【目的】花岗岩是干热岩地热能主要储藏的岩体之一,研究热及热冲击对花岗岩的损伤机制对于干热岩地热开采有一定的工程及理论意义。【方法】利用偏光显微镜分别对花岗岩从室温缓慢升高至600℃的全过程、在空气中自然冷却和在水中热冲击冷却至室温后的细观结构进行观察,并通过对视野中矿物面积和裂缝数量进行定量分析,来探究升温过程中及经不同冷却介质热冲击后花岗岩的损伤作用。【结果】结果表明:1)花岗岩在升温过程中矿物面积呈现随温度升高而增大的趋势;高温花岗岩经自然冷却后的矿物面积略大于热处理前,而水中热冲击后矿物面积略小于600℃状态下但显著大于热处理前。2)在升温过程中,视野内裂缝总体呈现小裂缝增多→小裂缝贯穿形成的大裂缝增多→大、小裂缝持续增多的规律,且300℃为小裂缝减少、大裂缝增多的临界温度。3)高温花岗岩在水中热冲击后,裂缝总数增加,其中0~100μm的裂缝显著增多;而空气中自然冷却后的花岗岩的裂缝总数减少,且0~100μm的裂缝显著减少,说明对冷却过程反应更敏感的是较短小的裂缝。4)通过对矿物收缩程度、裂纹数量变化的分析,发现高温花岗岩水中热冲击冷却造成的内部破裂更严重。

【Purposes】 Granite is one of the main rock masses for geothermal energy storage in  dry hot rocks. Studying the damage mechanism of granite caused by heat and thermal shock has certain  engineering and theoretical significance for geothermal exploitation in dry hot rocks.【Methods】The en⁃ tire process of slowly raising granite from room temperature to 600 ℃, natural cooling in air or thermal  shock cooling in water to room temperature was observed by using a polarizing microscope. The mi⁃ croscopic structures were analyzed by quantitatively analyzing the mineral area and the number of  cracks in the field of view to investigate the damage effects on granite during the heating process and  after thermal shock in different cooling media.【Findings】 The results indicate that:1) The mineral  area of granite increases with temperature rise during the heating process. After natural cooling from  high temperature, the mineral area is slightly larger than that before heat treatment, while after ther⁃ mal shock in water, the mineral area is slightly smaller than that at 600 ℃ but significantly larger than  that before the heat treatment.2) During the heating process, the overall trend of cracks in the field of  view shows an increase in small cracks, followed by the formation of large cracks through the pen⁃ etration of small cracks, and a continuous increase in both large and small cracks. The critical tem⁃ perature for a decrease in small cracks and an increase in large cracks is around 300 ℃.3) After ther⁃ mal shock in water, the total number of cracks in the high-temperature granite increases, with a sig⁃ nificant increase in cracks between 0−100 μm. In contrast, after natural cooling in air, the total num⁃ ber of cracks in the granite decreases, and there is a significant decrease in cracks between 0−100 μm.  This indicates that shorter and smaller cracks are more sensitive to cooling processes. 4) Through  analyses of the mineral contraction degree and cracks amount changes, it is found that internal fractur⁃ ing of high-temperature granite caused by thermal shock cooling in water is more severe.