富水砂卵石地层盾构近距离下穿既有线施工技术

Construction Technology of Shield Tunneling Closely Undercrossing Existing Subway Line in Sand-gravel Stratum

随着城市轨道交通快速发展,地铁新线穿越既有线工况越来越多,新线穿越施工必然引起既有线周边土层及结构变形,继而影响既有线运营安全,因此应充分认识盾构穿越施工中地铁保护的重要性和迫切性。以成都地铁9号线穿越既有4号线为背景,针对盾构在富水砂卵石地层近距离下穿既有运营线施工难题,采用袖阀管与管棚注浆措施对原有地层进行加固处理,并建立了出土参数与出土方量双控指标控制出土量。同时,在穿越过程中采用同步注浆措施,穿越后采用二次注浆填充管片背后间隙,可有效控制地层下沉与既有线结构变形,此外加强既有线自动化监测,及时反馈施工,取得良好效果。

With the rapid development of urban rail transit, there are increasingly more new subway lines crossing existing lines. The construction of new subway lines crossing existing subway lines will inevitably cause deformation of the surrounding soil layers and structures, thus affecting the safety of existing subway lines. Therefore, the importance and urgency of subway protection in shield tunneling construction should be fully recognized. In this paper, the method of grouting and strengthening the original ground cavity by using the sleeve valve tube and the pipe shed is proposed in accordance with the construction problem of the existing operation line for the water-rich sand and gravel stratum. Taking Chengdu Metro Line 9 crossing the existing Line 4 as an example, two parameters, i.e. unearthing parameters and unearthed quantity, are established to control over-excavation. Meanwhile, synchronous grouting measures were adopted during the traversing process, and the gap behind the segments was filled by secondary grouting after traversing, which can effectively control the subsidence of the formation and the deformation of the existing structure. In addition, desirable results have been achieved by strengthening the automatic monitoring of existing subway lines and timely feedback to construction obtain good effect.