地震地质 ›› 1980, Vol. 2 ›› Issue (1): 11-17.

• 科研简报 • 上一篇    下一篇

结构岩体变形、破坏与地震前兆关系的实验研究

李建国1,2   

  1. 1. 国家地震局地质研究所岩石力学实验室;
    2. 中国科学院盐湖研究所岩石力学研究室
  • 收稿日期:1979-08-31 出版日期:1980-03-04 发布日期:2009-11-25

EXPERIMENTAL STUDIES ON THE PROCESSES OF DEFORMATION AND FAILURE OF A TYPICAL ROCK MASS AND THEIR RELATIONSHIP TO BOTH THE SEISMIC PRECURSORS AND THE FORESHOCKS

1,2   

  1. 1. Rock Mechanical Laboratory, Institute of Geology, State Seismological Bureau;
    2. Rock Mechanical Lab., Inst. of Salt-Lake, Academia Sinica
  • Received:1979-08-31 Online:1980-03-04 Published:2009-11-25

摘要: 本文主要以岩石试件切口在单轴压缩条件下的扩张来模拟大陆内部断层端部扩张型地震的孕育过程。在实验中观测了试件在外力作用下的应力-应变关系、张裂纹和剪切破坏在时间和空间上的扩展顺序,以及由此引起的声发射和纵波走时变化特征。根据实验结果讨论了由断层端部扩展引起地震的前兆-如断层蠕滑、前震迁移路径、地下水和地形变等各类地震前兆上显示的差异性,对于观测前兆和前震区与主震区的相对位置,具有一定的指导意义。

Abstract: This paper deals especially with the propagation of a 2mm thick saw-cut inclined 45? to the axis of the rock specimen of 5?5?12.5cm and filled with epoxy so as to simulate the development of an earthquake of continental interior. The specimen was loaded in uniaxial compression and attached with a measuring system consisting of strain gages, acoustic emission and wave travelling.Characteristics of failure modes observed in this experimental studies were as follows:1. Creep along the fault face occurred at a very low compressive load without any foreshocks, of course, it would generate precursors such as groundsurface displacements and groundwater level variations.2. As the load increased, a tearing-off crack started to develop at the existing fault tip nearly perpendicular to the fault plane, and appeared to arise initially from the creep process. The propagation of this primary crack was stable and its path was curvilinear. After a considerable primary crack propagation, a second tension crack developed again at the same tip and extended downward to the edge of the specimen, but without any stress drop before overall rupture. During cracking, both the number of acoustic emissions and the wave travelling time increased as time going on. The former phenomenon is equivalent to and the latter is caused by the foreshocks.3. As the compressive load reached a critical level, shear rupture, behaving like mainshock, took place suddenly at the fault end" zone under intensively compressive stress concentration and directed relatively to the tension cracks with angles of varing about from >30? to<90?. Obviously, this was due to the distribution of both the unadmis-sible shear stress from the sliding plane and the tensile stress from the cracked zone to the neighbouring region capable of sustaining an increase of stress.Finally, our results in applying to the prediction of continental earthquakes suggest that large shock should be preceeded first by a fault creep and then by a number of small shocks in tensile cracked regions trending in different directions from the main shear failure plane. In other words, the processes of deformation and fracture of a rock mass would vary in time and in space, which may be used as a guide how to estimate as well as possible the relative locations of precursors and foreshocks to the mainshocks.