## 1 Introduction
[PERSON] [11] proposed a formula that integrates the boundary element method and finite element method for analyzing the interaction between piles and soil under horizontal loading. The formula was validated through analysis of a single pile case. [PERSON] [12] employed numerical simulation to investigate the lateral displacement of pile foundations under surcharge loading, identifying variations in the impact of different factors. [PERSON] [13], after modifying and improving the conventional strain wedge method, eliminated the need for a constant multiplier. The lateral behavior of piles and p-y curves can be predicted solely based on the pile inclination, soil properties, and pile-soil interaction. [PERSON] [14] revised the conventional strain wedge model, incorporating both the upper soil wedge and lower strain wedge, making it applicable for the analysis of piles under lateral loads on slopes. This expansion broadened the scope of applicability of previous strain wedge models. [PERSON] [15] conducted long-term monitoring of bridge structures and employed numerical simulation to study the impact of steep slopes on the stress and deformation of bridge piles. [PERSON] [16] designed model tests for rock-socketed piles subjected to axial and inclined tension. The uplift resistance of the piles significantly decreased under inclined loading compared to vertical uplift. [PERSON] [17], through model experiments, investigated the influence of slope angle, pile location, and load on the vertical bearing characteristics of bridge piles. Under the influence of surrounding soil surcharge, the damage to bridge pile foundations directly impacts the safety of both the bridge itself and the surrounding slopes or other facilities. Research on safety control measures primarily focuses on two aspects: support for the slopes and reinforcement of the bridge pile foundations. In terms of slope support, [PERSON] [18] devised vibration table tests for slope-bridge pile reinforcement using front and rear rows of anti-slide piles. Loading with varying peak EI Centeo waves revealed that the front row of anti-slide piles had an adverse effect on bridge pile deformation, while the rear row of anti-sliding piles played a seismic reinforcement role. In terms of bridge pile reinforcement, [PERSON] [19] implemented pile repair measures on both sides of piles eroded by water flow. The reinforcement was found to meet the load-bearing requirements and stabilize under strong seismic conditions. [PERSON] [20] initially removed the additional loads causing tilting and then employed lateral pushing methods to correct the displacement of some bridge piers and expansion joints that exceeded displacement limits. [PERSON] [21], based on bridge pier displacement monitoring and subgrade settlement observation data, established a relationship curve between pier displacement and settlement. The recommendation was made to unload piers with rapid displacement development, but analysis of the pile displacement mechanism was not provided. Previous studies have provided comprehensive analyses of the force distribution in bridge pile foundations. However, there is a paucity of research on the practical engineering aspects of constructing new piles on abandoned dreg body. This study, conducted in conjunction with a highway reconstruction and expansion project in South China, employs numerical simulation to investigate the stability of the original abandoned dreg body. This study also explores the influence of residue on the mechanical behavior of bridge pile foundations and addresses strategies for the prevention and mitigation of potential hazards. This paper aims to serve as a practical reference for similar abandoned dregs engineering projects during the construction phase.