Time And Temperature Dependent Stress And Displacement Fields In Salt Domes

The design of storage space or deep mining in rock salt should take into account not only time dependency of the rock salt behavior but also temperature effects. For deep mining of potassium salt the natural increase of temperature with depth may no longer be negligible. For the storage of cryogenic liquid gas in salt caverns more knowledge is nezded about the propagation of deep temperatures and their effects on the stress-strain-creep behavior of the surrounding salt. High temperature problems arise for nuclear waste storages in caverns or drill holes emitting radiation. A numerical model is proposed for the analysis of displacements and stresses including their time and temperature induced change. For the material behavior of salt constitutive equations are chosen composed of a combination of Hooke-Kelvin-Bingham-Newton-model based on experimental results (excluding at present deep cooling), Langer 1980. The parameters involved are depending on the stress level and the temperature. The finite-element-method is applied to rotationally symmetrical three-dimensional problems. The non-linear calculation method is based on an implicit method with respect to time. A modified Newton-Raphson-method and the initial strain approach are employed. Along with some experiences on suitable numerical procedures, examples are shown for the characteristical effects of time-temperature dependency. Having achieved convergency and reliability a method is now available for practical design and parametric sensibility studies.