水力冲击内蕴初始裂纹混凝土致裂机理

Crack formation mechanism of concrete with an initial crack under hydraulic impacting

为研究水力冲击内蕴初始裂纹混凝土破碎机理,采用光滑粒子流体动力学(SPH)方法建立了水力冲击含竖向裂纹混凝土数值模型,并基于图像处理技术,量化表征了混凝土致裂区破碎规律。研究表明:在初始裂纹弱作用区,水锤效应导致液固接触边界出现剪切断裂,贯通后形成近似"碗状"破碎坑;在初始裂纹强作用区,液固接触边界压剪应力和初始裂纹上部应力集中共同作用引发了初始裂纹上尖端裂纹;"水楔+砼楔"效应与初始裂纹下部应力集中导致了初始裂纹下尖端裂纹;水力冲击激发的应力波在自由边界和初始裂纹反射后相互叠加,引发了锥形裂纹;混凝土破碎度沿射流轴向呈非线性阶跃衰减,表明初始裂纹对混凝土破碎演化有明显阻断及强干扰作用。

In order to explore the breaking mechanism of concrete with initial cracks under hydraulic impacting, a numerical model was established based on the smooth particle hydrodynamics(SPH), and the evolution process of concrete crushed in the crack area was quantitatively investigated by using the image processing technology. The results show that at the weak influence zone of an initial crack, the water hammer effect causes shear fracture in concrete on liquid-solid contact boundaries, resulting in a bowl-shaped crushing pit. At the strong influence zone of the initial crack, cracks nearby the upper tip of the initial crack are induced by combined effects of the compression-shear stress on liquid-solid contact boundaries and the stress concentration at the upper zone of the initial crack. Then synergistic actions of the water wedge and concrete wedge effects, combined with the stress concentration at the lower zone of the initial crack produce the cracks nearby the lower tip of the initial crack. Conical cracks are caused by the superimposed stress waves reflecting on free boundaries and on the initial crack. The degree of concrete crushing decreases along the water jet axis direction with different attenuation rate, indicating that the initial crack has significant blocking effect and strong interference action on the evolution of concrete crushing.