全级配大坝混凝土断裂参数的试验研究和计算方法

Experimental studies and calculation methods on dracture parameters of fully-graded dam concrete

针对某大坝的实际工程，采用大坝拌和楼出料，浇筑最大骨料粒径为150mm的全级配混凝土楔入劈拉试件进行断裂试验。在裂缝尖端布置应变片，利用应变回缩法测定起裂荷载Pini。通过改善楔人劈拉试件的支承条件，消除了由外荷载竖向分力引起的附加力矩对裂缝尖端应力场和断裂参数的计算的影响。结合ANSYS软件，精确计算了非标准楔人劈拉试件的起裂断裂韧度和失稳断裂韧度（即双K断裂参数），并与《水工混凝土断裂试验规程》规定的标准尺寸试件断裂韧度计算结果及基于虚拟裂缝黏聚力理论的解析结果进行对比。结果表明：全级配大坝混凝土的脆性较强，普通混凝土软化曲线的经验参数对全级配混凝土并不适用；在本试验的支承条件下，规程规定的断裂韧度计算公式也适用于大尺寸非标准试件双K断裂参数的计算。

Fully-graded concrete wedge-splitting specimens made of raw materials of a dam,whose maximum aggregate size is 150 mm,were used in the fracture test.The initial cracking loads are specified by the retraction of strain gauges at the crack tip.Supporting conditions of the wedge-splitting specimen are adapted to abate the influence of additional vertical load induced moment on the stress field and the calculation of fracture parameters around the crack tip.With the software ANSYS, the initial fracture toughness and unstable fracture toughness （double-K frac- ture parameters） of non-standard wedge-splitting specimens in the test are calculated, which are compared with the fracture parameters calculated on the formulae specified by the ＂Norm for fracture test of hydraulic concrete＂ for standard specimens and on the fictitious crack model respectively. The results indicate that ful｜y-graded concrete has a higher brittleness,empirical parameters in bilinear softening curves of ordinary concrete are inap- plicable to fully-graded concrete.The method proposed bythe norm can also be applied to the calculation of non-standard large-size specimens.