In this paper, a detailed analysis is made to detect the morphology of Xuzhou marble from room temperature to 1400° using polarizing microscope and combine it with acoustic emission characteristic parameters from 200° to 800°. Some results are achieved: the marble samples would produce strong acoustic emission phenomena affected by high temperatures that the acoustic emission ring count rate increases with increasing temperature and acoustic emission activity becomes more frequent in the heating process. There is a corresponding relationship between rock acoustic emission characteristic parameters and its internal crack network formation. The ringing cumulative number of marble increases with increasing temperature which indicates that the internal cracks continue to expand with increasing temperature while it changes rapidly at two temperature ranges which are 200° to 400° and 600° to 800° indicating that 400° is the threshold value of crack growth and the cracks fully expand and format large transcrystalline cracks at 800°.
As typical brittle materials, the in homogeneity of rock is mainly reflected in its internal structure's rich in variety of defects (pores, micro-cracks, joints, cracks, etc.). Thus, rock will produce a large number of acoustic emission signals in its destruction process. The rupture of rock under high temperature is a very common engineering and natural phenomena which is also involved in a major issue such as energy exploitation and utilization.
Over the years, a lot of related researches about acoustic emission characteristics and mesoscopic failure mode involving the extension of cracks of rock under high temperature were made at home and abroad. Wu Jin-wen et al. [1],[2] tested the creep acoustic emission rule of granite (ϕ200mm×400 mm) under three different temperatures and studied the law of the acoustic emission of granite sample under triaxial stress (axial pressure 860 kN and confining pressure 1150 kN) with temperature by experiment. Wang De-yong et al. [3] invested the mechanical properties and acoustic emission evolution process of Jiaozuo limestone under the action of high temperature load by combining the methods of acoustic emission technique and uniaxial compression test. Jiang Hai-kun et al. [4] studied the deformation and failure timing characteristics of the acoustic emission of granite under 400MPa confining pressure and temperature range from 20° to 850°. ZUO Jian-ping et al. [5] observed and studied thermal cracking of Beishan granite under different temperatures full-digital hydraulic pressure and high temperature fatigue testing system with scanning electron microscope (SEM)which shows that the threshold temperatures of thermal cracking of Beishan granite is 68° to 88°. Zhang Zhi-zhen et al. [6] conducted experiments on granite under uniaxial compression at high temperatures of 25° to 850° and after high temperature of 25° to 1200° and observed the fracture surfaces by scanning electron microscope (SEM) to study the effect of temperature on rockburst proneness.
