Rock-mass behaviour modelling

The stress-strain behaviour of the rock, including fracture formation, is a crucial component of the aperture changes. As mentioned before the deformation normal to the fracture is considered in equation (S) in order to obtain aperture changes. If an elastoplastic model is considered for the rock mass behaviour, fracture initiation can be associated with tension stresses. Fracture orientation is sensitive to the stress tensor orientation so the plane where the minimum principal stress (compression positive) occurs defines the plane of fracture formation. 

Abstract As a part of the DECOVALEX 111 project—model predictions were carried out of thermomechanical (TM) rock-mass responses at the Yucca Mountain drift scale test (DST), Nevada. This paper presents model predictions of TM-induced rock displacements at the DST carried out by two independent research teams using two different approaches and two different numerical models. Displacements predicted by the two independent analyses compare reasonably well to the measured ones, both in trends and average magnitude. The analyses indicate that the rock mass behaviour is essentially elastic and that the in situ rock mass thermal expansion coefficient is well represented a temperature-dependent thermal-expansion derived from laboratory tests on intact rock. 

T-H-M-C MODELLING OF ROCK MASS BEHAVIOUR -1 THE PURPOSES, THE PROCEDURES AND THE PRODUCTS... 

Hudson, J. A. Andersson, J., 2003. T-H-M-C modelling of rock mass behaviour 2 - the input data and rock mass partitioning. Proceedings of the GEOPROC2003 conference, Stockholm. 

In order to model rock mass behaviour with a numerical code, it is necessary to input values for the relevant parameters. In a relatively simple code. 

Nguyen T.S., 2000-b. Mathematical Modelling of an in-situ Experiment for the T-H-M Behaviour of Unsaturated Bentonite and Granitic Rock Mass, Proc. Canadian Geotechnical Conference, Montreal, Bitech Publishers Ltd., Canada... 

All teams assumed linear elastic behaviour for the different media in addition, SKI used a notension model for the buffer and the backfill. Because of the crucial role of the rock mass permeability, three values of its initial intrinsic permeability have been considered lO lO (base case) and lO m. Moreover, a variation of tbe permeability with respect either to the porosity tp or to the effective mean stress Om (SKI) has been assumed ... 

The two-dimensional distinct element code, UDEC (Itasca, 2000) is applied for the modeling of mechanical and hydraulic behaviours. UDEC simulates the response of a fractured rock mass represented as an assemblage of discrete deformable blocks, subjected to the mechanical stress and hydraulic pressure boundary condition. Numerical experiment consists of 1) generation of a Discrete Fracture Network (DFN) as a geometric model, 2) application of various stress conditions, and 3) application of fluid boundary condition and calculation of equivalent permeability. 

Figure 1. The purpose of modelling THMC processes in rock masses is to be able to interpret previous behaviour and to predict future behaviour.

When modelling the behaviour of a rock mass it is convenient to consider the six main aspects of the modelling problem. 

It is of a great significance to understand how the mechanical behaviours and properties of rock masses change with temperature, such as for nuclear waste repositories and deep mining at certain temperatures. The key to this problem is how to make predictions to long-term response of rocks based on mechanical models and test results within a short time of experiments. It is put forward in this paper that the problem can be resolved by means of time-temperature equivalent principle for rocks. 

DAMAGE MODEL COUPLED WITH HYDRO-MECHANICAL BEHAVIOUR OF JOINTED ROCK MASS... 

Roy, N. (1993). Engineering behaviour of rock masses through study of jointed models. Unpublished doctoral dissertation, Indian Institute of Technology, Delhi, India. 

The Structure of a Reservoir Simulator A reservoir simulator is software for solving the porous medium flow equations with detailed models of the spatial distribution of rock properties, detailed models of the thermodynamics of phase behaviour, of the wells and how the wells coimect with each other through surface networks. Further, a reservoir simulator will have built-in support for optimisation software in that derivatives of specified flow diagnostics, such as well rates, or masses of chemical components in specified volumes, with respect to a variety of parameters can be computed. 

The numerical simulation of the fractured reservoir behaviour can be decomposed into two main parts. Namely, hydraulic fracturing part (here at first the values of the fracture shear dilation angles should be obtained for the typical rock in reservoir), and, after that, the model of the stimulated reservoir is employed for evaluating the heat and mass transfer processes during the production stage of reservoir exploitation. 

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