南京地铁软流塑地层盾构下穿既有隧道处理加固技术

新建地铁极近距离下穿既有运行地铁的设计和施工是其重点和难点,土质条件和地下水赋存等条件是其控制性因素.以南京地铁5号线三山街站-朝天宫站盾构区间隧道出三山街站下穿既有地铁1号线为研究背景,研究软流塑地层新建地铁下穿既有运行地铁的设计和施工要点.分别选取3种地层加固方案确保盾构机顺利穿越隧道:方案1(管棚+水泥土搅拌桩+袖阀管注浆联合加固)、方案2(微扰动注浆加固)、方案3水平旋喷桩全方位高压喷射(metro jet system,MJS)加固)],通过对方案加固效果进行对比分析,最终选定方案1.随后在选定方案的基础上研究了土舱压力和注浆压力对既有隧道位移的影响.结果表明:土舱压力在0.19 MPa以内变动时对隧道控制效果最显著,在实际施工过程中,注浆压力不宜过大,以防水泥浆液劈裂土体造成土体破坏,应实时进行监测.

Treatment and Reinforcement Technology of Shielding under Soft Flow Plastic Stratum through Existing Tunnel

Nanjing Metro Line 5 Sanshan Street Station-Chaotian Palace Station Shield Tunnel out of Sanshan Street Station through the existing Metro Line 1, in order to ensure the smooth passage of shield machine through the tunnel, In this paper, three kinds of formation reinforcement schemes are selected: scheme 1 (joint reinforcement of sleeve valve pipe grouting of cement-soil mixing pile in pipe shed), scheme 2 (micro-disturbance grouting reinforcement) and scheme 3 (horizontal rotary jet grouting pile (MJS) reinforcement). Through the comparative analysis of the reinforcement effect of the scheme, the scheme is finally selected. Then, on the basis of the selected scheme, the influence of soil cabin pressure and grouting pressure on the displacement of the existing tunnel is studied. When the soil cabin pressure changes within 0.19MPa, the control effect on the tunnel is the most significant. In the actual construction process, the grouting pressure should not be too large. In order to prevent soil damage caused by cement slurry split soil, real-time monitoring should be carried out.