Experimental study on wall-protecting mud modification of super-long bored pile in the alluvial plain region of the Yellow River

In this study, the effect of different additives (sodium carbonate, carboxymethyl cellulose, polyacrylamide, and barite powder) on modified mud performance and microstructure has been evaluated and the optimal proportion of the modified mud was determined. The specific gravity, viscosity, sand content, colloid rate, and water loss of modified mud has been investigated. The characteristics of mud cake in microstructure of modified mud have been also analyzed and evaluated by the scanning electron microscopy images (SEM). The results showed that adding bentonite dosage increased the specific gravity, the adding carboxymethyl cellulose increased the viscosity and dropped the water loss rate, and the pH value experienced a growth with the increasing sodium carbonate content. SEM tests revealed the additives made the overall structure of the mud cake more compact and enhanced the modified mud's wall protection effect and filtration loss reduction effect. The modified mud was successfully applied to the super-long pile of a project in the Yellow River alluvial plain area, which provided support for the dynamic adjustment of the mud proportion in the field construction.