Abstract

Geotechnical safety for a cavity field will be assessed on the basis of model computations. The statistical uncertainty of rock salt parameters as well as possible variations in the dimensions of a cavity field under design result in the necessity to carry out a parametric study. The purpose of the paper is to explain probabilistic modeling with respect to structural response computations, using sensitivity and uncertainty analysis. Probabilistic finite element computations have been carried out for a hexagonal cavity configuration, The results are discussed with respect to the variability of the following parameters and their interrelation: diameter, spacing, depth and height of the cavities, creep of the salt rock, and stiffness of the overburden.

Introduction

Salt deposits are being used not only as a source of minerals but increasingly also for the storage of primary energy reserves and for the permanent disposal of hazardous wastes. According to the favourable geomechanical properties of halite, namely steady state creep behavior, which allows the salt to close and to heal up any fissures or open gaps, a rock salt formation is functioning as a tight barrier. Moreover, rock salt allows the construction of large cavities without any particular support.

However, the proper design of cavities for the different purposes requires:

  • site specific investigations with respect to geological features,

  • planning and determining the most favourable geometrical dimensions of the cavity configuration, e.g. diameter, spacing, height and depth.

Besides that, the design of the cavities may demand for particular considerations for the different live stages concerning construction, operation and abandonment. The utilisation of salt cavities for the purpose of isolating hazardous wastes against the biosphere necessitates safety assessment with respect to long-term integrity of the host rock.

P. 761

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