Creep characteristics and nonlinear creep modeling of water-bearing sandy mudstone under triaxial loading conditions

Unsteady Creep Damage Model of Rock Considering Acid Solution Corrosion

This study investigates the triaxial creep mechanical behavior of Carboniferous surrounding rock under acidic solution corrosion with different pH values and establishes a novel viscoelastoplastic creep damage constitutive model considering pH–time coupling effects. Experimental results quantitatively indicate that acid corrosion significantly weakens the long-term bearing capacity of the rock. With the solution pH decreasing from 7 to 4, the peak bearing stress of rock declines from 50 to 30 MPa, representing a 40% reduction in the long-term bearing strength. Meanwhile, the maximum creep strain increases by 62.4%, and the steady-state creep rate rises obviously, accompanied by an earlier occurrence of accelerated creep. The experimental data fully validate the proposed model with all fitting correlation coefficients higher than 0.94. The theoretical curves precisely reproduce the full creep stages including instantaneous elastic deformation, decelerating creep, steady-state creep, and accelerated creep, which demonstrate that the established model can accurately characterize the time-dependent deformation and damage evolution of corroded rock. This model provides a reliable theoretical basis for the long-term stability evaluation of deep underground engineering under water–chemical coupling conditions.

Study on viscoelastic-plastic creep model of rock based on creep parameter degradation

Establishing a reasonable rock creep model is of great significance for analyzing the creep characteristics of rock and predicting the long-term stability of engineering rock mass. Based on the analysis of the nonlinear creep characteristics of rock, this paper innovatively proposes an unsteady Kelvin body that reflects the nonlinear characteristics of the attenuation creep stage. Based on the negative exponential function relationship between the viscosity coefficient and the stress and time, a nonlinear viscoplastic body that reflects the nonlinear characteristics of the accelerated creep stage is proposed. A viscoelastic-plastic creep model of rock considering the deterioration of creep parameters is constructed, and the creep equations of the creep model under one-dimensional stress state and three-dimensional stress state are derived. The model in this paper is used to fit and analyze the creep test data of sandstone and carbonaceous shale under different confining pressures. The results show that the fitting degree of the test curve and the model curve is good, with the coefficient of determination R2 generally above 0.98 and low RMSE/MAE values, indicating that the rock creep model considering the deterioration of creep parameters established in this paper can well describe the creep mechanical characteristics of rock. At the same time, the fitting effects of the model, the classical Nishihara model and the fractional Nishihara model are compared to further illustrate the correctness and advancement of the established model. The research in this paper not only enriches the theory of rock creep model, but also has certain theoretical reference value for the study of long-term stability of rock mass engineering.

An improved nonlinear creep model of rock considering the effect of confining pressure on accelerated creep characteristics

Study on the Interaction Between Surrounding Rock and Support in High-Stress Soft Rock Roadways Based on Rock Rheological Properties

High-stress soft rock roadways in deep underground engineering often exhibit significant time-dependent deformation due to strong rheological behavior of surrounding rock. To investigate the deformation characteristics and support effect, a composite viscoelastic constitutive model considering anchored and unanchored rock zones is established based on the Maxwell rheological framework. The equivalent stiffness contribution of rock bolts is incorporated to characterize the interaction between support and surrounding rock. Analytical solutions of radial displacement and creep rate are derived using viscoelastic theory and Laplace transform methods. The effects of bolt spacing, bolt length, and burial depth on the rheological response are analyzed. Numerical simulations based on FLAC3D creep analysis and field monitoring data are used to verify the proposed model. Results show that decreasing bolt spacing effectively reduces long-term deformation, while bolt length has a diminishing effect beyond a critical anchorage length. Increasing burial depth significantly increases creep rate and total deformation. The numerical results agree well with theoretical predictions (R2 ≈ 0.985), and field measurements show a relative error within 10%. The proposed model effectively describes the long-term deformation trend of high-stress soft rock roadways and provides a theoretical reference for support design under similar conditions.

Experimental study on creep characteristics and mesostructural evolution of silty clay in Western Henan

Thermal–Mechanical Coupled Creep Characteristics and a Fractional-Order Nonlinear Damage Model for Red Sandstone under Impact Disturbance

Deep rock masses in geothermal engineering, nuclear waste disposal, and deep mining are often subjected to the coupled effects of high temperatures and dynamic disturbances, leading to a significant deterioration in their long-term mechanical stability. However, existing research has rarely explored the coupled effects of thermal damage and impact loading on creep characteristics, and there is a lack of constitutive models capable of capturing the evolution of such coupled damage. In this study, uniaxial compressive strength tests and physical measurements were conducted on red sandstone after heat treatment (200°C–800°C), followed by impact creep tests under various temperatures and impact energies. A critical thermal threshold of approximately 400°C was identified, above which mass loss, volume expansion, and density reduction accelerated significantly, and the failure mode transitioned from splitting to shear-dominated patterns. Under impact loading, the first impact contributed the largest proportion of creep deformation, and cumulative creep deformation increased exponentially with rising temperature, while the steady-state creep rate exhibited a gradually slowing growth trend. Based on the Burgers model, a fractional-order nonlinear damage-creep constitutive model was developed by introducing a viscoplastic element and replacing the Newtonian dashpot with a fractional-order Abel dashpot. This model can effectively capture the entire creep process under coupled thermal and impact effects. The identified critical temperature of 400°C provides a practical reference for assessing the thermal stability of underground engineering, while the proposed constitutive model offers an effective tool for predicting time-dependent deformation of rock masses under the coupled effects of high temperatures and dynamic loads.