Abstract
Exploring mechanical properties of red bed rock of Badong Formation Section two (b2) from the Three Gorges Reservoir is crucial to determine the instability mode of reservoir slopes. In order to reveal the energy evolution laws for b2 rocks under different stress paths, loading tests, unloading tests, and cyclic loading-unloading tests were conducted, respectively. The results show that stress paths have significant influences on the mechanical properties and energy evolution characteristics of b2 rocks and the failure mechanism under three stress paths is revealed. Relative to the loading tests, the mechanical parameters of b2 rocks are deteriorated under the unloading conditions. In addition, the increasing trend of cumulative dissipation energy (CDE) is similar with that of total absorption energy (TAE) and the ESE-strain curves are characterized by multistep rise. For cyclic loading-unloading tests, the areas of hysteretic loop gradually increase as the cycle times increase, and the TAEs and the coefficient of the cumulative dissipation energy (CCDE) also increase gradually with approximately linear characteristics, while the CDEs gradually increase in an abrupt rate. This work can contribute to provide the failure mechanism of b2 rocks for evaluating the stability of reservoir slopes from the energy perspective.
Highlights
With the construction and implementation of large-scale hydropower projects related to rock mass in China, a large number of engineering geological problems, such as the excavation of abutment slope, the excavation and support of underground cavern, and geological structural movement, have arisen, which seriously threaten the safety of the project and people’s lives and property [1,2,3]
The process of rock deformation and failure is always accompanied by the accumulative, dissipation, and release of the energy, which is regarded as an instability phenomenon driven by the energy [6,7,8,9]. us, it is necessary to understand the connections between the mechanical characteristics, the energy evolution laws, and the deformation/ failure mechanisms
Based on the stressstrain curve of the rock under the loading or unloading condition, the energy distribution laws at a given stress state can be obtained as shown in Figure 1. e area of ABCDEN surrounded by the loading or unloading curve and the strain axis can be defined as the total absorption energy (TAE) that represents the total work done by the external forces to the rock. e area of ABCDO can be defined as the elastic strain energy (ESE) before peak strength (PS). e area of DENM can be defined as the cumulative dissipation energy (CDE) after the PS, and the area of PQM can be defined as the residual elastic strain energy after the PS
Summary
With the construction and implementation of large-scale hydropower projects related to rock mass in China, a large number of engineering geological problems, such as the excavation of abutment slope, the excavation and support of underground cavern, and geological structural movement, have arisen, which seriously threaten the safety of the project and people’s lives and property [1,2,3]. Many contributions have been made to utilize the perspective of energy to study the mechanical properties and the deformation/failure mechanism of the rock [10,11,12,13]. From initial damage to final failure, the failure of the rock undergoes three stages, including the failure of microstructures, the formation of mesoflaws and the coalescence of macrocracks [14, 15]. As both the formation and propagation of microcracks that lead to the failure of the rock consume much energy, the rock
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