This study explores the effectiveness of soft viscoelastic biopolymer inclusions in mitigating cyclic liquefaction in loosely packed sands. This examination employs cyclic direct simple shear testing (CDSS) on loose sand treated with gelatin while varying the gelatin concentration and the cyclic stress ratio (CSR). The test results reveal that the inclusion of soft, viscoelastic gelatin significantly reduces shear strain and excess pore pressure during cyclic shear. Liquefaction potential, defined as the number of cycles to liquefaction (NL) at an excess pore pressure ratio (ru = Delta u/sigma ' vo) of 0.7, is substantially improved in gelatin-treated sands compared to gelatin-free sands. This improvement in liquefaction resistance is more pronounced as the inclusion stiffness increases. Furthermore, the viscoelastic pore-filling inclusion helps maintain skeletal stiffness during cyclic shearing, resulting in a higher shear modulus in gelatin-treated sand in both small and large-strain regimes. At a grain scale, pore-filling viscoelastic biopolymers provide structural support to the skeletal frame of a loosely packed sand. This pore filler mitigates volume contraction and helps maintain the effective stress of the soil structure, thereby reducing liquefaction potential under cyclic shearing. These findings underscore the potential of viscoelastic biopolymers as bio-grout agents to reduce liquefaction risk in loose sands.
Using grout in construction and ground improvement has been common in various industries and construction projects. However, conventional grouts often need to be improved for their composition, durability, and environmental impact. Recently, there has been increased interest in exploring alternative solutions that are more sustainable and environmentally friendly. This comprehensive review aims to unravel the limitations of conventional grouts when exploring the potential of emerging biogrout technologies to achieve environmental sustainability in ground improvement. This review begins by examining the characteristics and limitations of traditional grouts, which highlights challenges such as inadequate durability and adverse environmental impacts. Then, the focus shifts toward emerging biogrout technologies, which harness the power of microorganisms to enhance soil stabilization. The principles, applications, and benefits of biogrout technologies are discussed thoroughly, along with case studies that showcase their successful implementation. A key aspect of this review is to highlight the environmental sustainability of biogrout applications in various civil engineering projects. Life cycle analyses (LCAs) are conducted to assess the environmental impacts of conventional grout, which sheds light on their drawbacks. In contrast, the environmental benefits and challenges that are associated with biogrout technologies are examined, which provides a comparative analysis between the two approaches. This review concludes by presenting prospects and challenges in this field. It discusses advances in conventional grout formulations to address their limitations and strategies to enhance the environmental performance of biogrout technologies. In addition, integrating sustainability principles into grouting practices is emphasized to achieve long-term environmental sustainability in ground improvement projects. Overall, this comprehensive review could contribute to the advances in sustainable ground improvement practices by providing insights into the limitations of conventional grouts and exploring the potential of emerging biogrout technologies. It could be a valuable resource for practitioners and researchers who seek sustainable solutions in ground improvement that align with environmental stewardship and sustainable development goals.