What type of soils is the sand cone method not suitable for?

The sand cone method is used for determining the in-place density of soils, which is essential for various construction and engineering applications. However, this method has limitations regarding the types of soils for which it can be effectively used.

Organic, saturated, and highly plastic soils can cause unpredictable results when using the sand cone method. These soils often exhibit compressibility and variability in moisture content, which can lead to inaccurate density readings and an inability to achieve reliable compaction testing.

In granular materials, while the sand cone method can be suitable, it is important to note that certain conditions, such as the presence of very fine particles or excessive moisture, may hinder accurate density results.

Soils containing appreciable amounts of material larger than 1.5 inches also pose a challenge for the sand cone method. The physical obstruction caused by larger particles prevents the accurate flow of sand in the device, making it difficult to measure the volume correctly.

Considering all these factors, the sand cone method is not appropriate for use on organic, saturated, highly plastic soils, granular materials under specific conditions, and soils with large particle sizes. Thus, the choice that encompasses all these limitations is valid.