Microbiological improvement of soils with Box-Behnken experimental design

Abstract

Soil improvement methods aim to enhance geotechnical properties such as strength, durability, and resistance to environmental loads. Among recent advances, microbially induced calcium carbonate precipitation (MICP) has emerged as a sustainable alternative to conventional chemical stabilizers. This study presents a novel application of Box-Behnken experimental design (BBD) for optimizing MICP parameters in sandy soils, focusing on the interaction between sand type, treatment solution molarity, and curing time. A total of 17 experimental runs were conducted under a structured response surface methodology to identify optimal conditions for maximizing unconfined compressive strength (UCS). The highest UCS value, 1297 kPa, was achieved using fine-grained sand treated with a 1.5 mol solution over 5 days. The key innovation of this research lies in the integration of statistical design techniques with microbial geotechnology, enabling efficient modeling of nonlinear interactions and minimizing experimental effort. Beyond laboratory findings, the results offer practical guidance for field-scale implementations by identifying critical parameter ranges that ensure microbial viability and performance stability. This integrated approach provides both methodological novelty and applied relevance, contributing to the advancement of bio-based soil improvement strategies in geotechnical engineering.