An Experimental Study On Fracture Properties And Influencing Factoers Of Dam Concrete

Crack will lead to the durability and seismic performance of dam and mass concrete structure greatly reduce,and shorten its service life,affects the normal operation of the dam.In recent years,in order to reduce the safety accidents of dam structure,many scholars conducted a lot of resarch work at home and broad for the concrete fracture test,and tried to find new ways to improve the fracture properties of dam concrete.But the fracture indexes measured under laboratory conditions with ordinary concrete by scholars cannot fully reflect or truly represent the actual fracture properties of dam concrete,and single test method for testing the concrete fracture properties was adopted by many researchers, the study of different methds for concrete facture test are also very poor.In order to more accurately reflect the dam fracture properties and analyse the difference of dam concrete fracture properties mesured by different test methods, three-point bending notched beam specimens and wedge splitting specimens, which employed the construction mix proportions of the Three Gorges dam project concrete were made,in order to investigate the influence of water-to-binder ratio,coarse aggregate size and specimen dimension on fracture parameters of dam concrete, three-point bending tests and wedge splitting tests were carried out. The following results can be obtained:(1) The double K fracture parameters,fracture energy,characteristics length,the critical crack opeing displacement,the equivalent crack length and subcritical crack extension of dam concrete are influenced differently with the change of water-to-binder ratio,and the differences of double K fracture parameters and fracture energy determined by different test methods for dam concrete are small,but there exist some differences for characteristics length,the critical crack opeing displacement,the equivalent crack length and subcritical crack extension.(2) When the coarse aggregate size D≤20 mm,the unstable fracture toughness,fracture energy and characteristics length of dam concrete increase with an increase in coarse aggregate size,and when D>20 mm,the unstable fracture toughness,fracture energy and characteristics length decrease and trend to be stable,but the critical crack opeing displacement is independent of D.(3) Based on the test results of three-point bending of beams, the double-K fracture parameters are rather size-independent,while for the wedge-splitting specimens,the double-K fracture parameters exhibit size effect to some extent,and fracture energy,characteristics length,the equivalent crack length and subcritical crack extension dertermined by different test methods have size effect to some extent.