水工混凝土高速水流空蚀破坏机制试验研究

Experimental Study on Cavitation Erosion Mechanism of Hydraulic Concrete under High Speed Flow

基于Venturi空化空蚀发生装置,开展了混凝土材料高速水流空蚀试验研究,探讨了空化泡溃灭区水动力荷载特性及影响因素、不同空化荷载作用下混凝土材料的破坏特征及空蚀破坏发展进程。研究表明,空化泡群溃灭在混凝土壁面产生高频、持续、非恒定的脉冲荷载,试验条件下实测主作用区荷载幅值为400~800 kPa,混凝土材料发生疲劳破坏可能性较大;混凝土材料空蚀破坏经历表面水泥浆到细骨料再到粗骨料逐渐发展的过程,表现为各种成分之间的剥离脆性破坏,各成分间的粘结强度是混凝土抗空蚀性能的主要影响因素;从空蚀形貌及蚀损面积看,空蚀过程可分为初期表面小的蚀坑并不断扩大、多个蚀坑连通表面加速破坏、大的空蚀区域边界稳定扩展三个阶段。

The experimental study on cavitation erosion mechanism of hydraulic concrete under high speed flow is conducted by using Venturi cavitation generator.The hydrodynamic load characteristics and influencing factors,concrete erosion characteristics under different cavitation conditions and concrete cavitation erosion developing process are investigated.The results show that,(a)the collapse of cavitation bubbles on concrete surface will generate high-frequency,constant and unsteady impulsive loads with a measured amplitude of about 400-800 kPa,so the fatigue failure of concrete material is more likely occurred;(b)the cavitation erosion of concrete endures a gradual development process from the surface cement paste to fine aggregate and then to coarse aggregate,which shows the brittle fracture of peeling between various components and the coherent strength among various components is the main influencing factor for the anti-cavitation performance of concrete;and(c)from the point of view of cavitation erosion morphology and area,the cavitation erosion process can be divided into three phases:the initial tiny surface erosion pits and its continuous expansion,the connection of multiple erosion pits and accelerated surface damage,and the stable expansion of large cavitation area boundary.