Abstract
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.
Highlights
The unloading relaxation of rock masses is mainly caused by the redistribution of the surrounding stress
It is necessary to study the anisotropic constitutive model reflecting the relaxation characteristics of the columnar jointed rock mass, and determine the scale of the relaxation area caused by excavation
Taking the No.4 diversion tunnel as an example, this paper studies the unloading relaxation of columnar jointed basalt
Summary
The unloading relaxation of rock masses is mainly caused by the redistribution of the surrounding stress. During the excavation of the diversion tunnel of the Baihetan Hydropower Station, a large section of columnar jointed rock mass was encountered. This rock mass exhibits obvious anisotropic mechanical properties and had significant unloading relaxation characteristics after excavation. It is necessary to study the anisotropic constitutive model reflecting the relaxation characteristics of the columnar jointed rock mass, and determine the scale of the relaxation area caused by excavation. The results of back analysis are used as mechanical parameters to simulate the diversion tunnel deformation, and the calculated displacements of the monitor points are recorded and compared with the measured displacements (Figure 7). The parameters of the model are shown in Table.
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