Question

Classify the following soil according to USCS

Although this soil has only 6% nonplastic silty fines, it has everything else! It has gravel content of 78% fine to coarse subrounded to subangular gravel, and 16% fine to coarse subrounded to subangular sand. The maximum size of the subrounded boulders is 500 mm. The uniformity coefficient is 40, while the coefficient of curvature is only 0.8. (After U.S. Dept. of the Interior, 1990.)

Answer 1

Group symbol: GP-GM

Group name: poorly graded gravel with silt and sand.

Step-by-step explanation:

According to the question, the soil has 78% gravel, which means that more than 50% is a coarse fraction, it follows that this soil is gravel, the percentage of fine particles is 6%, in this If the soil is made up of gravel with fine particles between 5% to 12%, those soils are represented by dual symbols. the value of the given coefficient of curvature is equal to 0.8, therefore its symbol is the GP. However, there are two symbols that could represent this type of soil, the GP-GM and GP-GC.

The GP-GM symbol is soil formed by gravel with a low level of silt and the GP-GC symbol is soil formed by gravel with a low level of clay. According to this information, the symbol for the soil in question will be GP-GM.