一、前言铁路是国民经济的大动脉,大交通系统中的骨干运输方式。我国铁路承担全国70%左右的货物周转量(1985年7913亿吨公里)和60%左右的旅客周转量(1985年2416亿人公里)。到本世纪末,铁路要具有运送货物25亿吨,旅客25亿人次,换算周转量达到24000亿吨公里的能力。铁路面临的任务十分繁重,而我国现有铁路仅52000多公里,其中复线近10000公 I. Introduction Railway is the backbone of the national economy and major transport system. Our railway undertakes about 70% of the country’s cargo turnover (791.3 billion tons in 1985) and passenger turnover of about 60% (2,416 billion kilometers in 1985). By the end of this century, the railway will have the capacity to transport 2.5 billion tons of cargo and 2.5 billion passengers, converting the turnover to 2.4 trillion tons of kilometers. The task the railway is facing is very heavy, while the existing railway in our country is only more than 52,000 km, of which nearly 10,000 km