高温对弱黏结中砂岩物理力学性质的影响

Effect of high temperature on the mechanical properties of the sandstone physical weak bond

基于弱黏结中砂岩经历400~1 000℃高温后进行物理力学参数测试,分析了高温后弱黏结中砂岩的物理力学参数与温度、围压的关系。结果表明:经历400℃以内高温对试样体积、质量和波速影响很小,超过400℃以后试样体膨胀率、烧失率随温度升高单调增加,波速随温度升高单调降低,经历400和800℃高温后试样的变形参数明显高于自然状态(25℃)单轴试验值,高温后试样的弹性模量和变形模量大幅度降低,极限应变随温度升高单调增加。试样的弹性模量、变形模量和峰值强度与围压呈正相关,试样峰值强度与围压符合Coulomb强度准则。经历800℃以内高温对试样黏聚力的影响不大,超过800℃以后黏聚力急剧降低。高温后试样的内摩擦角与温度呈正相关;经历1 000℃以内高温对弱黏结中砂岩具有强化作用,但超过800℃对试样材料强度有所弱化。Mohr-Coulomb预测理论破坏角与试验破坏角大致相当,试样的试验破坏角与围压呈负相关。

The relationship between the mechanical and physical parameters of weak bonding sand- stone and temperature and confining pressure was analyzed based on tests of the samples after high temperature （400-1 000 ℃）. The test results have shown that temperature has little effect on volume, mass and velocity of specimen after baking under 400 ℃; above 400 ℃ baking, volume expansion ra- tio and burning loss rate monotonically increase as the temperature rises; velocity monotonically de- creases as the temperature rises. The value of uniaxial compression deformation parameter after 400 ℃ and 800 ℃ is obviously greater than that in natural state （25 ℃）. Elastic modulus and deformation modulus decrease sharply after 1 000 ℃, and ultimate strain increases monotonically as the temperature rises. Elastic modulus, deformation modulus, and peak strength of specimens are positively correlated to the confining pressure; a good linear relationship exists between peak strength and confining pressure, which accords with Coulomb strength criterion. High temperature has little effect on cohesion of speci mens when temperature is below 800 ℃; but cohesion decreases sharply when temperature exceeas 800 ~C. Internal friction angle of specimens is positively correlated to the temperature. High tempera- ture below 1 000 ℃ has strengthening effect on weak bonding medium sandstone; and the effect will weaken when the temperature exceeds 800 ℃. Failure angles of Mohr-Coulomb theory are approxi- mately equivalent to test results, and negative correlation exists between the testing failure angles of the specimens and the confining pressure.