全风化红砂岩隧道支护结构安全性研究——以浩吉铁路阳城隧道为例

Study on the Safety of Supporting Structures of the Tunnel in Weathered Red Sandstone Stratum:a Case Study of Yangcheng Tunnel on Haolebaoji-Ji′an Railway

为进一步探究全风化红砂岩地层条件下隧道开挖过程中的支护结构受力特征,依托浩吉铁路阳城隧道进行现场监测,基于监测结果对支护结构的安全性进行研究。研究结果表明:1)围岩偏压严重且有向洞内挤压的趋势,三台阶施工及复合式衬砌能够保证隧道结构的稳定性。2)初期支护与二次衬砌间的最大接触压力值仅为围岩与初期支护间最大接触压力值的22.4%,初期支护承担荷载大于二次衬砌,二次衬砌主要作为安全储备。3)喷射混凝土最大压应力为极限强度值的41.3%,最大拉应力为极限抗拉强度的88.0%,格栅钢架最大压应力为极限抗压强度的53.8%,二次衬砌最不利位置的安全系数为28.55,支护结构具有较大的安全储备。4)喷射混凝土和格栅钢架的协调性较好,实际工程中可充分利用初期支护对围岩变形进行控制。

To further explore the structural force characteristics of support structures during excavation of Yangcheng tunnel of Haolebaoji-Ji′an railway in weathered red sandstone stratum,the safety of support structure is analyzed based on in-situ monitoring results The results show the following.(1)The surrounding rock is seriously unsymmetrial-loaded,which would lead to squeeze in tunnel.There-bench method and composite lining can guarantee the stability of tunnel structure.(2)The maximum compressive pressure between the primary support and the secondary lining is only 22.4%of that between the surrounding rock and the primary support.The load bore by primary support is larger than that bore by secondary lining,and the secondary lining is mainly used as a safety stock.(3)The maximum compressive stress of shotcrete is 41.3%of the ultimate strength,the maximum tensile stress is 88.0%of the ultimate tensile strength,and the maximum compressive stress of grid steel frame is 53.8%of the ultimate strength.The safety factor of the most unfavorable position of the secondary lining is 28.55,indicating that the properties of the primary support are not fully utilized.(4)The shotcrete and steel frame coordinate well,and the primary support should be well utilized to control the deformation of surrounding rock in practical engineering.