In addressing problematic soils,geotechnical engineers employ two key strategies:compatibility and improvement.This study focuses on soft and CL deltaic sediments,and seeks to enhance cementation by investigating micr...In addressing problematic soils,geotechnical engineers employ two key strategies:compatibility and improvement.This study focuses on soft and CL deltaic sediments,and seeks to enhance cementation by investigating microbially-induced calcium carbonate precipitation(MICP).Sporosarcina pasteurii bacteria,together with a cementation solution(urea and calcium-containing salt),were electrokinetically injected into deltaic clay soil from the Telar River in Iran.The initial samples,with a dry unit weight(γ_(d))of 12.75 kN/m^(3),underwent injections in two modes:simultaneous injection of the bacterial and cementation solutions and individual injection in a sequential order.Unconfined compression strength tests and laboratory vane shear tests were conducted to assess changes in soil strength parameters,while a consolidation test was performed to investigate alterations in soil settlement parameters.A comparative analysis with an electroosmosis control sample revealed a remarkable increase in compressive strength and undrained shear strength for MICP bio-electrokinetic improvement.Moreover,the consolidation test demonstrated that the compression index(C_(c))and recompression index(C_(r))exhibited a more pronounced decline in the simultaneous injection than individual injection.This highlights the dual impact of the bio-electrokinetic method,namely the enhancement of shear strength and the mitigation of settlement in deltaic clay soil.The calcium carbonate content was measured for the samples,and the results indicated a higher degree of participation for the samples subjected to simultaneous injection.Microstructure analyses were conducted on samples,and calcite and vaterite were observed in biocemented samples.展开更多
文摘In addressing problematic soils,geotechnical engineers employ two key strategies:compatibility and improvement.This study focuses on soft and CL deltaic sediments,and seeks to enhance cementation by investigating microbially-induced calcium carbonate precipitation(MICP).Sporosarcina pasteurii bacteria,together with a cementation solution(urea and calcium-containing salt),were electrokinetically injected into deltaic clay soil from the Telar River in Iran.The initial samples,with a dry unit weight(γ_(d))of 12.75 kN/m^(3),underwent injections in two modes:simultaneous injection of the bacterial and cementation solutions and individual injection in a sequential order.Unconfined compression strength tests and laboratory vane shear tests were conducted to assess changes in soil strength parameters,while a consolidation test was performed to investigate alterations in soil settlement parameters.A comparative analysis with an electroosmosis control sample revealed a remarkable increase in compressive strength and undrained shear strength for MICP bio-electrokinetic improvement.Moreover,the consolidation test demonstrated that the compression index(C_(c))and recompression index(C_(r))exhibited a more pronounced decline in the simultaneous injection than individual injection.This highlights the dual impact of the bio-electrokinetic method,namely the enhancement of shear strength and the mitigation of settlement in deltaic clay soil.The calcium carbonate content was measured for the samples,and the results indicated a higher degree of participation for the samples subjected to simultaneous injection.Microstructure analyses were conducted on samples,and calcite and vaterite were observed in biocemented samples.
