Nonlinear Creep Behavior and Viscoelastic‐Plastic Constitutive Model of Rock‐Concrete Composite Mass

Abstract

The joint force deformation of rock-concrete composite structures is different from that of simple rock specimens or concrete specimens, such as the tunnel surrounding rock-lining concrete, dam foundations, and concrete. In order to study the creep mechanical properties of rock-concrete composite structures under long-duration load, the TFD-2000 microcomputer servo triaxial creep testing machine is used to carry out step loading creep tests on rock-concrete composite specimens (hereinafter referred to as composite specimens) under different confining pressures (including the confining pressures σ3 = 0 MPa). The creep test results show that, under the same confining pressure, when axial deviatoric stress is applied step-by-step according to 10%, 20%, 30%, 40%, 50%, and so forth of the UCS (σ3 = 0 MPa) and TCS (triaxial compressive strength) of the composite specimens, the failure stress that the specimen can bear is closely related to the confining pressure. When the confining pressures are 0 MPa, 7 MPa, 15 MPa, and 22 MPa, respectively, the failure stresses that the composite specimens can bear are 60% (corresponds to 0 MPa), 50%, 30%, and 20% of the TCS under the current confining pressures, respectively. Under the same confining pressure, the initial creep rate of the composite specimen on each step shows a U-shaped change trend. Meanwhile, the instantaneous creep rate and failure creep rate of the specimen increase as the confining pressure increases. When the failure creep rate is excluded, the initial creep rate of other stepped loads at the same confining pressure level decreases step-by-step. The improved Nishihara model can better describe the whole creep process of rock-concrete composite specimens, especially in the accelerating creep step. The testing data and research results in this paper can serve as references for further research on mechanical properties of rock-concrete composite structures.

Deformation Prediction of Tunnel-Surrounding Rock Considering the Time Effect of the Viscosity Coefficient: A Case of an NATM-Excavated Tunnel

“…Nonlinear improvements have been made to the existing models, but no research has been conducted on the time effects under nonlinear conditions. Considering the influence of time and stress on creep, some scholars established a nonlinear creep damage model and the corresponding constitutive equation (Feng et al, 2020;Liu W. et al, 2020;Yan et al, 2020;Liu Y. et al, 2020). However, they did not study the influence of this model on the damage and deformation of surrounding rocks.…”

Dynamic splitting tensile behavior of rock–concrete bimaterial disc with multiple material types under different interface inclination angle

“…Rock-concrete combination structures mainly exist in the heavy construction such as dams, tunnels, and mine caverns, [1][2][3][4][5][6][7][8] where the concrete relies on the bonding properties with the rock to play a supporting role for the structure. However, the interface of the rock-concrete combination is prone to microcracking.…”

“…Extensive research has been conducted on rock–concrete structures, including basic mechanical properties, 2,3,11 durability, 9,12 and numerical simulation 13,14 of the assemblies. Based on the engineering structural properties of rock–concrete assemblies, the interfacial shear properties, interfacial roughness, fracture behavior, deformation behavior, and energy dissipation of the composite have been investigated by scholars from different perspectives 5,7,15–18 .…”

Experimental investigation of rock–shotcrete interface damage under dynamic splitting using digital image correlation and acoustic emission

“…The tensile damage at interfaces is the main type of structure instability damage in complicated stress condition 10 . The research of the interface damage of the rock‐concrete bimaterial engineering body and the interaction between the media bodies is a hot and difficult issue in the engineering field 11,12 …”

“…10 The research of the interface damage of the rock-concrete bimaterial engineering body and the interaction between the media bodies is a hot and difficult issue in the engineering field. 11,12 The current research on rock-concrete composite structures mainly focuses on the bonding properties of the interface, fracture criteria, and numerical simulation analysis of the nonlinear interface behavior. [13][14][15][16] Zhu comprehensively considered the influence of rock types, concrete strength, concrete admixtures, and interface roughness on the bond performance of the rock-concrete interface.…”