AASHTO R 13-12 (2020) PDF

Investigation and identification of subsurface materials and conducting subsurface investigations involve complex techniques that may be accomplished by many different procedures and may be variously interpreted. These studies are frequently site specific and are influenced by geological and geographical settings; by the purpose of the investigation; by the design requirements for the project proposed; and by the background, training, and experience of the investigator.

This standard practice for soil, rock, and groundwater investigation based on standard procedures will provide a more consistent, uniform, and rational methodology for site evaluations. An acceptable and consistent investigation, sampling, testing, and evaluation program will determine subsurface site conditions and thereby provide the information needed to bring about safer and more cost-effective transportation facilities.

This standard practice identifies recognized methods by which soil, rock, and groundwater conditions may be determined. The objective of the investigation should be to identify and locate, both horizontally and vertically, significant soil and rock types and groundwater conditions present within a given site area and to establish the characteristics of the subsurface materials by sampling and in situ testing. Laboratory testing of soil and rock samples is governed by other AASHTO and ASTM standards.