Research Overview
Research Approach
The main research objective in our lab is to understand natural subsurface bio-geochemical reactions that may be harnessed for geomechanical applications. This is met through employing a variety of mechanical, geophysical, microbial, and chemical experimental techniques. Our experimental observations are supported with numerical simulations to elucidate the mechanical and geochemical responses.
What is MICP?
Microbial induced carbonate precipitation (MICP) is a natural cementation process that occurs as a byproduct of bacterial ureolytic activity. Many indigenous soil bacteria are able to hydrolyze urea, which produces ammonium and bicarbonate. In the presence of cations such as calcium, calcium carbonate can precipitated often using the bacterial cells as nucleation sites. The precipitated calcium carbonate mineral can bond soil particles together, thus improving the mechanical behavior of the soil.
Research Group Interests Video
Example Projects, Past and Present
Stabilization of Mining and Energy Related Byproducts using Bio-Mediated Soil Improvement
The overall objective of the 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. 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.
Liquefaction Mitigation using Microbial Induced Carbonate Precipitation
Liquefiable soils lose their strength under cyclic loading, such as earthquakes. These soils pose a risk to the built environment with the potential for large deformations. Liquefiable soils are often improved using a variety of ground improvement methods, including densifying the soil with mechanical energy or adding a binding agent such as cement, epoxy, or silicates. However, silty soils (e.g., silty sands and silts) can be difficult to improve using traditional ground improvement methods. Therefore, a natural and sustainable solution is needed to improve silty soils to allow for continued infrastructure growth and mitigation. Bio-mediated soil improvement has shown to be an effective method to improve the strength and stiffness of liquefaction-prone sand. The focus of this research project is to extend the use of bio-mediated soil improvement to silty soils that are more difficult to treat.
Collaborators on this research topic include Drs. Ashly Cabas, and Matt Evans.
Bio-Mediated Soil for Mitigation of Scour at Anchoring Foundation Supporting Marine Hydrokinetics Devices
A wide variety of offshore Marine Hydrokinetics (MHK) power generators have been developed with various stages of deployment across the globe. The objective of this study is to investigate the use of bio-mediation to improve the soft soils’ shear resistance with the aim of reducing the scour hole’s dimension and scour rates. Such a development is needed to ensure less frequent maintenance and economical life-cycle cost of the deployed system. Model-scale testing is needed to demonstrate the performance of bio-mediated soil improvement as a scour mitigation in conjunction with MHK foundations. The treatment process will be developed for soft soil with a large hydraulic head and implemented within a desired zone around the foundations. The efficacy of the treatment will be evaluated using non-destructive process monitoring techniques, such as shear wave velocity and resistivity measurements, cone penetration, and impinging jet erosion tests. The results from the testing plan will be a treatment design for scour mitigation of MHK foundation.
Collaborators on this research topic include Drs. Aleja Ortiz and Mo Gabr.
Improving Resiliency of Coastal Systems using Bio-Mediated Soil Improvement
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. Applying this natural treatment technique to unsaturated coastal soils can improve the soil’s resiliency during large storm events. The purpose of the project is to establish proof-of-concept results for unsaturated treatment of beach sand, evaluate the reduction in erodibility of the beach sand due to MICP, and understand the effect MICP has on the sand dune ecology. Procedures established to treat soils under saturated conditions were modified to be used in unsaturated conditions, and optimization of the unsaturated treatment process in the presence of saltwater began. Bench-scale models and wave tank experiments were used to demonstrate MICP provides an improvement against soil erosion due to wave action.