拱北隧道管幕冻结法管间冻结封水效果实测研究

Effect of water-proofing in Gongbei Tunnel by freeze-sealing pipe roof method with field temperature data

基于现场实测数据,对拱北隧道管幕冻结法暗挖工程不同阶段的管间的实际冻结封水效果进行了分析。对于积极冻结期的两种不同交圈模式,利用单管公式对管间冻土厚度进行计算,结果表明在工程允许的时间内管幕间冻土即可形成交圈,从而说明管幕具有初步的封水性能。交圈后,利用双管公式对管间冻土厚度进行计算,结果显示冻土帷幕发展并不均匀,纵向上靠近中间的冻土发展好于端部的,横向上靠近下部的冻土发展好于上部的,此外台风等自然灾害对于地表附近冻土的影响是可控的。对于开挖期,管间温度实测数据表明:试开挖期间对施工进度的严格精细控制有利于减小管间冻土的弱化;正式开挖期间开挖热扰动对于接近紧挨开挖面的冻土造成显著影响,而稍远一些的冻土则几乎不受影响。考虑20cm的折减后,冻土帷幕仍能保持足够的冻土厚度以达到封水效果。研究验证了管间封水效果,论证了工法的合理性,为以后类似工程的开展提供了借鉴和指导。

The actual water proofing effect between the pipes at different stages of the freeze-sealing pipe roof(FSPR) method is analyzed based on the field measured data. For the two different intersection patterns in the active freezing period, the thickness of the frozen soil between the steel pipes is calculated by the single-pipe formula. The results show that the frozen wall can form the intersection within the time allowed by the project, so that the frozen wall has initial water sealing performance. After the intersection, the thickness of the frozen soil between the pipes is calculated by the double-pipe formula. The results show that the development of the frozen soil wall is non-uniform. The development of the frozen soil near the middle in the longitudinal direction is better than that at the end, and the development of the frozen soil near the lower part in the lateral direction is better than that near the upper part. In addition, the impact of natural disasters such as typhoons on the near surface soil is proved controllable. During the excavation period, the measured data of the inter-tube temperature indicate that the strict and fine control of the construction schedule during the test excavation is beneficial to reduce the weakening of the frozen wall between the pipes, and the thermal disturbance during the official excavation has a significant impact on the frozen soil close to the excavation surface while the frozen soil slightly far from the excavation surface is almost unaffected. The frozen soil wall can still maintain enough frozen soil thickness to achieve the sealing effect considering the reduction of 20 cm. The study has verified the effect of water proofing between pipes and demonstrated the rationality of the FSPR method, which may provide reference and guidance for similar projects in the future.