大理岩特征应力的加载速率效应研究

Study of loading rate effect on characteristic stresses of marble

摘要:

为研究加载速率对脆性岩石特征应力的影响规律,利用MTS815型试验机和声发射测试系统进行大理岩的单轴压缩试验.采用体积应变法、声发射法和基于微裂纹发育特性的黏结颗粒离散元法确定试样的特征应力,探究特征应力的加载速率效应.结果表明,3种方法确定的特征应力值较为接近,基于微裂纹数的黏结颗粒离散元法是一种较可靠有效的方法.在中低加载速率范围内,随加载速率增加,归一化特征应力值呈现减小规律.数值模拟结果显示,加载速率在中低和较高范围内增加时,归一化起裂应力和损伤应力均减小.当处于中低加载速率范围时,其归一化特征应力降幅较大.当处于较高加载速率范围时,归一化特征应力趋于平稳,尤其是归一化损伤应力.相比较而言,归一化损伤应力的加载速率效应整体上比归一化起裂应力明显.

Abstract:

To study the effect of loading rate on the characteristic stresses of brittle rocks, uniaxial compression tests were carried out using MTS815 test machine and acoustic emission (AE) test system. The volume strain method, AE method, and bonded particle model (BPM) method based on the development of micro-cracks were adopted to determine the characteristic stresses of samples and investigate the loading rate effect of characteristic stresses for marble. Results show that values of the normalized characteristic stress determined by the three methods are relatively close, and the BPM method based on the numbers of micro-crack is a reliable and effective method. Moreover, the normalized characteristic stresses decrease as loading rates increase in the range of medium and low. Numerical simulation results show that when the loading rates increased in a wide range, the normalized crack initial stress and crack damage stress both decrease. When the loading rates are in medium and low range, the normalized characteristic stresses decrease significantly. However, it tend to be stable when the loading rates are high, especially for the normalized crack damage stress. In comparison, the loading rate effect of normalized crack damage stress is more obvious than that of the normalized crack initial stress.