Browsing by Author "Khosravi, Mohammad"

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Effect of Fines Content on Calcium Carbonate Precipitation and Thermal Properties of Biocemented Sand
(American Society of Civil Engineers, 2024-04) Gunyol, Pinar; Khosravi, Mohammad; Phillips, A. J.; Plymesser, Kathryn; Parker, Albert E.
In this study, the impacts to soil thermal properties during and after biocementation via microbially induced calcite precipitation (MICP) method on silty silica sand specimens with varying fines content (0%, 5%, and 15%) were investigated. Firstly, calcium conversion was measured after each pulse; then, the MICP-treated specimens were tested for cementation uniformity. The evolution of thermal conductivity of silty soils with the MICP treatment was assessed using a thermocouple probe. The results show that thermal conductivity of silty saturated sands increased by 17% for specimens treated to 9.7% CaCO3. The improvement in thermal conductivity was attributed to the formation of calcium carbonate bridges binding the soil grains together. The results suggested that the thermal conductivity of silty soil depends on water content, the number of treatment pulses, and the treatment uniformity through the soil specimen. Presence of fines content in the soil was found to play an important role in the distribution and uniformity of biocementation through the soil specimen. However, no statistically significant difference in the thermal conductivity values of MICP-treated specimens with different fines content was observed (𝑝>0.05). The average calcium carbonate content ranged between 10.7% and 7.2% for the soils with 0% and 15% fines content, respectively. The findings of this research could be used to improve the efficiency of geothermal boreholes and other energy geostructures using MICP by improving thermal conductivity of dry and partially saturated soil.
Variation of Small-Strain Shear Modulus of Unsaturated Silt under Successive Cycles of Drying and Wetting
(2020-07) Khosravi, Ali; Hashemi, Amirhossein; Ghadirianniari, Sahar; Khosravi, Mohammad
A new framework is developed to extend an existing small-strain shear modulus (𝐺max) model to determine 𝐺max of unsaturated silty soils along different paths of the soil water retention curve (SWRC) including the scanning loops. The suitability of the proposed framework is validated against experimental results of a series of bender-element tests performed in this study and data reported in literature. Measured values of 𝐺max showed a slight hysteresis in the 𝐺max measurements along the scanning curves of the SWRC, with lower values along the wetting scanning paths. However, results indicated that the value of 𝐺max was recovered once the main drying path was reached. Results of this study also indicated that 𝐺max behavior of the silty specimen along the scanning curves was stress dependent. The model was observed to follow the experimental data along different paths of the SWRC including scanning curves.