Abstract: 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.

Key words: cast-in-situ bored pile, vertical bearing capacity, load test, lateral friction, post-grouting technology of pile tip, squeezed branch process