考虑泥浆触变性和管土接触特性的顶管摩阻力公式

顶进力是顶管工程设计和施工的重要参数,而顶管侧摩阻力对顶进力起控制作用,其大小主要受管土接触和管浆接触特性影响。为了更加准确地计算顶管摩阻力,假设隧洞孔壁在泥浆压力作用下保持稳定,管道周围同时存在管土接触和管浆接触,采用协调表面Persson接触模型分析管土接触特性,得出考虑接触压力分布影响的管土摩阻力;然后利用半无限弹性体中柱形圆孔扩张理论分析注浆压力对泥浆套厚度的影响,并结合泥浆触变性和流体力学平行平板模型计算管浆摩阻力。在此基础上考虑管道与隧洞的相对位置,同时将管道顶进时的滑动摩擦阻力作为下限值,顶管重启动时的静摩擦阻力作为上限值,总结出直线和曲线顶管摩阻力公式。通过与工程实例数据对比,结果表明该计算公式下限值与实测值最接近,证明其适用性。

Formulae for frictional resistance considering mud thixotropy and pipe-soil contact characteristics

The jacking force is the crucial parameter for the design and construction of pipe jacking projects. It is controlled by the lateral frictional resistance of pipe jacking and affected by the characteristics of pipe-soil contact and pipe-mud contact. In order to calculate the frictional resistance of pipe jacking more accurately, it is assumed that the excavation tunnel is stable under mud pressure. The pipes are contacted with soil and mud concurrently. By using the Persson's contact model for coordinated surface to study the pipe-soil contact characteristics, the pipe-soil frictional resistance can be obtained by considering the contact pressure distribution. By using the cylindrical cavity expansion theory in elastic half plane to analyze the thickness of mud screen influenced by the mud pressure, the pipe-mud frictional resistance is calculated by combining the mud thixotropy with the hydromechanical model for parallel plates. And on this basis, the frictional resistance formulae for the straight line and curved pipe jacking are summarized considering the relative position of pipe and excavation tunnel, the sliding friction as the lower limit value during jacking process and the static friction as the upper limit value at restarting of pipe jacking. Compared with the data of project cases, the results show that the lower limit value by the proposed formulae is the closest to the measured one, and thus its applicability is validated.