of ESP is 8%, which can achieve up to 30% strength improvement. The outcomes of this study indicate that ESP could be used as a non-traditional additive for Iowa soil stabilization.