K_(0)固结饱和黏土中打桩对邻近桩影响分析

Analysis of the Influence of Pile Driving on the Surrounding Pile in K;Consolidated Saturated Clay

动力打桩过程可能会引起既有桩基产生较大位移,进而影响建筑物安全稳定。本文在K;固结各向异性本构模型的基础上,推导了桩周土体破坏区和塑性区的半径计算方法,建立了打桩引起周围土体应力和超孔压的理论计算公式。在此基础上,以最小能量原理为理论依据,将超孔压视为外荷载,提出了其在向周围土层的传递方式,并在半无限空间体内推导了其对周围土体径向应力的影响,并结合天津典型软土对研究成果进行了分析。研究结果表明:建立的柱孔口扩张弹塑性理论计算结果与既有方法基本一致,超孔压在塑性区沿径向衰减速度明显较大;当桩间距较小时,打桩会使邻近已打设刚性桩产生较大水平位移。

The process of dynamic pile driving may cause large displacement of existing pile foundation, which will affect the safety and stability of buildings. Based on the anisotropic K;consolidated clay constitutive model, the calculation method of radius of failure zone and plastic zone of the surrounding soil is derived. Theoretical calculation formula of soil stress and excess pore pressure caused by pile driving is established. On this basis, taking excess pore pressure as external load, the transfer mode of excess pore pressure to surrounding soil is proposed based on the principle of minimum energy. The influence of excess pore pressure on radial stress of surrounding soil is deduced in semi-infinite space. Taking a project in Tianjin as an example, the research results are analyzed. The results show that the present closed-form elastic-plastic solution matches the existing solution fairly well, and the decay speed of the excess pore pressure in the plastic zone is significantly larger. When the pile spacing is small, the displacement of surrounding pile due to piling will be large.