Study on Unloading Relaxation Characteristics of Columnar Jointed Rock Masses Based on Displacement Back Analysis

We aim to understand the relaxation of columnar joint rock masses during the excavation process of the diversion tunnel of the Baihetan hydropower station. This paper inverts the deformation parameters of the relaxed columnar joint rock based on the displacement monitoring data, and introduces a relaxation factor to describe the deterioration degree of anisotropic parameters of the relaxed columnar jointed rock. The equivalent strain is proposed as the criterion of unloading relaxation and the threshold is also given. Based on the software Flac3d, a program for calculating anisotropic elastoplastic model is developed. The distribution of the relaxation zone of the diversion tunnel after excavation is simulated, and compared with the results of the acoustic detection to verify the correctness and rationality of the program, which can provide a necessary reference for the design and construction of hydropower projects.

Experimental Study on the Deterioration Rules of Anchoring Performance of Rock Mass under Different Joints Distribution

In order to analyze the influence of damage caused by corrosion on anchoring performance of a rock mass with different joints, the anchored rock mass specimens with different joints distribution were prepared. An electrochemical accelerated corrosion test of specimens was carried out, and the mechanical test of them under different corrosion time was also investigated. The results showed that the pitting corrosion is the main form of the anchor bar corrosion of an anchoring rock mass with different joints, and the shape of the etch pit is reverse semi-ellipse. With the increase of pitting ratio, the ultimate bond strength and the corresponding slide distance decrease gradually. The effects of pitting ratio on the slide distance of the anchor bar in an anchored joint rock mass are insignificant, but these on the bond strength of it are significant. The bond-slide model of the anchored joint rock mass with different pitting ratios was established. The research results of this paper can provide reference for analyzing the corrosion damage of a complex anchored joint rock mass in practical engineering and a theoretical basis for the design optimization of anchoring support in the complex jointed rock mass.