确定现场浇筑全级配水工混凝土双K断裂参数的最小试件尺寸

Determination of Minimum Size for Double K Fracture Parameters of Site-Casting Fully-Graded Hydraulic Concrete

文章通过试验分析确定了现场浇筑全级配水工混凝土双K断裂参数所需的最小试件尺寸.利用中国某特高拱坝施工现场拌合楼生产的混凝土拌合物,一次浇筑成型5组不同尺寸的骨料最大粒径d_(max)=150mm的全级配水工混凝土楔入劈拉试件.基于试验结果,分析了全级配水工混凝土的试件尺寸变化对断裂参数——起裂韧度K_(Ic)^(ini)及失稳韧度K_(IC)^(un)的影响规律.由试验研究结果可知,若得到不随试件尺寸变化的全级配水工混凝土双K断裂参数(K_(Ic)^(ini),K_(IC)^(un)),浇注试件的最小尺寸须满足:韧带高度H_2与骨料最大粒径d_(max)比值H_2/d_(max)≥6.基于相关试验成果,给出了无尺寸效应的双K断裂参数与骨料最大粒径d_(max)及拉伸强度f_t的经验公式.

This paper experimentally presents the minimum specimen size for determining the size independent double K fracture parameters of site-casting fully-graded hydraulic concrete.Different groups of fully-graded hydraulic concrete specimens with maximum aggregate size dmax=150 mm,one-time casting in the site of an actual super-high arch dam with its mixing tower system,were tested and analyzed.The double K fracture parameters,including initial fracture toughness KIciniand unstable fracture toughness KICunwere obtained.The effect of specimen size on double K fracture parameters was discussed.The research findings indicate that the minimum size for size independent double K fracture parameters( KIciniand KICun) of the sitecasting fully-graded hydraulic concrete should satisfy that ligament length H2 is six times larger than the maximum aggregate size dmax.The empirical formulas for size independent double K fracture parameters changing with the maximum aggregate size( dmax) and the tensile strength（ft） were obtained by analyzing experimental results.