高压水工隧洞透水衬砌渗流-应力-损伤耦合分析方法研究

Hydro-mechanical coupling analysis of pervious lining in high pressure hydraulic tunnel

在高压隧洞发电运行过程中,衬砌钢筋应力普遍小于设计预期,并未达到既安全又经济的效果。本文基于混凝土塑性损伤模型与透水衬砌理论,提出了透水衬砌渗流-应力-损伤耦合算法。基于大型通用有限元软件平台ABAQUS进行二次开发,通过Fortran语言调用实用程序GETVRM获取材料损伤,并利用子程序USDFLD实现了材料渗透系数随损伤的动态更新,完成了隧洞初次充水加压工况中衬砌损伤开裂的耦合分析过程,研究了衬砌损伤开裂、渗透孔压以及钢筋应力的演化特征,并探讨了衬砌与围岩有条件联合承载特性对耦合结果的影响。可以发现:计算所得的衬砌损伤开裂特征与衬砌压水试验结果吻合,完全联合承载与有条件联合承载两种情况下,衬砌钢筋应力表现出明显的差异,说明衬砌设计中未考虑衬砌与围岩相互脱离,即有条件联合承载,是隧洞发电运行时衬砌钢筋应力普遍小于设计预期的原因。本文提出的耦合算法所得到的结果与工程普遍规律相符,具有一定推广性,可以为衬砌设计问题提供一定参考。

For the engineering practices of the high pressure tunnel during the operation process, the rein- forcement stresses are generally much less than expected, indicating that the economical purpose is not achieved. The concrete plastic-damage model is used to simulate the lining concrete and the water load is treated as a body force applied to the interior of lining, thus a hydro-mechanical coupling algorithm is proposed. Based on the large-scale finite element software ABAQUS, the secondary development is carried out. The user subroutine in ABAQUS, USDFLD, is adopted to adjust the hydraulic conductivity with the material damage synchronously, and the utility routine GETVRM activated by the Fortran language is utilized to acquire the material damage. And the lining cracking process during the first water-filling period of the hydraulic tunnel is simulated. Moreover, the evolution characteristics of lining damage, pore pressure and reinforcement stress are studied. Additionally, the influence of the conditional cooperation between lin- ing and surrounding rock on the coupling results is discussed. It can be found that the lining cracking char- acteristic matches well with that in field tests. The evolution characteristic of reinforcement stress shows sig- nificant differences when the conditional cooperation considered, indicating that the detachment of lining from surrounding rock is the reason why the reinforcement stress values are generally much smaller than ex- pected. The results obtained by the coupling algorithm proposed in this paper consistent with the general en- gineering phenomena. It means that this algorithm can be applied to other engineering practices and provide some reference for the lining design problem.