静水压力下混凝土双K断裂参数试验测定

本文主要研究混凝土在机械荷载和水压力的双重作用下，裂缝的起裂、扩展和失稳断裂情况。试验采用楔入劈拉试件，试验时每间隔一定的机械荷载，施加一个循环的一定数值的水压力，直至试件断裂。试验采用“恒定裂缝张开位移”和“恒定荷载”两种加载方式，恒定裂缝张开位移是对水压力作用下的试件进行的定性对比分析，恒定荷载是对固定水压力作用下的试件，通过表面粘贴应变片的方法监测裂缝的起裂和扩展长度。采用混凝土裂缝扩展的双K断裂准则计算了粘聚韧度、失稳韧度和起裂韧度，并与试验测定结果进行了比较。结果表明，随着水压力的逐渐增大，试件的可承受最大荷载逐渐减小，裂缝的起裂提前。

Experimental determination of double K fracture parameters of concrete under water pressure

The wedge splitting test was carried out to experimentally study the initiation, propagation and unstable fracture of crack in concrete under mechanical loading combining with water pressure. In order to obtain the true load-crack mouth opening displacement(CMOD) curve in the process of loading, the specimens experienced the cyclic loading-unloading process of water pressure under the mechanical loading until fracture occurred. Two modes of loading control for test including maintaining the CMOD as constant and keeping the mechanical loading as constant were adopted to avoid the effect of water pressure. The variation of crack was monitored by means of strain gauges. The experimental data were compared with the calculated unstable fracture toughness and cohesive toughness as well as the initial fracture toughness based on double-K criterion for crack propagation of concrete. The result shows that the cyclic loading of water pressure accelerates the development of cracks and results in obvious decrease of the maximum bearing capacity of concrete.