Shear resistance of the interfaces of backfill components in nuclear waste deposition tunnels affected by changes in temperature, water content and salinity

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master_torres salvador_laura_2013.pdf (4.73 MB)

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School of Engineering | Master's thesis
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Date

2013

Department

Rakennustekniikan laitos
Department of Civil Engineering

Major/Subject

Pohjarakennus ja maamekaniikka

Mcode

Rak-50

Degree programme

Language

en

Pages

82

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Abstract

The aim of this project was to study how the interface shear strength of the tunnel backfill materials would be affected by the changes in temperature, ground water salinity and water content During the saturation of the deposition tunnels, the pre-compressed bentonite buffer would swell and generate high swelling pressures in the range of 7 to 15 MPa, Such high swelling pressures can cause upheaval and compression of the tunnel backfill that would eventually decrease the buffer density. Due to various reasons, the saturated buffer density must be kept within a narrow range of 1950 to 2050 kg/m3 at all times. Shear strengths of different tunnel backfill material interfaces become vital in this regard as they provide resistance to the swelling of the buffer. Proposed tunnel backfill materials such as Friedland clay blocks, bentonite pellets and granulated bentonite were used to form block/block, block/pellets and block/granulated bentonite interfaces and subsequently tested for interface shear strength. Tests were carried out using a large and a small direct shear boxes and Mohr Coulomb's shear strength parameters were determined. Material properties such as bulk density, dry density and water content were also determined. It was found that interface shear strength decreases with the temperature and water content. Nevertheless, when water (salty or distilled) is added to the block surface in small quantities, it leads to increased shear strength. The interface shear strength parameters obtained from this study will be used in the detailed modelling of the buffer-backfill interaction of KBS-3V.

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Supervisor

Korkiala-Tanttu, Leena

Thesis advisor

Sinnathamby, Gowthaman

Keywords

KBS-3, bentonite, interface shear strength, temperature, water content, salinity

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https://urn.fi/URN:NBN:fi:aalto-201802221581

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