砂岩在热湿循环作用下的卸荷损伤本构模型研究

Study on constitutive model for unloading damage of sandstone under effect of heat-wet cycle

针对在夏季高温多雨季节库岸边坡岩体的强度和稳定性下降问题,较多学者对干燥—饱水两种极端状态的循环作用进行了研究,这与实际情况相差较大。以三峡库区重庆段某典型边坡砂岩为研究对象,采用烘干—浸泡循环作用方式模拟岩石热湿循环过程,在前期进行的热湿循环试验方案及数据分析的基础上,定量对砂岩的劣化程度进行划分,对热湿循环作用下砂岩的卸荷损伤本构模型进行研究。研究结果表明:热湿循环10次内砂岩各力学参数的劣化效应比较明显,10～50次逐渐减弱并趋于平缓;基于热湿循环和卸荷相互作用,建立了完整砂岩在不同热湿循环次数下的卸荷损伤模型并绘制模型曲线;经过验证,模型曲线与试验所得的三轴卸荷应力-应变曲线吻合度较高,认为该模型具有较好的适用性。

For the problem of the decreases of the strength and stability of the slope rock mass on reservoir bank during the high temperature and rainy season of summer,many studies focus on the effect of the cycle of the two extreme states from the dry to the saturated,but it is quite different from that of the actual condition.By taking a typical slope sandstone of Chongqing Section of the Three Gorges Reservoir Area as the study object,the mode of the effect of the drying-soaking effect is adopted to simulate the process of the heat-wet cycle of the rock,and then the deterioration degree of the sandstone is quantitatively divided on the basis of the heat-wet cycle experiment scheme and the data analysis carried out during the early phase,while the constitutive model for the unloading damage of the sandstone therein under the effect of heat-wet cycle is made as well.The study result shows that the degradation effect on all the mechanical parameters of sandstone within the heat-wet cycle in 10 times is more obvious,which is gradually weakened and tends to be smooth during the cycle in 10~50 times.Under the condition of considering the interaction between the heat-wet cycle and the unloading effect,the unloading damage model for the intact sandstone under different heat-wet cycle times is established and the relevant model curve is drawn as well.It is verified that the model curve is highly coincided with the triaxial unloading stress-strain curve obtained from the experiment,thus it is considered that the model has a better applicability.