Characterising chalk-concrete interfaces for offshore renewable energy foundations

TY - GEN

T1 - Characterising chalk-concrete interfaces for offshore renewable energy foundations

AU - Ziogos, A.

AU - Brown, M. J.

AU - Ivanovic, A.

AU - Morgan, N.

PY - 2018

Y1 - 2018

N2 - Deployment of renewable energy foundations, be it piles or gravity based structures, may come into contact with chalk in southern UK waters and in other parts of European offshore and nearshore deployment. To aid more appropriate design it is useful to understand the interface shear strength between the foundation and the underlying rock where this is exposed at surface or where the foundation penetrates. In this paper, the interface shear strength between chalk and unbonded concrete is investigated for constant normal stress conditions over a range of normal stresses using tilt table and specialised interface shear testing apparatus. The results show that the interface strength of chalk is significantly influenced by the normal stress used during testing where at lower stresses the interface strength exceeds the basic friction angle determined for a chalk-chalk interface and degradation of the interface strength below the basic friction angle occurs when normal stresses exceed 73% of the tensile strength of the chalk material. This degradation is more severe at small displacements than previously observed for chalk-steel interfaces. At low normal stresses and displacements, the shear strength of the chalkconcrete interface can be represented by an alpha type approach related to the chalk unconfined compressive strength as previously developed for higher strength rocks.

AB - Deployment of renewable energy foundations, be it piles or gravity based structures, may come into contact with chalk in southern UK waters and in other parts of European offshore and nearshore deployment. To aid more appropriate design it is useful to understand the interface shear strength between the foundation and the underlying rock where this is exposed at surface or where the foundation penetrates. In this paper, the interface shear strength between chalk and unbonded concrete is investigated for constant normal stress conditions over a range of normal stresses using tilt table and specialised interface shear testing apparatus. The results show that the interface strength of chalk is significantly influenced by the normal stress used during testing where at lower stresses the interface strength exceeds the basic friction angle determined for a chalk-chalk interface and degradation of the interface strength below the basic friction angle occurs when normal stresses exceed 73% of the tensile strength of the chalk material. This degradation is more severe at small displacements than previously observed for chalk-steel interfaces. At low normal stresses and displacements, the shear strength of the chalkconcrete interface can be represented by an alpha type approach related to the chalk unconfined compressive strength as previously developed for higher strength rocks.

KW - Chalk

KW - interface

KW - Shear

KW - Renewable energy

KW - marine energy

KW - concrete

UR - https://www.scopus.com/pages/publications/85067663900

U2 - 10.1680/eiccf.64072.521

DO - 10.1680/eiccf.64072.521

M3 - Conference contribution

AN - SCOPUS:85067663900

SN - 9780727764072

SP - 521

EP - 527

BT - Engineering in Chalk

A2 - Lawrence, J. A.

A2 - Preene, M.

A2 - Lawrence, U. L.

A2 - Buckley, R.

PB - ICE Publishing

CY - London

T2 - Engineering in Chalk 2018 International Conference

Y2 - 17 September 2018 through 19 September 2018

ER -