Model Test Study On Bearing Capacity Of Root Foundation Under Complex Load

Root pile is a new type of pile foundation made by the principle of bionics,which is fully mobilized with the surrounding soil by grafting the root bond to increase its vertical and horizontal bearing efficiency.In view of the in-situ test and numerical simulation of root pile in China,the experimental examples of vertical compressive and horizontal tensile resistance of pile Foundation are few,so it is of great significance to increase the indoor test research on its bearing characteristics.At the present situation of domestic engineering,physical model test was used to carry out relevant research,and its indoor test on vertical compressive and horizontal tensile properties is completed.In the first part,5 kinds of pile types are selected for two groups of indoor tests on the vertical compressive bearing of pile foundation.The two groups of experiments investigated pressure resistant performance from the aspects of root key layer and arrangement position,compared the bearing limits of various types of root piles,and obtained that the arrangement of root key layer would improve the bearing performance of pile foundation,but the effect of changing root key arrangement position on bearing characteristics was not significant enough.At the same time,the paper focuses on the analysis of the axial force of the pile body,the friction resistance of the pile side and the pressure of the pile subsoil,and the root bond bears the partial axial force under the load and affects the friction resistance of the pile side,and makes the pressure diffusion of the pile subsoil more extensive.In the second part,three groups of indoor tests on horizontal tensile bearing characteristics were carried out with 7 kinds of pile types.The first set of experiments shows that the root bond of different layers has different influence on the horizontal bearing characteristics of pile foundation,and it is concluded that the increase of root key layer is not proportional to improve the horizontal bearing efficiency of pile foundation;The second set of tests shows that the optimal horizontal bearing effect of the root key plays out in the upper half of the pile foundation;The third set of tests shows that changing the root key arrangement position of the lower part of the pile Foundation has little effect on the horizontal bearing characteristics of the pile foundation.At the same time,it is concluded that the internal force of pile body changes complex at the root key,and the pressure transfer range of pile side soil is disturbed by the position of root key arrangement.The experimental results provide valuable suggestions for the application andpopularization of root pile in construction.