Analysis of removability and stability of rock blocks by considering the rock bridge effect

Abstract

In traditional block theory, the removability and stability of rock blocks are analyzed independently; that is, the stability of a removable block is analyzed in detail, and nonremovable blocks are regarded as stable. However, in practical situations, nonremovable blocks may pose more danger than removable blocks. This paper presents a unified method for analyzing the removability and stability of rock blocks. In this method, the cracking of rock bridges is considered and nonremovable blocks are not assumed to be stable. First, possible cracking rock bridges are identified by extending finite-sized fractures and comparing the boundary surfaces of the resulting blocks with those of the original blocks. Then, the sliding direction associated with each possible moving block is determined by solving an optimization problem. The normal force acting on each sliding surface is determined, and the resisting force on each rock bridge is calculated and integrated into the total resisting force when calculating the safety factor of a possible moving block. Procedures to determine all possible moving blocks are introduced, and the possible moving block with the minimum safety factor is regarded as the actual moving block. The corresponding minimum safety factor is defined as the actual safety factor of the block. The proposed method is verified by considering a few examples. The results show that nonremovable blocks may be unstable if the cracking of rock bridges is considered.

Geological discontinuity persistence: Implications and quantification

“…The term 'rock bridge' is defined as an area of intact/strong rock material separating coplanar or non-coplanar discontinuities in rock masses (Kim et al, 2007b;Zheng et al, 2015). Rock bridges usually occupy a part of the planar joint plane (Dershowitz and Einstein 1988); such rock bridges in coplanar joints are the focus of this review.…”

Extensions of the dynamic Newmark method for seismic stability analysis of a rock block

“…Another idea is to combine the Newmark sliding block method with block theory, as proposed by Shi 30–32 . Block theory has been widely used to research the stability of slopes, tunnels, and dam foundations 33–38 . To ascertain the seismic dynamic response of a complex rock block, Fu et al 39 .…”

Constructing boundary structures of rock blocks

“…The concepts involved in the element block–assembling approach are relatively simple, and the operations on convex blocks facilitate robust programs. In recent years, this approach has been extensively developed and applied to various practical projects …”

“…In recent years, this approach has been extensively developed and applied to various practical projects. [11][12][13][14][15][16][17] In the element block-assembling approach, the element blocks are constructed by temporarily extended fractures and therefore may preserve fictitious boundary surfaces that do not physically exist. As shown in Figure 1, two complex-blocks B 1 and B 2 are identified using the element block-assembling approach.…”