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Planning Subsurface Investigations

John Huang, Ph.D., PE and John Poullain, PE

This three-hour online course discusses the procedures used for planning subsurface investigations and provides guidelines for site reconnaissance and sources of existing geological and historical data. Also presented are guidelines for determining subsurface information by visual examination during drilling and the basic operations for boring and sampling equipment. The student will gain an understanding of the types of subsurface investigation and requirements for the minimum number of borings and the depths and spacing for boring layouts. Care and accurate identification of subsurface materials are stressed. The AASHTO and ASTM designations for frequently used drilling and sampling equipment and tests are provided.

From the initiation of a project, subsurface investigations progress through phases from the concept to construction and to operation and maintenance. Initially the investigations are general and cover larger areas such as for road studies. As the project develops from planning and concept phases to the plans and specifications for construction investigations become more detailed. It is important to follow established criteria and guidelines in order to select the appropriate drilling methods especially since subsurface exploration is expensive but not nearly as expensive as for a project failure caused by inaccurate or incomplete boring data.

Planning for subsurface investigations can be broken into these basic steps:

a. Historical and Geological Studies. Data is gathered and geological maps, topographical maps, aerial photographs, site histories and adjacent property developments are reviewed. Required proposed construction features are studied for access and to plan investigations. Land use, problems areas, subsoil information, terrain conditions will indicate the necessary subsurface investigations.

b. Site Reconnaissance. Comparisons are made with the existing surface features and topography of the site with the data gathered from prior historical and geological studies. Telltale signs of problem areas, soft terrain, wet areas, outcrops or changes in topography like cut or fill construction will be noted.

c. Subsurface Investigation Requirements. Number of subsurface investigations will depend on available subsurface data, geological data, groundwater variability, adjacent development and the proposed construction. Investigation progresses from generalized to more specific and detailed studies. Conceptual or preliminary subsurface investigations require limited laboratory and sampling work and are used to prepare possible routes or structures layout for evaluation. More detailed subsurface investigations including borings, samplings and testing are performed in order to design the selected route or structure location.

This course includes a multiple-choice quiz at the end, which is designed to enhance the understanding of the course materials.

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NY PE & PLS: You must choose courses that are technical in nature or related to matters of laws and ethics contributing to the health and welfare of the public. NY Board does not accept courses related to office management, risk management, leadership, marketing, accounting, financial planning, real estate, and basic CAD. Specific course topics that are on the borderline and are not acceptable by the NY Board have been noted under the course description on our website.