针对现有荷载-结构法得出的巨跨洞室二次衬砌结构厚度大、经济性和施工可操作性差等问题，基于某跨度超50 m的巨跨洞室的整体和局部稳定特点，提出巨跨洞室二次衬砌结构承担洞室剩余变形和块体不稳定荷载的作用机制，并论述二次衬砌结构设计的计算过程。得出结果如下： 1）巨跨二次衬砌结构承担洞室剩余变形和不稳定块体荷载这一力学模型符合巨跨洞室整体和局部稳定机制； 2）洞室剩余变形为极限沉降与既有沉降的差值，采用此方法得出的剩余变形值与二次衬砌和喷射混凝土接触压力实测值具有较高的一致性； 3）所提出的不稳定块体荷载是针对洞室薄弱部位重点设计，安全性高; 4）采用本文的设计方法得出的拱部及边墙二次衬砌厚度分别为0.8、1.4 m，相较于常规设计方法，厚度减少了27％~53％。
The secondary
lining structures designed by existing loadstructure methods often exist
with large covering thickness, low economic efficiency, and poor construction
operability problems. Therefore, based on the global and local stability
characteristics of a giant cavern with a span of greater than 50 m, the
mechanism of a giantspan cavern secondary lining
structure undertaking residual deformation and an unstable block load is
proposed, and the calculation process of secondary lining structure design is
demonstrated. The results indicate the following: (1) The mechanical model of
the giantspan cavern secondary lining structure
bearing residual deformation and unstable block load conforms to the global and
local stability mechanism of the giantspan cavern. (2)
The residual deformation of the cavern is the difference between the ultimate
and existing settlements; the results obtained using the proposed method are
highly consistent with the contact pressure of the secondary lining and
shotcrete. (3) The proposed unstable block load is designed for the weak part
of the cavern with high safety. (4) The secondary lining structure thicknesses
of the arch and sidewall obtained using the designed method are 0.8 and 1.4 m,
respectively, which are 27%~53% lower than those of the conventional design
method.
