A Study on Effects of Temperature on Critical Extensile Strain

对稻田花岗岩和白滨砂岩在0 ~ 80℃的水中进行了单轴压缩、巴西、CB和双扭转试验。本研究的主要目的是为了阐明温度对岩石临界拉伸应变等的影响。结果如下：Inada花岗岩随着温度从0℃升高到80℃：(1)平均单轴抗压强度下降6%；(2)平均临界压应变减小6%；(3)临界拉伸应变平均绝对值提高30%；(4)平均杨氏模量在40℃时达到最大值。80℃时的杨氏模量比0℃时小14%；(5)平均泊松比降低20%；(6)平均间接抗拉强度降低16%；(7)平均应力强度因子降低26%；(8)平均应力腐蚀指数降低50%。白滨砂岩：(1)平均单轴抗压强度降低10%；(2)平均临界压应变减小13%；(3)临界拉伸应变平均绝对值减小3%；(4)平均杨氏模量在20℃时达到最大值。80℃时的杨氏模量比0℃时小13%；(5)平均泊松比降低11%；(6)平均间接抗拉强度降低14%；(7)平均应力强度因子降低11%；(8)平均应力腐蚀指数降低20%。根据炭黑和DT试验的结果，估计Inada花岗岩和Shirahama砂岩的活化能分别约为220 kJ/mol和80 kJ/mol。有限元分析表明，稻田花岗岩因矿物热膨胀差异产生较大的热应力，白滨砂岩的热应力被粘土矿物吸收。

Uniaxial compression, Brazilian, CB and double torsion tests were carried out for Inada granite and Shirahama sandstone in water under 0℃ to 80℃. The main purpose of this study was in order to clarify effects of temperature on critical extensile strain of rocks etc. Results are as follows.For Inada granite, with temperature increase from 0℃ to 80℃ :(1) Average uniaxial compressive strength decreased by 6% ;(2) Average critical compressive strain decreased by 6% ;(3) Average absolute value of critical extensile strain increased by 30% ;(4) Average Young's modulus showed maximum value at 40℃. Young's modulus at 80℃ was 14% smaller than that at 0℃ ;(5) Average Poisson's ratio decreased by 20% ;(6) Average indirect tensile strength decreased by 16% ;(7) Average stress intensity factor decreased by 26% ; and,(8) Average stress corrosion index decreased by 50%.For Shirahama sandstone :(1) Average uniaxial compressive strength decreased by 10% ;(2) Average critical compressive strain decreased by 13% ;(3) Average absolute value of critical extensile strain decreased by 3% ;(4) Average Young's modulus showed maximum value at 20℃. Young's modulus at 80℃ was 13% smaller than that at 0℃ ;(5) Average Poisson's ratio decreased by 11% ;(6) Average indirect tensile strength decreased by 14% ;(7) Average stress intensity factor decreased by 11% ; and,(8) Average stress corrosion index decreased by 20%.Activation energy was estimated as around 220 kJ/mol and 80 kJ/mol for Inada granite and Shirahama sandstone, respectively from results of CB and DT tests. FEM analyzes showed that large thermal stresses due to difference in thermal expansion of minerals occurred for Inada granite and that thermal stress was absorbed by clay minerals in Shirahama sandstone case.