Abstract: The morphological characteristics and deformation failure modes of weak structures in rock and soil mass under certain loading conditions are of great significance to the slope stability in geotechnical engineering, while the visual analysis of the inner weak structural planes and their feature description often lack effective field testing means. Therefore, a method for the visual analysis of weak structural planes based on the characteristics of multiple frequency ultrasound imaging is proposed. This method obtains the ultrasonic scanning image of the weak structures at different angles and frequencies under corresponding conditions using multiple frequency ultrasonic waves, analyzes the reflection attenuation feature and the gradient feature of the difference image statistically, and establishes the qualitative and quantitative analysis of the imaging features, so as to realize the visualization analysis of the weak structure in rock and soil mass. The method realizes the real-time imaging detection and visual monitoring of internal weak structure of the rock and soil mass, and solves the existing drawbacks that the in-situ imaging detection of internal weak structures cannot be achieved and the problem of the precise analysis of local structure planes for rock and soil. It provides a new technical approach for the instability mechanism research induced by the weak structures of rock and soil mass during the geotechnical engineering and geological investigation.

Key words: ultrasound imaging, weak structural plane, visual analysis, reflection loss, morphological characteristics