An elasto-plastic and viscoplastic damage constitutive model for dilatancy and fracturing behavior of soft rock squeezing deformation

• Published in: Journal of mountain science Vol. 19; no. 3; pp. 826 - 848
• Main Authors: Huang, Xing, Liu, Quan-sheng, Bo, Yin, Liu, Bin, Ding, Zi-wei, Zhang, Quan-tai
• Format: Journal Article
• Language: English
• Published: Heidelberg Science Press 01.03.2022; Springer Nature B.V
• Subjects: Belt conveyors; Coal; Coal mines; Compressing; Confining; Constitutive equations; Constitutive models; Constitutive relationships; Creep tests; Damage assessment; Deformation; Dilatancy; Dredging; Earth and Environmental Science; Earth Sciences; Ecology; Elasticity; Environment; Excavation; Fracturing; Geography; Haul roads; Laboratory tests; Linear functions; Mathematical models; Original Article; Plastics; Rocks; Solifluction; Strain; Strain rate; Time dependence; Unloading; Yields; Squeezing deformation; Soft rock; Damage; Dilatancy; Elasto-plastic and viscoplastic damage constitutive model; Fracturing
• ISSN: 1672-6316; 1993-0321; 1008-2786
• DOI: 10.1007/s11629-020-6530-4

Soft rock squeezing deformation mainly consists of pre-peak damage-dilatancy and post-peak fracture-bulking at the excavation unloading instant, and creep-dilatancy caused by time-dependent damage and fracturing. Based on the classic elasto-plastic and Perzyna over-stress viscoplastic theories, as well as triaxial unloading confining pressure test and triaxial unloading creep test results, an elasto-plastic and viscoplastic damage constitutive model is established for the short- and long-term dilatancy and fracturing behavior of soft rock squeezing deformation. Firstly, the criteria for each deformation and failure stage are expressed as a linear function of confining pressure. Secondly, the total damage evolution equation considering time-dependent damage is proposed, including the initial damage produced at the excavation instant, in which the damage variable increases exponentially with the lateral strain, and creep damage. Thirdly, a transient five-stages elasto-plastic constitutive equation for the short-term deformation after excavation that comprised of elasticity, pre-peak damage-dilatancy, post-peak brittle-drop, linear strain-softening, and residual perfectly-plastic regimes is developed based on incremental elasto-plastic theory and the nonassociated flow rule. Fourthly, regarding the time-dependent properties of soft rock, based on the Perzyna viscoplastic over-stress theory, a viscoplastic damage model is set up to capture creep damage and dilatancy behavior. Viscoplastic strain is produced when the stress exceeds the initial static yield surface f s ; the distance between the static yield surface fs and the dynamic yield surface f d determines the viscoplastic strain rate. Finally, the established constitutive model is numerically implemented and field applied to the -848 m belt conveyer haulage roadway of Huainan Panyidong Coal Mine. Laboratory test results and in-situ monitoring results validate the rationality of the established constitutive model. The presented model takes both the transient and time-dependent damage and fracturing into consideration.