SS: New API Codes: Updates, New Suite of Standards RP2GEO: The new API Recommended Practice for Geotechnical Engineering
Authors: Jeanjean Philippe , Watson Phillip Geoffrey , Kolk Harry J. , Lacasse Suzanne 
Published: July 2010

The American Petroleum Institute (API), through the sub-committee on offshore structures, Sub-Committee 2 (SC2) and its Resource Group 7 (RG7) on geotechnical engineering, will soon publish a new recommended practice (RP) on geotechnical engineering, entitled RP 2GEO. This new RP, which covers both shallow foundations and pile foundations, is aligned to the greatest extent possible with the current ISO 19901-4 (for shallow foundations) and ISO 19902 (for pile foundations) standards on shallow foundations and fixed steel structures. The paper describes the key features of this new code and how its compares with existing ISO guidance and with previous guidance in API RP 2A WSD 21st Ed. The philosophy behind the technical changes in this new RP will also be explained. The authors of the papers are all members of RG7 or its ISO equivalent committee, Working Group 10 (TC7/SC7/WG10).

The "lumped" safety factor approach in use in API RP 2A WSD 21st Ed was retained. Key changes were implemented in the shallow foundation section where the Brinch Hansen method was adopted instead of the Vesic approach currently used in API RP 2A. The discussion on shallow foundation with skirts has also been extended. Greater emphasis is put on developing failure interaction diagrams and understanding failure modes. In the deep foundation section, recommendations on cone penetration test based methods for pile design in sands are now provided in the annex. The soil structure interaction curves, so called t-z curves, for sands have also been modified. Because ISO 19901-4 uses a load and material factor approach, and RP 2GEO a lumped safety factor, the two codes cannot compare exactly yet. Care was however taken so that the two codes provide foundations of comparable sizes for a given load.

INTRODUCTION

The API and ISO Structures for Geotechnical Engineering

Recommendations on geotechnical practice in API codes pertaining to offshore structures (i.e. RP 2A, RP 2FPS, RP 2RD, RP 2T, RP 2SK) are prepared and written by the geotechnical Resource Group 7 (RG7) (formally known as RG5). At the time of writing of this paper, this group is composed of fourteen members (five from operating companies operating in the U.S.A, eight from services companies, and one from academia), most of them based in the Houston, TX area. RG7 reports to API Sub-Committee 2 (SC2), the committee on offshore structures, which develops and maintains approximately 30 standards on the planning, design and construction of offshore structures, offshore construction materials, offshore cranes, station keeping and mooring, and non-destructive testing. Any text proposed by RG7 is balloted and approved by SC2.

In the International Standard Organization (ISO) structure, the equivalent group to RG7, is Work Group 10 (WG10) on Foundations, which reports to Sub-Committee 7 (SC7) on offshore structures, which itself reports to Technical Committee 67 (TC67) on materials, equipment and offshore structures for petroleum, petrochemical and natural gas industries. Work Group 10 is formally referred to as TC67/SC7/WG10. WG10 is accountable for the geotechnical content of such codes as ISO 19901-4, ISO 19901-7, ISO 19902, ISO 19904-1. Its membership includes 16 professionals based mainly in Europe, the Middle East, the Far East and Australia.