A decade of progress and turning points in the understanding of bio-improved soils: A review

Research and practice in the broader fields of civil and geotechnical engineering had long ignored the presence of living microorganisms in the subsurface and the way it impacts conventional practices. In the last 10 years, the term “microbial induced calcite precipitation”, or that of “biogrouting” have gained momentum in the scientific literature. They are often presented as the “next big thing” in geotechnical engineering applications that will solve many kinds of problems, ranging from soil erosion to landslide risk mitigation and liquefaction protection. Are the claimed benefits of the application of microorganisms in conventional geotechnical problems real? The present review work aims to shape a complete and comprehensive understanding of the progress reported in the field of bio-mediated soil improvement. Specific focus is put on pivotal points in this decade-long path which is marked by proof of fundamental concepts at multiple scales. Among the treated literature, reference is made to over forty studies produced after 2016. As soil bio-reinforcement makes its steps towards claiming a spot in mainstream geotechnical practice this review foresees to offer both a look back on how far research has gone and a look forward by evaluating opportunities and challenges which lie ahead.