Geometric characteristics of multi-scale discontinuities of Shazaoyuan granite masses in Beishan
HUO Liang1，2，WANG Guibin2，YANG Chunhe2，3，WEI Xiang4，TANG Minghao3
(1. State Key Laboratory of Nuclear Resources and Environment，East China Institute of Technology，Nanchang，Jiangxi 330013，China；2. State Key Laboratory of Geomechanics and Geotechnical Engineering，Institute of Rock and Soil Mechanics，
Chinese Academy of Sciences，Wuhan，Hubei 430071，China；3. State Key Laboratory of Coal Mine Disaster
Dynamics and Control，Chongqing University，Chongqing 400044，China；4. Chongqing
Technology and Business University，Chongqing 400067，China)
Abstract：Granite is a candidate wall rock for high-level radioactive waste repository in China. The development of multi-scale discontinuities has a key impact on the closure of the repository. Taking grades II，III，IV-V discontinuities of Shazaoyuan granite masses in Beishan as the research objects，the trace length and occurrence parameters of multi-scale discontinuities were obtained based on the literature investigation and field measurement. The trace length distribution of multi-scale discontinuities was analyzed by mathematical statistics. Compared with the exponential distribution，the power law distribution is more applicable to the trace length of multi-scale discontinuities，showing scale-independent scaling uniformity with a scale of 2.236. Adopting the K-means algorithm based on particle swarm optimization，the dominant attitude of multi-scale discontinuities was identified. The dominant trend and dip angle of grades II，III and IV-V discontinuities are，respectively，NW320°and 56°–76°，NW304°–314°or NE43.5° and 71.3°–72.9°or 82.3°，and NE38.8°–41.5° and 70.0°–70.9°，showing a scale-dependent difference. Based on the“ladder”formation mechanism of discontinuities and the model of secondary discontinuities generated by strike-slip strain，a“ladder-shear”model was proposed to explain the combination morphological reasons of multi-scale discontinuities and to establish the genetic relationship of multi-scale discontinuities in Shazaoyuan granite.
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2019, Vol. 38 
