@article{nafisi_liu_montoya_2021, title={Effect of stress path on the shear response of bio-cemented sands}, ISSN={["1861-1133"]}, DOI={10.1007/s11440-021-01286-7}, journal={ACTA GEOTECHNICA}, author={Nafisi, Ashkan and Liu, Qianwen and Montoya, Brina M.}, year={2021}, month={Jun} }
 @article{nafisi_montoya_evans_2020, title={Shear Strength Envelopes of Biocemented Sands with Varying Particle Size and Cementation Level}, volume={146}, ISSN={["1943-5606"]}, DOI={10.1061/(ASCE)GT.1943-5606.0002201}, abstractNote={AbstractMicrobial-induced calcium carbonate precipitation (MICP) is a bio-mediated technique that may be used to improve the strength and stiffness of soils. Various parameters affect the behavior ...}, number={3}, journal={JOURNAL OF GEOTECHNICAL AND GEOENVIRONMENTAL ENGINEERING}, author={Nafisi, Ashkan and Montoya, Brina M. and Evans, T. Matthew}, year={2020}, month={Mar} }
 @article{nafisi_mocelin_montoya_underwood_2020, title={Tensile strength of sands treated with microbially induced carbonate precipitation}, volume={57}, ISSN={["1208-6010"]}, DOI={10.1139/cgj-2019-0230}, abstractNote={ During large earthquake events where bending moments within soil cements are induced, the tensile strength of cemented soil may govern the deformational behavior of improved ground. Several studies have been conducted to assess the tensile strength of artificially cemented sands that use Portland cement or gypsum; however, the tensile strength of microbially induced carbonate precipitation (MICP)-treated sands with various particle sizes measured through direct tension tests has not been evaluated. MICP is a biomediated improvement technique that binds soil particles through carbonate precipitation. In this study, the tensile strength of nine specimens were measured by conducting direct tension tests. Three types of sand (coarse, medium, and fine) were cemented to reach a heavy level of cementation (e.g., shear wave velocity of ∼900 m/s or higher). The results show that the tensile strength varies between 210 and 710 kPa depending on sand type and mass of carbonate. Unconfined compressive strength (UCS) tests were performed for each sand type to assess the ratio between tensile strength and UCS in MICP-treated sands. Scanning electron microscopy (SEM) images and surface energy measurements were used to determine the predominant failure mode at particle contacts under tensile loading condition. }, number={10}, journal={CANADIAN GEOTECHNICAL JOURNAL}, author={Nafisi, Ashkan and Mocelin, Douglas and Montoya, Brina M. and Underwood, Shane}, year={2020}, month={Oct}, pages={1611–1616} }
 @article{nafisi_safavizadeh_montoya_2019, title={Influence of Microbe and Enzyme-Induced Treatments on Cemented Sand Shear Response}, volume={145}, ISSN={["1943-5606"]}, DOI={10.1061/(ASCE)GT.1943-5606.0002111}, abstractNote={AbstractMicrobial-induced calcium carbonate precipitation (MICP) and enzyme-induced calcium carbonate precipitation (EICP) are both soil improvement techniques that improve the shear response of sa...}, number={9}, journal={JOURNAL OF GEOTECHNICAL AND GEOENVIRONMENTAL ENGINEERING}, author={Nafisi, Ashkan and Safavizadeh, Shahin and Montoya, Brina M.}, year={2019}, month={Sep} }
 @inproceedings{nafisi_montoya_2018, title={A new framework for identifying cementation level of MICP-treated sands}, url={http://www.lib.ncsu.edu/resolver/1840.20/36315}, DOI={10.1061/9780784481592.005}, abstractNote={Microbial induced calcium carbonate precipitation (MICP) is a ground improvement technique that can be employed to increase soil stiffness and shear strength. Based on the treatment’s objectives, soil properties are improved to reach different levels of cementation. Shear wave velocity and mass of calcium carbonate can be used to categorize treated soils into various levels of cementation. However, the obtained results show that these two parameters are not sufficient in categorizing cementation and may be misleading. Therefore, a new framework which considers particle size, the dependency of shear modulus on confinement, shear wave velocity, and calcium carbonate content is proposed. In this paper, three types of poorly graded sands with different particle sizes were used. Shear modulus was measured at varying levels of cementation and confinement pressures to find out the amount of dependency of small strain shear modulus on confining pressure. According to the results, the finest soil needs more calcium carbonate to reach heavily cemented level, but the final shear wave velocity is lower compared to the coarser sands. Based on the obtained results, n (the slope of log Gmax against log of mean effective stress) values for lightly, moderately, and heavily MICP-sands are about 0.4, 0.3, and less than 0.1, respectively.}, note={annote: Nafisi, A., & Montoya, B. M. (2018). A new framework for identifying cementation level of MICP-treated sands. In Ifcee 2018: innovations in ground improvement for soils, pavements, and subgrades (pp. 37–47).}, number={296}, booktitle={Ifcee 2018: innovations in ground improvement for soils, pavements, and subgrades}, author={Nafisi, A. and Montoya, B.M.}, year={2018}, pages={37–47} }