多级升温及降温引起的饱和红黏土的热响应试验研究

An experimental study of thermal response of saturated red clay subjected to progressively heating and cooling processes

对温度和围压耦合作用下饱和红黏土的热力学特性进行多级升温及降温过程的室内试验研究。试验包括每级温度变化之间允许试样排水和不允许试样排水两组对比试验,温度变化等级为20℃→40℃→50℃→60℃→70℃→80℃→70℃→60℃…→20℃,围压包括50、100、150、200 k Pa共4种。分析了试样热固结过程中温度、孔隙水压力、固结体应变的演变过程以及热力学特征变化机制。研究表明,在多级升温级间排水以及后续逐级降温过程中,温度诱致孔隙水压力消散引起的固结排水量大于温度再降低至初始温度下的吸水量,最终表现为不可逆的体积收缩变形。另一方面,在多级升温级间不排水以及逐级降温条件下,温度升高后的孔隙水压力甚至可达到围压值,然后降至初始环境温度下时试样内仍保持较大的孔隙水压力,也表现为不可逆的热力学过程。

The thermal properties of saturated red clay subjected to progressively heating and cooling processes are experimentally studied under the combining impact of temperature and confining pressure. Two kinds of tests with and without drainage between temperature stages at four confining pressures（50, 100, 150 and 200 k Pa respectively） are performed. The temperature is appliedsequentially as 20 ℃→40 ℃→50 ℃→60 ℃→70 ℃→80 ℃→70 ℃→60 ℃…→20 ℃. In this study, the evolutions of temperature, pore pressure, volumetric strain, and the related thermodynamical mechanisms are analyzed. It is shown that during progressively heating/cooling with drainage between temperature stages, the volumetric strain due to the pore pressure dissipation associated with heating are greater than that due to the latter compression induced by negative pore pressure after progressively cooling, and eventually induces an irreversible shrinkage deformation. On the other hand, during progressively heating/cooling without drainage between temperature stages, the pore pressure induced by heating can even reach the applied confining pressure, and then maintains a significant residual pore pressure when the temperature of specimens falls to the initial temperature, revealing also an irreversible thermodynamic processes.