Abstract: Based on elasto-plastic theory of soils, a finite element model that takes many soil effects into account for simulating p-S curves of bored piles with expanded ends under vertical load is presented. Through computation of over 40 piles, the effects of f/D( ratio of camber and diameter of pile end )and d/D (d: pile diameter ) on the vertical bearing capacity are studied, and conclusions are drawn. The expanded end increases vertical capacity greatly but decreases allowable bearing capacity per unit area of the end.