砂岩蠕变力学特性及流变模型研究

水利枢纽工程中库岸高边坡流变现象显著,是工程长期稳定性的潜在隐患。以某大型水利枢纽工程近坝库岸高边坡石英砂岩为例,采用RLW-2000岩石三轴流变试验系统进行不同应力状态下的蠕变力学试验。结果表明,岩石瞬时应变、蠕应变随围压的增加而逐渐增大,初始、稳态和极限加速蠕变速率随围压的提升而递增;围压促进砂岩蠕变变形发展,高围压下的初始蠕变速率可能大于低围压下的极限加速蠕变速率;砂岩在围压5、10、15MPa下的长期强度分别为24.8、32.3、39.7MPa,长期强度随围压的增强而逐渐增大。结合试验成果,分析砂岩的流变性态为粘性-粘弹性-粘塑性,基于统一流变力学模型理论,确定H-H|N-N-N|S模型结构。由于传统元件模型难以辨识不同加速蠕变阶段曲线形态,引入SN和SP非线性元件改进传统模型,得到一个新的非线性蠕变力学模型,并将其拓展到三维情形。辨识蠕变试验数据,对比预测曲线和试验数据,证明了所建模型的可行性和合理性。研究成果可为水利枢纽工程的长期稳定性分析提供参考。

Study on Creep Mechanical Properties and Rheological Model of Sandstone

In the water conservancy project,the rheological phenomenon of high bank slope of the reservoir is remarkable,which is potential hidden danger for long-term stability of project.Taking quartz sandstone of high slope near dam bank of a large water conservancy project as an example,the creep mechanical test under different stress conditions was carried out by RLW-2000rock triaxial rheological test system.The experimental results show that the instantaneous strain and creep strain of rock increase gradually with the increase of confining pressure,and the initial,steady and ultimate accelerated creep rates increase with the increase of confining pressure;Confining pressure promotes the development of creep deformation of sandstone,and the initial creep rate at high confining pressure may be higher than the ultimate accelerated creep rate under low confining pressure;Long-term strength of sandstone at confining pressure of 5 MPa,10MPa and 15MPa is 24.8MPa,32.3MPa and 39.7MPa,respectively,and long-term strength increases gradually with the increase of confining pressure.Combined with the experimental results,the rheological behavior of sandstone was viscous-viscoelasticity-viscoplastic,and the structure of H-H|N-N-N|S model was determined based on the unified rheological model theory.Because the traditional element model was difficult to identify the curve morphology of different accelerated creep stages,SN and SP nonlinear elements were introduced to improve the traditional model to obtain a new nonlinear creep mechanical model and extend to three-dimensional case.The creep test data were identified.The feasibility and rationality of the model were proved by comparing the prediction curve with the test data.The research results provide references for long-term stability analysis of water conservancy project.