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Energy characteristics and micro cracking behaviors of deep slate rock under triaxial loadings

Zhang Anlin, Feng Tao, Jiang Liangwen, Wang Dong, Wang Zhewei, Zhang Ru, Feng Gan, Zhang Zhilong, Deng Jianhui, Ren Li

Acta Geophysica

2022

Vol. 70, no 4

1457--1472

Sichuan-Tibet railway tunnels are generally long and deep, and some of them pass through layered slate, which is prone to failure under high in situ stress. Insight into the mechanical behaviors of deep slate under different stress environments is critical to the safety of engineering practices in this area. To this end, we studied the energy characteristics and microcracking behaviors of slate samples under different triaxial loadings. The results showed that the confining pressure increased the strength, elastic modulus, Poisson’s ratio and crack characteristic stresses of the studied slate. As the confining pressure increased, the storage of elastic strain energy during the prepeak stress stage increased, and its release during the postpeak stress stage was inhibited. Additionally, we obtained the slate failure precursors by analyzing the acoustic emission (AE) evolution characteristics, i.e., “a sudden increase in AE metrics, followed by a quiet period, and then a sudden increase again” in terms of the AE count rate and AE energy rate after obvious expansion of the sample. Then, we further observed that with an increase in confining pressure, a gradual transition of the failure pattern from compressive shear to tensile shear occurred. Finally, we discussed the influence mechanisms of confining pressure on the slate failure behaviors and concluded that the change in the effective shear stress along the foliation planes played an important role in the failure mode transition.

Effective sensor placement based on a VIKOR method considering common cause failure in the presence of epistemic uncertainty

Duan Rong-Xing, He Jie-Jun, Feng Tao, Huang Shu-Juan, Chen Li

Eksploatacja i Niezawodność

2021

Vol. 23, no. 2

253--262

Owing to expensive cost and restricted structure, limited sensors are allowed to install in modern systems to monitor the working state, which can improve their availability. Therefore, an effective sensor placement method is presented based on a VIKOR algorithm considering common cause failure (CCF) under epistemic uncertainty in this paper. Specifically, a dynamic fault tree (DFT) is developed to build a fault model to simulate dynamic fault behaviors and some reliability indices are calculated using a dynamic evidence network (DEN). Furthermore, a VIKOR method is proposed to choose the possible sensor locations based on these indices. Besides, a sensor model is introduced by using a priority AND gate (PAND) to describe the failure sequence between a sensor and a component. All placement schemes can be enumerated when the number of sensors is given, and the largest system reliability is the best alternative among the placement schemes. Finally, a case study shows that CCF has some influence on sensor placement and cannot be neglected in the reliabilitybased sensor placement.