岩石劈裂试验声发射特征的有限元分析

为研究岩石劈裂破坏过程中声发射的时空特征与演化规律,利用有限元分析软件ANSYS/LS-DYNA,对岩石试件在不同加载条件下的准静态劈裂拉伸试验进行数值仿真模拟,并依据模拟结果,分析了加载条件对岩石劈裂破坏试验声发射特征的影响,探讨了各加载条件下巴西圆盘试验的有效性。结果表明:相较于平台加载和弧形加载,垫条加载条件下试件的声发射活动(含声发射事件累计数与声发射率)最先达到峰值,但峰值点却最低,最终劈裂破坏程度也最轻;声发射率的峰值点略提前于加载位移急剧增长的时间点,可据此预判花岗岩试件的破坏时刻,而这一特征在平台加载与弧形加载时尤为明显,在垫条加载时则不显著;平台加载与弧形加载条件下的巴西圆盘试验基本满足中心起裂条件,而垫条加载时却不满足;此外,由本文研究可知,运用ANSYS/LS-DYNA建立三维有限元模型来分析岩石劈裂试验的声发射特征是可行的,且与其他数值模拟手段相比,与实际工况更相近,普适性也更好。

Finite Element Analysis on the Acoustic Emission Characteristics of Rock in Splitting Tests

In order to study on the time-space characteristics and evolution laws of Acoustic Emission(AE)distribution during the process of rock splitting failure, the finite element analysis software ANSYS/LS-DYNA was used to do numerical simulation on granite quasi-static splitting tensile tests, under various loading conditions. By analyzing the simulation data, the influence of loading conditions on the AE characteristics of rocks split destructive tests was analyzed while the effectiveness of Brazilian disc tests under each loading conditions was discussed. The results show: Compared to arc loading and platform loading, the AE events (including the cumulative number of AE events and AE rates)simulated under article pad loading condition reaches the peak firstly, of which the peak point is the lowest and the final splitting failure is the lightest; The peak point of AE rates is slightly ahead of the time when the load displacement starts to grow rapidly, by which the failure time of granite specimens could be predicted, whereas this feature appears obviously under platform and arc loading conditions in spite of article pad loading condition; It is found that the Brazilian disc tests under arc loading and platform loading conditions both meet the requirement of initial cracking from center part, however the ones under article pad loading condition do not; At last, we can conclude from the paper that it is viable to analyze the AE characteristics by building 3D finite element model, using ANSYS/LS-DYNA, which is closer to the actual working situation than other numerical analysis methods, also more general.