Failure envelope surface of tripod pile foundations under V-H-M combined loading mode
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:① with 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=0.95V0+);② when the vertical load is small(V/V0+≤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/V0+≥0.75);③ the 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.
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