管节长度是拱北隧道曲线管幕设计和施工的关键参数，为了优化计算曲线管幕管节长度，通过分析顶进力和土体反力作用下的管节静力平衡条件，得出传统式和预调式2种曲线顶管土体反力分布模型。选取管幕顶部、中部、底部以及淤泥质层的顶管作为研究对象，分析不同管节长度和土体参数对管节土体反力的影响规律。结果表明： 传统式曲线顶管土体反力在首节管处最大，且随管节长度增加而减小； 相反，预调式曲线顶管土体反力在首节管处最小，且随管节长度增加而增大。初步分析确定管节长度为4~5 m，为减少超挖量、便于纠偏以及考虑到工作井尺寸等问题，工程最终采用管节长度为4 m的传统式曲线顶管法顺利完成。

The pipe length is a key parameter to the design and construction of Gongbei Tunnel curved pipe roofing. In order to optimize the pipe length, the pipe static equilibrium conditions under the effect of jacking force and earth counterforce is analyzed; the distribution models of earth counterforce in conventional and unit curving pipe jacking methods are obtained. The pipes located in the top, middle and bottom of the pipe roofing as well as mucky soil are selected as study objects so as to analyze the influencing rules of pipe length and soil parameters on earth counterforce. The results show that: 1) The maximum earth counterforce exists in the first pipe of conventional pipe jacking and it diminishes with pipe length increase. 2) On the contrary, the earth counterforce in the first pipe of unit curving method is the smallest and it increases with pipe length increase. The preliminary analysis determines the pipe length of 4-5 m. Considering the reduction of overbreak, the convenience of rectification and the size of working shaft, the project has successfully completed by employing 4 m long pipe with conventional pipe jacking method.