高溫下脆性岩石之力學與物理性質

Abstract

本室內研究進行之試驗主要以澎湖玄武岩為對象，於試驗控制不同溫度、 圍壓與變形速率，以環變形速率控制方法進行三軸試驗。求得不同溫度與 壓力之尖峰強度、包松比、勁度與變形性，並觀察應力-應變曲線受溫度 與壓力之影響。由實驗加溫過程中求得試體之體積膨脹係數。並藉由基於 Fourier原理自製而成的熱傳導試驗儀，求得澎湖玄武岩與中橫馬鞍壩址 段之變質石英砂岩之熱傳導係數，以探討不同溫度下之岩石熱傳性質。由 本研究試驗結果發現在150℃的溫度範圍內，玄武岩試體仍保持脆性行為 。對於溫度對岩石強度的影響，在無圍壓狀況下，玄武岩強度之變化較不 明顯。但是當圍壓與溫度結合時，則升高溫度會顯著降低岩石強度和彈性 模數。軸向應變受圍壓的影響亦相當的明顯，圍壓增加，造成尖峰強度增 加，相對應的軸應變量隨之增大。溫度、圍壓應變速率對柏松比的影響則 無法看出明確之關係。應變速率增加，玄武岩在不同溫度狀況下其強度分 別明顯增加，彈性模數亦有升高的趨勢。玄武岩與變質石英砂岩在40℃ ~100℃範圍內，熱膨脹係數在6~8×10e-5(1/℃)之間。熱傳導試驗結果顯 示熱傳導係數隨著溫度的增加有降的趨勢. Engineering projects such as nuclear waste disposal and deep tunnel under high mountain may involve site conduction of great depth. As depth at the considered site increase,both the temperature and pressure tend to elevate. The mechanical properties of rock at elevated temperature and pressures can be significantly different from those which are in the room mperature condition. Circumferential strain controlled triaxial tests wereformed to investigage the influnces of elevated temperature, pressure and strain rate on the peak strength, Poisson's rate stiffness,and deformability of the Basalt sample from Peng-Hu, Taiwan.The coefficients of thermal expansion of basalt andrtzite samples at elevated temperature are also found. Fourthermore,tests are carried out to determine the thermal conductivities of samples using the apparatus developed based on the one-dimensional Fourier theory. From experimental results,it is found that the basalt specimens display brittle behavior for temperature up to 150 C With high confining pressure, both the peak strength and elastic modulus tend to decrease with increasing temperature andcreasing circumferential strain rate.The magitude of the axial strain corresponding to the peak axial stress increases with the increasing cinfining pressure.The effect of elevatedmperature and confining pressure on Poisson's ratio can not be concluded from this study.The coefficients of thermalpansion of the tested samples are within the range of 6~8*10e-5(1/C)for temperature between 40 to 100 C. The coefficient of thermal conductivity slightly decreases with increasing temperature.