Growth Process and Characteristics of Drying Cracks on the Soil Surface of Yangguanzhai Site Cemetery During Archaeological Excavations

ABSTRACT

The primary challenge for the earthen sites of great historic and scientific value in China is attributed to drying cracks. We investigated 105 exposed partial-cave tombs in the Yangguanzhai Site Cemetery to understand drying cracks’ growth process and characteristics. Real-time monitoring and observations were further conducted toward one specific tomb during archaeological excavation for finer-grain records. Results show that these cracks grew rapidly on the soil surface during the early stage of the excavation and some then transformed to more severe deterioration, such as gullies and collapses. Intriguingly, most drying cracks found on the side surface grew initially from top areas and extended downward vertically and independently. By contrast, their counterparts on the bottom surface were curved and twisted with one another. The changes of the soil properties and water content in soil at different depths suggest that larger porosity and smaller-size soil particles facilitate faster water absorption and evaporation of superficial soil, whereas low rates of water evaporation and soil desiccation on the flat bottom surface slows down the formation of drying cracks. Further investigations and field experiments are the next steps in building complete growth models of drying cracks and fully understanding the underlying mechanism.

KEYWORDS:

• archaeological excavation
• characteristics
• drying cracks
• earthen sites
• growth process

Acknowledgments

We would like to acknowledge the collaboration of graduate students of School of Cultural Heritage of Northwest University for spending their time on observations and tests. We owe our gratitude to the archaeological team of Yangguanzhai Site in Shaanxi Academy of Archaeology for providing us with abundant data on partial-cave tombs. We thank MicroWise System Co., Ltd., in Xi’an, China for the providing us with monitoring sensors and data transmission service. And we would like to express our gratitude to the reviewers for reading this article and giving suggestions.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was funded by the National Key R&D Program of China (Grant Number: 2020YFC1522200), 111 project (D18004), and cooperative project of Northwest University and Shaanxi Academy of Archaeology (name of the project: conservation of cultural relics of Yangguanzhai Site in the process of archaeological excavations).