群桩效应对多井隔水导管锤入阻力的影响

Influence of group pile effect on hammering resistance of multi-well risers

群桩效应使多井隔水导管的锤入阻力增加、从而导致拒锤等复杂事故,严重影响隔水导管安装作业效率。针对群桩效应影响多井隔水导管锤入阻力的问题,通过单根隔水导管锤入模拟实验,探索了隔水导管锤入对周围土体的影响情况;通过多根隔水导管锤入模拟实验,研究了群桩效应对多根隔水导管锤入阻力的影响规律。结果表明,随着单桩隔水导管锤入深度的增加,隔水导管周围径向应力呈现先增大后减小的趋势;锤入完成后,随着静置时间的增加径向应力持续上升,静置24 h后径向应力逐渐趋于稳定。在粉土层中,随着多井隔水导管水平距离的增加,径向应力增量呈现减小趋势;当水平距离小于3.0 m(4.9倍桩径)时径向应力增量较大,群桩效应显著,而水平距离大于3.0 m时径向应力增量较小,群桩效应对锤入阻力的影响可忽略。对比不同位置隔水导管锤击数发现,中心桩隔水导管的锤入阻力为单桩的2.47倍,边桩和角桩的锤击数分别为单桩的1.66倍和1.69倍,多井隔水导管的锤入顺序设计时应将中心桩位置的隔水导管先锤入,避免中心桩在群桩效应的影响下锤入阻力过大而导致的拒锤等情况。

The group pile effect increases the hammering resistance of multiple well risers,leading to complex issues like repelling hammering,which severely affects the efficiency of installing the risers.To address the impact of the group pile effect on the hammering resistance of multiple well risers,a simulation experiment was conducted using a single well riser to explore its influence on the surrounding soil.In addition,a simulation experiment involving multiple well risers was performed to study the influence of the group pile effect on the hammering resistance of multiple well risers.The results show that with increasing hammering depth of single well riser,the radial stress around the riser initially increases and then decreases.After the hammering is completed,the radial stress continues to rise with the increase of the standing time,and the radial stress gradually stabilizes after standing for 24 h.In the silt layer,with the increase of the horizontal distance of the multi-well risers,the radial stress increment shows a decreasing trend.When the horizontal distance is less than 3.0 meters(4.9 times the pile diameter),there is a significant increase in the radial stress increment due to a prominent group pile effect.However,when the horizontal distance exceeds 3.0 meters,the increment of radial stress is relatively small,and the impact of the group pile effect on the hammering resistance can be ignored.Comparing the number of hammer strikes at different positions,it was found that the hammering resistance of the center pile is 2.47 times that of a single pile.The number of blows for edge piles and corner piles is 1.66 and 1.69 times that of a single pile,respectively.When designing the hammering sequence of multi well waterproof conduits,the waterproof conduits at the center pile position should be hammered first to avoid situations such as refusal of hammering caused by excessive hammering resistance of the center pile under the influence of pile group effect.