不同温度作用下砂岩热开裂的实验研究

Experimental research on thermal cracking of sandstone under different temperature

砂岩的热开裂研究具有广泛的工程背景,本文实时在线观察和研究了不同温度作用下平顶山砂岩的热开裂:温度低于150℃时,砂岩几乎不发生热开裂;温度从150℃升高到300℃过程中大量的热开裂发生.而不同的矿物成分发生热开裂的阈值温度不完全相同,因此热开裂的阈值温度或者阈值温度范围只具有统计意义.砂岩热开裂主要与矿物成分的热学与力学性质有关,除了受到矿物热膨胀不匹配及热膨胀各向异性的影响,更重要的还受到矿物颗粒形状的影响,如热开裂多发生在矿物颗粒的短轴方向、优势结晶取向、颗粒奇异界面等,且热开裂的分布具有随机性.实验还观察到砂岩表面微缺陷发生闭合的全过程,在冷却过程也有微裂纹形成等现象.

It becomes more and more important to study and understand thermal cracking of sandstone to meet the increasing demands of major engineering. The high temperature fatigue testing system with SEM was employed to online observe and study thermal cracking of Pingdingshan sandstone under different temperature effects in this paper. Experimental results indicate that thermal cracking does not appear in sandstone when the temperature is less than 150℃, and does happen severely when the temperature increases from 150℃ to 300℃. The threshold temperatures of thermal cracking for different mineral grains are different. Therefore, the threshold temperature is only valid statistically. Thermal cracking of sandstone is related with the thermal and mechanical properties of mineral components. Sandstone thermal cracking is not only affected by thermal expansion mismatch and thermal expansion anisotropy of minerals, but also the configuration of mineral grain. For example, thermal cracking can happen more easily along the orientation of minor axis, predominance orientation of crystallization, the interface of mineral and clay cement. And thermal cracking is distributed stochastically on the sandstone surface. Also a closing course of initial crack and thermal cracking coming into being in the cooling process are observed in our experiment.