Question

As the general contractor on the job site, you are responsible for overseeing the excavation and grading of the site. The soil conditions on the site consist of mostly clay. From the choices below, select the answer that is not true concerning the compaction of clay.

A compaction test will only be valid if the clay has the right amount of water.
As water content of the clay increases, the density will also increase.
If clay is too wet to pass a compaction test, drying the clay will probably allow it to pass the test on the second attempt.
Particles of clay slide into place when water acts as a lubricant.

Answer 1

The statement about clay compaction that is not true is that increasing the water content always increases the soil density, as excess water beyond the optimal moisture content will reduce the density. Soil compaction changes the soil composition by reducing pore space and affecting the soil's air and water retention capabilities. Proper moisture management is crucial for successful clay compaction on construction sites.

Step-by-step explanation:

From the choices provided concerning the compaction of clay, the statement that is not true is: "As water content of the clay increases, the density will also increase." This is not true because there is an optimal moisture content at which clay achieves maximum density through compaction. Beyond this optimal moisture content, the presence of excess water actually creates a lubricating effect that prevents soil particles from coming into close contact, thereby reducing density.

Soil compaction on a construction site, particularly with clay soils, can significantly change the soil composition by reducing the volume of pore space, thereby decreasing the soil’s permeability and its ability to retain air and water. This compaction process can sometimes increase the soil's strength and stability, making it more suitable for construction. However, it also means that if the soil is overly compacted, or the moisture content is not ideal, compaction efforts may yield poor results, hence the need for proper testing and conditioning of the soil before compaction.