1-D Loading of charred particles

1-D Loading of charred particles

Getrouw, N.A.S.

Ngan-Tillard, D.J.M. (mentor)

Civil Engineering and Geosciences

Geoscience & Engineering

Secion Geo-Engineering

2014-02-06

The countries who have signed the Malta convention in 1992 are committed to preserve in situ archeological sites instead of excavating them and wasting them for future generations. Unfortunately there are no tools available to predict the impact of civil engineering constructions on buried archeological sites. This report is focused on the mechanical behavior of charred organic matter. Small charred organic particles (seeds, nut shells or wood fragments) are among the most vulnerable archeological remains that are often investigated in archeological studies. Their study reveals, for example, information on the way of subsidence of former generations or help to determine the degree of conservation of an archeological site. Assemblies of charred particles were subjected, mixed on not with sand to 1D compression tests to understand the influence of void ratio, particle size distribution and the protective function of surrounding soil (sand) on particle damage. To characterize the integrity of the particles during scanning, we scanned a sample at several stages of loading in a micro-CT scanner. We assumed that particles fragmented in small pieces have lost their archeological value since they cannot be recovered during traditional archeological survey by sieving. As we had a limited source of real archeological charred particles, we investigated the possibility of using analogs (processed cereals) in trial mechanical tests. We assessed the resemblance between both materials by comparing their responses to individual crushing tests. We also investigated the possibility to reconstitute mixtures of clay and charcoal with a geotechnical centrifuge. The following conclusions have been drawn. When loading a sample of charcoal particles to 320 kPa in steps of 80 kPa, first rearrangement of the particles takes place. The particles will compact until failure occurs. The deformations of the particles vary from tensile failure, indenting neighboring particles, splitting and crushing of the individual particles. The maximum force which an individual particle can bear is about 0.012N. The analog material tested during this project is weaker than the material of interest so we can conclude that if the analog material can bear a certain force the charcoal will definitely stay intact under such conditions. The different conditions such as void ratio, magnitudes and strength of the particles play an important role in preservation.

1D loading compression charred particles

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Student theses

bachelor thesis

(c) 2014 Getrouw, N. A. S.