| Salt rock with low permeability can ensure the tightness of the storage in salt rock formation and its good creep behavior and ability of self-recovery of damage can lead to stable mechanical behaviors so that it can adapt well to the variation of the pressure of the storage. As a result, salt rock is a well-known ideal medium for the storage of natural gas. In light of our energy demand, the present status of energy storage and the distribution of salt mines, the whole country and many researchers have attached increasing importance to the construction of gas storages. Taking the first underground salt rock gas storage in our country (Jiangsu Jintan gas storage) as an example, the paper gives a systematic analysis of the mechanical problems involved in the two phases of the operation of the underground salt rock gas storage (the phase of gas injection and brine discharge and the periodic phase of gas injection and production). The main research results are as follows:1. With the mechanical characteristics of salt rock investigated by uniaxial and triaxial compression test, direct shearing test, and uniaxial and triaxial creep test, the parameters needed in numerical calculations are obtained for the creep damage constitutive model.2. In response to the fact that results of numerical calculation are difficult to testify in underground gas storages, the author works out a method that is proved to be reasonable both theoretically and practically by experiment and theory deduction. It is to build an observation well out of an abandoned cavity to monitor the volume contraction caused by creep. Then the monitored data can be used to obtain by optimization and inversion the actual creep parameters of the creep damage constitutive model which can later be applied into numerical calculations in each chapter.3. Provided that gas storage is subject to periodic load in the process of gas injection and production and taken into account the interaction between creep damage and fatigue damage, a new creep-fatigue damage constitutive model is produced by the means of theory deduction. The fatigue properties of salt rock under the effect of uniaxial and triaxial periodic load are investigated by making mechanical experiments. At the same time, the parameters of the creep-fatigue damage constitutive model are obtained from the experimented data. By making use of the interface left in the second development process of material constitutive model in numerical software, the creep-fatigue damage constitutive model of salt rock is programmed by VC++. 4. Based on the law of cavity pressure change in the gas injection and brine discharge system, how to identify the interface between gas and liquid while conducting gas injection and brine discharge is studied. Meanwhile, formulae concerning elements such as pressure of gas injection, height of gas and liquid level and speed of brine discharge are analyzed and established. In addition, the usability of such formulae in real projects is testified by making comparison between the values calculated through the theory of gas injection pressure and the data monitored on real sites. At last with a three-dimensional numerical model of the six cavities in Jintan successfully built, some researches are carried out to study the practicality of creep damage constitutive model and expanding Cosserat medium constitutive model in cavity during the period of gas injection and brine discharge as well as the influences of the tiny interlayer on the usability.5. The effects of three factors (constant internal pressure, rate of gas production and circling times) on the deformation law of gas storage volumes during the operation of gas production are considered by using creep damage constitutive model and creep-fatigue damage constitutive model, which leads to some helpful conclusions that can be applied to guide the formulation of a scheme for operating gas injection and production.
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