What is the standard method to test the load-bearing capacity of soil?

The standard method to test the load-bearing capacity of soil involves conducting a Standard Penetration Test (SPT). This test is widely recognized in geotechnical engineering for assessing the strength and behavior of soil under load. During the SPT, a sampler is driven into the ground at the site of interest by a specific weight dropped from a set height. The number of blows required to drive the sampler a certain distance is recorded, providing an indication of the soil's resistance to penetration.

The results from the SPT can be used to estimate the soil's density and can correlate with its shear strength, which is essential for determining how much load the soil can safely support. This method is preferred because it provides direct information about in-situ soil conditions, which are critical for the design of foundations and other load-bearing structures.

While other options like a soil moisture test, visual inspection, or the use of a penetrometer may provide useful insights into soil characteristics, they do not specifically measure load-bearing capacity in the systematic and reliable way that the Standard Penetration Test does. Therefore, the SPT stands out as the most standard and widely accepted method for this purpose.