Microscopic characteristics and microstructure evolution of loess after explosion

The accelerated demand for engineering services has led to the extensive utilization of engineering blasting techniques. Blasting-induced changes in loess microstructure (e.g. particle breakage, pore structure change) directly affect its macroscopic mechanical properties. However, there remains a notable lack of studies on the impact of explosions on loess microstructure and the quantification of loess microstructure. This study employed micro-computed tomography (μ-CT) technology to examine loess samples extracted from the surrounding area of the explosion cavity, systematically investigating the volume, orientation, and morphological characteristics of particles and pores. The research findings indicated that the explosion caused a break for the particles with a diameter larger than 10 μm, and the number of smaller particles increased. Blasting decreased the particle sphericity and orientation angle. The reduction in porosity was primarily attributed to a decrease in the volume of both macropores and mesopores, with a greater reduction in the volume of mesopores. Although the number of micropores increased, the volume change was insignificant. Furthermore, the explosion increased the pore fractal dimension and patch density, suggesting a more complex and fragmented pore structure. Moreover, the pore throat radius and channel length decreased with decreasing distance from the explosion cavity ( D EC ), indicating that the pore's connectivity reduced. The radius of the blasting cavity was approximately 0.35 m. Additionally, the loess zone surrounding the blasting cavity was divided into failure, plastic, and elastic zones using the D EC = 0.2 m and 1.2 m as the boundaries. The impacts of the explosion on loess were mainly within the range of D EC less than 1.20 m. The analysis of the traits, patterns, and mechanisms of explosions' impact on the loess's microstructure can provide microscopic insight into the macro-dynamic behavior, assess the impact of explosions on the surrounding loess, and identify the potential geological hazards triggered by blasting, which offers a theoretical foundation for the subsequent engineering design and security measures.