黄土塬区浅埋大断面隧道施工变形分析与控制技术

Deformation Analysis and Control Technology of Shallow-buried Large Cross-section Tunnel in Loess Plateau Area

针对黄土塬区浅埋大断面隧道开挖过程中,地表水沿着裂隙、黄土节理下渗导致地表沉陷、纵横向地表裂缝及初期支护结构破坏等问题,基于三维地质仿真模型方法,进行初期支护受力特征和变形规律分析,并模拟分析地层改良效果。结果表明:1)隧道拱部为支护结构受力最薄弱区,表现为拱顶衬砌下表面拉应力和剪应力值大,当埋深为10~15 m时下台阶至仰拱开挖阶段随含水率增加拱顶沉降变形量剧增,且累计沉降量>250 mm时隧道结构最不安全,易产生环向张拉裂缝;2)地表注浆能有效改善黄土的结构性能,有效控制地表沉降和围岩变形。

The phenomena,i.e.surface subsidence,longitudinal and horizontal surface cracks and primary support damage,are often caused by surface water infiltration along cracks and loess joints during the excavation of shallow-buried large cross-section tunnel in loess plateau.Hence,the stress characteristics and deformation law of primary support are analyzed based on 3D geological simulation model,and the improve effect of the stratum is analyzed.The results show that:(1)The tunnel crown is the weakest area of the primary support,accompanied with large tensile stress and shear stress in the lower surface of crown;when the buried depth is 10~15 m,the settlement of the crown increases sharply with the increase of water content,and when the cumulative settlement is more than 250 mm,the tunnel is in the most unsafe situation and prone to circumferential tension cracks.(2)The surface grouting can effectively improve the properties of loess,and control surface subsidence and surrounding rock deformation.