Discrete Element Modelling of Rock Creep Behaviour using Rate Process Theory

Rock creep behavior is crucial in many rock engineering projects. Different approaches have been proposed to model rock creep behavior; however, many cannot reproduce tertiary creep (i.e., accelerating strain rates leading to rock failure). In this work, a discrete element model (DEM) is employed, in conjunction with the rate process theory [Kuhn MR, Mitchel JK. Modelling of soil creep with the discrete element method. Eng Computations. 1992;9(2):277–287] to simulate rock creep. The DEM numerical sample is built using a mixture of contact models between particles that combines the Flat Joint Contact Model and the Linear Model. Laboratory uniaxial compression creep tests conducted on intact slate samples are used as a benchmark to validate the methodology. Results demonstrate that, when properly calibrated, DEM models combined with the rate process theory can reproduce all creep stages observed in slate rock samples in the laboratory, including and without using constitutive models that incorporate an explicit dependence of strain rate with time. The DEM results also suggest that creep is associated to damage in the samples during the laboratory tests, due to new micro-cracks that appear when the load is applied and maintained constant at each loading stage.

Prediction of Coronavirus Disease (covid-19) Evolution in USA with the Model Based on the Eyring’s Rate Process Theory and Free Volume Concept

A modification arguing that the human movement energy may change with time is made on our previous infectious disease model, in which infectious disease transmission is considered as a sequential chemical reaction and reaction rate constants obey the Eyring’s rate process theory and free volume concept. The modified model is employed to fit current covid-19 outbreak data in USA and to make predictions on the numbers of the infected, the removed and the death in the foreseeable future. Excellent fitting curves and regression quality are obtained, indicating that the model is working and the predictions may be close to reality. Our work could provide some ideas on what we may expect in the future and how we can prepare accordingly for this difficult period.

Infection Dynamics of Coronavirus Disease 2019 (Covid-19) Modeled with the Integration of the Eyring’s Rate Process Theory and Free Volume Concept

The Eyring’s rate process theory and free volume concept, two very popular theories in chemistry and physics fields, are employed to treat infectious disease transmissions. The susceptible individuals are assumed to move stochastically from one place to another. The virus particle transmission rate is assumed to obey the Eyring’s rate process theory and also controlled by how much free volume available in a system. The transmission process is considered to be a sequential chemical reaction, and the concentrations or fractions of four epidemiological compartments, the susceptible, the exposed, the infected, and the removed, can be derived and calculated. The obtained equations show that the basic reproduction number, R0, is not a constant, dependent on the volume fraction of virus particles, virus particle size, and virus particle packing structure, the energy barrier associated with susceptible individuals, and environment temperature. The developed models are applied to treat coronavirus disease 2019 (Covid-19) transmission and make predictions on peak time, peak infected, and R0. Our work provides a simple and straightforward approach to estimate how infection diseases evolve and how many people may be infected.

Heating-induced creep and potential creep rupture of clay liners for nuclear waste repository

The aim of this study is to assess the potential of encountering a heating-induced creep rapture of clay liners in nuclear waste repository. Groundwater and soil contaminations may occur if the elevated temperatures, expected in the vicinity of nuclear waste repository, trigger creep rapture of the clay liners. In this study, we utilize simulations based on the discrete element method (DEM) to understand the conditions under which heating-induced creep rupture can take place. In lieu of the conventional local/non-local damping mechanism usually utilized in DEM simulations to dissipate energy, the DEM simulations presented in this study incorporate the rate process theory as a damping mechanism to model soil creep. The results of a base anisotropic model at 70 °C show a dramatic increase in the creep rate at high temperatures showing creep rupture. Such undesired behavior can be mitigated by engineering clay liner materials to sustain and resist the expected high temperatures expected around nuclear waste repository.