Experimental Study On Mechanical Properties Of Migmatite Under High Temperature

In order to study the effects of geothermal temperature and crustal stress on the mechanical properties of migmatite,such as strength and deformation,in deep mining,.Using SAM-2000 type rock triaxial apparatus controlled by microcomputer,and triaxial compression test with monotonic load were carried out on the migmatite at three different temperature(25 ?,60 ?,100 ?)and three different confining pressure(5MPa,10 MPa,15MPa);Test of cyclic loading and unloading at 25 ? and60 ?.In monotonic loading triaxial test,the stress-strain curve of migmatite with high temperature is same as the normal temperature of 25?.Experienced four stages with densification,elasticity,plasticity and disruption.In the stage of elastic deformation,the deformation increased linearly.After peak stress,the sample's residual deformation linger for some time then falling slowly.The failure mode of sample with regular monotonic loading is shear failure that main fracture through completely.That is basically same as cyclic loading.Crushed rock and powder growing surge under high temperature and high pressure.It is more prominent under the experiment of cyclic loading.The axial peak stress upgrade firstly than descending latter.Reached highest in60?.Corresponding to the confining pressure of 5MPa,10 MPa and 15 MPa,the axial peak stress under 60? increased by 5.2 %,22.7% and 33.2% compared with the normal temperature of 25?,increased by 2.0% and decreased by 22.5% and 2%respectively in 100?.The elastic modulus of migmatite is upgrade firstly than descending latter with temperature increased under confining pressure of 10 MPa and15MPa.The increased rate is high in 60? and elastic modulus improved over60 %.Poisson's ratio had no same variation trends under three different confining pressure with temperature increased.In the test temperature of 60? and confining pressure of 5MPa,it is declined most with 37.1%,and increased most with 5.7% in100?.In the temperature 25 ?,axial peak stress under cyclic loading is higher than conventional monotonic loading.Increased by 19.3% under confining pressure of5 MPa.Increased by 1.6% with 10 MPa and for 15 MPa is 5.3%.The migmatites' axial peak stress under cyclic loading increased 30% than monotonic loading and raised15% than temperature 25 ?.Plastic strain is gradually increasing when the cycle index increases,and linear growth basically.Elastic modulus appeared to be rising with the cycle index increases overall.Elastic modulus rose with fluctuation under thetemperature of 25? and 60?.Fluctuated obviously for confining pressure of 5Mpa and narrower for 10 MPa and 15 MPa.