| Based on the systematically collecting, sorting and analysis of geological information and combining tectonic setting and evolution and the analysis of ancient tectonic stress field through mating field joint, the geological data of mine, structural development features, distribution and combination of mine and the tectonic superimposition and transformation rules of different period have been discussed. By utilizing the method of trend surface analysis, structural development pattern have been evaluate quantitatively; The stress-deformation environment of different tectonic period was revealed through tectonic deformation characteristics of coal, the finite strain analysis of coal vitrinite reflectance and petrofabric analysis. The structural features and their formation mechanism of Xinjing coalmine in Yangquan were deeply discussed. The following conclusions have been made:(1) The folds trending NNE~NE which controls the main formation of the mine are the main structures in Xinjing coal mine, and the development of multiphase superimposed folds have formed a domal uplift, basin structure and saddle. The faults aren’t developed and mainly appeared in small fault swarms. The faults of No.3 coal seam is relatively scattered, but give priority to NE and NW direction. The No.15 coal seam develops focus on NNE direction. Faulted structure combination forms have ladder-like combination and small graben horst on the section.(2) The mathematical model of coal seam floor contour trend surface was build. Based on 1-4 times trend surface and analysis of residual figure of No.3 No.15 coal seams floor contour, the overall form of No.3 coal seam is relatively close to No.15 coal seam. They reflect a high NE and low SW monoclinal structure, and the dip angle is small which reflect the overall attitude of mine formation characteristics. Residual plot clearly reflect the form of the fold. The syncline is negative and the anticline is positive. The dome structure and basin shape structure were relatively obvious showed. But the saddle structure cannot instruct significantly. Zero line in the three residual figures shows anticline alternate with synclines structure. The structure form is mainly NNE to NE-trending distribution.(3) High-dip Conjugate shear joints are developed in the study are. The preferred joints approximately strike NEE-trending, followed by NNW~NE and EW-trending, which shows different times and the action of different direction of tectonic stress field. Based on cross-cutting between the joints and observation and analysis of the mechanical properties, the characteristics and evolution law of ancient tectonic stress field was revealed. The structure of Xinjing coalmine is affected by three periods of tectonic stress after the formation of coal measures. EW-trending open folds are formed in Indosinian period, in which the average direction of maximum principal stress σ1 was 16 degrees. The coalmine tectonic framework is laid in Yanshanian period which the common developed large NNE ~ NE-trending folds and small minor-reverse faults, and NW-trending minor-normal faults are formed, the average direction of maximum principal stress σ1 in this period is 318 degrees, and the tectonic movement is the strongest. NE-trending minor-normal faults and NW~NWW-trending minor-reverse faults are formed in Himalayan period, which the average direction of maximum principal stress σ1 was 48 degrees. Mine seam more complex folds distribution and combination form are the result of a combination of three tectonic stress fields together.(4) The structures of Xinjing coalmine are formed in brittle deformation environment of middle-low temperature, the stress-strain environments forming tectonically deformed coal can be classified into three types, i.e. brittle cataclastic, ductile, and shearing. The regional NW~SE compression is revealed by the strain analysis results of coal vitrinite reflectance ellipsoid. Stress-Deformation. |
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