Influence of Silt and Clay on the Physical Performance of Sand-Soil Mixtures
- R. W. Whitmyer and
- G. R. Blake
Small variations in component characteristics of materials used for soil mixtures for landscaped areas, such as sportsfields, sometimes result in unpredictable performance. The objective of this research was to determine the effect of variation in the relative amounts of silt and clay in soil mixtures having high sand content on soil physical properties of importance to mixture performance. Soil mixtures having sand contents ranging from 80 to 92% by weight and silt/clay ratios varying from 0.2 to 4.8 were formulated using seven soils. For 28 mixture combinations, determinations were made for shear strength, air-filled porosity, saturated hydraulic conductivity, and hydraulic diffusivity. The extent and texture of particles migrating during saturated water flow were also determined. Sand content was the primary variable determining physical properties of the soil mixtures, the magnitude of measured differences being greater for variations in sand content compared to variations in the silt/clay ratio. Variations in the mixture silt/clay ratio did however result in significant differences in properties. As the silt/clay ratio increased from 0.2 to 4.8 in a soil sample having a sand content of 88%, shear strength decreased from 34 to 20 kPa (at a normal stress of 36 kPa), and air-filled porosity increased from 12 to 24 m3/100 m3 (at a water potential of −2.9kPa). Saturated hydraulic conductivities and the volume of migrating particles increased as the silt/clay ratio increased at a given sand content.
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