Keep the number of strata to a minimum. Remember that every small variation in a soil—such as a change in clay from “slightly sandy” to “sandy”—does not necessarily warrant a strata change. The logger must define strata that have significance to designers and contractors who will use the core log information. Designers and contractors are mainly interested in the primary and secondary soil or rock constituent and whether ground water is present.

Use the following charts to determine the density or consistency and hardness of material encountered.

Table 4-1: Soil Density or Consistency

Density (Cohesionless)	Consistency (Cohesive)	TCP Values	Field Identification
Very loose	Very soft	0 to 8	Core (height twice diameter) sags under own weight
Loose	Soft	8 to 20	Core can be pinched or imprinted easily with finger
Slightly compact	Stiff	20 to 40	Core can be imprinted with considerable pressure
Compact	Very stiff	40 to 80	Core can be imprinted only slightly with fingers
Dense	Hard	80 to 5 in./100	Core cannot be imprinted with fingers but can be penetrated with pencil
Very dense	Very hard	0 in. to 5 in./100	Core cannot be penetrated with pencil

Table 4-2: Bedrock Hardness

Mohs’ Hardness Scale	Characteristics	Examples	Hardness	Approximate TCP Values
5.5 to 10	Rock will scratch knife	Sandstone, chert, schist, granite, gneiss, some limestone	Very hard	0 in. to 2 in./100
3 to 5.5	Rock can be scratched with knife blade	Siltstone, shale, iron deposits, most limestone	Hard	1 in. to 5 in./100
1 to 3	Rock can be scratched with fingernail	Gypsum, calcite, evaporites, chalk, some shale	Soft	4 in. to 6 in./100

If any moisture exists, note the extent present. The samples will be assumed dry if the degree of moisture is not indicated. If free water is present, describe the soil as wet or water-bearing.

Describe the primary color, and restrict description to one color. If one main color does not exist in a sample, call it multicolored.

Identify the degree of cementation if any is present.

Use any descriptive adjectives that might further aid in the description.

This soil system is based on the recognition of the type and predominance of the constituents considering grain size, gradation, plasticity index, and liquid limit. It contains three major divisions of soil: coarse-grained, fine-grained, and highly organic. See ASTM D2487, Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System), for the procedure for determining soil classification. TxDOT test procedures, Tex-141-E, and Tex-142-E, may also prove useful in the determination of soil type.

Determine the RQD for rock core samples following ASTM Test Procedure D6032, Standard Test Method for Determining Rock Quality Designation (RQD) of Rock Core. Always note the RQD and percent recovery on logs of borings where rock is encountered.

For uniformity, use the standard log form 513, . Group the materials encountered into strata consisting of the same or similar constituents.