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本文叙述无水注入情况下,中心受压的大理石板(600×600×20毫米)破裂前,P波走时变化的实验结果。 路径穿过未来裂缝、靠近受压中心时,走吋上升一回降;不靠近受压中心则走时只上升。路径近于平行且靠近未来裂缝,走时一般不变。路径不穿过未来裂缝和受压中心,发射点附近形变小时,走时不变;发射点附近形变大时,走时一般下降。路径穿过受压中心吋,有些走时先上升后恢复再下降。有些则下降后回升。 这说明在岩石破裂前,破裂孕育区附近同时存在P波速正负异常区和正常区。 同时还观测到,P波速度负异常区随中心压力增加逐步扩大。 由裂缝一侧波源所得的正常区正好是由另一侧波源所得的负异常区。
This article describes the experimental results of the P wave travel time before the cracked marble plate (600 × 600 × 20 mm) under the condition of waterless injection. Path through the future cracks, close to the pressure center, go up inch down; not close to the center of pressure to go only when the rise. The path is nearly parallel and near the future cracks, travel time is generally unchanged. The path does not pass through the future fracture and compression center, the deformation around the launch point is small, and the travel time is unchanged. When the deformation near the launch point is large, the travel time generally decreases. When the path crosses the center of compression, some of them rise and then resume and then fall. Some are picked up and then declined. This shows that in the rupture of the rock before the rupture, P-wave positive and negative anomalies exist along with the normal zone. It is also observed that the negative anomalous region of P-wave velocity gradually expands with the increase of central pressure. The normal zone derived from the source of the wave on the other side of the fracture is just the negative anomalous zone derived from the wave source on the other side.