Experimental Investigation of Remolded Loess Mixed with Different Concentrations of Hydrochloric Acid

Abstract

The vibratory probe compaction method may sometimes fail to proceed smoothly due to the hard layer encountered during treatment of collapsible loess foundation. To this end, high-pressure water jetting around the traveling drill bit was used to soften the soil layer to assist the vibratory probe in sinking. However, due to the shortage of water resources in northwest China, a measure to reduce water consumption and add hydrochloric acid solution was adopted. To clarify the effect of the hydrochloric acid solution on the engineering characteristics of loess, this study conducted a series of geotechnical tests on remolded loess samples mixed with different concentrations of hydrochloric acid solution at the same dry density. The test results showed the pH values of all the sample leachates ranged from 7.83 to 7.64, and they had little effect on the surrounding environment. The coagula generated from the reaction between the acid solution with the original cementing material inside the loess enhanced the cementation between the soil particles and filled the gaps between the particles. The formation of this new structure gave the sample a strong ability to resist collapsing deformation, which was reflected in the acid-added sample having a smaller collapse coefficient than the water-added sample after the last stage of the collapsibility test. However, because the maximum dry density of the mixture increased with the increase of the acid concentration, the degree of compaction of the acid-added sample at the same dry density was insufficient, resulting in considerably bigger and more macro pores than that of water-added sample. It further caused the strength and disintegration characteristics of the sample to deteriorate with the increase of the acid concentration. The application of acid-added loess as a compacted filler is feasible for the construction of the vibratory probe compaction method in the loess area, which provides a new method for the treatment of collapsible loess foundation.