Matching Items (2)
Description
Bridge scour at piers is a major problem for design and for maintaining old infrastructure. The current methods require their own upkeep and there may be better ways to mitigate scour. I looked to the mangrove forests of coastal environments for inspiration and have developed a 2D model to test the efficacy of placing a mangrove-root inspired system to mitigate scour. My model tests the hydrodynamics of the root systems, but there are additional benefits that can be used as bioinspiration in the future (altering the surrounding chemistry and mechanical properties of the soil).Adding a mangrove inspired minipile system to bridge piers changes scour parameters within my 2D COMSOL models. For the volume of material added, the minipiles compare favorably to larger sacrificial piles as they reduce A_wcz and 〖τ'〗_max by similar (or even better) amounts. These two parameters are indicators of scour in the field. Within the minipile experiments, it is more beneficial to place them upstream of the main bridge pier as their own ‘mangrove forest.’ The value of A_wcz and 〖τ'〗_max for complex 2D models of scour is unclear and physical experiments need to be performed. The model geometry is based on the dimensions of the experimental flume to be used in future studies and the model results have not yet been verified through experiments and field trials. Scale effects may be present which cannot be accounted for in the 2D models. Therefore future work should be conducted to test ‘mangrove forest’ minipile systems in 3D space, in flume experiments, and in field trials.
ContributorsEnns, Andrew Carl (Author) / van Paassen, Leon (Thesis advisor) / Tao, Junliang (Thesis advisor) / Kavazanjian, Edward (Committee member) / Arizona State University (Publisher)
Created2021
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