The numerical calculation models were established based on the stratum-structure theory and the load-structure theory respectively,the influence law of rise-span ratio of the invert,lateral pressure coefficient and elastic reaction coefficient on the tunnel excavation stability and the bearing capacity of the secondary lining was studied. The results show that the displacement of the surrounding rocks caused by tunnel excavation decreases,the bending moment of the secondary lining decreases,the axial force and the safety coefficient of the secondary lining increase with rise-span ratio of the invert increasing,the safety coefficient of the secondary lining should be enhanced by increasing the lateral pressure coefficient and elastic reaction coefficient. It is suggested that small rise-span ratio of the invert structure should be adopted when the surrounding rocks have good lithology,the large rise-span ratio of the invert should be used under the opposite circumstance in the tunnel structure design,and the lateral pressure coefficient and elastic reaction coefficient should be the lower limit of the specification in order to ensure the safety of the tunnel structure.%基于地层-结构和荷载-结构理论分别建立了数值计算模型,研究了仰拱矢跨比、侧压力系数、弹性反力系数对隧道开挖稳定性、二次衬砌承载性能的影响规律.结果表明:随着仰拱矢跨比增大,隧道因开挖引起的洞周位移减小,二次衬砌弯矩减小,轴力增大,安全系数增大;增大侧压力系数或弹性反力系数,均可提高二次衬砌结构的安全系数.建议在隧道结构设计中,岩性较好时可采用小矢跨比的仰拱结构,岩性较差时可采用大矢跨比的仰拱结构;为确保结构安全性,同一围岩级别下侧压力系数和弹性反力系数可选择规范中的下限值.
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