Shear wave velocity of bio-cemented soil as determined by bender element test—A walkthrough and practical implications

Abstract

Microbiologically Induced Calcium Carbonate Precipitation (MICP) has emerged as a sustainable geotechnical solution for ground improvement, garnering significant global interest. Shear wave velocity (V_s) is a critical parameter for evaluating the small-strain shear stiffness of soil and serves as a non-destructive metric for monitoring cementation kinetics during biotreatment. While the compressive strength of bio-cemented soils is well-documented, standardized methodologies for V_s measurement in these materials remain comparatively sparse. This study proposes a comprehensive experimental framework for measuring V_s in MICP-treated soils and evaluates key considerations for data acquisition and interpretation. A standalone biotreatment system, integrated with bender element transducers, was developed and validated. The results demonstrate that V_s increases progressively with treatment cycles and CaCO₃ content, driven by the formation of cementitious bonds at particle contacts. Under percolation-based treatment, wave propagation was significantly influenced by the degree of cementation. The instrumentation of bender elements successfully facilitated the monitoring of the bio-cementation process in a scaled-up sand model experiment. Finally, empirical correlations between V_s and unconfined compressive strength were established, underscoring the advantage of shear wave monitoring for quality assurance in bio-mediated coastal defense applications.

Graphical abstract

Keywords

MICP / shear wave velocity / bender element setup / signal interpretation

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