浅层顶管施工引起地面沉降的预测

在软土地层中顶管施工所引起的地面沉降常常会造成邻近建筑物和地下管线的移动甚至破坏－ 通过对土与顶管的受力及变形的分析，在施工前预测特定顶管工程可能引起的地面沉降的幅度及其形态－ 理论分析和现场实测显示，顶管施工时管节周围土的运动是三维的－ 建立了处理上述三维问题的简便计算方法－ 基于半解析元法将顶管施工中三维土运动问题转换成一维数值计算－ 在轴向离散而在环向和径向取解析函数，建立了半解析单元的位移函数－ 给出了包括位移函数、刚度矩阵和荷载矩阵在内的理论分析过程－ 计算结果表明，半解析元法对于计算顶管施工中的地面沉降是行之有效的方法－ 根据分析与计算结果得到一些有价值的结论，包括结构与土的相互作用而言，顶管管节相当于隧道的衬砌－ 虽然顶管施工引起的地面沉降的沉降槽也近似于误差曲线，由于土的粘塑性变形，地面沉降的幅度在施工过程中是变化的－

Prediction of Ground Settlement Induced by Pipe Jacking in Shallow Underground Soils

Ground settlement induced by pipe jacking construction in soft ground often causes damages to the nearby structures and underground utilities. Based on the analyses of interacting forces between the soils and the jacking pipes and deformation of soils, the value and trough of ground settlement induced by individual pipe jacking construction project is predicted. Both theoretical analyses and field observations have proved that soil movements around pipes during the jacking construction are a three dimensional problem. An simplified method is deduced for effective calculation of the above three dimensional problem. By means of semi analytical element method, the three dimension ground movements problem of pipe jacking is simplified to a one dimensional numerical calculation. Semi analytical element displacement functions are developed with discretization in the axial direction and regular functions in both the circular and the redial directions. A procedure of theoretical analyses, including the development of displacement functions, stiffness matrix and load matrix,is presented. The results of the calculation prove that semi analytical element method is a reliable means of reducing computer processing time and increasing calculating efficiency for ground settlement associated with pipe jacking construction. Some valuable conclusions are drawn from the results of the analyses and calculations, among those are: as for the interaction between soils and the structure of jacking pipes, jacking pipes act as linings of the tunnel,but the friction in the axial direction exerts great influence on the soil movements.Although ground settlement trough induced by pipe jacking is, similar to those of other methods of tunnelling, approximately an error function curve, the magnitude of settlement is changing during construction due to visco plastical deformation of soils.