It is obviously conservative that the structure of shallow tunnel with smaller water content and smaller permeability coefficient in rock stratum is designed by the entirely covered waterproofing method according to the design code and traditional method. In this article, by using the FLAC3D program, the full-covered and half-covered waterproofing methods and grouting water plugging measures of shallow tunnel in low permeability rock stratum were analyzed synthetically. The analysis results show that it is feasible to adopt the drainage type structure for the railway tunnel in low permeability rock stratum. And then in actual project, by analyzing on the economic efficiency and water plugging ability of grouting, the seepage flow can be controlled with reasonable grouting parameters, the external water pressure can be reduced, and the purpose of structure optimization can be achieve.%对于岩石地层含水量和渗透系数均较小的浅埋隧道,如果依然按照规范和传统的防水模式采用全包防水进行结构设计,显然偏于保守.采用FLAC3D有限差分程序对低渗透性浅埋铁路隧道全包排水和半包排水2种排水结构形式以及注浆堵水控制措施进行综合分析,结果表明,低渗透性岩层铁路隧道采用排水结构是完全可行的,实际施工中对注浆的经济性和堵水性两方面进行综合分析,合理选用注浆参数通过注浆堵水控制隧道渗流量降低外水压力,达到结构优化的目的.
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