Recommended Practice for Geotechnical Explorations and Reports
By Ron Kelm
PREFACE
This document has been developed by a group of Structural Engineers in southeast Texas with the goal to attain the geotechnical information they believe is necessary to adequately perform their structural designs. Their need for this document has been prompted by a large number of residential and light commercial foundation problems, some of which have been the subject of litigation. As a result, this document has been prepared specifically for the Structural Engineers’ use. However, it is made freely available to the public through the Foundation Performance Association at www.foundationperformance.org so others may have access to the information and may adapt it to their work as they see fit. To ensure the document remains as current as possible, it is intended to be periodically updated under the same document number but with new revision numbers.
This document is a recommended practice only and is therefore intended to be neither comprehensive nor a substitute for engineering judgment or for local or standard codes and practices. The user should recognize that there is always the possibility this recommended practice might not be fully adaptable to the site being investigated and in those cases, the use of engineering judgment will be paramount. The intent of this document is to detail certain minimum requirements recommended for the geotechnical exploration and report, thereby ensuring that the Structural Engineer receives the information needed to perform an adequate foundation design. Thus, Geotechnical Engineers preparing proposals for a geotechnical exploration and report in accordance
with this recommended practice must all follow certain minimum proposal requirements, which can help ensure a more uniform selection process during the procurement of their services. In requiring the use of this recommended practice, the participating Structural Engineers understand that the request for the information specified herein would most likely increase the cost of the geotechnical work, since there is no intent to delete any of the work currently being executed in the geotechnical industry. However, they should also realize that this additional cost is necessary in order for them to better understand the soil characteristics of the site on which they plan to design a foundation.
When using this recommended practice, it is expected that the Client will provide a description of the foundations and structures proposed for the site. In addition, the Client should provide site plans that show the foundation outline(s), the foundation location(s), and the location and species of any trees that are planned to be removed and that have trunk diameters equal to or greater than 6 inches. If the lots are Wooded Lots, it is intended that the Client will provide a tree survey to the Geotechnical Engineer, showing the location, sizes, species and condition of the trees on each lot. The Client should not discount this requirement as something less than a necessity. Though not recognized locally to be a problem as recently as ten years ago, trees in this area are now known or at least suspected to be the main contributor in the majority of foundation problems in the local market. Therefore the recommendations addressing trees should not be taken lightly. This recommended practice addresses a geotechnical report prepared specifically for foundation design and construction. In new subdivisions, the type of geotechnical report that addresses the streets and utilities is not acceptable as a substitute for the work specified herein. Preferably, the borings for a new subdivision should be taken after the streets are cut and the lot’s fill is compacted. If however, the geotechnical exploration is made before the streets are cut, then it is the intent of this recommended practice that a separate exploration will later be procured in order to verify the required density, moisture content, and Atterberg limits for the fill material. This recommended practice is written specifically for use in Houston and the general southeast area of Texas. Therefore, it should be used with caution if utilized elsewhere or if adapted for foundations other than those supporting residential or light commercial structures. The main purpose of this recommended practice is to bring certain minimum requirements together into one document for local Structural Engineers to use in part or in whole, as they see fit. It is not meant to imply that problems will not occur if geotechnical explorations and reports comply in part or in whole with this recommended practice. The Foundation Performance Association and its
members make no warranty regarding the recommendations contained herein and will not be liable for any damages, including consequential damages resulting from the use of this document.