What must be avoided in a soil when using the sand cone method?

In the sand cone method, which is utilized for determining the in-place density of soil, it is critical to avoid oversize fragments within the soil sample being tested. The reason for this lies in the principles of how the sand cone method works.

In essence, the method involves filling a hole excavated in the soil with a specific quantity of sand from a calibrated cone or container. If oversize particles are present, they can prevent the sand from filling the voids effectively and uniformly. This leads to inaccurate measurements of the soil density, as it does not account for the actual volume of the soil that is being tested.

The mixed presence of oversize fragments introduces variability in the test, resulting in a potentially misleading density result which could mistakenly indicate a higher or lower density than what is accurate for the actual soil being assessed. Thus, ensuring the soil sample is free of oversized fragments is fundamental for the reliability and integrity of the density measurements obtained through the sand cone method.