Generalized Block Theory for the Stability Analysis of Blocky Rock Mass Systems Under Seismic Loads

• Published in: Rock mechanics and rock engineering Vol. 55; no. 5; pp. 2747 - 2769
• Main Authors: Wang, Shuaifeng, Zhang, Zixin, Huang, Xin, Lei, Qinghua
• Format: Journal Article
• Language: English
• Published: Vienna Springer Vienna 01.05.2022; Springer Nature B.V
• Subjects: Analysis; Block theory; Civil Engineering; Dredging; Earth and Environmental Science; Earth Sciences; Earthquake loads; Earthquakes; Excavation; Geophysics/Geodesy; Instability; Kinematics; Loads (forces); Original Paper; Probability theory; Rock masses; Rocks; Safety factors; Seismic activity; Seismic stability; Slope stability; Stability analysis; Statistical analysis; Theories; Blocky rock mass; Generalized block theory; Seismic loads; Evaluation parameter
• ISSN: 0723-2632; 1434-453X; 1434-453X
• DOI: 10.1007/s00603-021-02628-3

The stability analysis of rock blocks on man-made excavation faces (e.g. tunnel, cavern, and slope) subject to seismic loads is an important issue in the field of rock engineering. This paper proposes a generalized block theory (GBT) by combining a pseudo-static method and the traditional block theory to evaluate the stability of blocky rock masses during earthquake activities. In our analysis, the basic safety factors are derived considering time-varying seismic loads to determine the stability of a rock block at each time step. Afterwards, two new parameters, P u and V u , are used to evaluate the seismic stability of a rock block, where P u is the instability probability defined as the ratio of the time for the block becoming unstable to the total seismic loading time, and V u is the probabilistic instability volume defined as P u times the block volume. As for a blocky rock mass system, its probabilistic instability volume is the sum of V u of all seismically unstable blocks and the instability probability is the ratio of its probabilistic instability volume and total volume of seismically unstable blocks. Through the simulation of a generic slope excavation, we observe that seismic loads significantly affect the stability and kinematics of a rock block during an earthquake. For a blocky rock mass, both P u and V u decay with the epicentral distance, in general following an inverse power law trend. Furthermore, it is found that the local site effect also has a strong influence on the slope stability under seismic loads.