浅埋偏压连拱隧道穿越古建筑施工控制研究

Research on the Construction Control of Shallow-buried Unsymmetrical Pressure Double-arch Tunnel Crossing Ancient Buildings

研究目的:浅埋偏压连拱隧道具有围岩级别差、土层压力分布不均以及隧道断面大等特点,使得其在施工过程中易对结构严重风化、变形能力差的古长城墙体造成破坏。为探究浅埋偏压连拱隧道穿越古长城施工过程中变形规律与受力特征,本文以荣乌高速黄土岭隧道为背景,采用数值模拟对施工过程中隧道受力和变形进行分析,选出最合理施工方案,以期为偏压连拱隧道下穿既有建筑相关工程提供一定的理论指导。研究结论:(1)左右洞用侧壁导坑法进行开挖较CRD法以及CRD+CD法而言可有效降低地表沉降与拱顶沉降量,对施工而言最安全;(2)三种施工方法所形成的围岩应力数值不大,均处于安全状态;(3)三种施工工序下,导洞上方地表沉降与隧道拱顶沉降基本相同,但两侧导洞同时开挖可加快施工进度;(4)两侧导洞同时开挖时,中墙承受的应力最小;(5)为保证古长城不被破坏,最终沉降控制标准定为20 mm,爆破振速安全阈值为2 cm/s;(6)本研究成果可为浅埋偏压连拱隧道的施工提供一定借鉴。

Research purposes: The shallow-buried unsymmetrical pressure double-arch tunnel has the characteristics of poor surrounding rock grade, uneven soil pressure distribution and large tunnel section, which makes it easy to damage the wall of the ancient Great Wall with severe weathering and poor deformability during the construction process. In order to explore the deformation law and stress characteristics of shallow bias double-arch tunnel crossing the ancient Great Wall in the construction process, this paper takes Huangtuling tunnel of Rongcheng-Wuhai expressway as the background, uses numerical simulation to analyze the stress and deformation of the tunnel in the construction process, and selects the most reasonable construction scheme, so as to provide some theoretical guidance for the bias double-arch tunnel crossing the existing buildings.Research conclusions:(1)Compared with CRD method and CRD + CD method, the side heading method can effectively reduce the surface settlement and vault settlement, which is the safest for construction.(2) The stress values of surrounding rock formed by the three construction methods are small, and they are in a safe state.(3) Under the three construction procedures, the ground settlement above the pilot tunnel is basically the same as that of the tunnel vault, but the construction progress can be accelerated by simultaneously excavating the pilot tunnels on both sides.(4) When the pilot tunnels are excavated at the same time, the stress on the middle wall is the minimum.(5) In order to ensure that the ancient Great Wall will not be damaged, the final settlement control standard is set at 20 mm, and the safety threshold of blasting vibration velocity is 2 cm/s.(6) The research results can provide some reference for the construction of shallow bias double-arch tunnel.