Numerical Analysis Of The Behavior Of Large-diameter Long Pile Under Combined Vertical And Horizontal Loading

In the field of engineering environmental conditions result in pile foundations beingsubjected to combined loads, such as ports, bridges, retaining structures, towering structures andoffshore drilling platform. The conventional design method for pile foundations under combinedloads is based on superposition principle. It only provides reliable solutions to the conditions oflinear elastic deformation. So application range of this simplified method is limited.Theoretical study and model test study are the two main methods used to analyze the bearingcharacteristics of pile under combined vertical and horizontal loading. While the former did notconsider the deformation nonlinearity and continuity of soil; the real stress field could not beeasily simulated in the latter. The antecedent research is mainly focused on the interactionbetween vertical and horizontal loading. However study on the influence of inclination on thebehavior of pile foundations is rare. A failure locus defines the load conditions under whichfailure of pile foundations occur. The proposed failure equations are only based on severalspecial inclinations (30°,45°,60°,etc.). It is interesting to study the overall failure locus.Based on previous researches, bearing characters of large-diameter long pile in clay has beenstudied using software FLAC3D. The main achievements are shown as follow:(1) This paper adopts an algorithm to improve built-in assembly interface constitutive model.The validity of the improved model is verified by comparing the simulation results with twocases.(2) With the gradual increase of inclination, the carrying mode converts from vertical-loaddominated to horizontal-load dominated. When inclination varies in the range of 0°~10°, pilesettlement is not changed significantly. With the increasing of inclination, lateral displacementand maximum banding moment of the pile significantly increase, and end resistance decreases.The maximum resultant lateral soil pressure on the shaft almost increases linearly with theincreasing of the sine value of inclination. The maximum resultant lateral soil pressure in thefront side is influenced more seriously by the inclination than that on the back side.(3) A failure locus is presented for large-diameter long pile foundation, based on thenumerical calculation. The result shows that there is a critical angle of inclination in V-H loadingspace, on which the ultimate vertical and horizontal resistance of the pile foundation dictate thefailure of the pile foundation. Where the inclination angle is less than the critical value, theultimate vertical resistance dictates the failure of the pile foundation. Where the inclination angleis more than the critical value, the ultimate horizontal resistance dictates the failure of the pile foundation. The critical angle is about 20°in this paper. Inclination factor given by Koumotoand semiempirical relationshiop proposed by Meyerhof couldn't estimate the ultimate bearingcapacity accurately in the case of pile under an inclined load at the critical angle. The effect ofloading path on the failure locus is not significant.