Study on the Strength Characteristics of Columnar Jointed Basalt with a True Triaxial Apparatus at the Baihetan Hydropow
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ORIGINAL PAPER
Study on the Strength Characteristics of Columnar Jointed Basalt with a True Triaxial Apparatus at the Baihetan Hydropower Station Anchi Shi1 · Yufeng Wei2 · Yihu Zhang3 · Mingfa Tang1 Received: 23 November 2019 / Accepted: 6 July 2020 © Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract Columnar jointed basalt is widely distributed in the dam foundation and underground cavern of the Baihetan hydropower station, in which columnar jointing and microfractures are developed, the integrity of the rock mass is poor, and the material easily relaxes after excavation. Therefore, it is important to obtain the real mechanical parameters of columnar jointed basalt in rock mechanics problems. In the test cave at the dam site, six in situ samples with a size of 50 cm × 50 cm × 100 cm were successfully made, and in situ true triaxial test were carried out. This paper presents a method for obtaining the strength parameters of the Mohr–Coulomb criterion and Hoek–Brown criterion by true triaxial testing. The peak strength parameters under three states and yield strength parameters under one state were obtained by setting various stress paths for the undisturbed samples and failure samples. The strength characteristics of columnar joint basalt and the crack characteristics of the specimens are analyzed, and the results of the triaxial test and direct shear test are compared. By means of acoustic emission (AE) techniques and surface crack descriptions, the failure process and failure pattern of the samples were obtained. The abundant test results provide strong support for the selection of engineering rock mechanics parameters. Keywords True triaxial test · In situ · Columnar jointed basalt · Strength · Loading · Unloading · Stress path · Acoustic emission
1 Introduction With China’s western development policy and the implementation of west to east electricity transmission (Xue and Xiao 2017; Li et al. 2018a, b), many large hydropower projects, such as the Xiluodu, Dagangshan, Baihetan, Shuangjiangkou, and Lianghekou dams, have been constructed in * Yufeng Wei [email protected] Anchi Shi [email protected] Yihu Zhang [email protected] Mingfa Tang [email protected] 1
Powerchina Huadong Engineering Corporation Limited, Hangzhou, China
2
State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, Chengdu University of Technology, Chengdu, China
3
Yangtze River Scientific Research Institute, Wuhan, China
Southwest China (Li et al. 2018a, b). For the design and construction of rock engineering projects, it is vital to understand the rock mass deformation and its strength characteristics (Oliveira and Indraratna 2010; Alshkane et al. 2017), especially those of columnar jointed basalt distributed in Southwest China (Jiang et al. 2014; Jin et al. 2015a, b; Fan et al. 2017, 2018; Jia et al. 2018). These columnar jointed rock masses are generally in a triaxial stress state. To better understand the failure mode of columnar jointed rock masses, it is necessary to study the st
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