公路隧道围岩亚级开挖及支护设计参数研究

为了建立公路隧道在各围岩亚级条件下的支护体系，指导隧道的安全施工，在亚级分级方法、分级标准、物理力学参数等研究基础上，结合双车道公路隧道特点，通过理论分析、实例统计、数值分析等方法，研究了各亚级围岩下隧道开挖方法、预加固参数、支护类型、结构型式和初期支护参数。结果表明，Ⅲ1级围岩可采用全断面法、轻型承载型支护，Ⅲ2级采用台阶法、中型承载型支护；Ⅳ1、Ⅳ2、Ⅳ3级采用台阶法、重型承载型支护，但Ⅳ2、Ⅳ3级需通过预加固措施使加固区围岩强度提高到相当于Ⅳ1水平；Ⅴ1级采用台阶法和使加固区围岩强度提高到相当于Ⅳ1水平的预加固措施，Ⅴ2级采用CRD法和使加固区围岩强度提高到相当于Ⅳ3水平的预加固措施，Ⅴ1、Ⅴ2级也都可采用CD法和使加固区围岩强度提高到相当于Ⅳ1水平的预加固措施，且都采用特殊承载型支护；Ⅳ1、Ⅳ2、Ⅳ3、Ⅴ1、Ⅴ2级均需设置仰拱。

Research for excavation and support design parameters of highway tunnel surrounding rock sub-classification

To constitute the highway tunnel support system to direct the safe tunnel construction for all surrounding rock sub-classifications, based on the sub-classification method standard, the physico-mechanical parameters and characteristics of the double lane highway tunnel, the excavation methods, assistant measures, structure forms, support types and primary lining parameters for all sub-classifications have been ascertained by theoretical analysis, example statistics, numerical calculation. The results show that the full face excavation method and light load bearing support are fit for the rock class Ⅲ1, the bench cut method and medium load bearing support are fit for the rock class Ⅲ2; the bench cut method and heavy load bearing support are fit for the rocks class Ⅳ1, class Ⅳ2, class Ⅳ3; and the assistant measures which can raise the surrounding rock strength in reinforced area to the level of rock class Ⅳ1 are needed for the rocks class Ⅳ2 and class Ⅳ3; the bench cut method and the assistant measures which can raise the surrounding rock strength in reinforced area to the level of rock class Ⅳ1 are fit for the rock class Ⅴ1; the center cross diagram method and the assistant measures which can raise the surrounding rock strength in reinforced area to the level of rock class Ⅳ3 are fit for the rock class Ⅴ2; the center diagram method and the assistant measures which can raise the surrounding rock strength in reinforced area to the level of rock class Ⅳ1 are fit for the rocks class Ⅴ1 and class Ⅴ2; and the special load bearing support is needed for them; the inverted arch should be built for the surrounding rock sub-classifications from class Ⅳ1 to class Ⅴ2 .