Enhancing Stability of Sandy, Clayey, and Silty Soils through Microbial Biostabilization with Sporosarcina pasteurii

Diana Jumbo^1*Nancy Tillaguango¹Karlo Guerrero²Eduardo Moncayo^3,4Karla Vizuete⁵Alexis Debut⁵Stefany Solano-González⁶Armstrong Omoregie⁷Paulina Isabel Aguirre¹

• ¹Universidad Técnica Particular de Loja, Loja, Ecuador
• ²Universidad Tecnologica Metropolitana, Santiago, Chile
• ³Escuela Superior Politecnica Agropecuaria de Manabi, Calceta, Ecuador
• ⁴Grupo de Investigación y Desarrollo de la Biotecnología BioSin-Biociencias, Quito, Ecuador
• ⁵Universidad de las Fuerzas Armadas, Sangolqui, Ecuador
• ⁶Universidad Nacional de Costa Rica, Heredia, Costa Rica
• ⁷University College of Technology Sarawak, Sibu, Malaysia

Soil degradation and landslide susceptibility pose significant environmental challenges in steep terrains with inadequate soil management. This study investigates microbial-induced carbonate precipitation (MICP) using Sporosarcina pasteurii to improve the physicochemical and mechanical properties of sandy, silty, and clayey soils collected from active slopes in Loja, Ecuador. Following MICP treatment, calcium carbonate precipitation was detected in all soil types, with higher carbonate accumulation in finer-textured soils. Exchangeable calcium increased markedly, while sodium concentrations decreased in sandy and clayey soils, indicating ion exchange associated with carbonate cementation. The plasticity index decreased across all soils, with reductions of up to 65% in clayey soils, reflecting improved resistance to deformation. Geomechanical testing showed consistent increases in shear strength parameters across all soil textures. Cohesion increased by approximately 25–35% in sandy and clayey soils and showed a pronounced relative increase in silty soils, where initial cohesion values were extremely low. The internal friction angle increased by approximately 30–100%, depending on soil texture. Scanning electron microscopy and energy-dispersive X-ray spectroscopy confirmed the formation of calcite and vaterite precipitates bridging soil particles. Unlike most previous MICP studies using Sporosarcina pasteurii, which typically focus on a single soil type, this work provides a comparative evaluation of physicochemical, microstructural, and mechanical responses across contrasting soil textures from natural slope materials. These results demonstrate that soil texture strongly controls the magnitude and mechanisms of MICP-induced improvement and support the potential of MICP as a sustainable and environmentally friendly soil improvement strategy for near-surface slope stabilization.