脆性岩石在高溫/高壓下之力學性質

Abstract

近代岩石工程中常涉及較深的地下岩層，諸如深層核廢料儲存、地下能源 的開發，或高山深隧道開挖，其地面下之岩層隨深度的增加岩層中之岩壓 與溫度亦隨之增高。在溫度與壓力皆提高的條件下，岩石之工程力學性質 可能與常溫情況下有所差異。本研究真對中橫馬鞍壩址處之變質石英砂岩 ，在不同圍壓與溫度下，以環變形控制方法進行三軸試驗，研究脆性岩石 尖峰強度、柏松比、勁度與變形性等性質與溫度╱壓力之關係，並觀察應 力—應變曲線受溫度與壓力之影響。由本研究試驗結果發現脆性岩石之極 限強度明顯受圍壓與溫度的影響，圍壓增加強度迅速增加，溫度增加強度 會稍為減弱，但圍壓與溫度相結合時，其強度的減弱效果會明顯增大。此 現象推測為試體加溫時受圍壓束縛限制，其熱膨脹應力逐漸累積的結果。 隨圍壓的增加，應力—應變曲線愈趨於陡峭，彈性模數亦隨之增加。溫度 之增加對應力—應變曲線與彈性模數的影響則較不明顯。柏松比與膨脹應 力在不同圍壓與溫度影響下，由本次研究之試驗結果並無法看出明顯變化 。 Engineering projects such as nuclear waste disposal and deep tunnel under high mountain may invlove site condition of great depth undergroud. As depth at considered site increases, both the underground temperature and pressure tend to elevate. The mechanical properties of rock at elevated temperatures and pre- ssures can be significantly different from those which are in the room temperature condition. Circumferential strain controlled triaxial tests were perf- ormed to investigage the influences of elevated temperature and pressure on the peak strength, Poisson's ratio, stiffness, and deformability of a metamorphic quartzite. From experimental results, it is found tha the peak strenth of the tested rock increases with rising confinin pressure, and slightly decreases with increasing temperature. With high conf- ining pressure, the decrease of peak strength due to elevated temperature becomes more significant possiblly derived from the higher thermal stresses within the rock under high confining pr- essure. The stress- strain curve appears steeper and the elastic modulus is higher for higher confining pressure. The effect of elevated temperature on the stress-strain curve, Poisson's ratio, elastic modulus, and the expansion stress are not concluded from the ex- perimental results in this study.