Experimental Study Of The Self-healing Property Of Damaged Salt Rock By Brazilian Splitting

With the continuous development of China's economy,the demand of energy is increasing.In order to meet the needs of energy security and peak energy regulation,China has taken the lead in establishing a number of salt rock reservoirs in Jintan,Jiangsu province.As of 2017,there were nearly 30 salt caverns have been bulit in Jintan to store natural gas,with a total reserves of 110 million cubic meters.At the same time,besides energy storage,China is actively developing other uses of salt cavity.As salt rocks occur in large quantities in China,a large number of dissolved cavities will be formed every year when salt is mined,which not only has the risk of causing geological disasters such as surface subsidence,but also wastes a large amount of underground space.Therefore,the development of cavern reservoir construction is helpful to transform waste into treasure and make rational use of underground space.Compared with other underground reservoirs,the self-healing property of salt rock enables salt caverns to repair damage spontaneously,thus reducing permeability and improving stability.No matter what kind of underground storage,in excavation and construction,it is inevitable to produce disturbance to the surrounding rock and form excavation disturbance area around the cavity.Therefore,the study on the self-healing of salt rocks is helpful to better understand the damage evolution of salt cavern reservoir,so as to build a more safe and economical underground salt cavern reservoir.Because the safety and stability of underground salt cavern reservoir mainly involves two aspects:stability and tightness,the existing research mainly focuses on the stability,and the research on the tightness of underground salt cavern reservoir is less.For this reason,the author designed the self-healing experiment of fractured salt rock in Brazil based on the existing research results and the actual engineering status of salt rock underground reservoir at home and abroad.According to the mechanism of salt rock damage self-healing,the damage healing experiment of salt rock under different healing time,temperature,confining pressure and humidity was carried out,and the influence of different external environment on the self-healing effect of salt rock damage was explored.Finally,based on the existing research at home and abroad,combined with the factors of healing time,temperature and confining pressure,the damage healing model of salt rock is put forward,hoping to further promote the theoretical research of salt rock damage healing and obtain better practical engineering application.The main contents of the paper are as follows:(1)The effects of healing time,temperature,confining pressure and humidity on the healing effect of damaged salt rock were analyzed through the healing experiment of damaged salt rock.It was found that time,temperature,confining pressure and humidity were all positively correlated with the healing effect of the damaged salt rock.(2)It is found that different factors have different influences on the healing effect of damaged salt rock.The healing effect of damaged salt rock is the most sensitive to confining pressure.On the contrary,the influence of temperature on the healing effect of damaged salt rock is not significant enough,and the healing effect of damaged salt rock can only be improved by increasing the temperature in a small range.(3)It is found that under the condition of no stress,the damaged salt rock specimens can still produce healing effect under certain conditions,indicating that confining pressure is not a necessary condition for the damaged salt rock to heal.(4)The study found that under the condition of no stress,the specimen would not heal in the environment without external water supply,indicating that water is a necessary condition for the damaged salt rock to heal under the condition of no stress.By referring to the existing research results and combining with the experimental data,a self-healing model of salt rock damage,including the healing time,temperature and confining pressure,was proposed and calculated by using the model under the proposed working conditions.