Influence of water-insoluble content on the short-term strength of bedded rock salt from three locations in China

Unlike the presence of thick domes and thick layers of rock salt deposits in Europe and the USA, rock salt in China is mainly composed of thin layers (80–300 m), characterized by a high content of water-insoluble impurities. Thus, the influence of these impurities on the strength of rock salt is barely known and has become an important topic for basic research in the construction of underground salt caverns for energy storage in China. In this paper, the influence of water-insoluble content on the short-term strength of bedded rock salt, based on a series of combined laboratory tests including solubility, uniaxial and triaxial compression tests, on bedded rock salt samples from three locations in China, namely the Huai’an (HA) site in Jiangsu Province, the Pingdingshan (PDS) site in Henan Province and the Anning (AN) site in Yunnan Province, is presented. Samples in which the water-insoluble content was less than 50 % were defined as “rock salt” and the remainder as “impure rocks with salt”. Analysis of the experimental results for rock salt samples leads to the conclusion that the uniaxial strength, including the error in its measurement, increases with increase in the water-insoluble content in the sample. Meanwhile, the triaxial strength of rock salt will hardly vary with changes in the water-insoluble content. It can also be concluded that application of confining pressure will suppress the impact of the water-insoluble content on the short-term strength of rock salt, i.e. the inhibition will increase with increasing confining pressure. Application of Hou’s strength model to bedded rock salt from the three regions yields comparable results with the measured data, nevertheless with a bearable small degree of uncertainty. The modified Hou’s strength model has been proved to be more suitable for the determination of strength of bedded rock salt from the three study locations in China.