Comparison Of Different Fracture Models Of Dam Concrete And Analysis Of Fracture Mechanism

Concrete is a multiphase composite material widely used in modern building structures, to understand their basic fracture properties of concrete materials is very important significance, because the concrete is quasi-brittle materials, the development of the length of the fracture process zone monitoring is a very difficult thing, combined with the concrete characteristics of nonlinear etc, many scholars put forward some fracture model like some kind of quasi-brittle fracture model for concrete materials, and describing it as a tool for quantitative development of cracks.Based research group made by the Three Gorges dam concrete spillway fracture test of "wedge splitting test" results,Research Extremely massive concrete fracture, the experiment can be avoided resulting impact on their weight, while the requirements of the test machine stiffness decreased, Making it a simple fracture test of dam concrete,According to the German scholar V.Slowik’s software consoft,Solving the two-parameter fracture parameters fracture model, size effect model and double K fracture model, through the analysis of these models,we can draw the following conclusions:(1) In the two-parameter fracture model, with dams and wet-screened concrete specimen size increases, fracture toughness increase then tend to be stable.(2) In the size effect model and double-K fracture model, with increasing specimen size of wet-screened concrete, fracture toughness will be increased and then tend to be stable, however, to original grade concrete, with the increase of specimen size, fracture toughness showed an increasing trend.(3) With the increase of aggregate size, cohesion showed an increasing trend then decrease, in three forms of the softening curve, with the aggregate size from10mm to20mm, the cohesive toughness increases and then decreases, when the aggregate size increase from20mm to40mm,the cohesive toughness increases with increasing aggregate size.(4) In three forms of the softening curve, with the concrete compressive strength increases gradually,cohesive toughness increase, when the compressive strength reaches a certain numerical43.3MPa, with the increase of the compressive strength of concrete, cohesive toughness decreases.(5) For the full grade dam concrete, with the increase of concrete specimens size, in the dual linear, three-linear and curve-shaped curves of softening curves, cohesion toughness increases. (6) For the wet-screened concrete, in three different forms of the softening curve, with the increase of the size of the specimen,the cohesive toughness increases and then reduces.(7) For the double K fracture model, curved softening curve is more suitable to reflect the constitutive relationship of fracture process zone.