Experimental and numerical study on the effective length coefficient of pile legs under lateral soil resistance

• The axial compressed experiments are conducted to study the buckling behavior of the partially embedded slender rod under soil-structure interaction. • A segmented soil spring stiffness model is proposed to comprehensively consider the soil resistance effect. • The effect of embedded depth, soil characteristics and flexural stiffness on effective length coefficient are analyzed. • A simplified calculation method for effective length coefficient is proposed. Soil-structure interaction significantly affects the buckling behavior of partially embedded piles. This paper conducts the axial compressed experiments to investigate the effect of soil-structure interaction on the buckling behavior of pile. The results demonstrate that soil-provided lateral restraint effectively enhances the buckling resistance capacity of pile. Based on experimental results, a segmented soil spring stiffness model is proposed to quantify the soil resistance under different soil characteristics. By using the segmented model, the numerical simulations are employed to study the effective length coefficient (ELC) of pile with different coverage depth ratio (CDR), soil characteristics, and flexural stiffness. Results shows that ELCs decrease with the increase of CDR and soil resistance ratio factor (SRF). An apparent transition of buckling mode of pile occurs at the critical boundary where CDR is 0.15 or SRF is 20 MN/m 4 . ELC value will gradually converge when the CDR and SRF exceed this boundary. Conversely, the deterioration of buckling performance is accompanied by the increase of cross-sectional size of pile. Based on the parametric analysis, a simplified method is proposed for the rapid calculation of the ELC by considering the CDR, SRF, and cross-sections size.