What test is routinely used for estimating the relative density and friction angle of sand?

The Standard Penetration Test (SPT) is routinely employed in geotechnical engineering to obtain information on the relative density and friction angle of sand. During this test, a sampler is driven into the ground at the bottom of a borehole using a hammer. The number of blows required to drive the sampler a set distance (typically 18 inches) is recorded. This number of blows, known as the SPT N-value, provides insights into the density of the soil.

In sandy soils, a higher N-value indicates a denser, more compact state, which can correspond to a greater friction angle. This is crucial for engineering purposes, such as foundation design, where the behavior of sand under load must be fully understood. The SPT is advantageous in its simplicity and the ability to be performed on-site, providing quick and relatively inexpensive estimations of soil properties.

The other options listed serve different purposes: the CBR (California Bearing Ratio) is primarily used for evaluating subgrade strength for pavement design; Atterberg limits assess the plasticity and behavior of fine-grained soils rather than sands; and the Proctor test focuses on determining the optimal moisture content for soil compaction, which does not directly relate to the friction angle or relative