1 中铁二十局集团有限公司 目 录 第一章 总体概况说明 ············································· 1 第一节 编制依据 ············································· 1 第二节 工程简介 ············································· 1 第三节 地质、水文条件 ······································· 1 第四节 围岩级别及工程数量 ·································· 2 第二章 洞口段施工 ··············································· 4 第一节 地表水拦截和预加固 ···························