Research on the aggregation phenomena in moraine soil: a new approach to disperse them through a particle size analysis

Abstract

Moraine soils exposed to the moraine landscape surface due to glaciers retreating and global warming have been the subject of interest for researchers. The particle size distribution (PSD) of moraine soils is essential to understanding their engineering properties and soil characteristics. However, the wide aggregation phenomena observed in these soils introduce difficulties in particle size analysis. To overcome this, an experimental group test (EGT) and control groups test (CGT) were designed, which included a series of pretreatment methods to disperse particles, such as grain sieving test, laser diffraction test, microscopic observation, and scanning electron microscope. The tests were performed to record the aggregation phenomena and perform particle size test analysis. The results revealed widespread evidence of aggregation phenomena in each grain group (ranging from < 0.075 mm to 60 mm ~ 40 mm), encapsulated by three basic conceptual models (Core-coating, Core(s)-coat, and Coat-coring) for moraine soil. A new pretreatment method was developed, which involved the addition of 0.5% polycarboxylate in optimal ultrasonic dispersion to disperse aggregation phenomena before the sieving and laser diffraction tests. This method proved to be effective in removing the aggregation phenomena, which significantly impacted on the particle size distribution of moraine soils. The aggregation phenomena caused an overestimation of the content of the gravel group (about 7.91%) and an underestimation of the content of the silt-clay group (about 5.07%). After effectively removing the aggregation phenomena, many samples collected from poorly graded gravelly soils (GP) became silty sand soil (SM) and silty gravel soil (GM). Additionally, the average particle size was reduced by approximately 40%.