Geotechnical engineering reports are a tool-document that contain information on the application of scientific methods and engineering principles to the acquisition, interpretation and use of knowledge of soils and rocks to the solution of engineering problems.
The extent and the nature of the information supplied in a report could vary from the raw geotechnical data to the detailed foundation design which may use interpreted and processed data. Geotechnical reports often form the basis for other engineers (either Ministry or Consultants) to carry out design work. Geotechnical reports may also be used for outlining ground conditions for contractors. While some agencies provide geotechnical data reports only for reference, not part of the contract documents, other agencies include geotechnical interpretive reports and geotechnical design summary reports as part of the contract documents. Some project owners believe that presenting all available geotechnical information pertaining to the site in a clearly written comprehensive report, helps the project owner in obtaining a realistic bid and reduce contingencies. There are also project owners who fear that the reports may be used by contractors as a vehicle for claims.
Apart from the contractual concerns, the composition of a geotechnical report is also important from the quality management point of view. Any geotechnical report whether it is dealing with terrain evaluation, site investigation, route design investigation, foundation design, cut or fill (soil or rock) slope stability, contaminated site investigations, terrain evaluation, geological hazard evaluations, material source suitability, or pavement design, should contain the following generic format
Generic Format for preliminary or final geotechnical reports:
Table of Contents Executive Summary. Brief to the point summary not exceeding one page of findings and design recommendations
References. Outline terms of reference and scope, identify requesting source. Find out geotechnical requirements from the project manager, structural engineer or the geometric designer at the beginning of the assignment and keep track of changing requirements thus terms of reference.
Background information/ review of existing data. Provide site description. Describe, topography and geology (in terms of engineering significance and engineering properties), seismic ground motion data, lab data, groundwater and drainage information. Provide location map, National Topographic Series 1:50,000 map reference, e.g. 92B/12, Longitude and Latitude, Universal Transverse Mercator coordinates if possible. Provide plan profile where applicable, site history if available.
Site investigation. Describe what is needed in light of existing information, provide specific rationale for the scope and methods of site investigation to make it possible for reviewers to assess the adequacy of the investigation. Describe what was carried out. Show location of testholes or pits or geophysical lines if any. Present field test results using Ministry format (see E-Mail Attachments for sample borehole logs androck core logs). Include field observations at the site, soils and existing conditions.
Laboratory testing. List the tests done and present the results using Ministry format.
Evaluation and analysis. Discussion of the site investigation and laboratory test results and their implications on the proposed facility or the stability of the site investigated. The seismic assessment should be provided. Describe analyses performed, assumptions, parameters and methods used (use two methods for analyzing slope stability or calculating bearing capacities where practical). Provide foundation or slope design information in terms of both static and dynamic (seismic) design if required and state what safety factors are in place. Provide anticipated range of settlement for foundations and fills and FoS of fill. Apply your field observation of the site conditions and existing foundations if any, on your choice of foundation type. Sand and Gravel Sources/ Disposal Areas. Provide legal description, status (Crown, lease, etc.). Describe potential sand and gravel sources, tested or estimated material properties and projected quantities. Describe investigation methodology. Provide recommendations on waste or surplus material disposal areas.
Design Recommendations , including the Design of Pavement Structures. Point out possible foundation and construction difficulties, effects on the existing adjacent structures and suggest methods of overcoming these difficulties, recommend the preferred type of foundation, describe why and suggest possible alternatives (value engineering) where possible. Refer to findings of field investigation, lab test findings and analyses results. Point out that the geotechnical engineer should be given appropriate opportunity to review the geotechnical aspects of the completed design prior to construction. Discusspredicted effects of the recommended work on the environment (water quality, etc.). Provide recommendations on mitigation measures. Provide specifications and special provisions for construction contract. Provide cost estimates for the recommended work.
Literature References Provide a list of references used in the preparation of the report.
Appendices: Correspondence Soils & rock core logs (make sure standard disclaimers are included with the logs in contract drawings), test hole location plan, design profile for new roads, pit development plan, drawings, plan & profile, photos.
A geotechnical report may include involve a project included in the following table:
IDGeotechnical report subject:
Settlement of structures and roads.
Load capacity of piles and footings.
Levees, design of earth and concrete dams.
Earth retention structures, gravity walls, deep excavations.
Soil nailing walls, mechanically stabilized earth.
Slope stability and landslide problems.
Ground water cutoff, environmental cutoff barriers.
Geotextiles and geomembranes.
Tunnels and underground caverns.
Geotechnical seismic risks.
Each type of geotechnical construction has its own design and investigation requirements. Experience plays a major role in adopting the most efficient geotechnical design. A good geotechnical design will identify issues and will offer alternatives if unexpected conditions are encountered.
Deep Excavation LLC provides competitive geotechnical engineering services for any sized project. We are licensed in the US and in Europe. Through our associate network we can extend our services all around the world to meet your needs.
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