Understanding how to assess the density of soil in the field is crucial for effective construction, especially in highway projects. One widely employed method for this is the Field Density Test (FDT), specifically using the Sand Cone Method. This article breaks down the process into manageable steps, making it accessible for on-site application.
Compaction plays a vital role in constructing stable sub-base grades and other pavement layers. It enhances stability and reduces settlement in embankments. Ensuring the right moisture content during compaction is essential for achieving the desired dry density.
Different construction layers require specific compaction percentages:
Base Layer: Target compaction – 98%
Sub Base Layer: Target compaction – 98%
Type 1 Layer: Target compaction – 95%
ABC Layer: Target compaction – 100%
Step 1: Weighing the Sand Cone : Begin by weighing the empty sand cone. Fill it with dry sand and reweigh. This establishes the baseline for further calculations.
Step 2: Collecting Soil Sample : Excavate soil from the test hole and measure its weight. Collect a soil specimen to determine its water content.
Step 3: Sand Cone Placement : Place the sand cone on the test hole using the base plate. Open the control valve, allowing the sand to flow. Once it stops, close the valve and weigh the cone with the remaining sand.
Step 4: Calculating Dry Density : Calculate the dry density using the formula:
Dry Density = Wet Density×100%Moisture Content of Soil+100Dry Density / Moisture Content of Soil+100Wet Density×100%
If the test fails, compact the soil and repeat the test.
Volume of the Hole
Volume of the Hole = Mass of Sand in HoleDensity of Used SandVolume of the Hole / Density of Used SandMass of Sand in Hole
Wet Density
Wet Density = Mass of Wet Excavated SoilVolume of HoleWet Density / Volume of HoleMass of Wet Excavated Soil
Degree of Compaction
Degree of Compaction = Dry Density×100%Maximum Dry DensityDegree of Compaction / Maximum Dry DensityDry Density×100%
By following these steps and calculations, construction professionals can ensure effective soil compaction, contributing to the stability and longevity of the constructed infrastructure.
