Evaluation of a geotechnical compaction model to estimate sediment deformation

A geoarchaeological and pedoarchaeological approach to compaction disturbance is necessary for successful archaeological interpretation of potentially compacted deposits. When surface ruts from vehicle activity occur above archaeological deposits, there is a potential for impact to the archaeological record to occur. While impacts to the soil surface are relatively straightforward to describe, sub‐surface disturbances are more difficult to quantify. Compaction disturbances to buried archaeological deposits can impact the superposition of artefacts, buried soil horizons, and stratigraphy across space, and make interpretation difficult or impossible. Deposits can be damaged by both movement through surface disturbances, and by translocation from compaction events. It is important to consider and take both impact types into account. Here, we present a geotechnical compaction model that can be used to assist with sub‐surface characterization under vehicle ruts formed during off‐road travel. The model is based on a Boussinesq analysis of stress increase below a surface load. The change in bulk density resulting from compaction is assumed to be proportional to the stress increase. The model results were compared against pilot‐scale tests conducted with homogeneous sediment and field‐scale in situ tests. The results indicate that the model generally agreed with measurements to within 20%, although only a single soil type was evaluated in these studies, with a narrow range of initial bulk densities and rut depths. While application of the model across a broader matrix of soil types, bulk densities and rut depths would increase confidence in the model, it appears that the model may be suitable for use in archaeological field investigations. Potential uses include both compliance and research‐based field applications.