顶管施工对既有基坑的影响分析

Analysis on Influence of Pipe Jacking Construction on Existing Foundation Pit

既有基坑一侧有顶管施工时,顶管施工产生的附加应力会影响基坑支护的安全,对此种工况进行分析,可以为顶管施工提供参考价值。本文基于Mindlin应力解,推导了有关顶管施工掌子面推力和顶管摩阻力作用在支护结构上的附加应力荷载和应力的解析解答,并将计算结果与数值模拟进行对比。结果表明:沿轴线位置向上下附加荷载减小,减小速度很快,向下附加荷载最终减小到0 kPa,向上减小为负值;沿顶管施工方向,计算值和模拟值在顶管正面前(x>0)相似度较高,在顶管正面距支护结构距离x=2 m处,支护结构受顶管施工影响产生的附加荷载最大;基于Mindlin解的附加荷载最大值与数值模拟结果较为相似,附加荷载最大值可取解析值并对支护进行验算,进而保证支护结构的安全;顶管直径越大,附加应力越大;顶管与支护结构的水平间距越大,附加应力越小,附加应力见效的速度也越快;泊松比越大,附加应力越大。

When there is pipe jacking construction on one side of the existing foundation pit,the additional stress produced by pipe jacking construction will affect the safety of foundation pit support.The analysis of this working condition can provide reference value for pipe jacking construction.Based on Mindlin’s stress solution,this paper deduced the analytical solution of the additional stress load and stress on the supporting structure caused by the thrust fsand the friction fmof the pipe jacking construction face,and compared the calculation results with the numerical simulation.The results show that:along the axis position,the additional load decreases rapidly from up to down,and finally decreases to 0 k Pa,and decreases to a negative value from up;along the pipe jacking construction direction,the calculated value and simulation value have a high similarity in front of the pipe jacking front(x>0).When the distance from the pipe jacking front to the support structure x is 2 m,the maximum additional load of the support structure is caused by the impact of pipe jacking construction.The difference between the maximum value of additional load and the maximum value of numerical simulation is not big.The maximum value of additional load can be used to check the support structure to ensure the safety of the support structure.The larger the diameter of the pipe jacking is,the greater the additional stress will be.The larger the horizontal distance between the pipe jacking and the support structure is,the smaller the additional stress will be,and the faster the effect of the additional stress will be.The larger Poisson’s ratio is,the greater the additional stress will be.