Mechanical genesis of Henan (China) Yima thrust nappe structure

CAI Wu(蔡武)¹, DOU Lin-ming(窦林名)¹, HE Jiang(何江)¹, LIU Hai-shun(刘海顺)², LI Zhen-lei(李振雷)¹, DING Yan-lu(丁言露)¹

(1. State Key Laboratory of Coal Resources and Safe Mining
(China University of Mining and Technology), Xuzhou 221116, China;
2. School of Sciences, China University of Mining and Technology, Xuzhou 221116, China)

Abstract:Considering the serious coal and rock dynamic disasters around the main slip plane called F16 in the coal mining area) of Henan Yima (China) thrust nappe structure, the mechanical genesis of the Yima thrust nappe structure was studied comprehensively using geomechanics, fault mechanics, elastic mechanics, and Coulomb’s law of friction. First, using the centrifugal inertia force of Earth’s rotation as a source, a mechanical model of N-S compression superimposed with W-E reverse torsion was established to explain the formation of the early Yima coal basin and Jurassic Yima Group coal measures. Second, an equation for the ultimate stress in the forming stage of F16 was derived using the plastic slip-line field theory and the parabolic Mohr failure criterion. Moreover, the distribution of ultimate stress and the geometric characteristics of the fault profile were obtained using the field model parameters. Finally, the stress field of F16 and the mechanical genesis of the large-scale reverse thrust sheet were discussed based on elastic mechanics theory and Coulomb’s law of friction. The results show that the tectonic framework of the early Yima coal basin and the formation pattern of Jurassic Yima Group coal measures given by the model are consistent with the in-situ explorations. The geometric characteristics of the fault profile obtained by numerical calculation can better reflect the shape of F16 in its forming stage, and the mechanical genesis of the large-scale reverse thrust sheet also concurred with the field situations. Thus, this work can provide a foundation for further studies on the genesis of the thrust nappe structure, the mechanism of rock bursts induced by F16, and the characteristics of the residual stress field in the Yima mining area.

Key words:mechanical genesis; thrust nappe structure; centrifugal inertia force; fault mechanics; slip-line field theory; Coulomb’s law of friction