# Cross-Section Shape and Asymmetric Support Technology of Steeply Inclined Thick Coal Seam Roadway
## 7 Conclusions  
(1) Influence of Roadway Cross-Section Shapes on Surrounding Rock Stability  
The stress distribution and plastic zone extent in the surrounding rock of three typical cross-sections (inclined roof trapezoidal, rectangular, and arched) exhibit a descending order: inclined roof trapezoidal section > rectangular section > arched section. The arched section demonstrates the smallest plastic zone area (maximum failure depth of 1.2 m), reducing it by 42.9% compared to the inclined roof trapezoidal section, indicating its optimal stress distribution and self-bearing capacity. Limitations: The arched section is prone to interlayer shear slip failure when the coal seam thickness is <3.5 m (crossing the coal-rock interface). The inclined roof trapezoidal section, while reducing shear along bedding planes, suffers from long roof span instability and severe corner stress concentration (plastic zone depth up to 2.1 m), making it suitable only for thin coal seams (\(\leq\)3.5 m) with stable bedding. Optimal Selection: For steeply inclined thick coal seams (thickness 5.5 m, dip angle 42\({}^{\circ}\)), the arched cross-section is confirmed as the best choice, effectively suppressing stress concentration and plastic zone expansion in soft coal strata thicker than the roadway height. (2) Deformation Mechanism Induced by Coal Seam Dip Angle  
As the coal seam dip angle increases (0\({}^{\circ}\)-42\({}^{\circ}\)), stress-concentration areas deflect along the dip direction, with the lower sidewall foundation and upper sidewall arch shoulder becoming primary stress centers. When the dip angle is \(\geq\)20\({}^{\circ}\), vertical stress peaks decrease by 6-19%, but the horizontal stress asymmetry coefficient increases to 0.698, exacerbating non-uniform stress states. Failure Mode: Stress concentration triggers shear failure, with plastic zones expanding along the dip direction. The lower sidewall experiences shear failure up to 1.2 m in depth, while the upper sidewall roof undergoes tensile-shear composite failure, forming a diagonal failure zone (\"upper roof-lower sidewall\"). Driving Force: The non-symmetric deformation is fundamentally driven by the coupling of inclined stratum stress fields and roadway geometry, necessitating targeted reinforcement in stress-concentrated areas. (3) Effectiveness of Asymmetric Support Technology  
Optimized Support Scheme: The \"dip-oriented reinforcement\" asymmetric support scheme (Scheme 2) features the following:  
Rool bolt spacing reduced to 800 mm \(\times\) 800 mm, with cables arranged in a \"2-1-2\" pattern (spacing 1600 mm \(\times\) 800 mm);  
Inclined reinforcing cables added to the lower sidewall (spacing 1600 mm) to strengthen shear-prone zones. Numerical simulations show that Scheme 2 reduces the plastic zone area to 89 grid cells, a 32.6% decrease compared to symmetric support and 15.2% compared to Asymmetric Scheme 1, demonstrating superior stress optimization. Field Validation: After implementation in the 1502 roadway, roof-floor convergence decreased from 366 mm to 197 mm (46.17% reduction), and sidewall convergence decreased from 303 mm to 167 mm (44.88% reduction), confirming the scheme's effectiveness in controlling deformation within safe limits. Future Research Directions  
Further studies should investigate the coupled effects of mining-induced stress, hydrogeological conditions, and dynamic loading on roadway stability and develop intelligent dynamic support systems for complex mining environments. F.L. : Writing-original draft, Data Curation, Formal analysis, Investigation. B.Z. : Funding acquisition, Methodology, Supervision, Project administration. J.G. : Funding acquisition, Methodology, Conceptualization, Writing--review and editing. Z.L. : Writing--review and editing, Data curation, Validation. Y.X. : Writing-review and editing. Q.X. : Methodology. D.D. : Funding acquisition. All authors have read and agreed to the published version of the manuscript.