Experimental study on accumulated deformation characteristics of compacted gravelly soil under dynamic loading

Compacted gravelly soil is the primary filling material for runway subgrades of mountainous airports. Dynamic deformation caused by aircraft take-off, landing and taxiing degrades subgrade performance, seriously compromising its serviceability and flight safety, thus experimental research on the dynamic deformation characteristics of compacted gravelly soil is imperative.This study adopts GDS dynamic triaxial test to investigate the effects of cyclic stress ratio (CSR), stress path, water content and drainage conditions on the dynamic accumulated axial strain of compacted gravelly soil. Results show that accumulated axial strain increases with higher CSR, with its curves showing "stable" and "critical" characteristics and no specimen failure. Stress path exerts a significant influence: under the same CSR, two-way vibration yields notably smaller accumulated axial strain than one-way vibration, as the coupling of horizontal and vertical dynamic loads inhibits strain development. Higher water content accelerates the dynamic response of gravelly soil, undermining subgrade stability. Accumulated axial strain under the drain valve closed condition exceeds that under the drain valve open condition, indicating proper drainage can suppress strain accumulation. These findings provide valuable references for the design of mountainous airport runway subgrades.