Application of Microbial-Facilitated Stabilization for Sustainable Improvement of Expansive Pavement Subgrades

This project will develop and demonstrate the application of Microbial Induced Calcite Precipitation (MICP) technique, an environmentally-friendly soil stabilization method to mitigate volume changes in expansive subgrades. Work on Stage 1 is underway, which focuses on laboratory development and evaluation of the MICP technique to stabilize expansive soils. A Treatment Solution Delivery System (TSDS) capable of delivering nutrient solutions to microorganisms in soil samples at different pressures was designed and developed in the university workshop. Trial runs were made to ensure that there were no leaks in the system and pressures were staying constant over long durations of time, up to 7 days. Five artificial clay- sand mixtures with varying amounts of bentonite clay were prepared and being used for collecting baseline data. The soils were denoted as AM-1, AM-2, AM-3, AM-4 and AM-5 with clay contents 5, 10, 15, 20 and 50% respectively. Tests such as specific gravity, Atterberg limits, standard Proctor compaction, and unconfined compression were completed. The results indicate that specific gravity decreases with increase in clay content due to the lower unit weight of bentonite. Standard proctor tests yielded maximum dry density (MMD) values around 106 pcf for AM-1 thru AM-4 soils while that for AM-5 was recorded to be 96.4 pcf. This drop in MDD could be attributed to high amount of clay which has very low specific gravity. The values of optimum moisture content ranged from 15.40% to 20.0%, increasing with the clay (bentonite) content. The unconfined compressive strength ranged from 9 to 26 psi. From this data, it is seen that the unconfined compressive strength increases with the increase of clay content. This is typical for clayey soils as the presence of clayey particles improves the cohesion between particles and results in higher unconfined strength. It should be noted that with confinement high sand content will result in higher strength. In the next quarter, two additional tests including one-dimensional swell test and permeability test will be conducted to wrap-up the baseline data collection. After baseline data collection, soils will be mixed with a model ureolytic bacterium, sporosarcina pasteurii prior to compaction to replicate indigenous bacteria. Pressures required to push treatment solutions (at a rate of one pore volume per day) through compacted soil samples will be determined using TSDS, and samples will be tested to investigate the effect of variables such as composition of treatment solution, injection pressures, and bacterial population on effective treatment of expansive soils. In addition, durability of the treatment method will be evaluated by conducting wetting/drying durability studies. Both Micro and macro scale tests will be conducted to evaluate MICP performance. Work in Stage 2 will focus on field evaluation and technology transfer of MICP-based soil stabilization method. Two field sites will be identified in collaboration with the Idaho and Montana Depatments of Transportation (DOTs). Based on soil type and inherent microbial activity, appropriate MICP treatment solutions will be selectedand injected at strategically selected locations, based on site geometry and boundary conditions. The effectiveness of the treatment will be monitored. In addition, dynamic cone penetration (DCP) tests will be performed to evaluate strength improvement. Technology transfer efforts will be initiated in collaboration with participating DOTs by demonstrating the application of MICP method in field conditions.

Language

  • English

Project

  • Status: Active
  • Funding: $138000
  • Contract Numbers:

    Project 20-30, IDEA 192

  • Sponsor Organizations:

    National Cooperative Highway Research Program

    Transportation Research Board
    500 Fifth Street, NW
    Washington, DC  United States  20001

    American Association of State Highway and Transportation Officials (AASHTO)

    444 North Capitol Street, NW
    Washington, DC  United States  20001

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Project Managers:

    Jawed, Inam

  • Performing Organizations:

    Boise State University, Boise

    Department of Civil Engineering
    ET 201B
    Boise, ID  United States  83725
  • Principal Investigators:

    Chittoori, Bhaskar

  • Start Date: 20170108
  • Expected Completion Date: 20180930
  • Actual Completion Date: 0
  • Source Data: RiP Project 41387

Subject/Index Terms

Filing Info

  • Accession Number: 01622203
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project 20-30, IDEA 192
  • Files: TRB, RiP
  • Created Date: Jan 8 2017 1:00AM