采用双参数地基模型分析管棚变形及内力特征

管棚法在暗挖地下工程中已有较多的应用,通过对管棚力学特征进行理论分析,以期对其设计与施工有所帮助.以北京地铁4~#线西单站工程为例,建立管棚受力的双参数弹性地基梁模型,推导出管棚的挠度及转角、弯矩微分方程,并进行求解,根据管棚两端支撑条件,分析了其变形和内力特征.分析表明,管棚的最大挠度和最大剪力出现在掌子面附近已开挖未支护的部分,掌子面前方1.5～2.0倍开挖高度范围内的围岩有变形和松动.

An Analysis of Deformations and Internal Forces of the Pipe-roof by Double-parameter Elastic Foundation Beam Models

Pipe-proof supporting method has been widely applied in mining shallow tunnels.Mechanical characteristics of the pipe-proof are analyzed theoretically in order to be helpful to the design and construction of the pipe-roof supporting.Taking Xidan station engineering on Line 4** of Beijing Subway as an example, the double-parameter elastic foundation beam models for the pipe-roof are put forward.Differential equations of the corresponding deformations,turning angles and bending moments are deduced and the solutions of these models are given.The deformation and internal force characteristics of the pipe-roof are analyzed based on the supporting conditions of the pipe-roof ends.The analysis results show that the maximum deformation and the maximum shear of the pipe-roof are presented near the working surface at the excavated and non-supported section and the surrounding rock are loosened and deformed in the area of 1.5 to 2 times of the excavated height ahead the working surface.