Simulation of a Multi-Stage Stress Field and Regional Prediction of Structural Fractures in the Tucheng Syncline, Western Guizhou, China

The prediction of structural fractures in concealed coal-bearing strata has always been a complex problem. The purpose of this study was to clarify the tectonic evolution of the study area, i.e., the Tucheng syncline, since the coal-forming period and to predict the development of structural fractures. The tectonic evolution of the study area was divided into three stages using regional tectonic analysis. The paleotectonic stress field of the study area was reconstructed through the field investigation, statistics, and analysis of joints. Based on the tectonic deformation analysis, numerical simulation was used to reveal the stress field characteristics of different tectonic deformation stages, and combined with the Mohr–Coulomb criterion, the degree of structural fracture development in the target layers (No.17# coal seam) of the study area was predicted. This study concludes the following: (1) The study area underwent two tectonic deformations during the Yanshanian period, transitioning from an ellipsoidal columnar shape to a semi-ellipsoidal and stereotyped form, forming a superimposed short-axis syncline, and then tilting southeastward as a whole, and was locally cut by faults during the Himalayan period. (2) The distribution characteristics of the stress field in different tectonic stages vary. The stress concentration zones in the first and second stages have a more obvious symmetry, and the present-day stress concentration zone is located in the center of the syncline basin. (3) The superimposed rock fracture indices are larger in the edge zone parallel to the long axis of the syncline and at the bottom of the syncline, which also indicates a higher degree of structural fracture development at the corresponding locations.