Study On Creep Properties Of Salt Rock

The storage of oil or radiating wastes in underground salt rock caves is gaining increasing attention due to its tremendous industrious and commercial interests. Many developed countries have made extensive investigation to it, while much less has been done in China. A realistic prediction to the creep properties of salt rocks is important to the application of salt rock storage caves. In this thesis, the creep behavior of salt rock at high confined pressure and temperature is investigated both experimentally and theoretically. The main researches and contributions are as follows:The creep of salt rock at different longitudinal stress, confined pressure and temperature is systematically tested with a specially designed conventional triaxial creep testing device, the confined pressure varying between 0~50MPa, and the temperature varying between 30~90℃. The effects of longitudinal stress, confined pressure and the temperature on creep are elaborately analyzed.Based on the experimental observation and the corresponding analysis, a constitutive relationship is proposed for the elastic-visco-plastic behavior of the adopted salt rock, using a simple mechanical model consisting elastic, plastic and viscous components. It can be simplified and applied to the analysis of the creep of the salt rock. It contains less material constants and may easily be used in the analysis of practical engineering problems. The corresponding approach for the determination of material parameters is obtained. The creep of the salt rock at different longitudinal stress, confined pressure and temperature is analyzed, and the comparison with the experimental observation shows that the main characteristics of creep can be well described.Some existing extensively used models for the creep of salt rocks were also employed for the analysis of the creep of the salt rock and evaluated. The comparison between the results by these models and that by the proposed model also demonstrates the advantages of the proposed model. The experimental results and the proposed constitutive model are significant to the analysis of the elastic-visco-plastic behavior of salt rock, which is significant to the safety and stability analysis of the underground salt rock caves when they are used for the purpose to store oil or radiating nuclear waste. The proposed model is simple and easy to be applied in the analysis of practical engineering problems.