Study On Compressive And Uplift Bearing Properties Of New Bored Grouting PHC Nodular Pile

The new bored grouting PHC nodular pile was introduced into China lately, so there are almost no correlative studies. In order to learn about its bearing capacity, vertical compressive load test、pull-out load test and horizontal load test were conducted. And field testing data of bored piles and PHC piles were collected and censused. Comparing testing data of new composite piles with the statistical data, we find that bearing capacity of new composite pile is not lower than that of bored piles with the same diameter, and is much higher than that of PHC pile. It can prove that the new composite pile has advantages in compressive bearing capacity.For the sake of getting to know the compressive mechanical characters of new bored grouting PHC nodular pile, ABAQUS is used to simulate the vertical compressive load test. Studying the numerical results, we find that the radius of nodular stress influence is2-3times pile diameter; there is no friction on about1.6-1.8times pile diameter space around of the nodule; ultimate bearing capacity of the nodules from top to bottom increase linearly except of the first and the last one. Comparing displacement differences of pile-cemented soil and cemented soil-soil of different new composite piles and PHC piles, nodular distance plays an important place. Except of nodular distance, sickness of soil-cement. the modulus of soil of pile side and pile tip also influence ultimate bearing capacity of the composite pile. Base of studies above, a new formula of ultimate bearing capacity considering of nodular influence coefficient is proposed, and its validity is verified by field tests.Uplift mechanical characters are similar with compressive mechanical characters, except that the ultimate side resistance of uplift pile is lower than that of compressive pile. And the ratio is about0.6to0.8. Base on the studies of others and field tests, we find the failure mode is cylindrical shear failure, and fracture surface is between cemented soil and soil. Some theoretical expressions of uplift bearing capacity are listed and proved if it is suit for new bored grouting PHC nodular pile. And based on the formula of ultimate compressive bearing capacity, propose a new expression of uplift bearing capacity.