V-H-M复合加载模式下三桩基础的失效包络面研究

Failure envelope surface of tripod pile foundations under V-H-M combined loading mode

为了研究海上风机三桩基础在竖向荷载V、水平荷载H和弯矩荷载M复合加载模式下的极限承载特性,建立了350组三桩基础有限元极限分析模型,系统分析了三桩基础在单向加载、H-M双向加载和V-H-M三向复合加载条件下的失效包络面形态,探讨了深径比、距径比等因素对三桩基础失效包络面的影响规律。研究表明:①随着竖向荷载的增加,三桩基础在H-M平面上的失效包络线将持续收缩并整体向H和M坐标轴的负方向发生偏移,该影响在V=0.95 V_(0)^(+)时偏移现象尤其明显;②当竖向荷载V/V_(0)^(+)≤0.50时,三桩基础主要受水平荷载的影响发生倾覆破坏,而当竖向荷载V/V_(0)^(+)≥0.75时,基础则会发生竖直方向上的压入破坏;③三桩基础失效包络面尺寸随深径比与距径比的增大而增大;④所提出的经验公式可较为准确地预测三桩基础复合承载力大小。

In order to investigate the bearing capacity of tripod pile foundations under the combined vertical(V),horizontal(H)and bending moment(M)load,350 finite element limit analysis model has been constructed,the shape of the failure envelopes for tripod pile foundations under single directional loading,H-M two directional loading and V-H-M combined loading was systematically analyzed,the effect of the depth-diameter ratio and the spacing-diameter ratio on the failure envelope of tripod pile foundations was discussed.The investigation indicates that:①with the increase of vertical load,the failure envelope of tripod pile foundations on the H-M plane continuously shrinks and shifts toward the negative direction of the H and M axes as a whole,this effect becomes obvious when the vertical load is large(V=0.95 V_(0)^(+));②when the vertical load is small(V/V_(0)^(+)≤0.50),the failure of the tripod pile foundations is mainly affected by the horizontal load and behaves as overturned,while the failure will behave as crushed in the vertical direction when the vertical load is large(V/V_(0)^(+)≥0.75);③the size of the failure envelope of tripod pile foundations becomes larger when the depth-diameter ratio and the spacing-diameter ratio is increased;④the proposed empirical equation can accurately predict the combined capacity of the tripod pile foundation.