地下线 meaning in Chinese

counterpoise conductor
underground line

On the basics of guangzhou city urban mass transit line net development experiences , considering the research of resources sharing of guangzhou transit line net planning , this paper discusses the necessity , the main factors and principle of the route laying , makes an integrated analysis of the adaptable ranges of the ground line , the elevated line and the underground line , as well as their influences over land use , environment and engineering mat , which , as the authors hold , will provide the technique support for the route laying mode planning of the line net
摘要结合广州市城市轨道交通线网建设规划的经验，在广州市城市轨道交通线网资源共享规划研究的基础上，对线路敷设方式规划的必要性、主要内容、影响因素及确定原则进行了阐述，并对地面线、高架线、地下线三种形式在适用范围、对城市土地利用、对环境影响、工程造价等方面进行了综合分析比较，为线网线路敷设规划提供技术支持。