高温三轴应力下煤体弹性模量的演化规律

Elastic modulus's evolution law of coal under high temperature and triaxial stress

利用自主研制的"600℃20 MN伺服控制高温高压岩体三轴试验机"研究了500 m原岩应力状态下室温至600℃升温过程中大尺寸(200 mm×400 mm)晋城无烟煤和兴隆庄气煤弹性模量随温度的演化规律,对比分析了无烟煤和气煤弹性模量变化规律的异同,讨论了弹性模量突变临界温度和热解产气对煤体弹性模量的影响。结果表明:煤的弹性模量随温度升高变化过程可以分为3个阶段,即中低温平稳降低阶段、中高温剧烈降低阶段和高温缓慢降低阶段;煤体热解产气对弹性模量变化产生重要影响,随着温度升高,无烟煤弹性模量与热解产气速率呈明显的负指数关系;围压、温度和热解共同影响煤体弹性模量,在围压保持不变的条件下,温度和热解产气是影响弹性模量的主要因素,弹性模量在不同温度阶段呈现出不同的变化特征;煤的弹性模量随温度的变化规律较砂岩复杂,但同样存在弹性模量突变临界温度点,只是不同煤阶的煤体临界温度出现较大差异。

Utilizing the ＂600 ℃ and 20 MN servo-controlled rock triaxial testing machine with high temperature and high pressure＂ developed,performed experiments to research the elastic modulus＇s evolution law of anthracite and gas coal with the temperature increasing from room temperature to 600 ℃ under a pressure equivalent to the in-situ stress at 500 m.The anthracite was extracted from Jincheng coal field and the gas coal was extracted from Xinglongzhuang coal mine.Both the anthracite and the gas coal were shaped into 400 mm in height and 200 mm in diameter.The difference of elastic modulus between anthracite and gas coal was also analyzed.In addition,the mutation critical temperature and influence of pyrolysis on the coal elastic modulus was discussed.The research results indicate that：the process during which the elastic modulus of coal changes with temperature can be divided into three stages,that is,steadily decreasing stage in mid-low temperature,drastically decreasing stage in mid-high temperature and slowly decreasing stage in high temperature;the gas output for coal＇s pyrolysis influences on coal＇s elastic modulus severely,as the temperature increases,the anthracite＇s elastic modulus shows negative exponential relations with the rate of pyrolysis gas;the confine pressure,temperature and pyrolysis influence the coal＇s elastic modulus together,and the temperature and pyrolysis are main factors influencing the coal＇s elastic modulus when the confine pressure remains unchanged.and the coal＇s elastic shows different characteristics under different temperature stage;the law of coal＇s elastic modulus varying with temperature is more complicated than that of sandstone＇s.However,the elastic modulus of coal also has a mutation critical temperature.The difference lies in the large variance of critical temperature between different ranks of coal.