竖向荷载下GRF承载机制数值模拟研究

岩土加固基础（geo-reinforcement foundation，简称GRF）是一种新型岩土增强型桩基础，其承载机制目前尚未明确。通过建立GRF的三维非线性模型，并考虑地基中的桩-土接触、锚杆-土接触效应，利用岩土专业计算软件FLAC3D，分析研究了GRF桩土变形以及土体屈服特性、桩身轴力变化规律、侧阻力和端阻力的变化规律。数值计算结果表明：GRF更能调动桩周土体来承载，其侧阻力、端阻力、极限承载力均大于等直径桩；由于锚杆作用，GRF的桩身轴力在锚杆附近出现“台阶式”突降；锚杆作用的发挥与桩顶位移密切相关，只有在桩顶产生一定位移条件下，锚杆才能发挥其承载作用，且土体在锚杆上部形成松弛区，在锚杆下部形成压密区；锚杆随桩体向下移动，与桩体相互作用，锚杆下部及锚杆附近桩体内会产生拉应力。研究结果为GRF在工程中推广应用奠定了一定的理论基础，对设计GRF有一定的参考价值。

Numerical study of bearing mechanism of geo-reinforcement foundation under vertical load

Geo-reinforcement foundation(GRF) is a new type of reinforcement pile foundation of which the bearing mechanism is not clear at the present time.By building the 3D nonlinear model of geo-reinforcement foundation,considering the contact effects between pile and soil and that between anchors and soil,utilizing geotechnical professional calculating software FLAC3D,the pile and soil displacement of geo-reinforcement foundation is analyzed;and the soil yield characteristics,variation regularity of pile shaft force,side resistance and end resistance are also studied.The numerical calculation results show that geo-reinforcement foundation can arouse the soil around pile to bear load more efficiently;and the side resistance,end resistance,ultimate bearing capacity of geo-reinforcement are larger than that of straight pile with equal diameter;because of the anchor function,the pile shaft force is suddenly decreased,like a "step",near the anchors;the function of anchors is closely related with the displacement of pile top.Anchors function the bearing capacity only on the condition that the pile top displacement reached a curtain number.Relaxation region appears in the soil up the anchors and compaction zone occurs in the soil down the anchors;anchors move downward together with pile body and they interact with each other,which causes tensile stress in the lower part of the anchors and pile body near the anchors.The study has laid some basis for the extension and application of geo-reinforcement foundation in projects,which is valuable,to some extent,during the process of designing the geo-reinforcement foundation.