甘肃北山地区深部花岗岩的热开裂试验研究

 通过岛津SEM全数字液压高温疲劳试验系统，实时观察不同温度下北山花岗岩的热开裂过程，获得北山花岗岩的热开裂临界温度为68 ℃～88 ℃。在较低温度时，北山花岗岩热开裂以沿颗粒热开裂为主；在较高温度时，热开裂以穿颗粒热开裂及沿颗粒穿颗粒混合热开裂为主。热开裂不仅受到矿物颗粒的热膨胀性质不匹配及热膨胀各向异性的影响，还受到矿物颗粒的物理、力学、热学性质及矿物颗粒形状结构的影响。而花岗岩内流体包裹体也可能是影响北山花岗岩热开裂的一种重要因素，这是种新的影响机制。在微细观层次对热开裂模式进行分类，并由热开裂的分形模型定量解释沿颗粒和穿颗粒热开裂等发生的难易程度。当温度升高超过250 ℃时，北山花岗岩有可能存在热熔效应，这导致热开裂裂纹数有减少趋势，并且温度与其对应的热裂纹数量的统计关系符合Gauss曲线关系。

EXPERIMENTAL RESEARCH ON THERMAL CRACKING OF DEEP GRANITE IN BEISHAN REGION, GANSU PROVINCE

Full-digital hydraulic pressure and high temperature fatigue testing system with scanning electron microscope(SEM) is used to real-time observe and study thermal cracking of Beishan granite under different temperatures. Experimental results indicate that the threshold temperatures of thermal cracking of Beishan granite is 68 ℃–88 ℃. At the lower temperatures，intergranular thermal cracking is the main thermal cracking for Beishan granite. However，at the higher temperatures，transgranular cracking and coupling of intergranular and transgranular thermal cracking are the main cracking for Beishan granite. Beishan granite thermal cracking is not only effected by thermal expansion mismatch and thermal expansion anisotropy of minerals，but also effected by the physico-mechanical and thermal properties of mineral grains and mineral particle shape structures. Fluid inclusions within the granite may also effect the thermal cracking of Beishan granite，which is a new effect mechanism for thermal cracking. At microscopic and mesoscopic levels，thermal cracking has been classified；and different mechanisms for intergranular and transgranular thermal crackings can be quantitatively interpreted using the fractal models. When the temperature rises above 250 ℃，there is thermal melting effect in Beishan granite，which leads to a decrease in thermal cracking amount. The relationship between temperature and its corresponding thermal cracking amount fits Gauss curve well.