SAGITAIRE: An Artificial Intelligence Software Dedicated to the Geotechnical Engineering of Offshore Structures
Authors: Vergobbi Pierre , Puech Alain , Ferrer Gilles 
Published: October 2008

ABSTRACT
SAGITAIRE is an artificial intelligence software specifically developed to pezform in an integrated environment the complete chain of operations related to offshore foundation designs, from the acquisition of site investigation data to the design of pile foundations. The paper outlines the main advantages of the computer-aided design system, presents the architecture of the program and describes how the dataflow is managed and controlled during the elaboration of a geotechnical project.

1. INTRODUCTION
Geotechnical engineering calls to a large extend upon the individual experience of skilled engineers and is certainly less computerized than other engineering fields. This is mainly because the soil is a complex, multiphasic, heterogeneous natural material and also because soil mechanics is a rather young science.
In the particular case of foundation engineering of offshore jacket platforms the need for developing efficient and rational dimensioning tools has progressively emerged. The context is relatively favorable : an important flow of data has to be managed in a very short time, soil investigation techniques are practically standardized and dimensioning procedures are similar worldwide.
The availability of efficient computer-based techniques and expert systems, the improved capabilities of graphic and database management tools and the recent hardware developments have opened the door to a more comprehensive, rational and efficient application of computers in the geotechnical process. An artificial intelligence software, named SAGITAIRE, has been developed in order to assist, in an integrated user-friendly environment, the geotechnical engineer in the complete chain of operations related to offshore foundation designs.
This paper focuses on:some specific aspects of the offshore geotechnical practice;the objectives and general architecture of the software;the interest and applications of a computer-aided system in offshore geotechnics. It is particularly demonstrated how human errors and non rational choices can be avoided and quality control can be provided efficiently at any stage of the project;the detailed description of the software: description of the various databases; procedures used to interprete geotechnical data, derive boring logs and design parameters; methods introduced for the design of pile foundations; provision of typical documents and drawings;the possible further developments.

2. OFFSHORE GEOTECHNICAL PRACTICE
The engineering of offshore jacket platform foundations is characterized by four successive and complementary steps:site investigation and associated laboratory testing,interpretation of soil data and construction of boring logs,assessment of synthetic soil profiles and design soil parameters,foundation design computations.

Site investigation and laboratory testing
The techniques and tools used to perform offshore soil investigations are practically standardized: wire-line operated equipments, push or hammer sampling depending to soil conditions, quasi exclusive use of the cone penetrometer (cpt) as in-situ measurement technique. As the number of geotechnical contractors involved in offshore soil investigation is very limited, the procedures applied and the equipments used are quasi normalized and well controlled.