Salt rocks are commonly utilized as the geologic host rocks for storage of gas and crude oil, and are also being considered for the disposal of radioactive waste due to its low porosity and permeability, self-recovering damage and better plastic deformation ability. The Advances in researches of the mechanical behaviors of deep bedded salt rocks in China are reviewed comprehensively.
The engineering mechanical properties of bedded salt rocks were investigated for the purpose of the energy storage in deep bedded salt rocks formation. The compression tests showed that the presence of anhydrite interlayer affects strongly the deformation and failure characteristics of bedded salt rocks. A ‘stress drop’ phenomenon of stress-strain curves was observed for the low confining pressure cases, denoting the anhydrite layer fractures prior to salt rock. The creep tests on salt rock, anhydrite and composite rock samples implied that the steady-state creep ratio of interlayer was one order lower than that of the salt rock. The creep deformation of surrounding rocks of storage cavern will be controlled by the salt rock layer, while the anhydrite layers will restrict the longterm volume shrinkage. For investigation the mechanical properties of the interfaces between anhydrite and salt rock, the direct shear tests, Brazilian disk tests and SEM tests were carried out. These experiments showed that the interfaces between anhydrite and salt rock are bonded perfectly and are not a weak one as expected. This unique property of the bedded salt rocks would benefit greatly the sealability and stability of the energy storage caverns in bedded salt rocks. Finally, the Cosserat-like medium constitutive theory and its applications to the stability analysis of the salt caverns in bedded salt rock formation were introduced.
The main characteristic of the salt rocks in China is that it is usually composed by many thin salt layers and interlayers (e.g. anhydrite, mudstone, and glauberite etc.) alternatively [1, 2]. However, the theories suitable for the analysis of the stability and security of storage in such bedded salt rocks are lack so far. Following a brief introduction about the researches on salt rocks, this paper mainly introduces some recent advances of the study on mechanical characteristics of the bedded salt rocks in China.
The static and dynamic mechanical characteristics, and creep characteristics of the salt rocks have been studied by Hunsche et al. [3-5], Skrotzki , Wu et al. [7,8], and Yang et al. [9-12]. The Cosserat theory, in which the local bending effects caused by discontinuity surfaces can be taken into account, was imbedded into the finite element software or the finite difference software [13- 16]. The anisotropic characteristics have been studied by carrying out a series of model tests of the bedded rocks .
Recently, aiming at the bedded salt rocks in Yunying Salt Mine in Hubei province, the uniaxial and triaxial compression tests of three typical kinds of samples (salt rock, anhydrite, and rock salt containing anhydrite) were carried out by Li et al. , Liang et al. , and Liu et al. .