考虑轴线偏差的钢顶管允许顶力计算方法

钢顶管轴向稳定性直接影响到允许顶力大小。若顶力控制不当,顶管可能发生轴向失稳破坏。顶进过程中的轴线偏差会降低轴向稳定性。为解决存在轴线偏差的钢顶管允许顶力计算问题,考虑管周土体的约束、管土摩阻力的共同作用,将钢顶管顶进过程中的轴线偏差作为初弯曲,建立并求解能量方程,获得了临界顶力荷载的解析解。结合实际工程,提出了根据容许轴线偏差量与管长共同确定初弯曲的方法,计算了不同初弯曲条件下的稳定系数与允许顶力。稳定系数与轴线偏差呈二次曲线关系,轴线偏差越大,顶管轴向稳定性越低,允许顶力越小。钢顶管施工过程中,应根据轴线偏差造成的不同初弯曲计算稳定系数与允许顶力,以控制顶管顶力,避免发生轴向屈曲。

Allowable Jacking Force Calculating Method of Steel Jacking Pipe Considering Axial Deviation

The allowable jacking force of steel jacking pipe is directly dominated by the axial stability. Steel jacking pipe may damage due to axial buckling by improper jacking force during constructing. In jacking process, the axial deviation from operating would decrease the stability of pipe. The effects of constraint by surrounding soil and fraction between soil and pipe were taken into account to analysis the problem of axial buckling for steel jacking pipe with axial deviation. The axial deviation of pipe was treated as an initial bending of slender member to deduce the analytical solution of critical jacking force by energy method. On the basis of engineering case, the method to determine initial bending values was proposed from allowable axial deviation values and length of steel jacking pipe. The stability coefficients and allowable jacking forces were calculated. The results show that there is a quadratic curve relation between stability coefficients and axial deviation. The stability and allowable jacking force are decreasing with the pipe axial deviation increasing. Therefore, during the construction process, the allowable jacking force should be determined according to the actual values of axial deviation and guide the construction. The analytical solution of critical jacking force can be used to calculate the allowable jacking force, which provides the guideline to avoiding the steel jacking pipe axial buckling damage.