Abstract
Many columnar jointed rock masses (basalt) are present at the Baihetan hydropower dam site, and their seepage characteristics have a significant impact on the project’s safety and stability. In this study, model samples consisting of material similar to the columnar jointed rock mass with different inclination angles (0°–90°) were prepared and laboratory triaxial seepage tests were performed to study the seepage characteristics of the columnar jointed rock mass under maximum axial principal stress. The experimental results showed that the similar material model samples of columnar jointed rock mass showed obvious seepage anisotropy. The nonlinear seepage characteristics were well described by the Forchheimer and Izbash equations, and the fitting coefficients of the two equations were in good correspondence. The curves describing the relationship between the inherent permeability and the stress of the samples with different dip angles were U-shaped and L-shaped, and a one-variable cubic equation well described the relationship. The 45° angle specimen had the highest sensitivity to the maximum principal stress, and its final permeability increased by 144.25% compared with the initial permeability. The research results can provide theoretical support for the stability evaluation of the Baihetan hydropower station.
Highlights
A columnar jointed rock mass is formed by rapid cooling and shrinkage of high-temperature lava
Numerous densely developed slender columnar jointed rock masses are exposed in the dam foundation and underground powerhouse area of the Baihetan hydropower station in China (Figure 1) [1, 2]
Statistics have shown that more than 90% of rock slope failures are related to groundwater permeability, 60% of coal mine shaft damage is related to groundwater, and 30%–40% of dam failures of water conservancy and hydropower projects are caused by seepage [9, 10]. erefore, it is crucial to study the seepage characteristics of columnar jointed rock masses under stress in water conservancy and hydropower projects for practical engineering applications
Summary
A columnar jointed rock mass is formed by rapid cooling and shrinkage of high-temperature lava. Erefore, it is crucial to study the seepage characteristics of columnar jointed rock masses under stress in water conservancy and hydropower projects for practical engineering applications. Erefore, it is feasible and effective to conduct indoor seepage-stress coupling tests on rock samples to explore the seepage characteristics under stress. Erefore, the most effective and reliable method to analyze the permeability characteristics of a columnar jointed rock mass in indoor tests is the use of similar material for the samples. A true triaxial electrohydraulic servo seepage test machine is used to conduct a seepage-stress coupling test using distilled water as the measuring medium. e volume velocity of samples with different dip angles is determined under the maximum principal stress σ1 and different water pressures σs (0.2–0.8 MPa), and the change in permeability and the stress sensitivity of the columnar jointed rock mass is analyzed at different dip angles
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