Pile-soil interaction mechanism and bearing characteristics of roots in uplift process of piles

In order to clarify the load transfer model for root piles and the action law of pile-soil, the uplift bearing capacities of equal section pile, belled pile and root pile are tested.Meantime, the change rules of the bearing capacity under different densities of root are explored through numerical stimulation.The result shows that:(1)The root pile is more suitable under the conditions of complex load and strict requirements for displacement.Moreover, the multi-layer variable cross-section setting of the root pile makes the bearing capacity of material, play a further role and achieves the goal of economic saving.(2)In the test condition, the relationship between the crack rate of soil around piles and the load is exponential distribution.Under the same load, the higher the fissure rate, the lower the bearing capacity.Under the ultimate load, the higher the fissure rate, the more fully the bearing capacity of soil will be exerted.(3)Increasing the density of roots(cross-section area)is beneficial to reducing the earth pressure around the roots and preventing the plastic failure from happening in the original period of the foundation.In generally, the ratio of the roots to the branch cross-section area with the same diameter should be set from 0.1 to 0.3.