含硬包体试样破裂孕育过程中应变场的变化特征

在含硬包体的混凝土试样，双轴加压的破裂孕育过程中，观测自由面的应变场，随着应力增加，高应变区逐步形成，应变梯度增大，主破裂前，有的高应变区应变量与应变梯度均减小，有的则增加，主破裂发生应变及其梯度相对都较低的一个高应变梯度区，应变场区内不同测点，其应变随应力及时间的变化而形态不同，临皮裂前，距破裂带和包体近的测点应图像复杂，有的反向加速增大，有的同向加速增大，有的显著减小；而远处测点，变化迟缓且不

THE VARIATION STRAIN FIELD ON FREE PLANE OF THE SAMPLE CONTAINING HARD INCLUSION IN PROCESS OF FRACTURE DEVELOPMENT

Strainfield on free plane of concrete sample containing hard inclusion is observed inthe process of fracture development under biaxial pressure. With stress increase the highstrain areas are gradually formed, and the strain gradient rises. Impending over mainfracturing both strain magnitude and gradient in some high strain areas decrease, andsome increase. Main fracture occurs in the high gradient area where the strain and gra-dient are relatively lower. Variation forms of strain with stress and time are different atdifferent observation points in strain field areas. The strain patterns closed to the frac-ture belt and inclusion are complicated impending over fracturing, some increaseacceleratedly in reverse, some equidirectionally, and some obviously decrease. Varia-tions at other points are slow and unclear.