Experimental Study And Numerical Simulation Of Vertical Foundation Bearing Behavior Of Foot Foundations

With the further development of China's transportation business in recent years,the foundation of the bridge has become more and more important in engineering and the requirements on the foundation have become higher and higher.The long span bridges across the river has always been a problem for bridge design and construction.In this paper,a new type of basic foundation of variable cross section is proposed for the geological conditions of thick overburden,that is root foundation.Due to the lack of further research on the rootstalk arrangement of root foundation today,this paper using physical model tests to conduct relevant research.In this paper,the root foundation in improving the bearing capacity is studied through experimental data and numerical simulation.In this paper,the static load test of three sets of model and each set has three kinds of model pile were carried out to investigate the effect of the number and position of the root on the improvement of the basic bearing capacity,analyzed the axial force values and the lateral friction values of the pile body.Selected part of piles model in the ANSYS and import FLAC3 D to have load calculation,analysis corresponding settlement nephogram,the stress nephogram and rootstalk force values.The first group of model test showed that the root model pile significantly increased the ultimate bearing capacity.The second group proves that the rootstalk arrangement more downward can enhance the ultimate bearing capacity more.The third group verified the arrangement of the bottom rootstalk.Within a certain range,the lower rootstalk arrangement to enhance the ultimate bearing capacity could be similar to that of the five-layer root arrangement.With the increase of load and foundation settlement,the lateral friction resistance of pile body is gradually developed from top to bottom along the pile body.After increasing the rootstalk,the ratio of the lateral resistance of the root foundation to the total carrying capacity increases,and the proportion of the end resistance decreases accordingly.The number and location of rootstalks significantly affect the ultimate bearing capacity of piles.In the numerical simulation,the z-direction settlement curve is basically consistent with the model test.The stress value of the rootstalks showed the force trend and the direction of the bending moment,which agrees well with the experimental phenomena.The nephogram after loading showed the force conditions and stress concentration area under the pressure of vertical load.Three sets of model tests showed that the arrangement of rootstalks can obviously improve the bearing capacity of the pile foundation.The soil between the two layers of rootstalks can be regarded as a whole.The load add the pile mainly consists of the frictional resistance generated by the outer cylindrical surface with the same root diameter,the resistance of the bottom rootstalks and the end resistance of the bottom.The results of numerical simulation basically agreed with the model test data.Based on the results of model test and numerical analysis,it provided references for the field construction of root foundation.