组合岩样破裂孕育过程中应变场的动态变化特征

Dynamic Variation Characteristics of the Strain Field during the Process of Combined Rock Developing Fracture

利用花岗岩和砂岩拼合样品,进行双轴加压单面直剪试验,结果表明,对于力学性质差异很大的两种岩石的拼合岩样,破裂孕育过程中岩样上的应变是不均匀的,有的地方很高,有的地方很低。在大破裂发生前,应变在一些点沿原趋势加速上升或下降,在一些点则与原趋势相反,转而下降或上升,还有的点则基本平稳不变。应变场变化的共同特征是:①先出现高应变中心,接着这个中心沿未来剪切缝从砂岩边缘向拼合岩样中部转移,而原先的高应变中心却逐步变成低应变区——应变空区。②主破裂不是发生在高应变中心,而是在应变空区或高应变中心转变而成的低应变中心处,直至主破裂发生。③微破裂和宏观破裂都由砂岩向花岗岩方向发展。

A pedion shear test of biaxial compression is made on the combined sample of granite and sandstone. The results show that rock specimen matched by two rocks with different mechanical properties has inhomogeneous strain during the process of developing rupture, at some places which is very high but at some places which is low. Before macro-fracture occurring, the strain accelerated upward or downward at some points according to original trend, rose or drot3ped opposite to original trend at other points, and the strain changed stably at some points. The common features of the change are ： （ 1 ） a high strain center appears at first, ,then the center shift to the middle of the rock sample from the edge of sandstone along the future shearing lancing, and the original high strain center gradually turns into low strain region or strain gap; （2） the main rupture doesn＇t occur in the center of high strain but in the strain gap or the place of the high strain center turning into low strain center; （3） the micro-fracture and macro-fracture develop from the sandstone to the granite.