| Energy security is related to the overall situation and stability of a country’s economic and social development,and is crucial to the country’s prosperity and development and long-term social security.The caves after water-soluble mining of salt rock have good stability and air tightness,and are considered to be ideal places for storing energy such as oil and natural gas.However,the salt rock in my country has the characteristics of a large number of interlayers and thin thickness,It brings great challenges to the safe operation of salt caverns,so it is very important to study the deformation and failure characteristics of layered salt rocks under stress.In this paper,the digital image test method(3D-DIC)is introduced to test the uniaxial compression deformation process of pure salt rock,layered salt rock,and impurity-containing salt rock.The deformation and failure process of different types of salt rocks and their failure characteristics are summarized.Based on the full-field strain data obtained by3D-DIC,the damage model of salt rock was established and the damage evolution process was analyzed,and the numerical model of salt rock and layered salt rock was further constructed by discrete element method.The influence of interlayer distribution characteristics on the mechanics and deformation and failure characteristics of salt rock is studied.The research results provide a reference for salt cavern storage.The main research work is as follows:(1)The uniaxial compression test of salt rock,layered salt rock and impurity salt rock based on 3D-DIC was carried out,and the applicability and accuracy of the3D-DIC method were verified by comparing with the stress-strain curve obtained by the mechanical test system.According to the evolution cloud map of displacement field and strain field obtained by digital image method,the influence of impurities and interlayers on the deformation process and failure characteristics of salt rock was compared and analyzed,and the uniaxial failure forms of different types of salt rock were summarized.At the same time,combined with the full-field strain data of 3D-DIC,a model that can well reflect the damage,deformation and failure process of salt rock is established.(2)The discrete element models of pure salt rock and layered salt rock corresponding to the laboratory tests were constructed using the particle flow simulation software PFC,Through the sensitivity analysis of the main mesoscopic parameters,the grain mesoscopic parameters which can reflect the macroscopic mechanics of salt rock and stratified salt rock are obtained.According to the radial displacement evolution cloud,axial displacement evolution cloud,fracture diagram and force chain diagram of salt rock and stratified salt rock obtained by numerical simulation,the macroscopic strength and failure characteristics of numerical simulation and laboratory test are compared and analyzed,and the deformation and failure mechanism of salt rock and stratified salt rock is summarized.(3)To solve the problem of the rarity of salt rock samples with different intercalation characteristics and the difficulty of sampling,the numerical model of layered salt rock with different intercalation characteristics was constructed by using the particle flow simulation software PFC.By comparing the stress-strain curve,mechanical strength,displacement cloud and failure mode,the effects of intercalations at different positions,different numbers and different dip angles on mechanical strength and deformation characteristics of layered salt rock are discussed. |
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