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Experimental investigation and failure mechanism analysis for dacite under true triaxial unloading conditions
Abstract Strong unloading damaged zones at both slopes of the dam of a hydropower station in Southwest China have been attributed to the stress release. To study the deformation and failure mechanism of dacite (dam site material) under unloading conditions, three groups of true triaxial unloading tests were conducted on the rock sample with an initial minimum principal stress σ 3 0=5 MPa, and initial intermediate principal stresses σ 2 0= 10, 15, and 20 MPa. The experimental results indicate that the strain in the direction of σ 3 is the most sensitive to the unloading of σ 3, whereas the three principal strains are further suppressed with increasing σ 2. Ductile deformation is a failure precursor of dacite under unloading conditions. Based on the analysis of the failure mode and acoustic emission monitoring data, it has been concluded that the unloading failure of dacite is caused by the initiation, propagation, and coalescence of microcracks, which form localized tension macrocracks. The observed anisotropic damage evolution is found to be determined by stiffness degradation and quantified the degree of fracture during the final unloading stage. The results indicate that damage is anisotropic under the true triaxial unloading conditions, and that the damage ω 3 is the most sensitive to the unloading stress σ 3. Therefore, the deformation or damage in the direction of σ 3 can be used as a guide in the design of engineering excavation plans.
Highlights The effects of unloading σ 3 on dacite is studied under true triaxial conditions. The deformation in the direction of σ 3 is most sensitive to unloading. The unloading failure of dacite is tensile cracks propagation in the direction of σ 1. The evolution of damage is anisotropic under unloading conditions.
Experimental investigation and failure mechanism analysis for dacite under true triaxial unloading conditions
Abstract Strong unloading damaged zones at both slopes of the dam of a hydropower station in Southwest China have been attributed to the stress release. To study the deformation and failure mechanism of dacite (dam site material) under unloading conditions, three groups of true triaxial unloading tests were conducted on the rock sample with an initial minimum principal stress σ 3 0=5 MPa, and initial intermediate principal stresses σ 2 0= 10, 15, and 20 MPa. The experimental results indicate that the strain in the direction of σ 3 is the most sensitive to the unloading of σ 3, whereas the three principal strains are further suppressed with increasing σ 2. Ductile deformation is a failure precursor of dacite under unloading conditions. Based on the analysis of the failure mode and acoustic emission monitoring data, it has been concluded that the unloading failure of dacite is caused by the initiation, propagation, and coalescence of microcracks, which form localized tension macrocracks. The observed anisotropic damage evolution is found to be determined by stiffness degradation and quantified the degree of fracture during the final unloading stage. The results indicate that damage is anisotropic under the true triaxial unloading conditions, and that the damage ω 3 is the most sensitive to the unloading stress σ 3. Therefore, the deformation or damage in the direction of σ 3 can be used as a guide in the design of engineering excavation plans.
Highlights The effects of unloading σ 3 on dacite is studied under true triaxial conditions. The deformation in the direction of σ 3 is most sensitive to unloading. The unloading failure of dacite is tensile cracks propagation in the direction of σ 1. The evolution of damage is anisotropic under unloading conditions.
Experimental investigation and failure mechanism analysis for dacite under true triaxial unloading conditions
Wang, Susheng (author) / Xu, Weiya (author) / Yan, Long (author) / Feng, Xia-Ting (author) / Xie, Wei-Chau (author) / Chen, Hongjie (author)
Engineering Geology ; 264
2019-11-11
Article (Journal)
Electronic Resource
English
The time-dependent behaviour and failure mechanism of dacite under unloading condition
| Taylor & Francis Verlag | 2022