High-Temperature Influence On Physical And Mechanical Properties Of Diorite

High-temperature rock mechanics e.g.,development of hot dry rock(HDR)geotherm and deep-underground disposal of highly radiative nuclear waste,involve the effects of high-temperature on rock.Physical property,mechanical property and chemical components of rock can change dramatically under high temperature.Therefore,it has become a research hotspot to study the effect of high temperature on the physical and mechanical properties of rock in recent years.Granite,a widely-used rock type in high-temperature rock mechanics,the physical and mechanical properties of which have got increasing attention by most researchers.In this paper,granite samples,with different high temperatures processing,were set as the research object.The changing appearance and mineral morphology of granite,before and after high temperature,were observed,and the physical mechanics(quality,volume,density and longitudinal wave velocity)changes were measured before and after high temperature,The effects of high temperature on the physical properties of granite were then obtained.Additionally,granite samples,after different high temperature processing,were tested in uniaxial and triaxial experiments,resulting in the effects of high temperature on mechanical properties(compressive strength,peak strain,elastic modulus,cohesive force,internal friction angle)of graniteMain conclusions are as follows:(1)The temperature of 500?and below had little impact on physical and mechanical properties of granite;but from 600 ?,the temperature began to affect granite significantly,so 600? was the threshold of the physical and mechanical properties for granite;(2)The change law of granite physical property was mainly as follows: with the temperature increasing,the oxidational degree of melanocratic mineral was higher,the red brown of samples deeper,quality lower,size bigger,density smaller,and longitudinal wave velocity lower;(3)The surface cracks and alteration recrystallization on minerals were observed at 600?;the cracks widened and cut through at 800?,and even could be visible;Melting recrystallization ocurred at 1000?,and cracks reduced,surface of minerals blured;crack increased when 1000?;(4)With temperature increasing,it is clear that the compaction stage and the yield stage become longer,elastic deformation stage become shorter,and granite showed a softening characteristic;(5)Under the uniaxial condition,with temperature rising,the strength and the elastic modulus of granite decreased,but the peak strain increased.Under the triaxial condition,with the temperature rising,the granite strength changed small,the elastic modulus decreased,and the peak strain increased;(6)As the temperature rised,the granite cohesion decreased and the angle of internal friction showed an opposite trend;(7)Granite rock failure mode,under 500?,was shear failure,but above 600?,it showed tensile fracture when the confining pressure was under 15 MPa,and shear failure when the confining pressure was above 15 MPa.Therefore,the trasition confining pressure of granite failure mode was 15 MPa.