A strategy and a flow sheet for establishing the Final Rock Stress Model (FRSM) is proposed and described, see Figure 1. The development of FRSM consists of four major steps. In the first step one is defining the classes of rock stress and extracting existing data from databases. Together with geological and morphological information and borehole and drillcore data one establish the Best Estimate Stress Model (BESM). In the next step, called Stress Measurement Methods (SSM), newstress data from borehole methods and core-based methods are recorded and evaluated. Thereafter, data from direct and indirect stress measurements are combined in an Integrated Stress Determination (ISD) with or without support from numerical stress modeling. The combination of available information will generate the Final Rock Stress Model at a site or an area. Examples include the European stress map, stress decoupling in the North German Basin, stress perturbation from faults in Sweden of importance for radioactive waste disposal.
An exact prediction of the in-situ state of rock stress and its spatial and temporal variation is very difficult and for practical purpose impossible since the current state of stress at a site or an area is the end product of an often long series of past geological events. An obvious situation in which stresses are discontinuous is at contacts between rock masses of different lithology and where rocks are intersected by one or several sets of joints, faults and other structural features. Stresses not only vary in space but also with time. Geological processes like erosion, sedimentation, mountain building and other tectonic events act over millions of years. The stress related to each of the processes will adjust in space and time or continue to change with time in order to maintain equilibrium in the Earth's crust.
