A combined Mode I-II cohesive zone (CZ) elasto-plastic constitutive model, and a two-dimensional (2D) cohesive interface element (CIE) are formulated and implemented at small strain within an ABAQUS User Element (UEL) for simulating 2D crack nucleation and propagation in fluid-saturated porous media. The CZ model mitigates problems of convergence for the global Newton-Raphson solver within ABAQUS, which when combined with a viscous stabilization procedure allows for simulation of post-peak response under load control for coupled poromechanical finite element analysis, such as concrete gravity dam stability analysis. Verification examples are presented, along with a more complex ambient limestone-concrete wedge fracture experiment, water-pressurized concrete wedge experiment, and concrete gravity dam stability analyses. A calibration procedure for estimating the CZ parameters is demonstrated with the limestone-concrete wedge fracture process. For the water-pressurized concrete wedge fracture experiment it is shown that the inherent time-dependence of the poromechanical CIE analysis provides a good match with experimental force versus displacement results at various crack mouth opening rates, yet misses the pore water pressure evolution ahead of the crack tip propagation. This is likely a result of the concrete being partially-saturated in the experiment, whereas the finite element analysis assumes fully water saturated concrete. For the concrete gravity dam analysis, it is shown that base crack opening and associated water uplift pressure leads to a reduced Factor of Safety, which is confirmed by separate analytical calculations.

中文翻译：

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具有组合模式 I-II 内聚区弹塑性的多孔机械内聚界面元件，用于模拟流体饱和多孔介质中的断裂


在 ABAQUS 用户单元 （UEL） 内以小应变制定和实现组合模式 I-II 内聚力区 （CZ） 弹塑性本构模型和二维 （2D） 内聚界面单元 （CIE），用于模拟流体饱和多孔介质中的 2D 裂纹成核和扩展。CZ 模型缓解了 ABAQUS 中全局 Newton-Raphson 求解器的收敛问题，当与粘性稳定程序结合使用时，可以在负载控制下模拟峰后响应，以进行耦合多孔机械有限元分析，例如混凝土重力坝稳定性分析。介绍了验证示例，以及更复杂的环境石灰石-混凝土楔形断裂实验、水压混凝土楔形实验和混凝土重力坝稳定性分析。通过石灰石-混凝土楔形断裂过程演示了估计 CZ 参数的校准程序。对于水压混凝土楔形断裂实验，结果表明，多孔机械 CIE 分析的固有时间依赖性与各种裂口张开速率下的实验力与位移结果良好匹配，但错过了裂缝尖端扩展之前的孔隙水压力演变。这可能是由于混凝土在实验中部分饱和，而有限元分析假设混凝土完全水饱和。对于混凝土重力坝分析，结果表明，基层裂缝开裂和相关的水隆起压力会导致安全系数降低，这可以通过单独的分析计算得到证实。