富水强风化砂岩地层顶管隧道下穿既有铁路施工技术

为了解隧道下穿富水强风化砂岩地层施工对既有铁路的影响，依托某电缆隧道下穿广深铁路工程，通过理论分析、数值模拟与现场监测开展了相关研究，并分析了具体施工措施对隧道及地表变形控制的影响。结果表明：当不考虑地表列车荷载和地层富水时，开挖及顶进力为地表沉降、隧道变形的主要影响因素；当单独考虑列车荷载或地层富水弱化作用时，列车荷载会使得下穿段地表沉降和隧道拱顶沉降增大，而地层富水弱化对隧道进出口段沉降及下穿段底部隆起影响较大；当同时考虑列车荷载和地层富水时，隧道拱顶沉降及下穿段路基沉降均会大幅增加。对比分析现场监测、Peck公式预测和数值模拟计算结果，可知数值模拟结果与不考虑地层富水弱化时的Peck公式预测结果十分吻合，但由于其未考虑加固止水措施，地表沉降大于现场监测结果。电缆隧道下穿广深铁路现场施工严格执行现场监测和变形控制措施，将地表沉降值和隧道拱顶沉降值分别控制在6 mm和10 mm之内，隧道底部隆起控制在5 mm以下，可以保障项目的顺利实施与列车的运行安全，并为同类型工程提供一定的经验参考。

Study on construction technology of pipe-jacking tunnel in water-rich intensely weathered sandstone formation crossing underneath existing railway

To study the influence of the water-rich intensely weathered sandstone formation tunnel underpass construction on the exisiting railway, relying on a cable tunnel crossing underneath the Guangzhou-Shenzhen railway project, the related research is conducted through theoretical estimation, numerical simulation and on-site monitoring, and the influence of the specific construction measures on the tunnel deformation control is analyzed. The results show that excavation and jacking force is the main factor affecting the surface subsidence and tunnel deformation without taking the train load and the water-rich rock formation into consideration; when the train load or the water-rich weakening effect of formation are considered alone, the train load causes the increase of surface subsidence and tunnel vault subsidence of underpass section, while the deteroration of the water-rich rock formation has a greater influence on the settlement of tunnel entrance and exit the tunnel upheaval of underpass section. Taking both the train load and the water-rich rock formation into account, tunnel vault subsidence and surface subsidence of underpass section will grow greatly. Comparing the results of on-site monitoring, Peck formula and numerical simulation, it can be seen that the numerical simulation results are consistent with the Peck formula prediction results without considering the water-rich rock formation, while it are larger than on-site monitoring results without considering the reinforcement water-stop measures. The on-site monitoring and deformation control measures are strictly realized in the construction of the cable tunnel crossing underneath the Guangzhou-Shenzhen Railway, and the settlement values of ground surface and the tunnel vault are controlled below 6mm and 10mm respectively, and the upheaval of the tunnel bottom is controlled below 5mm, ensuring the smooth implementation of the project and the safe operation of the train, which provides a certain reference for similar projects.