Which soil compaction test involves drilling a 1 inch hole 12 inches deep?

The soil compaction test that involves drilling a 1-inch hole to a depth of 12 inches is known as the Nuclear Density Test. This method uses nuclear densitometers to assess the moisture content and density of the soil beneath the surface. The process involves inserting a nuclear source into the drilled hole to measure the density of the soil, which provides immediate feedback regarding the effectiveness of the compaction effort.

In the context of this test, the drilling of a hole is necessary because it allows for the penetration of the nuclear source into the soil, which is essential for accurate measurement. The nuclear density test is highly regarded for its ability to provide quick, in-situ measurements without the need for labor-intensive sampling and laboratory analysis.

Other soil compaction tests, such as the Standard Proctor and Modified Proctor, involve laboratory preparation of soil samples and are based on mechanical means to determine moisture-density relationships, rather than in situ measurements like the nuclear method. The field density test, although related, does not typically involve drilling a hole and instead assesses compaction by calculating the density of compacted soil directly, often using methods such as sand cone tests or balloon tests.