Pore Structure, Morphology, and Strength of Self-Compacting Foam Material Backfilled Behind the Underground Pipe-Wall of Yellow River

The backfill material for the underground pipe wall of Yellow River embankment was developed to avoid the high settlement and environmental damage caused by high filling and excavation. The interrelation between microstructure and compressive strength of the self-compacting foam backfill material with different water–binder ratios and density grades was investigated. The results indicated that the average pores size of the foam backfill material increased with increasing the water–binder ratio. Moreover, the compressive strength of the foam backfill material first increased and then decreased with continuously increasing the water–binder ratio. Based on the observation and the analysis of the computed tomography (CT) image, it can be found that the pore size of the foam backfill material decreased with the increment of the density grade. The overall findings demonstrated that the pore size and volume played an important role in affecting the performance of the foam backfill material used for the construction of the underground pipe wall of Yellow River embankment.