Sensitivity of the stability assessment of a deep excavation to the material characterisations and analysis methods
- Authors: Ghadrdan, Mohsen , Shaghaghi, Tahereh , Tolooiyan, Ali
- Date: 2020
- Type: Text , Journal article
- Relation: Geomechanics and Geophysics for Geo-Energy and Geo-Resources Vol. 6, no. 4 (2020), p.
- Full Text: false
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- Description: Due to the spatial variability of material characterisations in deep and large scale excavations, stability assessment is often a challenging task. Numerous slope stability analysis methods based on a range of assumptions and principles are implemented in commercial software packages to ease the process of stability assessment of non-homogeneous and multi-layered slopes. However, the selection of a suitable method remains crucial as the application of an unrealistic or unsuitable method may lead to catastrophic consequences. Besides material shear strength parameters, and analysis methods, non-strength characterisations such as permeability and creep can affect the result of slope stability analysis significantly. In this study, the sensitivity of the stability assessment of a deep excavation in Australia to material characterisations such as friction angle, cohesion and permeability and creep is investigated by the use of different formulations and assumptions of the Limit Equilibrium Method (LEM) and the Finite Element Method (FEM) as the two most common slope stability methods. The results show that the stability assessment is highly sensitive to the applied method and assumptions. Moreover, the role of material strength and non-strength parameters and the selection of a suitable constitutive model in slope stability assessment is presented. © 2020, Springer Nature Switzerland AG.
Waveform features and failure patterns of hollow cylindrical sandstone specimens under repetitive impact and triaxial confinements
- Authors: Wang, Shiming , Liu, Yunsi , Du, Kun , Zhou, Jian , Khandelwal, Manoj
- Date: 2020
- Type: Text , Journal article
- Relation: Geomechanics and Geophysics for Geo-Energy and Geo-Resources Vol. 6, no. 4 (2020), p.
- Full Text:
- Reviewed:
- Description: In underground engineering practice, the surrounding rocks are subjected to a nonuniform stress field with various radial gradients. In this study, a series of conventional triaxial repetitive impact tests using hollow cylindrical sandstone (HOS) specimens were conducted to reveal the impact waveform features and failure properties of rocks under nonuniform stress conditions. The tests were conducted using a modified large diameter split Hopkinson pressure bar testing system. The confining pressure was set as 5, 10 and 12 MPa. The data of specimens under equilibrium stress states were chosen and analyzed, and the results showed that more applied numbers of cyclic impact loads were needed to break rocks with the increase of confining pressure. Three types of cracks, i.e., ring-shaped cracks around the hole in the center of specimens, axial cracks located in the outer cylindrical surface, and lateral cracks fracturing rock fragments into small pieces appeared in HOS specimens. The failure degrees of HOS specimens could be judged by the waveform features of the reflected wave, and the waveform features of reflected wave are similar in the same failure mode, regardless of the impact velocity and the number of impacts, which only affect the failure degree. © 2020, Springer Nature Switzerland AG.
- Description: The work reported here is supported by financial grants from both the National Natural Science Foundation of China (51774326, 41807259, 51604109 51704109).