Numerical Simulating And Experimental Study On The Concrete Hydrodemolition

Affected by load, weather, temperature and other factors, the surface of concretestructures such as road, bridge, tunnel, dam and other types of buildings, usually take onlower intensity, crack, collapse, etc. It needs to maintain the original framework andgrassroots and eliminate, repair the damage surface. Hydrodemolition is a new concreteclean technique using high pressure water jet, which is rapidly developed internationallyin recent years. Compared with the traditional methods of mechanical techniques,hydrodemolition has many significant advantages of high efficiency, safety andenvironment friendly. Otherwise, there are few studies on its action mechanism andperformances in china and abroad.The mechanism and performances of concrete hydrodemolition have been studiedsystem systematically through theoretical analysis, numerical simulating andexperimental analysis.(1) Considering the characteristics of concrete hydrodemolition, the concretehydrodemoliting mechanism was put forwarded from the aspects of waterjet impactcrushing and water wedge broking, using rock crushing, fracture injury, microscopicdamage and concrete structure theories. It shows that the water wedge action played amain role in the broking process, when the stress factor of the water static pressure isgreater than that of the fracture toughness of concrete, the macroscopic crack on theconcrete surface will bring out the instability expansion, after expansion goes throughthe cracks, and the concrete is peeled off massively.(2) The macroscopic crack and microscopic damage finite element analysis modelare established applying ANSYS software. The cracking process of macro-cracks andthe jet dynamic impact of concrete hydrodemolition are numerically studied. The resultsshow the broken effects are mainly influenced by the waterjet pump pressure. Moreover,only when the pump pressure exceeds324Mpa, the concrete can be broken, and thecrushing depth increases rapidly as the pump pressure increasing, which match with themechanism analyzing results.(3) The concrete hydrodemolition performances were experimentally studied usingthe high pressure waterjet testing table. The results indicate that the effect of concretebroken are influenced mainly by the working parameters, such as the horizontal speed,range, pump pressure, feeding frequency. In all parameters, the pump pressure is the most significant effect factor, when pump pressure excesses threshold pressure, crushingdepth increases with increasing of pump pressure nearly linearly.Two main mechanisms of jet impingement and water wedge effect in concretehydrodemoliting process are revealed, and the effects performances of the pumppressure and flow rates have been put forwarded. The results establish the basicdesigning theory of the concrete hydrodemolition equipment.