Study On The Damage Evolution Mechanism Of Saturated Rock Mass Under Oil Immersed Condition

As one of the key points in the study of rock mass mechanical properties and underground engineering problems currently, the damage and failure mechanism of rock mass concern the long-term stability and normal use of underground structures such as tunnels, oil depots and so on. Compared with common underground caverns, the surrounding rock mass of underground water sealed oil storage depot is always in a saturated state during normal operation. Moreover, the saturated rock mass around the cavern is under the long-term influence of the stored oil, and the physical and mechanical properties might be changed, which will in turn exert an important effect on the damage and fracture of rock mass. However, the study of the surrounding rock of underground water sealed oil depots mostly adopt conventional theoretical analysis models, which neglect the effects of oil and water. Hence it is needed to strengthen the investigations of the damage and failure mechanism of saturated rock mass under oil immersed condition.In allusion to the underground water sealed oil storage depot, this paper explored the damage and failure mechanism of oil immersed saturated rock mass from two aspects, which are the experiment and theoretical model respectively. The main researches are as follows:1 Througth the uniaxial compression test on oil immersed saturated sandstone cylindrical specimen, the influence of oil on elasticity modulus, Poisson's ratio, uniaxial compression strength, failure mode and other macroscopic properties of saturated rock under the effect of environment conditions are obtained. Furthermore, coupled with the acoustic emission incidents and energy detected by acoustic emission inspection instrument, influence of oil immersed conditions on the failure and damage evolution law of saturated rock is analyzed.2 Under oil immersed condition, uniaxial compression tests on rectangular saturated sandstone specimens which contain nonpenetrative cracks are conducted. The difference of the pre-existing cracks coalescence patterns under oil immersed and non-oil immersed situations are both compared and analyzed. In the meanwhile, the effect of oil as well as the different crack inclinations and arrrangement modes on saturated sandstone specimens containing nonpenetrative cracks are analyzed.3 On the basis of the properties of oil immersed saturated rock mass, thethermodynamic framework, the damage mechanics and according to the theory of mixtures and the averaging methods, the deformation work of rock mass is deduced.Besides, the influence of oil-water environment on the deformation of rock mass is analyzed preliminarily. Using the two stress state and combining the effective stress principle with criterion, a new plastic yield condition concerning factors of oil and water is proposed, and the effect of oil and water saturability and capillary on rock mass strength and stiffness is discussed ulteriorly. Finally, a new rock mass damage model of rock mass under oil and water coupled environment is established combining the damage criterion and damage evolution rule. The validity of the theory is verified by the comparation and analysis between the theoretical calculation results and experimental results.4 The damage model of rock mass under oil and water coupled environment is applied to a practical engineering— the Huangdao water sealed underground storage depot. By simulating and analyzing the stability of the underground storage depot during normal operation as well as comparing with the existing research results, the correctness and feasibility of the theoritical model are verified.