The Study On The Marble Macroscopic And Mesoscopic Mechanical Deformation Characteristics Under The Periodical Change Of Temperature

The rock disaster caused by the period temperature stress is a subject of extreme complication and momentously economic implications. How to construct projects and sustain its stability economically and effectively in such rock is always a problem puzzling many experts in rock mechanics and engineering geology. When the rock get damage caused by temperature stress, the evidently change of rock compression strength will happen, which seriously influences the stability of engineering.The whole stress-strain curves of marble under different period temperature are achieved through the marble uniaxial compression tests under different temperature and heating period in this paper. The inner microcrack extended pattern of rock is analyzed by the fracture mechanics theory. The theory of the rock mechanics and damage mechanics is used in analyzing the results of tests, then the constitutive equations is gained. Finally, by researching on scan imagery of sample fracture and analyzing the damage degree, some conclusions are summarized as the following:(1) The relations between the marble compression strength, elastic ratio, peak strain and the changes of the temperature, heating period are achieved by analyzing the uniaxial compression tests of marble which was effect under different periodic temperature stress. The higher the heating temperate and the more frequent the heating period, the lower the marble compression strength and elastic ratio, but the larger the peak strain.(2) The inner microcrack extended law of rock which is effect under the temperature is analyzed by the fracture mechanics theory. After going through once the process of the heating and cooling, the initial microcrack will extend, at the same time, the new microcrack will generate because of the different between the rock inner crystals and junctional complex in the coefficient of thermal expansion. After multiple the same temperature periods, the rock inner microcracks which have finished expansion will not develop, but the new microcracks generated in this process will develop, or converge with initial microcracks, and aggravate the rock damage.(3) By compared the elastic ratio, the rock damage is defined and the avianize phase of the rock damage caused by uniaxial pressure force can not be ignored because of the massive development of the rock microcracks caused by temperature stress. The completely closing point will be found in process of the uniaxial compression. Based on predecessor's achievement, the damage constitutive equation of the marble uniaxial compression under action of period temperature stress is constituted.(4) The microcrack area in the fracture image and the area ratio of it in the whole picture are gained by analyzing the fracture image of the sample.