Pile foundations are frequently used in the construction of bridges, offshore platforms, and offshore wind turbines, which are often subjected to complex lateral cyclic loading from wind, wave, or current. These lateral loads usually come from different directions or constantly change their direction, which is ignored by most existing calculation models. A two-dimensional p -y model is proposed in this study for the lateral response of the pile subjected to multi-directional cyclic loading in sand. Without introducing additional parameters, the p -y response in two dimensions is coupled by developing the model within the framework of the bounding surface p -y model. Combined with the collapse and recompression model, the effect of sand collapse around the pile during cyclic loading is considered to approach reality. The pile lateral displacement and soil resistance are obtained in incremental form using the finite difference method in the two-dimensional case. By comparing with the model test results, it is demonstrated that the proposed model is able to reasonably predict the lateral cyclic response of the pile as well as the effects of multi-directional cyclic loading. The distribution and variation characteristics of the soil resistance are further discussed by analyzing the results calculated by the proposed model.

Pile foundations supporting wind turbines and offshore platforms are always subjected to asymmetric lateral cyclic loads from wind and waves. To calculate the lateral response of the pile in sand under asymmetric cyclic loading, this paper proposes a p- y curve model to deal with different levels of load reversal. According to the state of the soil around the pile under asymmetric cyclic loading, the scaling factor of the reloading curve is modified. The soil collapse-recompression model is also extended to apply to different cases of asymmetric cyclic loading according to the characteristics of soil convection during asymmetric cyclic loading. By modifying the shape and position of the p- y curves to different degrees, the lateral response of the pile under asymmetric cyclic loading can be obtained in combination with the improved finite difference method. The validity of the proposed model is demonstrated by comparing the results with the centrifuge model tests. Then, the pile displacement accumulation, the variation of the bending moment, and the soil resistance under asymmetric cyclic loading, are further discussed.

This study puts forward a reliability analysis for the bearing performance of piles subjected to the coupled action of chloride corrosion and scouring. A chloride diffusion model was constructed based on the stiffness degradation factor and Fick's law. The Monte Carlo simulation method, along with the consideration of the scouring effect of water flow on the pile foundation, was employed to assess the impact of key factors on the failure probability, considering both the bending moment and lateral displacement damage criteria. The results show that for the same exposure period, the failure probability increases as the bending moment, lateral and vertical loads, and seawater velocity increase; furthermore for the same conditions, the failure probability increases with longer exposure times. According to a particular case study, the mean bending moment, mean lateral and vertical loads, and seawater velocity all have an impact on the lateral displacement failure criterion, making it more sensitive than the bending moment failure criterion.

The paper introduces a semi-analytical approach for predicting the pile-soil response under cyclic lateral loads in sands, incorporating the cavity expansion/contraction theory with an anisotropy and non-associated constitutive model, Simple ANIsotropic SAND (SANISAND). The pile hole is regarded as a cylindrical cavity, and the cyclic loading process is reasonably treated as a cavity expansion/contraction problem. A superposition principle is introduced to determine the superimposed stress states around the cavity. The geometric relationship, quasistatic equation, and boundary conditions are integrated into a standardized solving procedure to obtain the stress-strain distribution surrounding the pile. Subsequently, the derived cyclic p-y curve is used in conjunction with the deflection equilibrium differential equation and finite-difference method to determine the pile-soil response under lateral cyclic load. The method's validity and capacity are further demonstrated through two well-examined centrifuge tests, which shows a good agreement with the experimental data. The cumulative deformation, hardening and ratcheting behaviors of pile-soil system can be captured in this study, which provides a novel approach to figure out the pile-soil response in sands under cyclic lateral loads.

Dynamic response of soil-pile system in liquefiable layered sloping ground under the effect of static axial load as well as ground motions simultaneously is an issue of utmost importance. The present study is performed using an advanced nonlinear finite element-based 3D numerical model for filling up this research gap. Two typical soil profiles of Kolkata city such as Normal Kolkata Deposit and River Channel Deposit (RCD) have been chosen for this study. The input motions considered for present analysis are 1940 Imperial Valley and 2001 Bhuj earthquakes. Multi-yield surface plasticity model is adopted to incorporate soil nonlinearity. Fully coupled u-p formulation is used to simulate pore water pressure generation because of soil-fluid interaction. The applicability of the present numerical model is verified using the past experimental works. Then, parametric study has been conducted to evaluate the effect of different vital parameters on dynamic response of soil-pile system. It is observed that the residual soil displacement in RCD soil increases with an increase in ground slopes indicating liquefaction-induced lateral spreading. Parametric studies also showed that the amplification factors of bending moment for sloping ground with respect to level ground due kinematic and combined loading are 3.50, 5.50, 6.75 and 1.09, 1.13, 1.18 for 2.5-, 5.0- and 10.0-degree ground slopes, respectively. The combined peak lateral displacement and bending moment coefficient decrease by 62.60% and 44.20%, respectively, when slenderness ratio decreases from 42 to 21. Also, the peak combined lateral displacement decreases by 48.7% and combined bending moment coefficient increases by 14.3% when soil condition changes from liquefiable state to dry condition. Finally, bending-buckling interaction diagram is presented for safe and economical designing of piles in liquefiable sloping ground under combined loading condition.