Generalized Semi-Analytical Solution for Laterally Loaded Pile in Multi-Layered Soils With Transfer Matrix Method

Zhu, Ming-xing (Jiangsu Electric Power Design Institute (JSPDI) Co., Ltd. of China Energy Engineering Group) | Lu, Hong-qian (Jiangsu Electric Power Design Institute (JSPDI) Co., Ltd. of China Energy Engineering Group) | Wang, Lei (Jiangsu Electric Power Design Institute (JSPDI) Co., Ltd. of China Energy Engineering Group) | Gong, Wei-ming (Southeast University)

OnePetro 

ABSTRACT

Determining the response of the laterally loaded piles analytically is one of the challenging problems due to the complexity of soil-pile interaction models and the difficulty to solve governing difference equations. In this paper, a general solution for laterally loaded piles is proposed for multilayered soil systems with any forms of p-y curves. The generalized solution of laterally loaded pile was formulated based on the transfer matrix approach. The elastic and plastic transfer matrix coefficients for pile segment at any depth were analytically obtained through Laplace transformation. Validations of the proposed method are performed through comparison between our predictions with the results from existing methods. Good agreements are reached which implies that the proposed method can be employed as an alternative method to effectively evaluate the response of laterally loaded piles. Moreover, a parametric study on pile bending stiffness is performed to investigate its influence on the ultimate capacity of laterally loaded piles in the same soil profile. We found that these three piles with different bending stiffness would have the same limit state distribution of soil resistance along the pile with the same rotation center below soil surface, which will yield identical ultimate lateral bearing capacity and corresponding maximum bending moment (Mmax) for the piles. Under the concept of the maximum bending moment (Mmax), it would be more rigorous to define a rigid pile when plastic moment Mp along the pile exceeds Mmax and to define a flexible pile when Mp is less than Mmax, especially for piles in multilayered soil deposits.

INTRODUCTION

Piles are extensively used as foundations not only to transfer vertical loads from upper structures to surrounding soils, but also to bear horizontal forces and moments simultaneously. In offshore engineering (e.g., offshore wind turbine and oil production platforms), the piles are mainly designed to resist the lateral loads mainly from the wind to the upper structure, water pressure and seismic activity to the foundation (Basu et al., 2008). The subgrade reaction concept of laterally loaded piles was introduced since the piles behave as Winkler model against lateral loads. To determine the pile responses rigorously is one of the challenging problems due to the complexity of soil-pile interaction and difficulty of solving the governing fourth order differential equation on the basis of subgrade reaction approach.