EXPERIMENTAL STUDY OF INTERACTIONS BETWEEN TWO FLANKS OF A CLOSED CRACK
YIN XIANG-CHU LI SHI-YU LI HONG WANG MIN(Institute of Geophysics, State Seismological Bureau, Beijing)
In order to investigate the interaction between the two flanks of a seismic fault in the course of an earthquake, four groups of fracture experiments with different states of crack surfaces have been made. The experimental results showed that the states of crack surfaces have strong effects on the critical value of σc for specimens with crack of length 2a. The experimental results have been analized according to fracture mechanics.The following key techniques have been resolved in our experiments:1. A new method to produce pre-cracks in centre of the specimen has been used. Central penetrating cracks in plate specimens of glass, plexiglass and rock can be produced by means of three points bending which leads to local tension and crack initiation at one side of the specimen and penetrating the two sides.2. The strain gauges were placed at the crack tip areas, across which the crack are expected to grow, to monitor the crack initiation and to measure the corresponding strength σc of the experimental materials.