Analysis of the Seismic Performance of a Rock Joint with a Modified Continuously Yielding Model

Abstract

The problem of seismic wave transmission at a rock joint is a critical issue for aseismic affairs of underground rock engineering. Little attention has been given to the normal cyclic loading behavior of a joint during wave propagation. This paper introduces a modification to Cundall’s continuously yielding (CY) model. The original normal behavior of the CY model is upgraded by adding the capacity to account for sophisticated characteristics during normal cyclic loading. The proposed modified-CY (M-CY) model is verified through comparison with existing experimental data. The effects of various parameters in this M-CY model are discussed, indicating that the M-CY model is capable of fitting realistic test data. Subsequently, P-wave transmission across a M-CY joint is numerically performed and evaluated. The results show that the M-CY model exhibits more transmission and consequently less reflection than the linear model as the velocity magnitude of an incident impulse approaches its peak value. Furthermore, the compatibility of the joint under an incident P-wave can be revealed by the M-CY model. The seismic stability of the tailrace tunnel of the Baihetan Hydropower Plant, which is controlled by a large fault, is studied as an engineering application of the proposed model. Seismic analysis suggests that the tunnel’s main failure mode under an earthquake would be shear slip at the intersection of the tunnel ceiling and fault. A comparison between the proposed model and original CY model illustrates that the original model would give a failure mode that overestimates the fault opening during the earthquake.