Constitutive behavior of reinforced rock unit anchored by an energy-absorbing bolt.

• Theoretical model was proposed to analyze the time-dependent behavior of RRU; • The model was used to analyze the convergences of roadway in a mining project; • Good agreements were achieved from analytical solutions and field monitored data; • Stress in rock decayed over time when sudden stress was imposed on the RRU. The energy-absorbing bolt is an advanced reinforcing element in rock mass to absorb the deformation energy. In this paper, the time-dependent reinforcement provided by the energy-absorbing bolt was analyzed based on assumptions of the reinforced rock unit (RRU) model for systematic bolting. The energy-absorbing bolt was simulated with an ideal elastic–plastic material law. The rheological behavior of the energy-absorbing bolt was represented by the connection of a Hookean elastic element and a Saint Venant element in series. The constitute model and creep behavior of the RRU under a sudden stress change were obtained by assuming the rock was a general Kelvin material. It showed the RRU exhibited an instantaneous jump in the strain, transient creep, and steady-state creep under a sudden change of external stress. The resulting stress in the rock decreased progressively as that in the energy-absorbing bolt could sustain the loading as large as its designed yielded stress. The constitutive models of RRU were applied to predict the convergences of surrounding rock mass in a mining roadway, in Anhui province, China. Good agreements were achieved between the analytical solutions and the field-monitored data. [ABSTRACT FROM AUTHOR]