Scale Tests to Estimate Penetration Force and Stress State of the Silica Sand in Windfarm Foundations

Jorge Soriano Vicedo,Jorge Luengo Frades,Vicente Negro Valdecantos,Javier García Barba

doi:10.3390/en14185904

Jorge Soriano Vicedo, Jorge Luengo Frades + Show 2 more

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https://doi.org/10.3390/en14185904

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Abstract

The analysis of the soil behavior when the pile is driving into the seabed in offshore wind platforms is one of the major problems associated with this new form of clean energy generation. At present, there are no scaled studies carried out analyzing the mechanical and deformational behavior of both the material of the pile supporting the engine (large steel hollow piles with a diameter of 8 m and a thickness of 15–20 cm) and the soil where the pile is driven. Usually, these elements are installed on sands with a very small grain size displaced from the limits of dry–wet beach (water limit) toward the offshore limits, which prevents them from returning to their previous location in a natural way. This paper presents results obtained from scale tests in a steel pool to analyze the behavior of the sand where the piles were installed. First, the California Bearing Ratio (CBR) test was carried out to estimate the soil behavior in similar conditions to the steel pool. The scale tests consisted of the penetration of the steel tube into the sand using a hydraulic press. The objective was to compare the results for three tubes with different diameters, three different speeds, and two kinds of ending on the extreme of the tested element.

Highlights

The target of this article was to analyze the mechanical and deformational behavior of the soil and study the results from scale tests carried out to estimate penetration force into and stress state of the soil, as well as its application to real driven works for monopile foundation
The monopile foundation covers 81% of the foundation typology of all wind farms installed in the world (Figure 1)
One of the important advantages of this typology is its cost of fabrication, which is cheaper than other typologies such as jackets

Summary

Introduction

The target of this article was to analyze the mechanical and deformational behavior of the soil and study the results from scale tests carried out to estimate penetration force into and stress state of the soil, as well as its application to real driven works for monopile foundation. There are no full-scale trials at sea analyzing the behavior of the seabed, and the trials carried out onshore did not take into account the geotechnical characteristics of the soil being very different to that existing in the seabed This is one of the conditioning factors, along with the several phenomena [3,4]) that lead to monopile foundations being currently oversized to ensure the stability of the structure These structures reach weights of about 600 tons, diameters of 8 m, and thicknesses up to 15 cm [5,6,7,8,9,10,11,12,13]. These structures are driven up to 30 m into the seabed [14]

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