دانلود رایگان مقاله اثر درجه حرارت بالا بر مقاومت کششی ماسه سنگ

abstract

Heating at high temperature will make the tensile strength of sandstone change due to the loss of water and minerals and the effect of thermal stress. In this paper, the sandstone samples are heated from room temperature to 900
C in a high temperature furnace and then are subjected to Brazilian test with a computer-controlled hydraulic universal testing machine. The longitudinal wave velocity, total energy absorbed per unit thickness of disc and mass loss rate are comprehensively investigated. The results show that the tensile strength changes in the following four phases: from room temperature to 300
C, 300– 600
C, 600–800
C and 800–900
C, among which the tensile strength decreases rapidly in the second (300–600
C) and fourth phases (800–900
C) owing to the thermal stress that the most conspicuous effect is the expansion of quartz. The changing trends of tensile strength, longitudinal wave velocity and total energy absorbed per unit thickness of disc along with the temperature are similar.

5. Conclusion

In order to study how the tensile strength of sandstone varies after high temperature, Brazilian test was conducted, with the focus of such study of its variation with temperature as longitudinal wave velocity, total energy absorbed per unit thickness of disc and mass loss rate. The following conclusions can be drawn: (1) Temperature has a significant impact on the tensile strength of sandstone, which is related to the loss of water and minerals and the effect of thermal stress. The changing trends of tensile strength, longitudinal wave velocity and total energy absorbed per unit thickness of disc are similar. (2) The variation of tensile strength with temperature can be divided into four phases: from room temperature to 300
C, 300–600
C, 600–800
C, 800–900
C. The first phase corresponds to the escape of free and combined water. Between 300
C and 600
C, the most conspicuous effect of the thermal stress is the expansion of quartz, contributing to the rapid decrease of tensile strength. The melt of minerals, decomposition of dolomite and fracture of metallic bonding are demonstrated as the sustained reduction of tensile strength from 600 to 800
C. Finally, tensile strength decreases sharply due to the formation of macro-fissures above 800
C.