Research On Softening Relationships Of Dam Concrete Based On The Wedge Splitting Tests

Wedge-splitting specimens which have relatively small ratio of weight to volume and relatively long ligament can avoid influence of self-weight to experimental results. This loading mode decreases the requirement of testing machine rigidity and simplifies the operation. The mechanical behavior at the tip of crack in concrete can be well described by the fictitious cracking model (FCM). Based on the wedge-splitting test results and FCM, tri-linear and tetra-linear softening curves of dam concrete and wet-screened concrete were obtained by inverse analysis procedure with FORTRAN language.Based on the principle of fracture mechanics of concrete, a method of data processing for P-CMOD curve of specimens for each group was presented and a representative P-CMOD curve including 20 points for each group was achieved. Parameter identification approach in the inverse analysis was studied and the influence of finite element meshing to inverse analysis results was discussed. It was shown that meshing of the both ends of ligament have a comparatively large influence on the inverse analysis results. The method of mesh densification at the both ends of the ligament, especially at the back-end of the ligament, was proposed.Based on the results of the softening curves of dam concrete and wet-screened concrete by inverse analysis, the following conclusions were achieved:(1) The maximum crack opening width wc and the fracture energy GF increase with increase of coarse aggregate size. However, the wc and GF decrease with increase of concrete compression strength. (2) The influence of size of specimen on the tensile strength ft is insignificant. The GF and wc all increase with increase of specimen size and show size effect.(3) The ft of fully-graded dam concrete is smaller than the corresponding wet-screened concrete, the GF and wc of the former are larger than those of the latter.(4) The results of fracture energy by the inverse analysis method are in substantial agreement with those by the direct tension test method.