上砂下岩地层中矿山法隧道下穿建筑物技术研究

Study on the Technology of Mining Tunnel Passing through Buildings in the Upper-sand and Lower-rock Strata

以青岛市地铁3号线万年泉路站—李村站区间隧道下穿中国银行李村支行、万隆商厦建筑物为例,从注浆加固砂层、加强隧道初期支护措施、岩层开挖施工控制及地面预加固等方面提出上砂下岩特殊地层条件下隧道下穿建筑物变形控制措施。采用数值模拟手段研究上部砂层注浆加固后隧道应力及地表变形规律,并对比分析注浆加固、不加固两种工况下地表变形情况。计算结果表明,隧道开挖后地表沉降值随洞身范围内砂层分布区域增加而增大,揭示了地表沉降主要是由洞身范围内砂层开挖引起;砂层注浆加固对控制地表变形效果明显,将地表变形值控制在允许范围内,可优化建筑物地表预加固措施。现场监测结果显示,隧道施工期间洞内拱顶沉降及净空收敛最大值分别为4.5,1.57 mm,建筑物最大沉降量仅为3 mm,累计变形以隆起为主,远小于建筑物变形控制指标,验证了设计方案可行性。

With reference to the tunnel passing through Bank of China Licun Sub-branch and Wan-Long Building between Wannianquan Road Station and Licun Station of Qingdao Metro No.3,deformation control measures for the tunnel underneath the building under special conditions of the upper-sand and lower-rock are proposed from the aspects of grouting to strengthen the sand layer,strengthening the initial support of the tunnel,rock layer excavation construction control,and ground prereinforcement.The numerical simulation method is used to study the stress and surface deformation of the tunnel after grouting reinforcement in the upper-sand layer.Ground deformation under the two conditions of grouting reinforcement and unreinforcement is compared and analyzed.The calculation results show that the surface settlement after tunnel excavation increases with the increase of the distribution area of sand layers in the cave area,revealing that the surface settlement is mainly caused by the excavation of sand layers in the cave area.Sand layer grouting reinforcement has obvious effects on controlling surface deformation.Controlling surface deformation within the allowable range can optimize the pre-reinforcement of the building surface.On-site monitoring results show that,during tunnel construction,the maximum values of the arch vault settlement and headroom convergence are 4.5 mm and 1.57 mm respectively.The maximum settlement of the building is only 3 mm,and the cumulative deformation is mainly uplift,which is far less than the control index of building deformation.The feasibility of the design scheme is verified.