To investigate the influence of drilling method on the bearing characteristics of pile foundation in loess areas

statically loading tests on four tested piles were carried out on two sites of the Yongshou-Xianyang Expressway project

and the loading transfer behavior of pile foundation with different drilling hole methods is analyzed. The experimental results show that the drilling method has significant influence on the bearing characteristics of pile foundation. The bearing capacity of bored pile by churning is much higher than that of circulation bored pile with slurry protection wall in loess area. The reason is that the borehole wall needs protecting during drilling

the formed mud cake significantly weakens the exertion of pile shaft resistance. This can result in a minor ultimate friction resistance and a larger tip resistance accounting for a larger percentage of the load on pile top. Loess structure is destroyed after immersion in water

so that the bearing capacity of pile decreases compared with the test pile in original state. Due to the fact that the collapse settlement of overlying loess is small

negative skin friction is not produced by the soils in immersion state at pile side