有关混凝土Ⅱ型断裂的试验研究是混凝土断裂问题中的热点和难点问题。通过6组24个四点剪切试件对裂缝的剪切扩展过程以及断裂韧度KⅡc进行试验研究，由试件的荷载-应变(P-ε)曲线、荷载-时间(P-t)曲线和荷载-裂缝尖端滑移位移(P-CTSD)曲线，确定试件的破坏荷载、裂缝尖端混凝土应变以及裂尖滑移位移。试验中可见，试件裂缝扩展方向并不平行于剪力方向，而是从裂缝尖端扩展至近加载点附近，表现为倾斜裂缝。试验结果表明，混凝土试件的Ⅱ型断裂韧度KⅡc变化范围为0.5～1.1(MPa·m0.5)。KⅡc随近加载点与预制缝之间的距离减小而增大;KⅡc随初始缝高比的增大而增大。经分析可知，试验过程中形成加载的高窄剪力区容易引起混凝土的剪切断裂。
Abstract
The experimental study on mode-Ⅱ fracture of concrete is a difficult and hot issue among concrete fracture problems. Tests on 6 groups including 24 specimens about fracture propagation and mode Ⅱ fracture toughness were carried out. The parameters of failure load, concrete strain of crack tip, and crack tip sliding displacement(CTSD) were obtained through P-ε (load and strain) curve, P-t (load and time) curve and P-CTSD (load and crack tip sliding displacement) curve. The directions of crack extension was not parallel to shear force direction, but expanded from the tip of precrack to the vicinity of loading point and displayed as inclined crack. Results showed that mode Ⅱ fracture toughness varied from 0.5 MPa·m0.5 to 1.1 MPa·m0.5, and increased with the shortening of the distance from the vicinity of loading point to precrack and with the increase of initial seam height ratio. Shear fracture is prone to happen with a high and narrow shear zone.
关键词
混凝土 /
四点加载 /
剪切断裂 /
断裂韧度 /
影响因素
Key words
concrete /
4-point loading /
shear fracture /
fracture toughness /
influencing factor
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