Experimental Study On Permeability Evolution Of Granite Considering Temperature Effect

The physical characteristics of granite have an important influence on the energy exploration and exploitation tools of nuclear waste repository.Under the action of high temperature,the physical and chemical properties of granite will change significantly,such as mineral composition,pore structure and seepage characteristics.In order to study the influence of high temperature on the physical and chemical properties of granite,a series of basic physical property experiments,pore structure characterization laboratories and permeability experiments were carried out on granite at different pretreatment temperatures(20?-800?).The specific results are as follows:(1)With the increase of pretreatment temperature,the quality and wave speed of granite gradually decrease,but the relative change rate of quality is different in different heating stages.(2)With the increase of temperature,the clay minerals in the mineral composition of granite basically change little.When the temperature exceeds 400?,the calcite disappears.For clay minerals,smectites disappear after 105°C,while the content of illite increases first,and after 200°C,its content remains basically unchanged.(3)The change of temperature also leads to the evolution of the pore structure of granite,and the evolution of the pore structure is closely related to the change of gas mineral composition.(4)Temperature changes have a certain effect on the gas permeability of granite,especially when the temperature exceeds 500?,the gas permeability changes greatly,which is closely related to the evolution of its mineral composition and pore structure.(5)According to the results of SEM scanning image processing,it is found that new pores and fractures are formed in the granite,and some pores and fractures disappear due to the thermal expansion of particles.However,on the whole,the new pores and fractures are greater than the disappeared ones,which further reflects the internal causes of the increased permeability of granite.There are 34 figures,14 tables and 91 references in the thesis.