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加卸载响应比方法为非均匀脆性介质的灾变预测提供了新的思路,该方法用加载与卸载响应的差别来定量刻画介质的损伤演化过程。已有的岩石实验研究和地震震例研究,发现在岩石破裂或者地震发生之前,加卸载响应比都会出现异常明显的升高及回落,表明加卸载响应比峰值异常具有良好的灾变前兆意义。震例研究中发现,加卸载响应比峰值异常特征时间呈现区域特性。因此,首先用链网模型模拟了压缩载荷下非均匀脆性介质的损伤演化至破裂的过程,同样发现加卸载响应比在试样发生宏观破裂之前出现了峰值回落的现象,再次从数值计算的角度证明了加卸载响应比峰值的灾变前兆作用。其次重点考察了不同非均匀性程度试样的加卸载响应比演化情况,发现峰值出现到试样破裂发生的特征时间T2与介质非均匀性程度指标Weibull指数m存在如此关系:m值越大,T2值越小。表明介质的均匀性程度越高,特征时间T2的值就越小,破裂发生也就越突然。该文得出的介质非均匀性程度与峰值异常特征时间的关系将为提高加卸载响应比地震预测的时间能力提供某些线索。
The method of loading-unloading response ratio provides a new idea for catastrophic prediction of non-uniform brittle media. The method quantitatively characterizes the damage evolution of media by using the difference between loading and unloading responses. The existing rock experimental studies and earthquake case studies show that before the rock burst or the earthquake occurred, the loading-unloading response ratio showed an abnormally significant rise and fall, indicating that the loading-unloading response has a good catastrophic precursory significance than the peak anomaly. In the earthquake case study, it is found that the unloading and response ratio shows the regional characteristics when compared with the peak anomaly characteristics. Therefore, firstly, the damage evolution of the non-uniform brittle medium under compressive load was simulated by the network model. It was also found that the unloading response ratio peaked before the macroscopic rupture of the specimen. From the point of view of numerical calculation It proves the role of catastrophic precursors of peak load and unload response. Secondly, focusing on the different loading and unloading response evolution ratio of different degree of heterogeneity samples, it is found that the characteristic time T2 from the peak value to the occurrence of specimen rupture and the Weibull index m of the degree of heterogeneity of the medium have the following relationship: T2 value is smaller. It indicates that the higher the homogeneity of the medium, the smaller the characteristic time T2 and the more sudden the rupture occurs. The relationship between the degree of medium heterogeneity and peak anomalous characteristic time obtained in this paper will provide some clues for improving the time-ability of loading-unloading response to earthquake prediction.