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利用自行研制的岩石高温加热装置,对砂岩试件单向约束、双向约束、无约束3种试验条件下高温前后的纵波波速进行试验研究.结果表明:单向约束试验中,随着温度的升高,砂岩Y,Z方向波速与温度的关系曲线基本成二次函数变化,X方向近似直线下降,700℃时砂岩波速降到了2.096km/s;双向约束试验中,砂岩3个方向的纵波波速随温度升高均呈直线下降;700℃时双向约束试验中砂岩纵波波速最多下降了51.793%,无约束试验中1 200℃时砂岩纵波波速最多下降了80%.高温作用后,岩石内部微结构发生变化,温度越高变化越大,主要表现为岩石内部水分不断蒸发,含水矿物的脱水、相变和岩石部分熔融,孔隙率增加,颗粒边界裂纹出现、发展、贯通,微裂隙产生、演化,矿物成分分解,胶结物强度降低,内部结构热应力扩散,矿物颗粒相互摩擦挤压等.
The experimental research on the longitudinal wave velocity before and after high temperature under unidirectional, biaxial and unrestrained tests of sandstone specimens was carried out by means of self-developed rock high temperature heating device.The results show that in the unidirectional restraint test, as the temperature rises The curves of wave velocity and temperature in Y, Z direction of sandstone basically changed quadratically, and the X direction decreased approximately linearly. The wave velocity of sandstone dropped to 2.096km / s at 700 ℃. In the two-way constrained test, the longitudinal wave velocity With the increase of temperature all showed a straight line descending. The longitudinal wave velocity of sandstone decreased by 51.793% at the maximum at 700 ℃, and the longitudinal wave velocity of sandstone decreased by 80% at most at 200 ℃ in unconstrained test. After the high temperature, The results showed that the higher the temperature, the bigger the change was. The main features were the continuous evaporation of water inside the rock, the dehydration of water-bearing minerals, the phase transformation and partial melting of the rock, the increase of porosity, the emergence of grain boundary crack, development, Mineral composition decomposition, cement strength decreased, the internal structure of the thermal stress diffusion, friction and other mineral particles squeezed.