实时低温对干燥和饱和状态花岗岩Ⅰ型断裂韧性的影响

Effect of Saturation on Fracture Toughness of Granite in Real-time Low Temperature Conditions

研究岩石在低温下的断裂韧性对评估硐穴式液化天然气地下储库结构的稳定性具有十分重要的意义。采用半圆弯曲SCB法研究了实时低温(-60,-40,-20,0,25℃)对干燥和饱和状态花岗岩I型断裂韧性的影响,并通过扫描电子显微镜对试样微裂纹进行分析。试验结果表明:干燥和饱和状态花岗岩的断裂韧性都随温度的降低而增大。0℃以下,饱和状态的断裂韧性明显大于干燥状态。干燥试样的初始压密段随着温度的降低而减小,峰值位移没有明显变化。饱和试样的初始压密段和峰值位移都随温度的降低而增大。-60℃时,花岗岩内部的微裂纹明显增多,导致断裂韧性增长变缓。

To study the fracture toughness of rocks at low temperature is of great significances for evaluating the stability of underground chamber storage structures for liquefied natural gas(LNG).The effects of real-time low temperatures(-60,-40,-20,0 and 25℃)on the fracture toughness of granite mode I in dry and saturated state were researched by the semi-circular bending(SCB)method,and the microcracks of specimens were analyzed by scanning electron microscopy(SEM).The results showed that the fracture toughness of both dry and saturated granite increased with decrease of temperatures.Below 0℃,the fracture toughness of the saturated state was significantly greater than that in the dry state.The initial compaction stage of dry specimens decreased with decrease of temperatures,while the peak displacement was almost unchanged.Both the initial compaction stage and the peak displacements of saturated specimens increased with decrease of temperatures.At-60℃,the microcracks inside the granite increased significantly resulting in a slower growth of fracture toughness.