Study On Damage Evolution Law And Stability Of Surrounding Rock In Underground Oil Storage Space Of Abandoned Gypsum Mine

Oil is an essential energy material for Chinese economic development and national defense and security construction.As of 2021,Chinese foreign dependence on oil still exceeds the international warning line.In order to ensure the balance and stability of oil demand and supply,the construction of a strategic oil reserve system is imperative.However,at present,most of Chinese oil is stored on the ground,and the storage space is insufficient,making it difficult to meet the requirements of strategic oil reserves.The redevelopment and reuse of abandoned mines have become a hot research direction today.In order to realize the concept of oil storage in goafs of abandoned mines,it is urgent to carry out basic mechanical experiments and theoretical analysis on the stability of surrounding rock,and select appropriate numerical software for simulation of oil storage conditions,etc.Based on the background of the abandoned gypsum mine in Pizhou City,Jiangsu Province,this thesis analyzes its suitability as an underground oil storage space and the physical properties of surrounding rocks.According to the change of oil content,the mechanical properties of unweathered and weathered gypsum rock under two conditions are studied.The evolution law of damage and failure is analyzed based on the damage characteristics of the pillar stability,which provides theoretical research and engineering practice basis for the study of oil storage in abandoned mines.The main research results of the thesis include the following aspects:（1）Based on the analysis of the physical properties of the surrounding rock of the gypsum mine,the main components of the gypsum rock are Ca SO₄·2H₂O and Ca PO₃（OH）·2H₂O;the oil content of the unweathered and weathered gypsum rock increases exponentially with time,but the growth rate becomes gradually smaller;based on the mechanical properties test of gypsum rock under different oil content,it can be seen that with the increase of oil content of gypsum rock,the compressive strength,tensile strength and elastic modulus of unweathered and weathered gypsum rock gradually decrease,and in the early stage of immersion,the compressive strength of gypsum decreased rapidly,and the peak strain increased linearly.（2）Based on the macroscopic cracks of unweathered and weathered gypsum rock under single and triaxial compression failure,the crack development characteristics of SEM scanning,energy evolution law and acoustic emission characteristics,etc,the damage crack development of unweathered and weathered gypsum rock under different oil content is revealed.The results show that the two gypsum rocks are softened by gasoline,and the number of cracks generated after the gypsum rock is damaged decreases with the increase of the oil content;the weathered gypsum rock has more primary cracks,which leads to a reduction of the total energy released relative to th eunweathered gypsum rock,lower elastic energy,and higher dissipative energy.（3）By introducing the statistical probability distribution of micro-element strength,the damage constitutive models of gypsum rock with different oil content under uniaxial compression and energy characteristic triaxial compression are established respectively.Studies have shown that the uniaxial damage constitutive equation curve changes with the parameters m and F control.where the parameter changes the radian of the constitutive model curve.The radian of the simulated curve gets larger as the value of m gets smaller.The slope of the triaxial damage constitutive equation curve decreases as the damage of the gypsum rock increases,and the data obtained based on the constitutive model are highly consistent with the experimental data.（4）Numerical research on the stability of underground oil storage space based on oil storage damage characteristics of different gypsum rocks shows that the vulnerable parts of different gypsum rock underground oil storage spaces occur at both ends of the pillar,and the oil storage increases the plastic zone and deformation of the pillar,resulting in reduced oil storage space and poorer stability,and the stress value and deformation of the weathered gypsum ore pillars are larger than those of the unweathered gypsum ore pillars monitoring.The thesis has 45 figures,10 tables,and 100 references.