断层间距对拉张雁列构造破坏过程及能量释放影响的模拟

Effects of fault spacing on the deformation,failure process and released energy for the extensional echelon faults:a numerical simulation

对拉张雁列断层复杂力学行为的研究有助于增进对一些地震及地质现象的理解.基于提出的非均质应变软化本构模型,本文采用FLAC-3D模拟了断层间距对拉张雁列区(岩桥)贯通前后的变形、破坏过程及能量释放规律的影响.在平面应变及小变形条件下,对3个仅断层间距或重叠量不同的标本进行了计算.研究发现,在拉张雁列区贯通过程中,雁列区内部释放了一定的拉伸应变能,而在远离雁列区之外的断层上释放了大量的剪切应变能.随着断层间距的增加,雁列区贯通变晚、变难,断层相互作用减弱,剪切应变能释放量增加.在拉张雁列区贯通之前,拉伸应变能释放率在较低水平上以较小的幅度波动,在贯通之后则不然.因此,从拉伸应变能释放率-时步数曲线上可发现雁列区贯通的标志,这与雁列区内部单元发生拉破坏有关.

Studies of the mechanical behavior of the extensional echelon faults can enhance the understanding of some seismic and geologic phenomena. Based on the proposed heterogeneous and strain-softening constitutive model, the influence of fault spacing on the deformation, failure process and released energy for the extensional echelon faults is investigated numerically during the jog failure by use of FLAC-3D. Three samples in plane strain and small strain mode are calculated, each with the same fault spacing and overlap. It is found that certain tensile strain energy is released in the jog, while a great deal of shear strain energy is released on fault segments far away from the jog. With an increase of fault spacing, the jog failure is delayed and becomes difficult due to the relatively weak echelon fault interaction, and the corresponding released shear strain energy is increased. Before the jog failure, the energy release rate in tension fluctuates with small amplitudes and at a relatively lower level, but not after the jog failure. Therefore, an apparent indicator for the jog failure can be found from the evolution of the energy release rate in tension. This is related to the fact that the io^z is subiected to tensile failure.