富水砂卵石地层双层衬砌类圆形断面矿山法地铁隧道适应性研究

针对富水砂卵石地层条件下矿山法隧道下穿既有地铁盾构隧道,首先从工期要求与既有工程经验方面进行总体方案设计,明确矿山法隧道近距离下穿既有隧道的优势;随后基于规范要求与富水砂卵石地层特性,提出施工变形控制标准;最后对初期支护+双层衬砌结构型式下的沉降变形、结构内力等进行深入分析,并与常规初期支护+二衬结构型式进行对比分析,明确双层衬砌结构型式的优势。研究结果表明:类圆形断面在减小隧道开挖轮廓与改善结构受力性能等方面具有明显优势,同时本工程双层衬砌构造型式,围岩荷载主要由二次衬砌承担,永久结构(三次衬砌)承担的荷载较小,永久结构在承载力与稳定性,尤其是安全储备方面具有明显的优势。

Feasibility Study of Round Cross-section Mining Tunnel with Double Lining in Water-rich Gravel Stratum

As for the tunnel mining beneath the existing shield tunnel in water-rich sandy gravel stratum,the overall design program is made based on construction period and relevant experiences,and the advantages of the tunnel mined beneath the exiting shield tunnel are made clear. The deformation control standard during tunneling is put forward based on the characteristics of sandy gravel stratum and relevant specifications. At last,the settlement and structure stresses of the double lining structure with primary support,second lining and third lining are analyzed and compared with those of the conventional structure with primary support and second lining. The advantages of double lining structure are justified. Research results show that round cross-section mining tunnel has obvious advantages in reducing excavation contour and improving mechanical performance; the formation load is mainly carried by the second lining and little load is acted on the third lining. The advantages of double lining structure in bearing capacity,maintaining stability and emergence capacity in particular are obvious.