静水压力下混凝土断裂韧度率相关性分析

Rate dependence of concrete fracture toughness under water pressure

基于裂缝中有、无水压的混凝土三点弯曲梁断裂试验,研究了加载速率对裂缝中有、无水压力混凝土双K断裂韧度的影响。试验加载速率为2×10^(-3)、2×10^(-2)、2×10^(-1)、2 mm/s。基于新型裂缝密封装置在混凝土梁的裂缝中形成0.3 MPa水压力,并开展了24组无水压的混凝土梁和12组含水压的混凝土梁断裂试验。拟合试验结果,建立了基于名义起裂荷载率和临界裂缝扩展率的混凝土双K断裂韧度的率相关性模型。对比分析得到,起裂断裂韧度的率相关性与水压力无关但是失稳断裂韧度的率相关性与水压力有关,加载速率的增加导致裂缝中含水压的混凝土的失稳断裂韧度的增量较无水压混凝土显著增加。

Inordertostudyinfluencesofloadingrateonconcreteunderwaterpressure,aseriesofthreepoint bendingtestsofconcretebeams within water pressure were carried out under different loading rates.At first,the verification of the effectiveness of the sealing device was conducted.Then,three point bending tests of concrete beams within 0.3 MPa water pressure under 2×10^(-3),2×10^(-2),2×10^(-1) and 2 mm/s were conducted.Based on the test results,the relationships between the fracture parameters and loading rates were found.It was shown that initiation fracture toughness and unstable fracture toughness increase with increasing loading rate.Adding 0.2 MPa water pressure into the crack,initiation fracture toughness and unstable fracture toughness decrease.Prediction models of the influence of the loading rates on the fracture toughness of concrete with and without water pressure were proposed and compared.A s increasing loading rate,the increment of initiation fracture toughness with or without water pressure is basically the same,but the increment of unstable fracture toughness with water pressure is larger than without water pressure.The increment of unstable fracture toughness is the reason of the decrease of water pressure in the crack.