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For a long time in the practice of geotechnical engineering, soil has been viewed as an inert material, comprising only inorganic phases. However, microorganisms including bacteria, archaea and eukaryotes are ubiquitous in soil and have the capacity and capability to alter bio‐geochemical processes in the local soil environment. The cumulative changes could consequently modify the physical, mechanical, conductive and chemical properties of the bulk soil matrix. In recent years, the topic of bio‐mediated geotechnics has gained momentum in the scientific literature. It involves the manipulation of various bio‐geochemical soil processes to improve soil engineering performance. In particular, the process of microbial‐induced calcium carbonate precipitation (MICP) has received the most attention for its superior performance for soil improvement. The present work aims to shape a comprehensive understanding of recent developments in bio‐mediated geotechnics, with a focus on MICP. Referring to around one hundred studies published over the past five years, this review focuses on popular and alternative MICP processes, innovative raw materials and additives for MICP, emerging tools and testing methodologies for characterizing MICP at multi‐scale, and applications in emerging and/or unconventional geotechnical fields.

Fiber Bragg grating (FBG) acoustic emission (AE) sensors have been used in many applications. In this paper, based on an FBG AE sensor, the sensing principle of the interaction between the AE wave and the sensor is introduced. Then, the directionality of the FBG AE sensor on the surface of a thin polymer-bonded explosive (PBX) material is studied. Finally, the time coefficient location method is proposed to correct the AE time detected by the FBG AE sensor, thereby improving the accuracy of location experiments.

Acoustic emission technology has been applied to many fields for many years. However, the conventional piezoelectric acoustic emission sensors cannot be used in extreme environments, such as those with heavy electromagnetic interference, high pressure, or strong corrosion. In this paper, a novel fiber-optic ring acoustic emission sensor is proposed. The sensor exhibits high sensitivity, anti-electromagnetic interference, and corrosion resistance. First, the principle of a novel fiber-optic ring sensor is introduced. Different from piezoelectric and other fiber acoustic emission sensors, this novel sensor includes both a sensing skeleton and a sensing fiber. Second, a heterodyne interferometric demodulating method is presented. In addition, a fiber-optic ring sensor acoustic emission system is built based on this method. Finally, fiber-optic ring acoustic emission experiments are performed. The novel fiber-optic ring sensor is glued onto the surface of an aluminum plate. The 150 kHz standard continuous sinusoidal signals and broken lead signals are successfully detected by the novel fiber-optic ring acoustic emission sensor. In addition, comparison to the piezoelectric acoustic emission sensor is performed, which shows the availability and reliability of the novel fiber-optic ring acoustic emission sensor. In the future, this novel fiber-optic ring acoustic emission sensor will provide a new route to acoustic emission detection in harsh environments.