Abstract
Taking the “11.28” rockburst occurred in the Jinping II Hydropower Station as the engineering background, the evolution mechanism of structure-type rockburst was studied in detail based on the particle flow code. The results indicate that the failure mechanism of structure-type rockburst includes a tensile fracture induced by tangential compressive stress and a shear fracture caused by shear stress due to overburdened loadings and shear slip on the structural plane. In addition, it is found that the differences between structure-type rockburst and strainburst mainly include (a) the distribution of the local concentrated stress zone after excavation, (b) the evolution mechanism, and (c) the failure locations. Finally, the influence of four factors on the structure-type rockburst are explored. The results show that (1) when the friction coefficient is greater than 0.5, the effect of structural plane is weakened, and the rock near excavation tends to be intact, the structural-type rockburst intensity decreases; (2) the dissipated and radiated energy in structural-type rockburst reduces with rockmass heterogeneity m; (3) the lateral pressure coefficient has a significant effect on the intensity of deep rock failure, specifically in the form of the rapid growth in dissipative energy; (4) and the structural-type rockburst is more pronounced at a structural plane length near 90 mm.
Highlights
It needs to be noted that the flat-joint model (FJM) model is used for all the particles of the rock mass, while the SJM model is only used for the particles of the structural plane
(3) The failure locations for strainburst mainly exist in the middle of both side walls, while the failure locations for structure-type rockburst are closely related to the location of the structural plane
In order to explore the evolution mechanism of the “11.28” rockburst from the view of discrete element methods (DEMs), based on the field observations, this problem was considered as the Particle flow code (PFC) 2D plane strain model at the laboratory scale, e.g., the interaction mechanism between the single joint and the circular hole under high geostress and unloading induced by excavation
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The main difference between structure-type rockburst and strainbursts is that the former is obviously impacted by the structural plane, which makes the two distinct in terms of the mechanisms of energy release and the excavation damage processes [5]. Based on the rockburst in the diversion tunnel of Jinping II Hydropower Station, they [23] further conducted a series of shear tests to study the effect of the structural plane on rockburst. This study numerically further investigates the evolution mechanism of structure-type rockburst using PFC 2D, a well-known discrete element numerical method, taking into account the interaction between the tunnel and the structural plane after excavation. The calculation time of the 3D model for PFC is usually longer than that of the 2D model due to excessive particles in the 3D model, so the latter is generally given priority
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