基于PFC流固耦合的细观尺度混凝土水力劈裂研究

Study on concrete hydraulic fracturing on meso-scale by fluid-solid coupling model based on Particle Flow Code

针对其他数值方法模拟水力劈裂的局限性,基于PFC颗粒离散元法建立了细观尺度混凝土水力劈裂流固耦合模型。模拟中提取随机圆形骨料信息生成不规则多边形骨料三相细观模型,通过平行粘结体现界面相力学,流体域之间管流体现混凝土各相渗流特性,并且各相取各自的平行粘结力学及渗透参数。通过创建存储渗流管道信息的链表,确保了渗流管道孔径与颗粒间作用力的耦合关系。将改进的流固耦合模型结果与试验结果进行对比,验证了所建模型的合理性。开展不同轴压作用下的混凝土水力劈裂数值试验,得到的临界水压随轴压的增加而线性增大,且模型表现为法向张拉破坏。该细观模型为进一步研究复杂受力状态下混凝土水力劈裂的细观破坏机理提供了新途径。

Aiming at defects of other numerical methods on simulating hydraulic fracturing,a fluid-solid coupling model of concrete hydraulic fracturing on meso-scale was created by Particle Flow Code.Three phases meso-model with irregular polygon aggregates was generated based on the information of random circular aggregates.Mechanics of the interfacial phase was simulated by parallel bonds,and the seepage characteristics of each phase in concrete were simulated by pipe flow between domains.Each phase has its own value of parallel bond and permeability parameters.A linked list for seepage pipes was created in order to achieve the coupling relationship between apertures of pipes and forces applied on particles.The results obtained by the improved fluid-solid model were compared with experiment results to verify the rationality of the model.Numerical tests for hydraulic fracturing were carried out by the meso-model under different axial pressures.The results showed that the critical water pressure increased linearly with the increasing axial pressure,and the model was damaged because of normal tensile failure.This meso-model provides a new method to investigate the meso-mechanism of concrete hydraulic fracturing under complex stress conditions.