倾斜面上岩体结构面加权节理密度(wJd)的获取

Determination of weighted joint density(wJd) from inclined surface observations in rock masses

考虑结构面与观测面间夹角大小修正的岩体wJd指标,理论上能更为合理地评价岩体结构特征;其操作的关键和难点(尤其是在倾斜斜面上),在于两面夹角的确定。基于wJd原始定义,根据结构面迹线侧伏特征,采用其侧伏角、倾角、及其与测面的倾向夹角等实测要素,导出倾斜斜面上wJd指标的等价形式,并探讨各要素所引起的修正精度的误差分析和控制。以此为基础,通过对3个实例的岩体结构精细测量数据挖掘,初步尝试整网法、叠网法、细单元法等取样方式的wJd值求解。与Jv值(条数法)统计类似,其结果以1 m×1 m细单元的方式平均取值最理想,可缓减迹长差异所引起的分歧。研究表明,倾斜斜面上wJd指标的等价定义严格、数据基础详实,统计结果可靠,为一般方位观测(坡)面上的wJd取值提供了一项理论支撑和推广空间。

The weighted joint density（wJd） method was revisited and modified by considering the angle between the structural plane and the observation surface,which offered better information for characterizing the degree of joints in the rock mass. The accuracy of the method relies on the measurement of the angle between each joint and the observation surface,and in particular,for the inclined surfaces. A modified wJd method was derived for the inclined surfaces based on the original form of wJd method calculated from the geometrical relationship between the angels of pitch/dip and strike. The accuracy of the modified method was validated in practice and discussed in the paper. Validation was performed in light of the dataset obtained from three case studies to calculate and compare the values of wJd with different sampling methods,including the global grid method,the overlying gird method,and the elementary unit method. The results were compared with the corresponding values obtained using the volumetric joint count（Jv） method,and the elementary unit method（1 m×1 m） yielded the most optimal outcome and reduced the bias induced by the offset of traces. The results demonstrate that the modified wJd method provides a novel and reliable means of evaluating rock mass quality for inclined surfaces.