Zum langfristigen Tragverhalten von verschlossenen solegefullten-ein neuer Ansatz zu physikalischer Modellierung und numerischer Simulation

摘要

The abandonment of salt cavities has been studied since several years,considering especially the aspects of long-term maintenance-freedom as well as safety and environmental compatibility.At first a gas and fluid tight as well as long-term persistent borehole sealing must be developed.Secondly,the long-term load bearing behaviour of the sealed liquid-filled cavity has to be analyzed.Thereby rock mass convergence depending on cavern depth and size as well as rock salt mass quality have an important influence.A first article [1] is presenting a new physical model together with a computer code for numerical simulation of those geo-mechanic-geohydraulic coupled processes that are active in the salt rock mass after cavern sealing.The numerical simulation is taking into account three different phases,namely (I) pressure-buildup,(2) pressure induced infiltration and (3) seepage flow according to Darcy's flow model along the pathways just created in phase (2).The new physical model is related to simulation of phase (2) and founded on the hydro-mechanic coupled mechanism of fluid-pressure forced infiltration.With help of a computer code called INFIL the hydro-mechanic coupled processes during the three different phases can be quantified.This article shows the handling of the computer code INFIL using a representative cavern configuration.Furthermore it shows typical calculation results that give a perhaps surprising insight into the load bearing behaviour of the liquid-filled sealed cavity.At first the convergence of the sealed cavity will be calculated in dependence of cavern inside pressure.Afterwards it is shown how the numerical simulation can be done,e.g.during infiltration approach of a constant rock mass stress field or approach of a changing rock mass stress field relating to the cavern pressure.There are shown several diagrams like time-dependent development of infiltration front,the development of cavern inside pressure and pore pressure in salt rock mass respectively as well as the spatial extension of the infiltration region in salt rock mass.Furthermore,starting with the secondary porosity a secondary permeability is estimated within the infiltrated rock mass region with help of a poroperm-model.This secondary permeability determines together with the hydraulic gradient and the rock mass convergence the seepage flow which takes place on the pathways created by infiltration process.The infiltrated rock mass region may possess a modified mechanical behaviour due to increased brine content and micro-fissures.Furthermore,pore pressures are active in this region with influence on the mechanically effective stress field.Rock mechanic analysis and interpretation of calculation results will identify the most important questions with respect to load bearing behaviour and also answer them.