Results of experiments on the compaction and permeability behavior of crushed salt
- Federal Inst. for Geosciences and Natural Resources, Hannover (Germany)
In the Federal Republic of Germany, the final disposal of heat generating radioactive waste is planned in boreholes and drifts excavated by conventional mining in an evaporite deposit. Because of the chemical-mineralogical and thermo-mechanical compatibility with the host rock, crushed salt is intended for use as backfill material to fill in the remaining cavities in the repository. To determine the compaction behavior of dry crushed salt with two different grain size curves, more than thirty samples were compacted in a heatable oedometer cell at temperatures of 50 to 200 C and compaction rates of 6.9{times}10{sup {minus}5} to 6.9{times}10{sup {minus}10} sec{sup {minus}1}. The grain distribution of the material in grain size curve 1 was selected to match the raw material excavated by a part-face header in the Asse mine. Grain size curve 2 consisted of fine-grained materials. The stress (backfill resistance) built up in the sample as a result of compaction, increases with an increase in compaction rate, a decrease in the void ratio, as well as with a decrease in temperature, and approaches the value of compacted rock salt (void ratio e = 0) asymptotically. The test results were evaluated and recalculated according to the constitutive law of Zhang et al. (1993). The determined parameters produced good agreement between the test and calculated values over the whole compaction range. Permeability tests were carried out on crushed salt with various grain size compositions and densities in an uniaxial compaction-permeability apparatus. Permeabilities of 10{sup {minus}18} to 10{sup {minus}19} m{sup 2} were measured at porosities of n = 0.05 to n = 0.01.
- OSTI ID:
- 182959
- Report Number(s):
- CONF-950917--; ISBN 0-7918-1219-7
- Country of Publication:
- United States
- Language:
- English
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