Identification of structural domains by considering multiple discontinuity characteristics: a case study of the Songta Dam

Discontinuities formed by different geological processes strongly affect the inhomogeneity of a rock mass. Demarcation of statistically homogeneous regions is useful to speculate the tectonic evolution history. Therefore, a new method is introduced to divide the homogeneous structural domains based on multiple discontinuity characteristics. The new method is divided into three steps. Firstly, the 34-patch network on the lower-hemisphere Schmidt projection and the correlation coefficient are adopted to quantify the similarity of discontinuity orientation. Secondly, the Wald–Wolfowitz runs test is utilized to identify the similarity for trace length and trace type. Thirdly, the structural domains are comprehensively identified based on the similarity of discontinuity orientation, trace length and trace type. The comprehensive method is subsequently adopted to divide the structural domains within the Songta right abutment rock mass. The results illustrate that the rock mass around PD222 and PD234 belongs to the same structural domain D1 and the rock mass around PD224 and PD236 belongs to the other structural domain D2. The D2 located at the high elevation suffers longer and stronger unloading effect of the river valley, which is more likely to form the long discontinuities. However, the D1 located at the low elevation develops mainly the short discontinuities. Hence, it is reasonable and consistent with geological development background that the abutment rock mass is divided into two structural regions along the vertical direction using the new method.