Brina Montoya

Within the area of bio-mediated soil improvement, the majority of the research effort (both the community���s and my own) has been elucidating the change in the soil���s mechanical behavior and overall performance (i.e., ���soil improvement���). The soil improvement has almost exclusively been achieved by using ureolytic bacteria that induce carbonate precipitation. My proposed pivot will be to expand the ���bio-mediated��� aspect of the research area by uncovering active soil microbial communities through advance molecular techniques, specifically metaproteomics. I plan to achieve this by specific training in metaproteomics in Dr. Manuel Kleiner���s lab, with complementary training in metagenomics through the Biotechnology program at NC State. The proposed activities meet the track goals by allowing the PI and graduate student to gain research fluency in advance molecular techniques that may lead to the discovery of more sustainable microbial mechanisms that alter the soil���s behavior. The overall research objective is to identify mechanisms capable of improving soil behavior by using state-of-the-art methods to assess the functions and interactions of the indigenous complex microbial communities. The improved soil behavior will enhance the resiliency of civil infrastructure. The collective skill set obtained through the proposed pivot will enable the research team to understand the composition and activity of soil microbial communities to be used for geotechnical purposes. The proposed project will initially focus on training in metaproteomics through Dr. Kleiner���s lab, classes, and related seminar series in the Microbiomes and Complex Microbial Communities Cluster at NC State. The techniques developed in the first year of training will be used to investigate complex microbial communities in microcosms studied in the PIs past projects (e.g., surficial dune sand, subsurface/offshore saturated granular soil, ore mine tailings) with the anticipated outcomes of developing 1) a framework to incorporate metaproteomics into geotechnical site investigation and 2) preliminary results of potential communities of interest to explore further with the goal to utilize more sustainable biochemical reactions (potential examples in flowchart below). The following years of the project will expand the training in molecular microbiology and establish proof of concept to identify microbes via metaproteomics and utilizing them to change soil behavior. The anticipated contribution near the end of the project will be to establish more sustainable bio-mediated methods for byproduct stabilization (building upon CAREER results). The outcomes of the proposed project will provide more sustainable and economical biologically-mediated methods to improve soil performance and protect infrastructure, and integrate advanced microbial background into geotechnical students��� knowledge. A portion of the DEI activities will include developing a citizen scientist program with connection to communities effected by byproduct impoundments to provide alternative, sustainable soil improvement methods targeting site-specific microbes.

When seeking solutions to today's elevated atmospheric CO2 levels, it is critical that we include data from the past, because atmospheric CO2 concentrations have fluctuated throughout Earth history. In fact, CO2 levels have been consistently higher in the past������������������often significantly higher, at times perhaps as much as 6x pre-industrial values. The biological response of life on Earth to these global conditions, from their onset to their cessation, is recorded in the rock record. Intriguingly, Konservat Lagerst��������tte (e.g., sedimentary deposits that preserve fossils in extraordinary detail) occur more frequently in the distant past (i.e., deep time) than in more recent depositional environments. Could these be linked? We hypothesize that ancient microorganisms responded to pre-Cenozoic high atmospheric CO2 by sequestering carbon through very rapid precipitation of carbonate minerals in terrestrial, as well as marine settings. This increase in microbial precipitation of carbonates, sometimes as concretions, created conditions favorable to the stabilization of normally labile tissues and the exclusion of exogenous, degradative influences. These factors very likely contributed to exceptional preservation of fossil remains, including persistence of non-biomineralized (i.e., ����������������soft���������������) tissues. Although microbes have been invoked as agents of preservation as well as destruction, because they act to ����������������seal��������������� sediments surrounding bone to form a relatively closed system, to date, the effect of contemporaneous atmospheric CO2 levels on microbial carbonate precipitation, and its implications for preservation, have not been explored. The convergence research we propose would enable us to design and implement empirical studies that directly test this idea, and characterize the microbial influence in depositional environments producing exceptionally preserved fossils. Thus, we ask the following: 1) Did the elevated CO2 in Mesozoic atmospheres play a role in microbially mediated exceptional preservation? 2) If this can be demonstrated through actualistic experiments and fossil studies, could this mechanism of fossil preservation also shed light on microbial sequestration of atmospheric CO2 in terrestrial environments? 3) Furthermore, can this understanding of microbially mediated CO2 sequestration be harnessed for development of robust, scalable carbon-capture systems? To test these hypotheses, we propose a two-pronged approach. We will conduct empirical tests that involve growing known microbially induced carbonate precipitation (MCIP) strains, as well as microbial communities from relevant environments, under conditions of Mesozoic proxy atmospheres. We will compare the rate and degree of precipitation in organisms grown in enriched CO2 with those of the same strains grown in ambient atmospheres, to characterize the effects of elevated CO2 on precipitation rates. Then, we will examine: 1) the sediments surrounding exceptionally preserved fossils, 2) the composition of concretions that contain fossil material, 3) the morphological and molecular preservation of the fossils themselves, and 4) biomarkers associated with microbes in these fossil materials, using a combination of chemical and molecular techniques. Our interdisciplinary team will work synergistically to examine the role of microbes in both fostering and impeding exceptional preservation, the relationship of exceptional preservation to elevated atmospheric CO2, and potential microbial pathways that can be exploited to accomplish terrestrial carbon sequestration. Such pathways are rarely considered in the dialogue regarding potential solutions to anthropogenic carbon release, but may present a viable, cost-effective mitigation measure

Traditional practice of bridge local scour estimation relies upon the use of analytical models such as the one specified in Hydraulic Engineering Circulars, HEC-18 and HEC 20 (Arneson et al., 2012). Models such as HEC-18 were however developed based on data collected mainly from flume testing on sand. The data used for HEC-18 model development were mainly for narrow pier erosion in sand (scour depth/pier width>1.4) per Benedict and Knight (2017). Yet the model is applied in practice to intermediate and wide pier cases as well. In addition, the materials classified as ���soils��� include sand, and/or silt, and/or clay with a grain size distribution that can yield a bed soil behavior that may not be captured by a single parameter, such as D50. Approaches such as the HEC-18 model also lump the flow channel and bridge hydraulic and geometrical parameters with the bed erosion resistance parameters in one equation. While such an approach is simple to use, there is consensus in literature that it yields overly conservative scour estimates. On a fundamental level, the magnitude of erosion and scour can be assessed through knowledge of the flow-induced shear stress, the soil���s erodibility parameters, which include the critical shear stress (��c), co- efficient of erodibility (��'), and m, which is ���an exponent defining the functional variation of the soil erosion rate with the flow-induced shear stress.��� This approach is fundamentally implemented in the FHWA Hy- draulic Toolbox and adopted by the NextScour Program. In parallel, geotechnical site investigation by the North Carolina DOT commonly involves the performance of SPT, and the retrieval of soil samples for characterization of physical and engineering properties. As such, there is an opportunity to obtain the site- specific erodibility (��c, ��', and m) through linking such parameters with the geotechnical data for a rational assessment of site-specific scour magnitude, accounting for variability of channel-bed soil layers with depth.

The integrity and reliability of flood-control earthen dams and levees are essential components to homeland safety. The failure of such systems due to natural or man-made hazards may have monumental repercussions, sometimes with dramatic and unanticipated consequences on human life and the country������������������s economy. The levees network in the Sacramento-San Joaquin Delta support exceptionally rich agricultural area (over a $500 million annual crop value). Currently, the risk of levee failure in this area from potential flooding or draught threatens the lives of individuals living behind the levees, but also, the water quality in this water-transfer system. Preliminary risk assessment demonstrated a 40% chance that at least 30 islands within the Delta area would be flooded by simultaneous levee failures in a major earthquake in the next 25 years. The teamwork proposed herein will extend the remote sensing monitoring by InSAR and Joint Scatterer interferometry (JSInSAR) to monitor levees deformation with a resolution on the order of a few millimeters. The research team ay NCSU will participate by integrating the use of measurement data and modeling techniques, using the concept of performance limit states, to effectively achieve a performance based health assessment of the delta levees network.

Liquefaction-induced large lateral displacements (i.e., lateral spreading) after earthquakes represent a major geohazard in earthquake-prone regions leading to significant human and economic costs. This one-year collaborative proposal by North Carolina State University and Bucknell University aims to improve the prediction of liquefaction-induced lateral spreading. In pursuit of that goal, we aim to (1) incorporate geomorphic factors that control large lateral displacements (LD) into empirical predictive models, (2) define an improved ground motion (GM) characterization that includes the duration of ground shaking and the time to the onset of liquefaction triggering, and (3) reduce bias and variability in lateral spreading predictions. The outcome of the proposed work will be a framework that incorporates relevant geomorphic variables in lateral spreading models.

Soils play a fundamental role in myriad global processes. The need to understand the flow of elements, energy, and water through soils is immense and widely accepted across the geosciences community. Yet, the number of scientists trained with specific soils expertise is rapidly declining. The BESST REU Site utilizes a diverse, multi-disciplinary team of scientists to deliver individualized student research experiences in state-of-the art soil science topics, synergized through unifying themes and team training opportunities. Specific objectives are to: i) recruit outstanding students without extensive previous experience in soil science, with an emphasis on those from under-represented groups; ii) train these students by providing a substantive research experience and exposure to broad opportunities in basic and environmental soil science; and iii) develop a pool of future professionals empowered to advance understanding of soils in the geoscience community. Activities are supported by a university with well-developed infrastructure for undergraduate student research, and hosted by a department with a long-standing tradition of international excellence. Student recruitment is pursued through departmental and university collaboration with undergraduate-serving institutions, HBCUs, and national undergraduate research organizations. The program is assessed by external experts to ensure that it is rigorously evaluated and didactic impact maximized. The intellectual merit of the REU Site lies in constructing a critically needed pipeline for the next generation of geoscience researchers, equipped to address wide-ranging basic and environmental research problems in soils. Broader impacts are derived from training a diverse group of students to engage in addressing important societal and ecological issues throughout their careers. The REU site seeks to develop a new paradigm for soil science, extending student recruitment and training beyond traditional foundations in agriculture, and transforming soil science into an integral part of the geoscience research community. Student research opportunities highlight relationships between human activities and terrestrial environments, which are central topics in modern soil science that are broadly applicable to many other sub-disciplines of the Earth and environmental sciences.

Infrastructure resilience has become an important topic for North Carolina. Recent hurricanes and other extreme events have caused more than $450 million in damage to the States������������������s transportation infrastructure. In addition to the cost of the infrastructure, the NCDOT spent considerable resources to redesign and repair many elements after each event. A review of the NCDOT records following Hurricane Florence indicates that more than 3,000 disruptions resulted from that event alone. Some of these locations were identical to those damaged during Hurricane Matthew but, the amount of damage was different between the two events, suggesting that DOT strategies were effective. However, detailed quantification of the performance differences have not been completed and thus NCDOT engineers must rely on qualitative and anecdotal evidence as to the effectiveness of various strategies. Though many agencies have studied the topic of infrastructure resilience to extreme events, the literature suggests that the generalizability of their findings is limited because of the contextual sensitivity of the available strategies. In this case, data on the effectiveness of design and repair strategies within the context of North Carolina is required. Thus, research is needed to identify and evaluate the specific elements of the new infrastructure that positively contributed to the improved performance during Hurricane Florence and those that did not positively contribute. With respect to this need, the proposed research plan will achieve four objectives; 1) evaluate the design process for roadway infrastructure that was repaired following Hurricanes Matthew and Florence, 2) identify the specific elements of the new infrastructure that positively contributed to improved performance during Hurricane Florence, and 3) develop recommendations on design elements that improve the resilience of NCDOT roadways. These objectives will be met with five tasks. 1. The relevant literature on resilient infrastructure and practices for ensuring transportation infrastructure resilience to extreme events will be reviewed and documented. 2. Locations where roadway infrastructure failed during Hurricanes Matthew and Florence will be identified, mapped, and compared. 3. The performance of different maintenance, repair, and reconstruction strategies deployed in the aftermath of Hurricane Matthew will be evaluated and quantitatively assessed. 4. A series of detailed case studies will be performed to identify the design factors and repair/maintenance decisions that led to better performance during Hurricane Florence. 5. A final report summarizing the methodology, results, and recommendations will be prepared The primary outcome of the proposed research will be data on the effectiveness of design strategies used to repair infrastructure following hurricanes specifically and extreme events in general. This knowledge can be helpful to improve the design and repair methodologies to be more robust and resilient against future extreme events. The research will also produce a set of guidelines and recommendations for hydraulic design, repair, and reconstruction that may improve the resiliency of roadway design in North Carolina. The guidelines that results from this research will allow NCDOT engineers to deploy design strategies that are proven to be cost effective in the long run. For example, the primary focus of engineers after the event is restoring mobility. For some cases, once this mobility is restored it may be cost effective to redesign or reconstruct a more robust design so that future events do also cause disruptions. This work will provide evidence as to when and how such major repairs can be effective. The proposed work is significant because it will provide quantified evidence as to the efficacy of existing strategies to provide this long-term effectiveness. Ultimately, the deployment of these strategies can reduce agency costs while also improving roadway resilience to extreme events.

Dunes often present the first line of defense for the built environment during extreme wave surge and storm events. In order to remain effective, dunes must resist erosion in the face of these incidents. Understanding the physics of dune erosion is critical for devising ways to mitigate it, and this is an active area of ongoing research. We propose to explore a novel approach using microbial induced carbonate precipitation (MICP) to stabilize and enhance natural protective structures. We will explore multiple treatment implementation techniques and assess their performance under extreme conditions. In the process, a case study of MICP treatment in an unsaturated dune environment will advance MICP towards more established in situ implementation. Furthermore, the numerical investigation will provide insight into when (e.g., anticipated loading conditions) each treatment implementation alternative is preferred, and the treatment design (e.g., required treatment dimensions) to have minimal impact to ecology with required engineering performance.

The North Carolina Department of Transportation (NCDOT) routinely performs assessment of scour potential at bridge foundations. The availability of representative approaches for estimating first order scour magnitude is needed as such information is used for the design of new bridges, designating bridges as ����������������scour- critical,��������������� and for deciding on the need for implementing scour countermeasures. As stated by Mr. Jerry Snead, the applicability and potential modification of USGS Scour Envelope Curves, developed for the state of South Carolina, to North Carolina soils is the focus of the research proposed herein. Such investigation is needed to assess the robustness of the first order scour estimates and to provide reliable quality control measure to ensure the reasonableness of bridge scour magnitudes estimated by other means.

CAREER: Stabilization of Mining and Energy Related Byproducts using Bio-Mediated Soil Improvement The overall objective of the proposed project is to provide biologically mediated treatment methods to improve the performance of mining and energy related byproduct material. Mining for material and energy needs generates large volumes of waste materials, and these materials must be stored for hundreds to thousands of years. Safely storing these waste materials is a necessity to keep society and the environment safe since these materials often have toxic trace elements embedded within them. Mining and energy related byproducts tend to be stored in either tailing ponds or tailing piles. These storage mechanisms have inherent engineering concerns, specifically: 1) failure of the stored material due to inadequate shear strength, 2) spreading of the stored material due to erosion from wind or surface water, and 3) leaching of toxic trace elements into nearby surface and ground water sources. The proposed project will address these concerns by using bio-mediated soil improvement. The hypothesis for the proposed research project is that bio-mediated soil improvement methods will improve the mechanical performance and environmental concerns of mining and energy related byproduct materials. Established ureolytic-driven microbial induced calcite precipitation (MICP) methods will be used to improve the shear strength and structural stability of the stored byproducts, reduce the potential of erosion due to wind and surface water, and immobilize trace elements that may potentially leach into nearby water sources. In addition, alternative biological metabolic pathways, such as iron and sulfate reduction, will be explored that may result in similar bio-mineralization products. Since the storage life of the byproduct material is orders of magnitude longer than typical engineering projects, the permanence of the treatment techniques will also be assessed. The stabilization of the byproduct material will improve the storage of existing and newly generated materials and help facilitate resource recovery in the future. Bio-mediated soil improvement is an innovative technology that improves the physical characteristics of soil; the proposed research plan will answer fundamental questions to apply these treatment processes to byproduct materials. The byproduct material targeted in the proposed project will consist of a variety of ore mining tailings, such as uranium tailings, and fly ash. These materials represent intermediate, or silty, soils with a wide rage of fines contents. These materials also have unique physical characteristics; this is especially true for fly ash. The improvement in shear strength of the intermediate soils from the treatment methods established in the proposed project will be evaluated for both drained and undrained loading. Novel assessments of the bio-treatment processes, such as its ability to immobilize trace elements and its permanence over long periods of exposure, will be conducted in the proposed project. Furthermore, metabolic pathways, such as iron and sulfate reduction, that have yet to be explored in the bio-mediated soil improvement community will be evaluated for use with mining and energy related byproducts. The proposed project will also focus on exposing the public to the treatment process and benefits of bio-mediated soil improvement in order for it to become a viable ground improvement alternative. The objective of the proposed educational plan is to educate various audiences, including K-12 students, university students, the general public, and the state legislature, on sustainability in geo-systems, specifically the storage of mining and energy related byproduct materials. This will be achieved through summer camp programs, innovative course modules implemented into existing courses, interactive Museum After Hours activity, and state legislative receptions. This topic is especially relevant to the citizens of North Carolina, where the storage of coal ash is a daily news item. The recruitment and retention of female engineers in academia will also be a focus of the proposed educational plan, building upon previous efforts of the PI through the departmental program, We are Women in Engineering.

Roadbeds supporting coastal highways in North Carolina are susceptible to erosion during large storm events. During large storms, such as hurricanes and nor������������������easters, storm surge and waves are able to erode the soil and undermine the highway. Coastal highways in North Carolina have experienced over-washing due to coastal storm surges, which led to pavement damage and even highway closure. Direct storm wave action on the seaward side of the highway and weir-flow damage on the landward side of the highway can undermine the roadbed, erode the supporting soil, and lead to pavement failure and road closure. In addition, slopes supporting roadways in sandy material are designed with a 3:1 (horizontal:vertical) slope due to the erodibility and stability of the material. More competent material may be designed with a 2:1 slope, thereby reducing the right-of-way extent. By reinforcing vulnerable coastal subgrades and slopes, erosion potential can be reduced and vital infrastructure can be maintained.

Liquefaction associated with earthquake and tsunami events in the past decades have caused significant damage worldwide. If ports, harbors, coastal bridges, naval facilities, and (nuclear) power plants are damaged due to liquefaction from an earthquake or tsunami event, then this damage results in significant consequences for the region and the country. It is paramount that we protect critical infrastructure and buildings from impending earthquake and tsunami events. Cemented soils are significantly less prone to liquefaction than loose granular materials. Cementation can occur naturally due to the precipitation of certain minerals such as salts, iron oxides and calcite. Typical chemical cementing agents include lime, ordinary Portland cement, and gypsum. Novel biological techniques such as microbially induced calcite precipitation may also be used to mimic the natural cementation process. The objective of the proposed work is to explore the effects of biocementation on both the small-strain and the large-strain behaviors of sands using a tightly integrated numerical-experimental program. Special emphasis will be placed on the analysis of decementation for different loading paths since the direct measurement of the amount of cementation is extremely difficult in physical experiments. A suite of bench-scale laboratory experiments will be performed to assess the element-scale response of artificially biocemented sands and to better understand the effects of varying biological and geotechnical parameters on material behavior. Microscale material response will be assessed via tests on surface energy, individual grains, and X-ray tomography. Results from the physical experiments will be used to develop and calibrate numerical models capable of predicting the bulk response of biocemented sands when subjected to quasi-static and dynamic loads in design situations. This ability to forward-predict the behavior of biocemented sands based on knowledge of (e.g.) biological loading and nutrition inputs is essential for the successful implementation of a biocementation program for liquefaction prediction at the field scale.

TSA: Grain Size Testing

Soils play a fundamental role in myriad global processes. The need to understand the flow of elements, energy, and water through soils is immense and widely accepted across the geosciences community. Yet, the number of scientists trained with specific soils expertise is rapidly declining. The proposed REU Site utilizes a diverse, multi-disciplinary team of scientists to deliver individualized student research experiences in state-of-the art soil science topics, synergized through unifying themes and team training opportunities. Activities will be supported by a university with well-developed infrastructure for undergraduate student research, and hosted by a department with a long-standing tradition of international excellence. Student recruitment will be pursued through departmental and university collaboration with undergraduate-serving institutions, HBCUs, and national undergraduate research organizations. The program will be assessed by external experts to ensure that the BESST REU is rigorously evaluated and didactic impact maximized.

The current specification for acceptance of Aggregate Base Course (ABC) materials consists of a band-type gradation specification, which is essentially a ����������������recipe��������������� that dictates the mass percentages of the individual particle sizes constituting the ABC. The ����������������recipe��������������� specification is based on the assumption that the product will achieve the desired engineering performance as long as it meets required gradations and is placed and compacted properly in the field. However, the biggest disadvantage of the ����������������recipe��������������� specification is that it cannot quantify the mechanical behavior of the aggregates under different traffic and weather conditions, which will determine the stress states and moisture variations. Recent developments in mechanistic-empirical pavement design (i.e., Pavement ME Design) utilize mechanical material properties and structure to predict pavement performance, which includes properties of the unbound aggregates. Therefore, understanding the mechanical properties of ABC is critical for prediction of pavement performance, and consequently design. Unfortunately, the current ABC specification is disconnected with the design process and required parameters. A more comprehensive approach to test, evaluate, and accept aggregate base course material is needed. Understanding of the material behavior due to stress conditions and moisture variations is important to ensure adequate pavement performance. Gradation alone is insufficient to adequately capture mechanical properties of different aggregates. Incorporating easy to measure physical characteristics of the ABC (e.g., angularity, shape, and texture) and aggregate packing theory into the material specification will aid in linking easily measured ABC properties to observed mechanical properties. Developing a relationship between the material properties and the mechanical behavior will allow the new specification to be directly related to the design parameters. Additionally, the re-appraisal of the ABC specification should include tests that are practical enough to be used routinely to evaluate the necessary variables. To best meet the objectives of the proposed research, first, a literature review of current practices for ABC specification used throughout the US, identification of critical properties governing ABC mechanical behavior, and state-of-the art test methods to efficiently characterize the identified properties will be conducted. The literature review will be followed by a testing program that focuses on both physical material properties and mechanical behavior of the ABC material. The testing program will be complimented with modeling the ABC material using aggregate packing theory and the discrete element method. The material and behavioral testing and modeling results will be compiled to develop a relationship between the material properties and pavement performance, which in term will be used to propose a new specification for ABC material.

The proposed project addresses two needs: improving the resiliency of coastal systems and increasing the female engineering population. The primary research goal of this project is to assess the potential for microbial induced calcite precipitation (MICP) to be used as a soil improvement method to protect coastal systems, such as sand dunes. MICP has the potential to reinforce the coastal sand dunes without damaging the natural ecology of the dunes. Assessing the potential for MICP to be used to protect coastal systems will be achieved by the following overarching objectives: 1) evaluating the increase in shear strength and reduction of erosion potential, 2) addressing the potential effects (either adverse or beneficial) that the MICP treatment process may have on the coastal ecology. 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. The proposed outreach program has been designed expose female students to different career paths in engineering and provide female engineering role models the students can connect to throughout their educational career.

Recent events in North Carolina have illustrated how important it is to ensure coal fly ash ponds are resistant to mechanical and chemical instability issues during storage. Bio-cementation is a novel approach to improve the stability of the coal ash sediments by using natural, biological processes to cement the particles together. The bio-cementation process is ideal because the cementation increases the strength of the coal ash and prevents particle migration while maintaining the permeability of the sediment to allow for drainage during dewatering. The bio-cementation process also has a tendency to capture heavy metals into the calcite cement through co-precipitation and prevent the heavy metals from migrating. The result of the bio-cemented coal ash would be stronger material resistant to slides and internal erosion. The objective of this work is to perform laboratory experiments to determine the feasibility of the bio-cementation process for ponded fly ash, and to quantify potential strength gains and reduced leachability.

Recent events in North Carolina have illustrated how important it is to ensure coal fly ash ponds are resistant to mechanical and chemical stability issues during storage. It is common for fly ash to be stored in ponds to allow it to be dewatered, yet these storage ponds can face stability issues over time. The ponded fly ash can experience global stability issues due to loss of strength which can lead to slides, as well as internal stability issues that can result in leaking of fly ash material. In addition to these mechanical stability issues, fly ash storage ponds can experience chemical leaching of the heavy metals (e.g., arsenic, lead, mercury, selenium and chromium) that remain in the material after coal combustion. Natural bio-cementation techniques can be used to strengthen the ponded fly ash to prevent mechanical and chemical stability issues during storage. The bio-cementation will increase the fly ash strength, prevent particle migration, and capture heavy metals to prevent leaching. The results of the proposed project will optimize the bio-cementation treatment process for fly ash, and quantify the improvement in mechanical and chemical stability of the bio-cemented fly ash.

Vital coastal lifelines can be vulnerable during large storm events. Large wave action and high sea levels erode the sandy soil that supports coastal infrastructure, including highways, pipelines, structures, and other utilities. Damage from these events can result in severe property damage, loss of revenue, and large repair costs. Natural bio-geochemical methods can be used to reinforce the erodible sandy soil to help prevent damage to the infrastructure. Utilizing naturally-occurring biological metabolic activity, calcite cementation can be induced in situ to bind the sand grains together, thereby improving the strength and stiffness of the soil and in turn preventing erosion of the coastal deposits. Microbial induced calcite precipitation (MICP) has been shown to be an effective method to improve the soil behavior in saturated conditions subjected to undrained monotonic and seismic loading in both laboratory and centrifuge tests. Applying this natural treatment technique to unsaturated coastal soils can improve the soil?s resiliency during large storm events. The purpose of the proposed project is to establish proof-of-concept results for unsaturated treatment of beach sand. Procedures established to treat soils under saturated conditions will be modified to be used in unsaturated conditions, and initial optimization of the unsaturated treatment process will be conducted. Bench-scale models will also be used to demonstrate that MICP provides an improvement against soil erosion due to wave action.