primary lining 采用矿山法进行暗挖施工时，围岩支护一般分为初期支护和二次衬砌，二次衬砌一般是混凝土或钢筋混凝土结构。在二次衬砌施作之前，刚开挖之后立即进行的支护形式称之为 初期支护一般有喷射混凝土、喷射混凝土加锚杆、喷射混凝土锚杆与钢架联合支护等形式。 隧道开挖后，为控制围岩应力适量释放和变形，增加结构安全度和方便施工，隧道开挖后立即施作刚度较小并作为永久承载结构一部分的结构层。
The loading ratio is 40% and 60% respectively for the initial supports and secondary linings. The stress of the secondary lining is pressure stress,which is the largest on the upper arch loin and is smaller on the inverted arch.
在标准断面地铁隧道中左、右线墙脚位置初期支护与围岩之间接触压力较大,表明这两位置承受了大部分垂直压力;初期支护与二次衬砌承受的荷载比例为40%和60%;二次衬砌混凝土基本受压,拱腰及以上位置应力较大,仰拱处应力较小。
参考来源 - 黄土地区浅埋暗挖地铁隧道衬砌受力分析This measure can not only reduce the costs for engineering,but also shorten construction period. (2) Ground deformation is analyzed in details under the condition of early support and second lining.
针对数值模拟情况下,施加初期支护和二次衬砌时隧道的地层变形情况进行详细分析,重点研究了拱顶上方竖向位移,拱腰水平方向的位移和拱圈各个关键点位移随开挖的变化特点。
参考来源 - 隧道开挖与支护的效果分析·2,447,543篇论文数据，部分数据来源于NoteExpress
初期支护技术、量测技术的应用；
The application of supporting technology in early period and surveying technology.
深埋隧道软弱围岩与初期支护的相互作用是地下工程研究的重要课题之一。
The interaction between soft-weak Surrounding Rock and initial support of deep buried tunnels has become one of the most important subjects in underground engineering research.
大拱隧道受结构和跨度的影响，其初期支护与二次衬砌各自承受不同的围岩压力。
The primary support and the second lining of large-spanned tunnel have endured different surrounding rock stress because of the influence of structure and span of tunnel.
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