Equivalent Constitutive Model for Jointed Rock Masses and Its Application in Large Underground Caverns

Jointed rock masses with different orientations and spacings are widely exposed in rock engineering applications, such as underground caverns, slopes, and tunnels, which significantly influence the rock engineering stability and mechanical behavior of the rock masses. To better evaluate the mechanical response of the jointed rock masses during the engineering excavation period, an equivalent constitutive model for the jointed rock masses was established based on the joint compliance tensor (JCT) and was adopted to analyze the excavation-induced mechanical performance of Jinping II hydropower station underground caverns. First, the calculation method of the joint compliance tensor and equivalent elastic compliance matrix of the rock masses containing multiple joint sets was established considering the deformation characteristics of the joint system comprehensively based on the Oda fracture tensor theory and linear superposition principle. Second, an equivalent constitutive model for the jointed rock masses was established considering the joint spacing and connectivity. Finally, combined with the field investigation and monitoring data, the mechanical mechanism of unloading failure of the jointed rock masses in Jinping II hydropower station underground caverns was analyzed using the proposed model and numerical simulation.