基于峰前和峰后能量演化特征的岩石脆性评价

为了准确评价油气储藏水力压裂及岩爆等工程中岩石的脆性，总结了目前国内外已有的基于能量理论计算岩石脆性的方法，并指出了它们的局限性.综合考虑岩石峰前和峰后的能量演化特征，建立了一种基于全应力应变曲线的反映岩石变形破坏全过程的脆性指数评价方法，更加全面地描述岩石的脆性特征.为了验证新方法的合理性，收集了4组岩石力学试验对新指数进行检验.试验结果表明:由峰前指数与峰后指数合成的脆性指数都随着围压的增加而减小，低围压下煤岩和页岩2组均具有较强的脆性，而高围压下红砂岩和页岩1组的脆性明显减弱，表现了随围压增大岩石发生脆延转换的特性.在实际边坡工程中通过对板岩进行脆性评价，验证了本文所提出的脆性指数在工程应用中的合理性，该成果有望对岩石脆性评价提供参考. 

Brittle Evaluation Based on Energy Evolution at Pre-Peak and Post-Peak Stage

Rock brittleness is one of the important mechanical properties of rock mass, which is so crucial for accurately evaluating hydraulic fracturing of oil and gas reservoir and rock bursting engineering. Existing methods of rock brittleness based on energy theory were summarized, and limitations of these indexes were analyzed in detail. In this study, energy evolution characteristics at pre-peak and post-peak stage are comprehensively considered. A new method to determine brittleness index of rocks based on complete stress-strain curves is established, which more reasonably describes the rock brittleness. To verify the rationality of the method, four sets of rock mechanics tests are collected to test the new index. Test results show that the new brittleness index gradually increases with the increase of confining pressure. Under low confining pressure, both coal and group 1 of shale exhibit strong brittleness, while under high confining pressure, the brittleness of red sandstone and group 2 of shale is obviously weakened, showing that the characteristics of brittle-ductile transition of rocks with increasing of the confining pressure. Then in actual slope engineering, the rationality of the new brittleness index is further validated by the tests of slate, which may be expected to offer some references for evaluating rock brittleness.