Matching Items (3)
Description
Enzyme-Induced Carbonate Precipitation (EICP) has emerged as a promising biogeotechnical solution for mitigating fugitive dust emissions. EICP mitigates fugitive dust emissions by inducing carbonate precipitation to bind soil particles together and enhance soil strength. Traditional dust mitigation approaches, such as applying water and chemical treatments, are limited by concerns surrounding cost, safety, and sustainability. In contrast, EICP treatment may offer a more eco-friendly and sustainable strategy for controlling fugitive dust emissions. Nevertheless, the lack of field-scale implementation has impeded the adoption of EICP treatment. This study is part of a larger effort to demonstrate the efficacy of EICP treatment at the field-scale by performing bench-scale and field-scale testing on three distinct soil types obtained from different field sites. The three soil types included a silty sand from fallow farmland in Pinal County, Arizona, clayey sand from an interim soil cover at a landfill site in Maricopa County, Arizona, and mine tailings from an abandoned mine site in Yavapai County, Arizona. Testing conducted for this research included evaluating wind erosion resistance using the Portable In-Situ Wind Erosion Laboratory ( PI-SWERL) on untreated and EICP-treated materials as well as soil characterization and penetrometer tests. The characterization tests included micro-scale analysis methods, such as carbonate content, scanning electron microscopy (SEM), and X-ray diffraction (XRD. The results of this study demonstrate the ability of EICP to mitigate fugitive dust in three different geotechnical materials by forming a soil crust on the ground surface via the precipitation of carbonate.
ContributorsYu, Xi (Author) / Kavazanjian, Edward EK (Thesis advisor) / Salifu, Emmanuel ES (Committee member) / Khodadadi Tirkolaei, Hamed HK (Committee member) / Arizona State University (Publisher)
Created2023
Description
In the marine ecosystem, mangrove forests protect the coastline due to their unique prop root system functions as a natural barrier to stabilize sediment and mitigate erosion. Such distinct characteristics provide a design inspiration to reduce local scour around underwater foundation systems such as the monopile foundation of offshore wind turbines. In this study, a ring of skirt piles in a circular layout inspired by the mangrove root structure has been proposed which aims to protect the centered monopile foundation. Three main aspects of the mangrove prop root system have been extracted to investigate the scour mitigation effect from the hydraulic, geotechnical, and bio-cementation perspectives. Laboratory flume tests have been conducted to evaluate the anti-scour potential using the proposed skirt pile groups. 3D reconstruction using the photogrammetric method has been employed to reconstruct the scoured bed for quantitative analysis. Computational fluid dynamics (CFD) and discrete element method (DEM) simulations have been performed to investigate the pile-flow and pile-sediment interactions, respectively. Results indicate the proposed skirt pile group reduces the scour depth and the volume of the scour hole by up to 57% and 85%, respectively. DEM simulation implied the installation of skirt piles demonstrates not only hydraulic but also geotechnical benefits due to the soil plug effect. In addition, a reactive transport model framework that simulates the bio-grouting process using microbially induced calcite precipitation (MICP) via shallow underwater injection has been developed to model the key processes such as bacterial attachment and detachment, urea hydrolysis, and calcite precipitation. The simulated cementation distribution exhibits a decent agreement with the experimental results, which could potentially be served for strategic optimization before conducting large or field-scale underwater injection tests. The model framework has been incorporated to simulate the MICP injection using skirt piles. Preliminary findings from this study demonstrated the feasibility of using mangrove-inspired skirt piles to mitigate scour for underwater foundation systems.
ContributorsLi, Xiwei (Author) / Tao, Junliang JT (Thesis advisor) / van Paassen, Leon LVP (Committee member) / Kavazanjian, Edward EK (Committee member) / Arizona State University (Publisher)
Created2024
Description
Enzyme-induced carbonate precipitation (EICP) is an emerging technology for ground improvement that cements soil with calcium carbonate to increase strength and stiffness. EICP-improved soil can be used to support new facilities or it can be injected under existing facilities to prevent excessive deformation. The limitations for commercial adoption of EICP are the cost and the lack of implementation at field-scale. This research demonstrated two ways to reduce the cost of EICP treatment at field-scale. The first was a modification to the EICP solution such that lower amounts of chemicals are needed to achieve target strengths. The second was to use a simple and inexpensive enzyme extraction method to produce the enzyme at a large-scale. This research also involved a two-stage scale-up process to create EICP biocemented soil columns using a permeation grouting technique. The first stage was at mid-scale where 0.6 m x 0.3 m-diameter EICP biocemented soil columns were created in boxes. This work confirmed that conventional permeation grouting equipment and methods are feasible for EICP soil treatment because the columns were found to have a uniform shape, the injection method was able to deliver the EICP solution to the edges of the treatment zone, and downhole geophysics was effectively used to measure the shear wave velocity of the biocemented soil mass. The field-scale stage was performed in the Test Pit facility at the Center for Bio-mediated and Bio-inspired Geotechnics' Soils Field Laboratory. Seven biocemented soil columns were created with diameters ranging from 0.3-1 m and heights ranging from 1-2.4 m. Effective implementation at this scale was confirmed through monitoring the injection process with embedded moisture sensors, evaluating the in situ strength improvement with downhole geophysics and load testing, and testing of the excavated columns to measure shear wave velocity, dimensions, carbonate content, and strength. Lastly, a hotspot life cycle assessment was performed which identified ways to reduce the environmental impacts of EICP by using alternative sourcing of inputs and extraction of byproducts. Overall, this research project demonstrates that EICP is a viable ground improvement technique by way of successfully producing field-scale biocemented soil columns.
ContributorsMartin, Kimberly Kathryn (Author) / Kavazanjian, Jr., Edward (Thesis advisor) / Zapata, Claudia E. (Committee member) / van Paassen, Leon (Committee member) / Arizona State University (Publisher)
Created2021