CHAPTER 16 SOILS: SURVEYING AND EXPLORATION/CLASSIFICATION/FIELD IDENTIFICATION

CHAPTER 16 SOILS: SURVEYING AND EXPLORATION/CLASSIFICATION/FIELD IDENTIFICATION In this chapter you will be introduced to the topics of geological and pedological surveys and will learn about various methods used for this type of surveying. Additionally, you will further your knowledge of soils exploration and you will learn how to classify soils based on their textural and plasticity-compressibility characteristics using the Unified Soils Classification System. Finally, you will learn various field tests that are useful for expedient soil classification. Much of the discussion in this chapter assumes that you are by now knowledgeable of the physical properties of soils and that you are experienced with laboratory testing procedures, such as mechanical analysis and Atterberg limits, that are necessary for accurate identification and classification of soils. Should it be necessary, you may find it helpful to review chapter 15 of the EA3 TRAMAN and chapter 13 in Part 1 of this TRAMAN before beginning your study of this chapter. SURVEY SUPPORT FOR GEOLOGY AND PEDOLOGY In this section you will be provided a brief familiarization with the topics of geological and pedological surveying and mapping. Although these topics could have been included in a separate discussion of topographic surveying, they have been included in this chapter since both are related to soil exploration and investigation. GEOLOGICAL SURVEYS In essence, surveys in support of geology are topographic surveys; however, you must be aware of the other specialized data that may be included as required by the geologist or the soil engineer when you are collecting data for engineering studies for naval construction projects. The end product of most topographic surveys is a topographic map. In geology or other related sciences, the topographic survey is the first part of a series of interrelated surveys. The end product is a map containing not only topographical information but also other specialized data keyed to it. In geologic surveys, a geologist makes systematic observations of the physical characteristics, distribution, geologic age, and structure of the rocks as well as the groundwater and mineral resources that the rocks contain. These observations are expressed in finished form as geologic maps and texts. The objective of the geological survey is to portray, in plan or in cross section, geological data required for subsequent constructions or for other uses. Pure geological data has little direct application to naval problems; however, if the field information is interpreted into specialized lines, it is of considerable use in Naval Construction Force (NCF) planning and operations. NCF requirements may necessitate regional geological study and mapping, surveys of more limited areas, or development of detailed geological data at a construction site. Methods of Geological Surveying Most geological data is gathered from an examination of rocks in the field. In addition, examination of drainage and relief patterns on detailed maps or aerial photographs provides considerable supplementary data on rock structures and distribution. In the field, the geologist conducts his survey by examining the rock. He looks to see if it is exposed at the surface and not covered by soil or other material. At such exposures, called outcrops, he systematically records the physical characteristics of the rock, thickness of exposure, inclination of the rock, inclination of rock bedding, and develop- ment of joints or fractures. In addition, he deter- mines the age of the rock from fossils or the sequence of rock units. Rock investigations are not confined to surface exposures, as the deeper seated rocks are examined by using samples obtained from auger or boreholes. The information gathered by the geolo- gist is placed on a map base by plotting the rock types in color with other data incorporated as symbols 16-1