液氮冷却作用下三类高温岩石力学性能试验研究

为了研究液氮冷却对高温岩石物理力学性能的影响,对不同温度下(25~350℃)的花岗岩、片麻岩和砂岩试样进行液氮冷却处理,开展了一系列的物理力学试验研究,结合微观观察结果分析了各类岩石的损伤机理.结果表明,提高加热温度能够加剧液氮对岩石内部结构的损伤,随温度的升高,岩石的孔隙率、峰值应变逐渐增大,而纵波波速、抗压强度和弹性模量则相反.高温和液氮冷却所产生的热应力导致岩石内部裂纹的萌生和扩展,且微裂纹主要沿石英矿物边界发育.随着加热温度的升高,微裂纹的数量呈逐渐增加的趋势,这是岩石宏观特性退化的主要原因.三类岩石对加热和液氮冷却处理的敏感度不同,这与岩石在成岩作用、矿物成分、胶结类型以及孔隙结构方面的差异有关.

Experimental Investigation of Mechanical Properties of Three Types of High Temperature Rocks After Liquid Nitrogen Cooling

In order to investigate the effect of liquid nitrogen on the physical and mechanical properties of high-temperature rocks, a series of laboratory tests were carried out on granite, gneiss and sandstone specimens cooled with liquid nitrogen at different temperatures(25~350℃). The damage mechanisms of the three types of rocks were analyzed in combination with microscopic observations.The results show that the increase in temperature exacerbates the damage to the internal structure of the rock induced by liquid nitrogen. With the increase of temperature, the porosity and peak strain of the rock gradually increase, while the P-wave velocity, compressive strength and elastic modulus of the rock decrease. Thermal stresses generated by heating and liquid nitrogen cooling lead to the initiation and propagation of microcracks mainly along quartz mineral boundaries within the rock. The sensitivity of the three types of rocks to heating and liquid nitrogen cooling differs, depending on the lithogenesis, mineral composition, type of cementation, and pore structure of rocks.