Research On Calculation Method Of Bearing Capacity Of Rifid-pile Composite Foundation On Account Of Pile-soil Interction

Rifid-pile composite foundation is a kind of soil foundation treatment method,which has been widely used in China.The bearing capacity of rifid-pile composite foundation is calculated from the bearing capacity of pile,the efficiency factor of bearing capacity of natural foundation,and bearing capacity of natural foundation.The research on the bearing capacity of rifid-pile composite foundation and the efficiency factor of bearing capacity of natural foundation is not comprehensive in China.The proposed by present of the efficiency factor of bearing capacity of natural foundation in the current composite foundation code are different and wide ranges,bearing capacity of rifid-pile composite foundation.Based on the interaction between pile and soil,the logarithmic spiral sliding surface of the soil between piles appears in the limit state of the rifid-pile composite foundation.The equations for bearing capacity of rifid-pile composite foundation considering the interaction between pile and soil is derived,and on this basis the equations for efficiency factor of bearing capacity of natural foundation is derived.Firstly,the Mohr-Coulomb model and the finite element software ABAQUS were used to simulate the 3D modeling of the rigid-pile composite foundation.The limit state of the rigid-pile composite foundation under vertical load and the shape of the soil sliding surface between the piles are discussed.At the same time,the p-s curve of the rigid-pile composite foundation is obtained by numerical simulation,that is,the ultimate bearing capacity of the rigid-pile composite foundation.In theoretical analysis,according to the numerical simulation results of the rigid-pile composite foundation when it at bearing ultimate state,combined with the working principle of composite foundation,considering the side friction of the interaction between the rigid-pile and the soil between the piles at bearing ultimate state,the equations for bearing capacity of rifid-pile composite foundation is derived,and the equations for bearing capacity of rifid-pile composite foundation is obtained.The orthogonal analysis method and MATLAB software are used to analyze the influence of some influencing factors on the bearing capacity of the composite foundation and the efficiency factor of bearing capacity of natural foundation.The influencing factors are: internal friction angle of soil,cohesion of soil,gravity of soil,width of foundation,pile replacement ratio,etc.The research shows that when internal friction angle is large,the bearing capacity of rifid-pile composite foundation with the increase of the width of foundation,and the opposite occurs when the internal friction angle is small;The efficiency factor of bearing capacity of natural foundation increases with increasing internal friction angle and distance of piles,and decreases with increasing cohesive strength,width of foundation and pile replacement ratio;When the internal friction angle is greater than 0,thelimit bearing depth correction coefficient of rifid-pile composite foundation is greater than 1.0.