Research On Temperature-creep Coupling And Creep-damage Coupling Of Nuclear Waste Repository In Salt Rock

Compared with the traditional energy,such as coal and oil,nuclear energy owns the characteristics of high efficiency,cleanliness,and large scale continuous supply,strong applicability.With the rapid development of China’s economy,science and technology,nuclear energy is widely used throughout the world as a renewable energy.At the same time,a large number of nuclear waste has been produced which is in urgent need of treatment.In order to make better use of nuclear,we must take measures for safely and permanently dispose of nuclear waste.Numerous studies show that the rock salt becomes an ideal place for nuclear waste disposal with its superior geological conditions,good physical properties and the economic rationality.In this paper,we give numerical simulation research on the temperature-creep coupling and creep-damage coupling of nuclear waste repository in salt rock by using FLAC^3D,based on the fundamental principle of the thermodynamics,the rheological mechanics and the damage mechanics.The main content is as follows:（1）We perform study on the temperature-creep coupling of nuclear waste repository in salt rock with the isotropic heat model and WIPP creep model.The results show that:under the action of decay heat source,the temperature of disposal roadways’surrounding rock rises quickly and then declines slowly,and heat transmits from near to far field of the disposal roadways.The phenomenon of temperature superposition appears and leads to higher temperature near the middle disposal roadway.We draw the conclusion that 10m is more reasonable disposal roadways’spacing by analyzing the disposal distance’s influence on the temperature distribution.Nuclear waste repository in salt rock has an obvious tendency to self-sealing,the distribution of deformation is corresponded to the distribution of temperature inside the disposal roadways,and the deformation of surrounding rock is larger in the high temperature zone.The distortion phenomenon appears particularly in the base part of the disposal roadways.Under the action of temperature stress,large tensile stress appears near the surrounding and bottom plate of the disposal roadways,which produces adverse effect on the stability of the disposal roadways.（2）We perform study on the creep-damage coupling of nuclear waste repository in salt rock with WIPP creep model and Userc_d creep damage model.The results show that:the deformation and stress condition of the two different models have the same trend,but the rheological deformation of repository’s surrounding rock develop faster and larger under the action of Userc_d creep damage model.Besides,under the action of creep-damage coupling,the damage value of the salt rock around disposal roadways and between the adjacent disposal roadways reaches 0.8 in the early stage and remains unchanged.But over time,the damage scope of the salt rock that above and below disposal roadways reduces obviously.In the engineering,in order to avoid the rapid development of damage causing the formation damage of nuclear waste repository,we need to backfill the disposal roadways and apply the lining.