Research Of Response Mechanism Of Temperature Memory Effect On Rocks For Different Temperature Paths

Rock mass existed in engineering,such as deep resource and energy exploitation,volcanic and geothermal systems and deep buried disposal of high-level nuclear waste,as well as repeatedly fired rock mass,experience cyclic high temperature with different temperature paths.By analogy with stress Kaiser effect,the memory ability of rock to the highest temperature is so called temperature memory effect,and the corresponding acoustic emission characteristics are called thermal Kaiser effect.Three typical lithology rock,granite,marble and red-sandstone are selected as the research objects,which are divided into three groups by thermal treatment process: group A undergo single thermal treatment,and group B are treated by two different heating and cooling cycle,while group C experience three thermal treatments with same temperature but different order.Around the subject of rock temperature memory effect,the same physical parameters(mass,size,volume,density and p-wave velocity)and mechanical parameters(uniaxial compressive strength-UCS and Brazilian splitting strength-UTS)of specimens in group A,B and C are measured.The temperature memory effect on rock physical and mechanical properties and TAE characteristics are explored and investigated.The main research results and conclusions of this paper are as follows:(1)For group A,the color of granite and red-sandstone gradually becomes lighter,and the grain boundary of the three rocks becomes obvious as the rising temperature.As the thermal treatment temperature increases,the mass loss rates of the three kinds of rocks increase uniformly.The change rates of volume,density,UCS and UTS of the three rocks are similar: slowly change at low temperature and rapidly change at high temperature with the critical temperature ranges from 300°C to 500°C.After 600°C,the damage factors from large to small are marble,granite and red-sandstone respectively.(2)The response characteristics of thermal Kaiser effect of three rocks,during thermal treatment with temperature path of RT-400°C-RT-600°CRT(RT are the room temperature),were explored by TAE test.Taking “AE phenomenon rarely occurs when the temperature of rock reheating does not exceed the highest historical temperature” as a marker to judge the Kaiser effect of rock.The results are follows: the thermal Kaiser effect is obvious in granite and marble;red-sandstone does not manifest the thermal Kaiser effect,but usually manifests the thermal Felicity effect.(3)The rock temperature memory effect to a parameter is called “the lower temperature heat treatment has no further aggravating effect on the parameter change of rock”.The comparative analysis results show that: 1)granite and marble show temperature memory effect on mass loss,volume expansion and density reduction,but red-sandstone does not;2)the granite and marble in control groups have equivalent thermal damage,while the red-sandstones have non-equivalent thermal damage(more non-equivalent as lower temperature difference).3)granite appear obvious temperature memory effect on UCS;marble only shows less obvious temperature memory effect.However,red-sandstone shows no temperature memory effect,and the weakening effect increases with the decrease of temperature difference.4)granite,marble and red-sandstone have the temperature memory ability to UTS,and the temperature memory effect of marble and red-sandstone on UTS is more obvious than that of granite.(4)After three thermal treatments with the same value but different sequence,the basic physical and mechanical parameters of granite,marble and red-sandstone are basically the same.The comparison results between group C and group A(the control group was formed according to the highest temperature)further proved the response characteristics of temperature memory effect of the rocks to the above-mentioned parameters.There are 67 figures,24 tables and 95 references in this paper.