中砂和软黏土中桩顶竖向力 对桩身水平承载力影响对比分析

为探讨中砂和软黏土地基中桩顶既有竖向力对桩身水平承载力的不同影响规律，基于ABAQUS建立了单桩基础三维有限元分析模型，并结合已有载荷试验结果验证了模型的合理性.在此基础上，采用Probe法分别获得均质稍密中砂和软黏土地基中2种不同桩身长径比（L/D）的单桩基础在保持不同桩顶既有竖向力（V）不变时，水平力（H）引起的桩身位移、桩身极限承载力及承载力包络线.结果表明：桩顶既有竖向力从桩身竖向极限承载力（Vult）0.2倍增加至0.8倍时，稍密中砂地基中的桩身水平极限承载力（Hult）提高13.6% ~ 41.2%；反之，软黏土中Hult降低2.2% ~ 6.5%，且L/D较小时这种影响差异更趋明显.最后，通过对比分析加载过程中桩周地基土中的竖向应力、桩侧摩阻力及桩侧土抗力的分布与变化特征，讨论了这种影响差异的内在机理.
To analyze the influence law of existing vertical force（V） on the horizontal bearing capacity of piles in the medium sand and soft clay subsoil， a 3D finite element analysis model of a single pile was set up firstly by ABAQUS and then validated by using available loading test results. By keeping various constant values of V at the pile top and using the probe method， the horizontal load （H） was sequentially applied to obtain the lateral displacement， ultimate bearing capacities and bearing capacity envelopes of the shaft with two kinds of slenderness ratios （L/D） in homogeneous medium sand and soft clay， respectively. It was shown that， under the same variation range of V from 0.2 Vult to 0.8 Vult， the ultimate horizontal bearing capacity（Hult） of the pile in medium sand was increased by 13.6%~41.2%， while the value of Hult for soft clay subsoil was decreased by 2.2% to 6.5%. Furthermore， a more obvious effect was observed for the piles with a smaller L/D. Finally， the different influencing mechanisms of the existing vertical load on the horizontal bearing capacity of a single pile in the medium sand and soft clay subsoil were discussed in detail by analyzing the distribution and variation characteristics of the vertical stress in the subsoil， the side friction and lateral resistance along the pile shaft during the loading process.