近距离下穿既有隧道的盾构施工参数研究

Study on the Construction Parameters of Shield Tunnelling in Short-Distance Undercrossing the Existing Tunnel

采用数值模拟方法分析不同埋深的既有隧道下方土压力分布规律可知:既有隧道对其下方土压力的横向和深度影响范围均为隧道外直径的1.5倍,且沿横向分为3个区域,即接近既有隧道的逐步降低段、穿越时保持最低位和穿出的逐步增加段;既有隧道下方最小土压力与上覆土厚度呈负指数关系,与距离隧道底的间距呈对数关系。根据既有隧道下方土压力的分布规律,提出近距离下穿既有隧道的盾构施工参数设定应分为3个区,并给出各区长度和施工参数建议设定值的计算公式。结合某隧道近距离下穿运营中的既有隧道工程可知,施工参数的实测值与建议设定值吻合较好,且将既有隧道的竖向变形控制在5 mm内。

Using the methods of numerical simulation, earth pressure distribution below the existed tunnel of different buried depth was studied. It is shown that the lateral range and the depth of earth pressure affected by the existing tunnel are both 1.5 times of the tunnel external diameter. The affected partition can be divided into three areas along the lateral direction, including gradually reducing area before traversing, keeping minimum traversing and gradually resuming area after traversing. The relationship between the minimum earth pressure and the buried depth of the existing tunnel is negative exponential, while the relationship between the minimum earth pressure and the distance from the bottom of the existing tunnel is logarithmic. According to the distribution law of earth pressure under the existing tunnel, it is proposed that the construction parameters of shield tunnelling in short-distance undercrossing the existing railway should be divided into three areas. The formulas which are used to calculate the length of different areas and the recommended set construction parameters are provided. Based on a typical project of shield tunnelling in short-distance undercrossing the existing tunnel in operation, the measured construction parameters agree well with the recommended set values, and the vertical deformation of the existing tunnel is controlled within 5 mm.