Abstract: In this paper, the relationship between thestress-strain of the piles and the soil nearby based on the horizontaland vertical deformations between them is derived under thelinear elastic conditions. The formula of the pile-soil stress ratio atthe yield point of the pile is obtained. Meantime the ultimate bearing capacityof the gravel piles is derived under the ultimate equilibrium state.It is shown that the reinforcement by the gravel piles in the weakground is significant. But for the ground deformationmodulus over 8MPa, the reinforcement is not significant.At last the results in this paper are compared with the testin an engineering example.