Let us suppose that soil in a given area is to be tested (such as the area on which a structure is to be erected). The officer in charge of soil exploration decides how many points are needed and where they must be located to produce a representative test of the soil in the area. This information is recorded in a sketch like the one shown in figure 15-3.

This figure shows the locations of exploratory points along a highway, the point locations referenced by the center-line station and the distance from the center line. To the left of the center line, between stations 2 + 80 and 4 + 60, there is a borrow pit, from which soil for fill is taken. The soil here is tested by samples taken from a 60-ft trench (T1), located at station 3 + 20, 300 ft from the highway center line; from two borings (B1 and B2) at stations 3 + 60 and 3 + 80, 230 ft and 420 ft from the center line, respectively; and from a 20-ft- square pit (P2) at station 4 + 20, 300 ft from the center line.

Besides the borrow pit exploration, there is a boring (B3) at station 4 + 80, 125 ft to the right of the center line; another boring (B4) at station 6 + 00, 100 ft to the left of the center line; and a 20-ft-square pit (P3) on the center line at station 7 + 20.

Each sample taken is tagged according to the location from which it was taken. Locations are given in consecutive numbers; for those shown in figure 15-3, the numbers might run from the bottom up, with T1 being No. 1; B 1, No. 2; and so on. A sample is tagged with the project symbol (the symbol for the project shown in fig. 15-3 is BF) and the location symbol (such as T1 or B1). If more than one sample is taken from the same location, you need to use additional numbers. For example, a sample taken from B2 in figure 15-3 maybe tagged BF-B2-4, "boring No. 2, location No. 4, the first of 6 bag 1 of 6." This means taken from that location."

The sample identification is printed with a marking pencil or pen on two tags, one of which is placed inside the bag, and the other of which is tied on the outside. Gummed labels may be similarly used to identify samples that are placed in moisture content boxes, cylinders, or jars.

Samples taken by hand scoops, auger borings, shovels, or any other convenient hand tool with no attempt to obtain the material in its natural state of structure or density is known as a DISTURBED sample. These samples are used for mechanical analysis, plasticity, specific gravity, frost susceptibility, compaction, and laboratory compacted CBR tests. The size of the sample taken will depend upon the tests to be performed.

When taking individual samples from a pit, trench, or exposed face (fig. 15-4), first shave off loose and dried soil to obtain a fresh surface and to expose any soil variations clearly. Then take a typical sample of each type of soil or of those requiring additional investigation. When sampling in auger holes, place typical portions of the soil obtained

along a row in correct order, as shown in figure 15-5.