Abstract
Loess collapse is one of the most developed geohazards in loess area, and the acoustic emission active waveguide model is an important tool for monitoring and early warning of loess collapse geohazards and acquisition of precursor information. In this study, the acoustic emission active waveguide model is used as the research object, and by carrying out the acoustic emission active waveguide model pressurization test and wavelet noise reduction processing of the acquired acoustic emission data, the evolution of acoustic emission signals in the process of acoustic emission pressurization of primary Malan loess is revealed in various phases, including compaction, elasticity-plasticity deformation, destruction, and post-destruction phases. The attenuation characteristics of the AE signal propagation paths of the structures comprising the active waveguide model, including geometric diffusion attenuation, material absorption attenuation, and coupling attenuation, are described. The study also showed that the integrated damage form was identified based on the acoustic emission RA-AF value characteristics, and 63% of the high RA value and 37% of the high AF value, which is "high RA value and low AF value", indicating that the integrated damage form of the in-situ loess collapse damage under this monitoring condition is shear damage. At the same time, the acoustic emission b-value characteristics of the collapse damage of the primary Malan loess were investigated, with a rapid increase and a small amount of acoustic signals at the early stage of pressurization, a rapid decrease and more acoustic signals at the middle stage of pressurization, and a continuous decrease and a large amount of acoustic signals at the middle and late stages of pressurization. The early warning precursor information obtained from in situ loess acoustic emission monitoring provided in this paper can be used in the construction of monitoring and early warning system for geologic disasters such as loess collapse in loess areas.