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The dynamic properties of a clean sand under different degrees of saturation is investigated using a modified custom built Direct Simple Shear (DSS) apparatus at the University of New Hampshire. The specific characteristics of the DSS are presented and the testing procedures are discussed. The device utilizes the axis translation and tensiometric techniques to control the matric suction in the soil specimen. The investigation on F75 Ottawa Sand shows a decrease in shear modulus and an increase in damping by increasing the shear strain over the tested range of strains for various degrees of saturation; dry, saturated, and partially saturated. The modulus reduction in the applied range of medium shear strains regardless of the degree of saturation demonstrates the capability of the DSS in consistently capturing the changes of dynamic properties. Experimental results indicate that the matric suction can have a substantial effect on the stiffness of the soil. However, the extent of this effect may depend on the induced strain level the effective stress in unsaturated soil. In addition, partially saturated specimens resulted in lower dynamic compression.
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Reducing Soil Permeability Using In Situ Biofilm-Forming Bacteria: Overcoming Testing Apparatus Challenges
Growing biofilm in saturated sand has been shown to reduce the permeability of soil by one or more orders of magnitude and may be a viable approach to reducing seepage in the field; however, obtaining laboratory permeability results in soil samples where biofilm is being developed is difficult. Adding nutrients results in the formation of biofilm in the soil but also the formation of biofilm in the piping and other areas of the permeability testing apparatus. In addition, some bacteria produce gas as a product of metabolism and this gas can collect in the apparatus and interfere with fluid flow. This paper presents an approach to permeability testing that effectively minimized the growth of biofilm and the collection of gas in the testing apparatus for multiple sand samples treated with a nutrient solution over a period of more than 60 days.
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- Award ID(s):
- 1632963
- PAR ID:
- 10097428
- Date Published:
- Journal Name:
- Geo-Congress 2019
- Page Range / eLocation ID:
- 187 to 195
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1061/9780784482117.018
