鲁灰花岗岩蠕变特征转变温度门槛值的实验研究

Experimental Study on the Temperature Threshold Value of Creep Property Transition in Lu Gray Granite

采用中国矿业大学的“20MN高温高压岩体三轴试验机”进行了高温三维应力下大尺寸乃200mm×400mm鲁灰花岗岩蠕变特性的实验研究，研究发现：在300～400℃之间存在一个温度门槛值，在温度低于这个门槛值时，鲁灰花岗岩的蠕变变形具有瞬态蠕变阶段，在温度高于这个值时鲁灰花岗岩的蠕变变形不具有瞬态蠕变阶段，而直接进入到稳态蠕变阶段。鲁灰花岗岩蠕变变形发生这种现象是因为一方面应力闭合了裂隙，裂纹和孔隙的空隙使鲁灰花岗岩的可压缩性消失。另一方面温度造成了部分矿物或胶结物熔融，充填和堵塞原有的孔隙，裂隙和裂纹，使鲁灰花岗岩的可压缩性降低甚至消失。实验得到的结果对深入认识鲁灰花岗岩在高温下的蠕变变形规律有重要的意义。

Making use of the 20 MN servo-controlled triaxial rock testing machine with high temperature and high pressure manufactured by China University of Mining and Technology, we carried out experimental study on creep property of large size Lu gray granite specimens of Ф200 mm×400 mm. The research reveals that there was a temperature threshold between 300℃ and 400℃. The creep formulation of Lu gray granite contains transient creep below temperature threshold value. But the creep formulation do not contain transient creep and goes directly into steady-state creep above temperature threshold value. There are two reasons to explain this phenomenon. First, the stress closes the void of pore, fracture and crack, and makes the compressi- bility of Lu gray granite decreased or even disappeared. Second, some minerals and cements melts under high temperature. The molten materials fill and clog the void pore, fracture and crack, and also make the compressibility of Lu gray granite decreased or even disappeared. The experimental result has an important significance on understanding the creep formulation law of Lu gray granite under high temperature.