Application of bio-cementation to enhance shear strength parameters of soil-steel interface

In this study, the microbially induced calcite precipitation process is introduced to a sandy soil-steel interface. A series of modified direct shear tests designed based on the Taguchi design of experiments method are conducted to examine the bio-cemented soil-steel interface strength parameters. The primary test results are analyzed using the ANOM and ANOVA approaches, and the predictions of the Taguchi method are compared with the test results. The effects of the initial soil moisture content, density ratio of urea/CaCl2, and rate of injection of the cementation solution on the response of the bio-cemented sand-steel interface are scrutinized. Both the ANOM and ANOVA show that the density of the cementation solution is the most influential parameter, while the initial soil moisture content is the least influential factor in the bio-cementation process of the sand-steel interface. The test results show that introducing bio-cementation process to the soil-steel interface is an effective approach in enhancing the interface properties, increasing the sand-steel interface shear strength 3 to 7 times, depending on the normal stress used in the tests. The results also show that the initial moisture content that yields the highest gain in the interface shear strength due to bio-cementation is near the optimum moisture content of the soil obtained from the modified compaction test. (C) 2021 Published by Elsevier Ltd.