Dr. Montoya’s research interests involve developing bio-mediated stabilization approaches to improve the sustainability and resiliency of infrastructure. Applications of microbial induced carbonate precipitation (MICP) on which she has focused include infrastructure subjected to natural hazards, such as earthquake-induced liquefaction and coastal/offshore erosion, and mitigating storage-related hazards of energy-related wastes. Specifically, her research program has focused on elucidating the performance of MICP cemented geomaterials, including: 1) shear response and volumetric behavior, 2) erosion behavior, and 3) physico-chemical influences of MICP.
- Effects of microbially induced carbonate precipitation on diffuse double layer and particle fabric of oil sands fine tailings , CANADIAN JOURNAL OF CIVIL ENGINEERING (2022)
- Framework for the Development of Strain-Based Ultimate Performance Limit State Criterion for the Stability of Earthen Embankments , JOURNAL OF GEOTECHNICAL AND GEOENVIRONMENTAL ENGINEERING (2022)
- Bridge Pier Scour: An overview of factors affecting the phenomenon and comparative evaluation of selected models , TRANSPORTATION GEOTECHNICS (2021)
- Distribution and Properties of Microbially Induced Carbonate Precipitation in Underwater Sand Bed , JOURNAL OF GEOTECHNICAL AND GEOENVIRONMENTAL ENGINEERING (2021)
- Effect of stress path on the shear response of bio-cemented sands , ACTA GEOTECHNICA (2021)
- Microbial-Induced Calcium Carbonate Precipitation to Accelerate Sedimentation of Fine Tailings , JOURNAL OF GEOTECHNICAL AND GEOENVIRONMENTAL ENGINEERING (2021)
- Quantifying probability of deceedance estimates of clear water local scour around bridge piers , JOURNAL OF HYDROLOGY (2021)
- Scour Mitigation and Erodibility Improvement Using Microbially Induced Carbonate Precipitation , GEOTECHNICAL TESTING JOURNAL (2021)
- Effect of repeated rise and fall of water level on seepage-induced deformation and related stability analysis of Princeville levee , ENGINEERING GEOLOGY (2020)
- Shear Strength Envelopes of Biocemented Sands with Varying Particle Size and Cementation Level , JOURNAL OF GEOTECHNICAL AND GEOENVIRONMENTAL ENGINEERING (2020)
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 pastÃƒÂ¢Ã¢â€šÂ¬Ã¢â‚¬Âoften 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 LagerstÃƒÆ’Ã‚Â¤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., ÃƒÂ¢Ã¢â€šÂ¬Ã…â€œsoftÃƒÂ¢Ã¢â€šÂ¬Ã‚Â) tissues. Although microbes have been invoked as agents of preservation as well as destruction, because they act to ÃƒÂ¢Ã¢â€šÂ¬Ã…â€œsealÃƒÂ¢Ã¢â€šÂ¬Ã‚Â 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
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 StatesÃƒÂ¢Ã¢â€šÂ¬Ã¢â€žÂ¢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 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 countryÃƒÂ¢Ã¢â€šÂ¬Ã¢â€žÂ¢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.
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 ÃƒÂ¢Ã¢â€šÂ¬Ã…â€œscour- critical,ÃƒÂ¢Ã¢â€šÂ¬Ã‚Â 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 norÃƒÂ¢Ã¢â€šÂ¬Ã¢â€žÂ¢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