ABSTRACT

The results of onshore axial and lateral pile load tests for steel pipe piles drilled and grouted into soft to medium hard calcareous clay stone are presented as well as a description of how these results may be applied to offshore pile design. This paper describes the geological conditions at the test site, the philosophy behind the testing program, the instrumentation and loading system, and the method of performing the tests. Five 0.406 meters (16 in) diameter piles were installed by a drilling and grouting technique matching as closely as possible the offshore procedures. Three were tested in tension and two in compression. Two piles were also tested laterally to high loads into the range of non-linear rock response. Further small diameter axial pile tests were performed to assess the effect of different drilling fluids on the bond strength. The emphasis of the paper is on the field test results and on the application to the offshore foundation design.

INTRODUCTION

Pile tests were performed at a disused quarry, adjacent to the river Ural, and close to the Village of Zamia, Gliipuzcoa, Spain. Geotechnical conditions at this site consisted of medium hard reddish brown calcareous clays tones and are similar to those encountered at offshore locations in the Bay of Biscay, Spain. The tests comprised five axial tests on drilled and grouted steel pipe piles of 0.406 meters diameter (main-piles), being three in tension and two in compression, and nine axial tension tests on piles of 0.118 m diameter (mini-piles). Subsequent to the axial test program, cyclic lateral loading tests were performed on two of the main piles.

The purpose of the tests on the main piles was threefold:

  • to determine the ultimate axial shaft resistance

  • to obtain data on the load transfer characteristics of the piles and

  • to obtain data on the lateral response characteristics of the piles.

The tests on the mini-piles were carried out in order to examine the influence of different drilling fluids on the shaft resistance.

This paper- presents the results of the pile tests and the conclusions derived from the examination and analysis of these data. A detailed engineering analysis of the field data will be presented at a later date.

GEOTECHNICAL CONDITIONS AT TI-E TEST SITE
Soil Borings

Three boreholes (ZU-3, ZU-4 and ZU-5) were drilled at the selected site to determine the soil stratigraphy and obtain samples for laboratory tests. The position of the borings in relation to the site and test pile locations is shown in Figure 1. It can be seen that the test piles were situated near to, and along lines parallel to the line defined by borings ZU-4 and ZU-5 in a NW-SE direction.

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