灌注细石混凝土微型桩在软土地基上的抗拔性试验研究

摘要

Behavior of four 2 ×2 piles groups are studied,in order to study the uplift bearing ca-pacity and uplift bearing capacity of single pile.Experiments show that the four uplift piles and four popu-lations of uplift pile load displacement curves are steep,uplift load is relatively small,mainly by the upper part of the side friction resistance of pullout load,with the gradual increase of the pullout load,the lower part of the side friction gradually play.In the pullout test process,the bearing is the largest corner pile, followed by the side of pile,pile bearing force is the smallest,in the ultimate load value 1 #corner pile of reinforced stress is 78.05 MPa in 3 200 kN,5 #pile reinforcement should force 35.12 MPa,1 #corner pile of reinforced stress than 5 #pile to 55% higher.The bigger the pile spacing is,the bigger the effect coeffi-cient is,the more obvious the group pile effect is.In the preliminary design of similar projects in the pile effect factor of 0.79 is more appropriate to calculate.%以单桩4根，4种2×2群桩为研究对象，通过对灌注细石混凝土微型桩在软土地基上抗拔承载机理及其抗拔承载力计算方法进行了研究。试验表明，4根抗拔桩和4种群抗拔桩荷载－位移曲线均为陡增型，抗拔荷载较小时，上部侧摩阻力抵抗抗拔荷载为主因，抗拔荷载逐渐增大时，下部的侧摩阻力为主因。在抗拔试验过程中，承力最大是角桩，其次是边桩，中桩的承力最小，在极限荷载值为3200 kN 时，1＃角桩的钢筋应力为78.05 MPa，5＃中桩钢筋应力为35.12 MPa，1＃角桩的钢筋应力比5＃中桩要高出55％。群桩效应系数取值与桩间距有关，间距较大时，群桩效应不明显。初步进行设计的类似工程中可将抗拔群桩效应系数取为0.79进行计算较为合适。