预设穿透型诱导缝的碾压混凝土等效强度及其断裂韧度尺寸效应研究

为了研究拱坝诱导缝强度和断裂特性，在两种尺寸的碾压混凝土长方体试件内埋设了不同削弱度的一片、两片穿透型诱导缝板。对其进行的轴拉试验表明，诱导缝等效强度存在明显的尺寸效应：对于相同削弱度，试件尺寸增加，等效强度降低，对本试验试件其最大降低值为0．278MPa。含诱导缝的结构断裂韧度随着削弱度的减小而增加：削弱度由0．342变为0．208时，小型和中型试件的断裂韧度分别从0．488MN／m^3/2、0．506MN／m^3／2增加到0．519MN／m^3／2、0．581MN／m^3／2。最后，在相同尺寸和削弱度下，诱导缝布置由一片改为两片及增大两片缝的闻距，都对降低等效强度有很大的作用：如对于削弱度为0．342，诱导缝布置由一片改为两片时等效强度最大降低了36．5％。对于小型试件，当缝距b／a从2．69降低到1.92时，等效强度降低了26．5％。对于大型试件，当缝距b／a从3．46降低到1．92时，等效强度降低了24．1％。这一试验结果表明实际大坝中合理布置诱导缝比单纯增加削弱度对降低诱导缝等效强度更有效。

Size effect on equivalent strength and fracture toughness of RCC with pre-induced penetrated crack

One or two penetrated crack weakened in different variant were embedded in RCC-cuboid specimen with diverse size to study the fracture and strength property of crack director in RCC arch dam.Experimental data about the equivalent strength and fracture toughness of the crack director are obtained from direct tension experiments.The experimental evidences reveal that there exists obvious size effect on the equivalent strength:its maximum value decreases 0.257MPa while the size increases 32.62510~(-3)m~3.Besides,with the increase of weakened variant,the value of fracture toughness decreases:the weakened variant go down from 0.342 to 0.208,the fracture toughness of two types of specimens rose from 0.486,0.537 to 0.522,0.685 MN/m~(3/2) respectively.The setting of two crack directors is more helpful to reduce the equivalent strength than one director,which has the same weakened variant as the former.At the same time,the interval between two edges of crack directors has great impacts on the value of equivalent strength:as the interval reduces from 3.46 to 1.92,the equivalent strength falls 32%.The results of the experiment indicate that reasonable setting of crack director in arch dam is more effective to decreasing the equivalent strength than only increase the weakened variant.