针对城市地铁竖井横通道转正洞施工难度大、工序繁杂的特点，通过方案比选，提出竖井横通道转正洞采用大包施工工法。该工程现已顺利竣工，工程实践表明，大包法施工安全可靠，技术经济和社会效益显著，可供类似工程参考。

The conversion from horizontal adit driving to main tunnel driving of Metro works has great construction difficulties and complex construction procedures. It is proposed, on basis of construction scheme comparison, that full-envelope construction method should be adopted for the conversion from horizontal adit driving to main tunnel driving. The works has already been successfully completed. The works practice demonstrates that full-envelope construction method can provide safe and reliable construction and significant technical, economical and social benefits. The paper can provide reference for similar works in the future.