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岩石质量指标(RQD)是岩土工程与地质工程中的重要概念,在岩体性质分析中起到了重要作用,但RQD存在着明显的尺寸效应与空间效应,这在以后岩体工程设计计算中并没有引起充分的重视。为研究RQD的空间效应,采用三维裂隙网络模拟方法模拟现场真实岩体,并在模型中设立大量测线获取岩体中不同位置的RQD值。结果表明,岩体中不同位置的RQD值并不相同,存在明显的空间效应。为获取可整体代表岩体好坏程度的RQD值,需在大量RQD样本的基础上进行分析。另外,为更好地体现岩体的非均质性,研究不同阈值下的RQD范围,最终确定可充分反映待分析岩体的最佳阈值,为4 m。尺寸效应是RQD参数的重要性质,通过改变测线长度的方法探讨RQD在不同尺度下的变化情况。总结、提出RQD的计算模型与公式,即:A-A模型、T-T模型、A-A-S模型、Priest-Hudson公式与Senz-Kazi公式。分别研究与对比不同模型下RQD的尺寸效应,结果表明,采用A-A-S模型可充分减少尺寸效应带来的RQD的计算误差;当阈值较大时,Priest-Hudson公式与Senz-Kazi公式存在一定的误差,基于三维裂隙网络模拟的方法进行RQD的计算将会更为准确。
Rock quality index (RQD) is an important concept in geotechnical and geotechnical engineering and plays an important role in the analysis of rock mass properties. However, RQD has obvious size effect and space effect, which can be used in rock mass engineering design calculation Did not attract enough attention. In order to study the spatial effect of RQD, a 3D fracture network simulation method was used to simulate the real rock mass in the field and a large number of survey lines were set up in the model to obtain the RQD values of different locations in the rock mass. The results show that RQD values at different positions in rock mass are not the same, and there is obvious spatial effect. In order to obtain the RQD value which can represent the quality of rock mass as a whole, it needs to be analyzed based on a large number of RQD samples. In addition, in order to better reflect the heterogeneity of rock mass, the range of RQD under different thresholds is studied, and finally the optimal threshold value which can fully reflect the rock mass to be analyzed is 4 m. The size effect is an important property of RQD parameters. The change of RQD at different scales is discussed by changing the length of measuring line. In conclusion, the calculation models and formulas of RQD are proposed, namely A-A model, T-T model, A-A-S model, Priest-Hudson formula and Senz-Kazi formula. The size effect of RQD under different models is studied and compared. The results show that the AAS model can sufficiently reduce the calculation error of RQD caused by size effect. When the threshold is large, the Priest-Hudson formula has some errors with Senz-Kazi formula , The calculation of RQD based on the 3D fracture network simulation method will be more accurate.