Benchmark Portfolio: CIVE 334 - Introduction to Geotechnical Engineering

This Benchmark Portfolio is for CIVE 334 “Introduction to Geotechnical Engineering”. The course description is provided as “soil composition, structure and phase relationships; soil classification; principles of effective stress; loading induced subsurface stresses; load history; deformation and failure of soils; elastic and limit analysis with applications to design for bearing capacity, settlement, retaining walls, and slope stability; steady-state seepage.” This course is mandatory for students in the department of civil engineering, and the only mandatory class in the sub-discipline of geotechnical engineering. Therefore, this course is critical for students to have foundational knowledge about soil mechanics and geotechnical engineering, and essential to understanding other advanced topics in the sub-discipline of geotechnical engineering. After successfully passing this course, the instructor wants that students become capable of the following aspects: (1) understand soils as an important construction material; (2) understand how soils can be categorized into different groups (e.g., fine-grained and course-grained soils) based on their index and physical properties; (3) understand the hydraulic properties of soils in relevance to their classification; (4) understand the mechanical behavior of soils (deformation, stiffness, and strength) with their classification and presence of water; and (5) apply mathematical formulae to predict such a hydraulic-and-mechanical response of soil materials. Main purpose of this benchmark portfolio is to examine how students achieve these key learning objectives and look for possible improvements. The benchmark portfolio consists of benchmark memo 1, 2, and 3, followed by summary and reflection

Feasibility of electromagnetic soil heating using magnetic nanoparticle-coated geotextiles

This paper reports a new way of soil heating using a woven and a non-woven geotextile coated with magnetic nanoparticles (MNPs) that generate heat when exposed to a magnetic field. The MNPs were synthesised in the presence of the geotextile, creating and simultaneously coating the MNPs onto the geotextile. The fixation of MNPs on the geotextile was confirmed by direct observation by way of scanning electromagnetic images and an induction heating test. When the prepared geotextile was placed inside a soil medium, heat was generated immediately as the geotextile was exposed to a high-frequency alternating magnetic field, subsequently transferring heat from the MNP-coated geotextile to the surrounding soil. The soil heating performance was greater with the non-woven geotextile than with the woven one, which implies a better capacity to retain the MNPs with a rough surface. However, the effect of different soil types (sand and clay) on heating performance was insignificant. A follow-up study on the heat transfer on a field scale will provide a practical strategy for field application. Overall, the innovative heating method can potentially provide additional functionality to geotextiles as an attractive option for soil heating

Experimental study on the characteristics of formation and dissociation of CO2 hydrates in porous media

Geologic carbon sequestration (GCS) has pursued as a feasible strategy to store the large amount of CO2 to curb its emission to the atmosphere in an effort to mitigate the greenhouse effects. CO2 hydrate, which can form when the pressure and temperature satisfy its stability condition, can provide a self-trapping mechanism for an offshore CO2 geologic storage. For example, direct sequestration of CO2 in the form of hydrate cystals an be achieved in the storage zone an potentially provide a secondary caprock. These application, however, require a thorough understanding of the formation and dissociation of CO2 hydrates in porous media, which are largely unknown yet. In this manuscript, a laboratory study on the formation and dissociation of CO2 hydrates in two different environments, a two- (CO2-water) or three-phase (CO2-water in glass beads) condition, is presented. Based on the experimental results, it can be anticipated that the pressure and temperature change will be negligible when the formation of CO2 hydrate is induced for GCS in the actual soil/rock layers. Besides, the formation of CO2 hydrate in porous media may be faster, compared to the two-phase bulk condition that has been typically used in many laboratory studies, as solid grains help accelerate the hydrate formation by providing nucleus sites of crystals. Further elaborations on the role of solid grains would bring a clear path for the feasible application in the subsea area

Experimental Study: The Effect of Pore Shape, Geometrical Heterogeneity, and Flow Rate on the Repetitive Two-Phase Fluid Transport in Microfluidic Porous Media

Geologic subsurface energy storage, such as porous-media compressed-air energy storage (PM-CAES) and underground hydrogen storage (UHS), involves the multi-phase fluid transport in structurally disordered or heterogeneous porous media (e.g., soils and rocks). Furthermore, such multi-phase fluid transport is likely to repeatedly occur due to successive fluid injections and extractions, thus, resulting in cyclic drainage–imbibition processes. To complement our preceding study, we conducted a follow-up study with microfluidic pore-network devices with a square solid shape (Type II) to further advance our understanding on the effect of the pore shape (aspect ratio, Type I: 5–6 \u3e Type II: ~1), pore-space heterogeneity (coefficient of variation, COV = 0, 0.25, and 0.5), and flow rates (Q = 0.01 and 0.1 mL/min) on the repetitive two-phase fluid flow in general porous media. The influence of pore shape and pore-space heterogeneity were observed to be more prominent when the flow rate was low (e.g., Q = 0.01 mL/min in this study) on the examined outcomes, including the drainage and imbibition patterns, the similarity of those patterns between repeated steps, the sweep efficiency and residual saturation of the nonwetting fluid, and fluid pressure. On the other hand, a higher flow rate (e.g., Q = 0.1 mL/min in this study) appeared to outweigh those factors for the Type II structure, owing to the low aspect ratio (~1). It was also suggested that the flow morphology, sweep efficiency, residual saturation, and required pressure gradient may not severely fluctuate during the repeated drainage—imbibition processes; instead, becoming stabilized after 4–5 cycles, regardless of the aspect ratio, COV, and Q. Implications of the study results for PM-CAES and UHS are discussed as a complementary analysis at the end of this manuscript

Evaluation of Equivalent Thermal Conductivity for Carbon Fiber-Reinforced Bentonite through Experimental and Numerical Analysis

Bentonite is widely used as a water-proof material in engineering, and fibers are added to reduce the crack development of bentonite after drying. Carbon fiber can reinforce bentonite in heat-sensitive projects because of its high thermal conductivity and potential inhibition of bentonite cracking. Thus, it is important to determine the thermal conductivity of carbon fiber-reinforced bentonite. This study evaluated the thermal conductivity of carbon fiber-reinforced bentonite by analytical solution, experiment, and finite element method (FEM) simulation and discussed the effects of carbon fiber content, fiber length, fiber distribution, and the porosity of bentonite on the thermal conductivity of reinforced bentonite. The results show that the addition of carbon fiber can effectively improve the thermal conductivity of bentonite, and the thermal conductivity of the mixture is positively correlated with the content of fibers and the dry density of bentonite. When the content of carbon fiber with a thermal conductivity of 1000 W/(m K) is 1.0 %, and the porosity of bentonite is 0.4, the thermal conductivity of the composite can be increased by up to 390 %. At the same time, the distribution of fibers plays a vital role in thermal conductivity, and the thermal conductivity in the case of parallel distribution is 1.48 and 2.91 times that of random distribution and serial distribution. In addition, longer fiber length will help improve the thermal conductivity of the mixture. The thermal conductivity of the mixture for 1-inch fibers is 1.11 and 1.29 times that of 1/2-inch and 1/4-inch fibers. This study provides evidence of the possibility of improving the thermal conductivity of carbon fiber-reinforced bentonite

Promotional Effect on Selective Catalytic Reduction of NO x

W and Ce are known to be a good promoters to improve selective catalytic reduction (SCR) activity for V2O5/TiO2 catalysts. This work aimed at finding the optimum ratio and loading of promoters (W and Ce) on V2O5/TiO2 catalyst in order to improve SCR reactivity in low temperature region and to minimize N2O formation in high temperature region. In addition, we changed the order of impregnation between W and Ce precursors on V2O5/TiO2 catalyst during the preparation and observed its effect on SCR activity and N2 selectivity. We utilized various analytical techniques, such as N2 adsorption-desorption, X-ray diffraction (XRD), and temperature-programmed reduction with hydrogen (H2 TPR) to investigate the physicochemical properties of catalysts. It was found that W- and Ce-overloaded V2O5/TiO2 catalyst such as W/Ce/V/TiO2 (15 : 15 : 1 wt%) showed the most remarkable DeNOx properties over the wide temperature region. Additionally, this catalyst significantly suppressed N2O formation during SCR reaction, especially in high temperature region (350–400°C). Based on the characterization results, it was found that such superior activity originated from the improved reducibility and morphology of W and Ce species on V2O5/TiO2 catalyst when they are incorporated together at high loading

Experimental and Numerical Studies on Thermally-Induced Slip Ratcheting on a Slope

Mild temperature fluctuation of a material sitting on a slope may only cause a small slip, but a large number of the repeated temperature changes can amplify the magnitude of the overall slip and eventually bring an issue of structural instability. The slip accumulation starts from the minor magnitude and reaches the extensive level called “slip ratcheting”. Experimental evidence for such thermally-induced slip ratcheting is first provided in this work. It is implemented with an acryl sheet placed on an inclined wood with a mild angle; it is found that the temperature fluctuation of the acryl sheet causes the sheet to slide down gradually without any additional loading. The numerical model is then attempted to emulate the major findings of the experiments. From the simulation work, the location of a neutral point is found when the acrylplate is heated, and another neutral point is observed when cooled down. The shift of the neutral point appears to be a major reason for the unrecovered slip after a temperature increase and decrease cycle. Finally, a parametric study using the numerical model is carried out to examine which parameters play a major role in the development of residual slips

Symmetrical Aspects of Urban Regeneration in Seoul

Korea has developed very rapidly since 1980s highlighted with Seoul olympic, and urbanization necessarily incurred. Population grew with increasing housing demands, but old towns could not provide enough land. The old town was already congested, and living conditions fell off. Therefore, new towns outside the old town were planned and built through three sequential phases. This suburbanization brought about heavy load on commuter transportation and air pollution. At the same time, improper infrastructure and amenities turned new towns into bedtowns. To escape from bedtowns, people returned to the old town, and urban remodeling was needed to accommodate adequate living conditions. In doing so, local characteristics were lost. Urban regeneration aroused as a countermeasure to this mishap. In this study, urban regeneration reinforced with smart technologies is suggested to revive lost placeness, communal connectivity, and urban orientation. Gentrification is another important issue to be resolved for the sustainable urbanization. This study focused on symmetrical aspects of the successful urban regeneration

Experimental study of pipe-pile-based micro-scale compressed air energy storage (PPMS-CAES) for a building

Compressed air energy storage (CAES) technology has been re-emerging as one of the promising options to address the challenge coming from the intermittency of renewable energy resources. Unlike the large-scale CAES, which is limited by the geologic location, small- and micro-scale CAES that uses a human-made pressure vessel is adaptable for both grid-connected and standalone distributed units equipped with the energy generation capacity. The research team recently suggested a new concept of pipe- pile-based micro-scale CAES (PPMS-CAES) that uses pipe-pile foundations of a building as compressed air storage vessels. To ascertain the mechanical feasibility of the new concept, we conducted lab-scale pile loading tests with a model test pile in both a loose and dense soil chamber that emulates an actual closed- ended pipe pile. The test pile was subjected to a repeated cycle of compressed air charge (to Pmax=10 MPa) and discharge (to Pmin=0.1 MPa) during the experimental study. The displacement at the top of the test pile, with and without a structural loading, in loose and dense sand, was closely monitored during the repetitive air pressurization-and-depressurization. It was observed that the vertical displacement at the pile head under different conditions was accumulated during the extended cycle of air charge and discharge, but the rate of displacement gradually attenuates during the cycle. And, the presence of structural load and density of soil affected the magnitude of the accumulated vertical displacement. From the analysis, it can be concluded that the concept of PPMS-CAES is not likely to compromise the mechanical integrity of pipe piles while showing a promising capacity for energy storage