为提高软弱地层中辅助坑道进隧道正洞挑顶施工的安全性，有效控制应力集中部位的初期支护变形，解决传统挑顶工法中交叉口部位工序错综复杂、应力转换频繁的问题，以渝昆高铁昭通隧道2号斜井进正洞施工为依托，在充分分析斜井段膨胀土地质特征的基础上，开展上联洞+门架法挑顶施工技术研究。通过在辅助坑道与正洞交叉口后方设置独立式上联洞掘进至正洞拱顶，多工作面同步实施正洞挑顶和斜井衬砌，结合密排门架法挑顶工艺，可以更好地拟合正洞开挖轮廓，实现安全、快速的挑顶作业。上联洞+门架法挑顶技术可以很好地解决辅助坑道交叉口段衬砌与正洞挑顶的施工干扰问题，实现2项作业的同步平行施工，加快挑顶施工进度，并通过工法革新有效规避了多种安全风险因素的叠加。
The complicated working procedure and frequent stress
transformation at the intersection between main and auxiliary tunnels are big
challenges in the traditional roof-lifting method. To improve the
safety of the roof-lifting construction of the
auxiliary tunnel entering the main tunnel in soft stratum and to effectively
control the primary supporting deformation at the stress concentration
position, a case study is conducted on the construction of Zhaotong tunnel
inclined shaft No. 2 entering the main tunnel of Chongqing-Kunming high-speed railway. The roof-lifting technology of the upper connecting hole + portal frame
method is studied based on the full analysis of the geological characteristics
of expansive soil in the inclined shaft section. An independent upper guide
tunnel is set behind the intersection between the auxiliary and main tunnels to
excavate the main tunnel crown. Meanwhile, multiple working faces are performed
synchronously with the roof of the main hole and the lining of the inclined
shaft. Additionally, the application of the close-row
gantry roof-lifting technology can effectively fit the
excavation contour of the main tunnel, realizing a safe and fast roof-lifting operation. The construction results show that the
interaction effect of the auxiliary and main tunnels can be minimized,
obtaining a synchronous, safe, and fast construction.
