基于截面极限承载力曲线的衬砌结构安全性评价方法研究

复合式衬砌由初期支护、防水层和衬砌组成，是中国现行山岭隧道的主要结构形式，而衬砌是保证隧道长期运营安全的关键。衬砌结构的安全性评价一般根据相关的隧道设计规范进行。现行规范中素混凝土衬砌和钢筋混凝土衬砌的安全性检算公式分别给出，在某些截面内力条件下，不能直接按照安全系数大小进行安全性比较。针对这种状况，首先对现行的衬砌结构安全性评价方法进行简化，提出衬砌截面安全包络线的概念，根据衬砌截面内力是否位于安全包络线内侧，即可判定衬砌截面的安全性。然后，在探讨截面安全包络线与极限承载力曲线关系的基础上，提出利用截面极限承载力曲线计算衬砌截面安全系数，进而评价衬砌安全性的方法。研究结果表明：根据衬砌截面安全包络线的概念，对于任意截面内力可简便直观地判定衬砌截面是否安全；衬砌截面内力点（M，N）位于极限承载力曲线关于坐标原点的几何相似曲线上，坐标原点和截面内力点的连线与极限承载力曲线相交，交点到原点的距离与内力点到原点的距离的比值则为衬砌截面的安全系数；利用考虑材料非线性的衬砌截面极限承载力曲线，避免了现行规范中出现素混凝土衬砌比钢筋混凝土衬砌截面极限承载力大的现象。研究成果对衬砌截面安全性评价及衬砌结构设计理论的完善具有一定的参考意义。

Research on Evaluation Method of Lining Safety Based on Ultimate Bearing Capacity Curve of Lining Section

Composite lining, which consists of initial support, a waterproof layer, and lining, is the main structural form of mountain tunnels in China. In these tunnels, lining is key in ensuring long-term operation safety. At present, the safety evaluations of lining structures are generally carried out according to the relevant tunnel design specifications.For the safety evaluation method of lining structure given in the current code, the checking formulas of plain concrete lining and reinforced concrete lining are provided,respectively.It is not possible to compare the safety of lining structures using the safety factors for the internal force states of lining sections. In this study, the current safety evaluation method of lining structure was firstly simplified, and the concept of the safety envelope of a lining section was proposed. Then the safety of a lining section could be judged according to whether the internal forces of the lining section were located inside the safety envelope. Furthermore, on the basis of discussing the relationship between the section safety envelope and ultimate bearing capacity curve, an evaluation method of lining safety based on the section ultimate bearing capacity curve was proposed. The results show that the safety envelope of the lining section can be used to judge the safety of the section simply and intuitively. The state of section internal forces (M, N) is located on the geometric similarity curve of the ultimate bearing capacity curve with respect to coordinate origin.By the geometric relationship of the relevant line segments, section safety factors can be calculated. The section ultimate bearing capacity curve considering the material nonlinearity can avoid some limitations in comparison the safety for both plain and reinforced concrete lining in the code. These research results are useful for section safety evaluations and lining design theory.