Experimental study of vertical bearing capacity behavior of large-diameter bored cast-in-situ long pile

The vertical load field test of nine large-diameter cast-in-situ bored piles is made in Tangshan LNG tank area,in which three piles are of tip post-grouting;three piles are of expanded branches and bells by 3-way extruding arms;three piles are of squeezed branch.Based on the static load and pile stress test results,the vertical load transfer laws of these three kinds of different construction techniques of cast-in-situ bored piles are analyzed.The results show that: the loading-settlement curves of three different construction technology piles have no obvious inflection point;the post-grouting pile load transfer process performs the characteristics of friction piles;pile lateral friction bears all load;the piles of expanded branches and bells by 3-way extruding arms and the squeezed branch piles load transfer performs the end bearing the characteristics of friction piles,pile tip resistance is 20% to 30% of the total load;the axial force and the pile-soil relative displacement variation of these three different construction technology test piles are similar;the tip resistance and lateral friction play asynchronous and influence each other;the pile lateral frictions have shown intensification.The entire tank area requirements of the single pile bearing capacity is not less than 8 100 kN,the bearing capacities of three construction technology piles can meet the requirements.