Sand dunes are an invaluable geologic feature of our coastal environment. During Hurricane Sandy in 2012, coastal infrastructure protected by sand dunes had much less damage than the infrastructure that was not protected. The sand dunes naturally dampen the energy from the large wave action and prevent damage and erosion further inland. Large wave action and high sea levels erode the sandy soil that supports coastal lifelines, including bridges, highways, pipelines, and other utilities. Damage from these large storm events can result in severe property damage, loss of revenue, and large repair costs. Preventing the erosion of the sandy soil can improve the resiliency of these coastal systems by minimizing damage, reducing repair costs and allowing communities to recover quicker after the storm events. Current methods to reduce coastal erosion, such as hardened structures, increase down drift erosion and replace the natural environment with man-made infrastructure. Coastal sand dunes are also an integral part of the coastal ecology; therefore a process used to reinforce the erodible sandy soil should not disrupt the natural coastal ecology.
The proposed project will provide a new soil improvement method to reinforce vulnerable lifelines in coastal communities. Applying MICP treatment methods to coastal sand dunes will require assessing the improved soil properties under new loading conditions and evaluating the effect the treatment process has on the surrounding ecology; hence, advancing the knowledge of bio-mediated soil improvement.
Microbial Induced Calcite Precipitation (MICP) has the potential to reinforce coastal sand dunes while preserving the natural ecology of the dunes. MICP utilizes urea hydrolysis with calcium chloride as the chemical reaction to increase the alkalinity of the pore fluid and induce calcite precipitation. Sporosarcina pasteurii, a common alkalophilic soil bacterium, has a high urease activity and is used to facilitate the chemical reaction. The MICP process occurs naturally in situ cementing sand into sandstone; however, it can be harnessed and accelerated to be used as a natural soil improvement process.
Assessing the ability for MICP to be used to protect coastal systems will be achieved by addressing the following objectives: 1) designing a MICP treatment process suitable for coastal soils, 2) evaluating the increase in shear strength and reduction of erosion potential, 3) addressing the potential effects (either adverse or beneficial) the MICP treatment process may have on the coastal ecology.
Broader Significance and Importance:
Over half of the global population lives near coastal communities, and these communities often struggle to rebound after large storm events. The proposed project is developed to advance bio-mediated soil improvement by developing new sustainable treatment methods for extreme loading conditions while minimizing the treatment?s impact on the local ecology. With the implementation of the treatment process developed within this project, lifelines will be able to resist the loading from large storm events while preserving the natural environment, which will improve the resiliency of the coastal infrastructure. In the broader context, the scientific advances from this project would also be applicable for liquefaction prevention, slope stability concerns, and roadway support.
Broadening Participation of Underrepresented Groups in Engineering:
In parallel with the bio-mediated soil improvement research, an outreach program is designed to promote female students to pursue a career in engineering. Society will benefit from an increase in female engineers by providing a diverse perspective to solve today?s challenges. The diversity-related goals of this project include increasing the interest of engineering among young female students and increasing the recruitment and retention female university students into graduate programs and academic careers. This goal will be met by exposing female students to different career paths in engineering and by providing female engineering role models the students can connect to during their elementary, middle school, and university education.
This research has been funded through the Broadening Participation Research Initiation Grants in Engineering solicitation, which is part of the Broadening Participation in Engineering Program of the Engineering Education and Centers Division.
