随着地铁建设环境日益复杂，洞桩法地铁车站地面降水变得越来越困难，有必要研究洞桩法车站地下降水的方案。传统的地下降水方法是在车站外侧单独设置降水导洞，但会导致废弃工程量大、工程造价高、环境扰动大等一系列问题。以北京地铁8号线工程王府井站为工程背景，研究对比若干种地下降水的方案。根据洞桩法的工艺特点，创新性地提出将洞桩法车站上层施工导洞适当放大或合并，提供打设降水井的空间，在临时工程增加不大的情况下解决了洞桩法车站的地下降水问题。对于不同的施工导洞内降水方案，实施过程中应根据车站的结构型式、水文地质条件等进行选用。

Due to the complex environment in urban area, the ground surface dewatering for Metro stations constructed by PBA method becomes more and more difficult. As a result, it is necessary to study the underground dewatering technology. According to the conventional underground dewatering technology, a separate dewatering heading is installed outside the main structure of the Metro station, which has such disadvantages as huge abandoned works, high cost and serious influence on the environment. In this paper, comparison and contrast is made among several underground dewatering schemes, with the dewatering of Wangfujing station on No. 8 line of Beijing Metro as an example. An innovative underground dewatering method for Metro stations constructed by PBA method, i.e., enlarging or combining the upper headings of the Metro station to provide space for underground dewatering, is proposed on basis of studying on the characteristics of PBA method. In the end, the problem of underground dewatering for Metro stations constructed by PBA method has been successfully solved. The authors also suggest that proper schemes of dewatering in headings should be selected according to the structure types and hydrological conditions of the Metro station. 