A method for calculating soil pressure overlying human burials Glenys McGowan, Jonathan Prangnell * School of Social Science, The University of Queensland, Queensland 4072, Australia article info Article history: Received 13 May 2014 Received in revised form 15 September 2014 Accepted 17 September 2014 Available online 6 October 2014 Keywords: Soil Weight Vertical load Taphonomy Burial Exhumation Cemetery abstract While damage to the human skeleton due to vertical pressure exerted by overlying soil is a common observation at archaeological excavations, comparatively few studies have attempted to quantify the magnitude of this pressure. As part of a suite of taphonomic studies of a nineteenth-century cemetery located in Brisbane, Australia, a soil loading calculation equation usually employed in civil engineering is used to calculate soil vertical pressure at various depths for both child and adult graves. This cemetery was characterised by extreme vertical compression of coffin burials to the extent that human remains were sandwiched between the coffin base and lid to a thickness of just a few centimetres. Calculations determined that, because of their narrower grave shafts, the burials of children experienced between 40% (1.83 m depth) and 27% (0.91 m depth) less vertical soil pressure than those of adults buried at similar depths. Further calculations for different soil types showed that coarser grained soils such as gravel and sand exerted less vertical pressure than a similar volume of saturated clay due to the amount of air trapped between the coarser grains. It is anticipated that the equation utilised in this study could find widespread applications in the fields of archaeology, physical anthropology, forensic archaeology and cultural heritage management. © 2014 Elsevier Ltd. All rights reserved. 1. Introduction The potential for vertical soil pressure to contribute to bone degradation was highlighted during a salvage excavation con- ducted at the North Brisbane Burial Ground (NBBG), a nineteenth- century cemetery in the centre of Brisbane, Queensland, Australia. Many of the burials had suffered damage due to extreme vertical compression (Fig. 1). In the majority of these the wooden coffin lid had fallen in and been pressed against the human remains and the coffin base. The sides of the coffins were deformed in response to soil movements, and had lost some of their vertical height, but still remained relatively upright (Fig. 2). Three wooden coffins with lead liners were generally more resistant to compression, with the sides showing inward buckling in response to vertical pressure (Fig. 3). It is estimated that the NBBG received approximately 5000 in- terments between 1843 and 1875, in separate cemeteries according to religious denomination (Rains and Prangnell, 2002). The ceme- teries were each located on dissected slopes of clay developed over phyllite bedrock (McGowan, 2008:197). Generally, bodies were buried in hexagonal wooden coffins covered inside and out with textiles (Prangnell and McGowan, 2013). There is contemporary documentary evidence that some burials were interred at quite shallow depths. In 1875, the Brisbane Courier (5/3/1875:2) reported that children's and adults' graves in the Anglican cemetery were only being dug to a depth of 3 ft (0.91 m), apparently upon in- structions from the Trustees. After its closure, the Burial Ground became overgrown and neglected for a period of 36 years, before being redeveloped into parkland (Prangnell and McGowan, 2013). Low-lying parts were used as a municipal landfill and nightsoil disposal site from 1914 until the early 1960s (Prangnell and McGowan, 2009). Earlier this century, the building of a new sports stadium on the site necessitated the excavation of 397 burials discovered during the preparation of foundations and service trenches (McGowan and Prangnell, 2011). Human remains, coffin wood, textiles and metal artefacts were found to be in a surprisingly poor state of preser- vation after only 160 years of burial, a comparatively brief time span by archaeological standards. By the time of excavation, 6% of coffin wood, 77% of textiles and 22% of metal coffin furniture had completely disappeared from the archaeological record (McGowan, 2008:364). Of the 397 burials excavated 54.2% contained only soil silhouettes, 29.9% contained highly compressed and powdered skeletons, 12.3% contained compressed and fragmented bones (Fig. 1), 3.4% had broken bones in anatomical position and one burial was well preserved with a complete but disarticulated skeleton (Fig. 3). * Corresponding author. Tel.: þ61 733652887. E-mail addresses: g.mcgowan@uq.edu.au (G. McGowan), j.prangnell@uq.edu.au (J. Prangnell). Contents lists available at ScienceDirect Journal of Archaeological Science journal homepage: http://www.elsevier.com/locate/jas http://dx.doi.org/10.1016/j.jas.2014.09.016 0305-4403/© 2014 Elsevier Ltd. All rights reserved. Journal of Archaeological Science 53 (2015) 12e18