Abstract: A soft soil foundation treated with plastic drainage boards and cement-soil mixing piles prior to subgrade stacking may negatively affect neighboring pipelines. ABAQUS finite element software is employed to simulate the construction process and analyze its impact on the pipelines. Based on the analysis, pipeline protection measures are proposed and demonstrated feasible through field measurements. Additionally, the deformation of pipelines at various distances from the slope toe and corresponding suitable protection measures are examined. Results indicate that after soft soil treatment, the impact range of roadbed construction reaches 40 m. Protective piles shall be installed near the pipelines, and the effects of pile construction shall be considered simultaneously. The following protective measures are suggested based on the distance (L) between the pipeline and the slope toe: for 5 m≤L<10 m, plain concrete pile with variable section should be placed 2 m from the slope toe; for 10 m≤L<15 m, plain concrete long piles should be positioned 6 m from the slope toe; for 15 m≤L<20 m, plain concrete long piles should be placed 12 m from the slope toe; for 20 m≤L<25 m, variable-section cement-soil piles should be installed 16 m from the slope toe; for 25 m≤L<30 m, long cement-soil piles should be utilized 22 m from the slope; toe; for 30 m≤L<35 m, long cement-soil piles should be placed 27 m from the slope toe; for 35 m≤L＜40 m, back pressure protection road measures should be implemented simultaneously with subgrade piling; for L≥40 m, pipelines are in a safe state, requiring only enhanced monitoring.

Key words: soft soil subgrade, plastic drainage board, pipeline, numerical simulation, protection measures