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目的:在城市地铁的建设过程中,地下水渗流对地表沉降存在较大影响。然而,渗透性地层中浅埋暗挖法施工的案例报道较少,地表沉降规律尚不明晰。本文以深圳地铁5号线和7号线重叠段工程为例,详细分析在渗流作用下浅埋暗挖法施工引起的地表沉降特征以及小导管注浆区和初支衬砌渗透性对地表沉降的影响,并进一步研究超前排水措施在沉降控制方面的作用。创新点:1.系统分析了富水渗透性地层中浅埋暗挖隧道施工引起的地表沉降的发展过程以及沉降特征;2.验证了三维流固耦合数值模型模拟富水环境下重叠隧道施工过程的可行性;3.研究了小导管注浆区、初支衬砌的渗透性和超前排水措施对地表沉降的影响。方法:1.结合隧道施工方案和地表沉降监测数据,分析渗流作用下的地表沉降特征(包括沉降影响范围、沉降槽宽度以及与拱顶沉降的关系等);2.通过三维流固耦合数值模型,研究小导管注浆区和初支衬砌渗透性对地表沉降以及地层孔压变化过程的影响;3.通过模拟掌子面前方水平排水孔,研究超前排水措施对掌子面稳定性和地表沉降发展的影响。结论:1.对于渗透性地层中的浅埋暗挖隧道工程,地下水渗流引起的固结效应是地表沉降量以及沉降范围大幅增长的主要原因。2.全断面注浆能够很好地控制地表沉降,而小导管注浆的效果则十分有限。3.降低小导管注浆区的渗透性,尤其是初支衬砌的渗透性,可以减少地层孔压的下降程度,进而降低地表沉降。4.打设超前水平排水孔可以显著提高掌子面稳定性,却对地表沉降影响有限;当无法进行全断面注浆时,推荐采取小导管注浆与超前排水相结合的方式施工。
Objective: During the construction of urban subway, seepage of groundwater has great influence on surface subsidence. However, there are few cases of shallow excavation in the permeable stratum, and the law of surface subsidence is not clear yet. Taking the overlapping section of Metro Line 5 and Line 7 in Shenzhen Metro as an example, this paper analyzes in detail the characteristics of ground subsidence caused by the construction of shallow buried tunnel under seepage and the influence of the permeability of the small duct grouting zone and the lining on the ground settlement Influence and further study the role of advanced drainage measures in settlement control. Innovative points: 1. The development process of surface subsidence caused by the construction of shallow buried tunnel in deep water-permeable stratum and the settlement characteristics are systematically analyzed.2. The numerical simulation of three-dimensional fluid-solid coupling numerical simulation of overlapped tunnel construction process The feasibility of the experiment; 3. The influence of the small conduit grouting zone, the permeability of the primary lining and the effect of the advanced drainage on the settlement of the ground surface. Based on the tunnel construction scheme and surface subsidence monitoring data, the surface subsidence characteristics (including the influence range of subsidence, the width of settlement channel and the relationship with the settlement of vault) under seepage flow are analyzed.2. By the three-dimensional fluid-solid coupling numerical model , To study the influence of the permeability of the small conduit grouting zone and the lining on the surface subsidence and the formation pore pressure; 3. To study the effect of the advanced drainage on the stability of the face and the surface subsidence Impact of development. Conclusions: 1. For the shallow buried tunnel in permeable formations, the consolidation effect caused by groundwater seepage is the main reason for the large amount of surface subsidence and subsidence. 2. Full-face grouting can well control surface subsidence, while the effect of small pipe grouting is very limited. 3. Reduce the permeability of small conduit grouting area, especially the permeability of the initial lining, can reduce the decline of formation pore pressure, thereby reducing the surface subsidence. 4. Set the level of advance drainage holes can significantly improve the stability of the dough surface, but the impact on the ground settlement is limited; when the whole section can not be grouting, it is recommended to take a small conduit grouting and drainage in combination with the advanced way of construction.