Deadweight of dam , hydraulic pressure , temperature and concrete creep can result in high local tensile stress near the orifice in arch dams , which lead to concrete cracking . it can affect the safety of the arch dam , so steel bars are needed near the orifice 拱坝的孔口附近区域在坝体自重、库水压力、孔内水压、温度和徐变等多种作用影响下会产生较大的拉应力，从而导致孔边混凝土开裂，对大坝的整体安全性造成影响，因此须进行配筋。
According to character of procession of concrete material having size effect , effective crack propagation of concrete crack was investigated with size effect formula of fracture toughness , and formula of effective crack propagation was obtained based on size effect rule 摘要根据混凝土材料断裂过程区存在尺寸效应这一特点，结合断裂韧度尺寸效应公式对混凝土有效裂缝扩展长度做了相应的研究，得到了基于尺寸效应规律的有效裂缝扩展长度的表达式。
