Abstract
A numerical time-dependent deformation model of rock by incorporating the stress corrosion model into a three-dimensional discrete element code was established to investigate time-dependent deformation and fracture evolution of surrounding rock around underground excavations with circular, inverted U-shaped and rectangular cross-sections. The mesoscale model input parameters were calibrated to replicate the mechanical behavior and failure patterns of the rock observed in laboratory. Numerical simulations on the time-independent and -dependent deformation and fracturing evolution of the rock around underground excavations with different shapes under hydrostatic stress were studied. The results show that the maximum time-independent displacements of circular, inverted U-shaped and rectangular openings are 11, 15, and 34 mm at left roof, right floor and left side, respectively. It shows that the surrounding rocks around the circular, inverted U-shaped openings are much more stable than that around the rectangular opening. The cracks within the surrounding rock around different shaped openings gradually increases as time goes by, and the tensile cracks are dominant. The progressive failure process of the circular openings under varying lateral pressures was further modeled. The results show the failure zone at the roof wall and floor wall becomes more evident with an increase in the lateral pressure coefficient.
Highlights
Deformation and fracture around underground openings are widely observed, under high and complex in-situ stress (Pan and Dong 1991a; 1991b; Gioda and Cividini 1996; Diederichs 2007; Sterpi and Gioda 2009; Zhao et al 2010; Gao et al 2019)
These observations suggest that a thorough understanding of time-independent and -dependent deformations around an underground opening is essential for their design and construction under in-situ stress condition
The stress corrosion model was further incorporated into 3DEC-GBM to mimic timedependent response around underground openings at mesoscale, which is the same method of time-dependent deformation presented in Fu et al (2020)
Summary
Deformation and fracture around underground openings are widely observed, under high and complex in-situ stress (Pan and Dong 1991a; 1991b; Gioda and Cividini 1996; Diederichs 2007; Sterpi and Gioda 2009; Zhao et al 2010; Gao et al 2019). G., months or years) passes owing to rheological behavior, which greatly effects the determination of the support method for the underground opening (Sulem et al 1987; Malan 2002; Kontogianni et al 2006; Xu et al 2012; Wu and Shao 2019) These observations suggest that a thorough understanding of time-independent and -dependent deformations around an underground opening is essential for their design and construction under in-situ stress condition. This study simulates the progressive fracturing processes around an underground excavation considering both time-independent and time-dependent behaviours at mesoscale (i.e., grain scale). The timedependent behaviour around underground openings with circular, inverted U-shaped and rectangular cross-section were numerically studied by a rheological model using stress corrosion theory under the hydrostatic stress conditions. Deformation and fracturing of the surrounding rock around the circular openings were further analyzed under varying coefficients of lateral pressure
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