Evaluation Of Offshore Penetration Tests At El Palito Refinery,Venezuela

Abstract

ABSTRACT Data from an offshore study in the western part of Venezuela are presented in terms of the penetration test data and liquefaction evaluation. Two types of penetration test were performed (SPT and DCPT) and the results of each are compared. This was made possible by the comparison testing performed at two different locations where the separation between boreholes with different penetration tests was small enough to allow direct comparison of theresults. To the authors' knowledge, this is the first time that dynamic cone measurements have been made in an offshore environment. Comments in relation to the evaluation of liquefaction resistance based on the results of the offshore penetration testing are made. INTRODUCTION CORPOVEN, S.A. is planning to increase the available berthing and loading facilities at the El Palito Refinery in western Venezuela, approximately 10 kIn west of the city of Puerto Cabello. As part of the preparatory phase for thedesign of the jetty and loading platforms, separate geophysical and geotechnical studies were performed. (The geophysical study was performed by a third party and will not be discussed here.) The geotechnical study was performed by Geohidra Consultores, C.A. with Geocognetics, Inc. as subcontractor for the offshore drilling and testing. The geophysical study provided information for the preliminary siting of the offshore facility and suggested the presence of possible buried reefs, paleochannels and faults within the study area. The subsequent geotechnical borings were performed to verify the geophysical data and provide information for the foundation design of the jetty and loading platforms. The project was defined in two stages. A short term projection for the construction of two loading berths and a longer term option for the construction of a further jetty extension leading to an additional two loading berths. The present soil study was defined in order to provide information for the short term option. The project consists of the following components:access jetty, comprising prefabricated concrete sections founded on either driven steel or concrete piles,access T, between the jetty and platforms built on similar type foundations as the main jetty,loading platforms on which the main installations will be placed.dolphins located at the ends of the loading platforms for berthing and mooring. SCOPE OF GEOTECHNICAL STUDY The original scope of the geotechnical study included the drilling and testing of 13 boreholes along the line of the jetty, platforms and dolphins. Of the 13 borings, 8 were to be performed using standard offshore SPT techniques, while the remaining 5 were to be performed using a dynamic cone testing technique (DCPT). Based on the initial results from the borings at the locationof the short term platform, it became apparent that the soil conditions were somewhat different from those interpreted from the geophysical study, particularly in terms of the absence of the suspected buried coral reefs. The position of the platforms had been initially chosen to be outside the area of the buried reef. The absence of the reef meant that the platform could now be relocated, closer to the shoreline.