<p>Heritage rammed earth represents a unique geomaterial shaped through the interaction of local material sourcing, manual ramming, and long-term environmental processes. Understanding how its microfabric forms and transforms is fundamental to the conservation of earthen heritage. This study investigates 35 representative sites across northwestern China, encompassing five climatic zones and five historical periods from the Han to Qing dynasties. By integrating 3D surface scanning, scanning electron microscopy, and high-resolution paleoclimate reconstruction, the research systematically explores the synergistic mechanisms linking material provenance, ramming techniques, and environmental weathering. Results indicate that the aspect ratio of constituent particles decreases progressively from west to east (approximately 1.54 → 1.42), reflecting a transition from elongated, angular grains derived from proximal alluvial-diluvial sources to rounded, equant particles produced by long-distance fluvial transport. The Compaction Index (CI), derived from 3D roughness, pit area ratio and rhythmicity, shows a consistent negative correlation with structural parameters such as coordination number (<InlineEquation ID="IEq1"> <EquationSource Format="TEX">$C_{{\text{n}}}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>C</mi> <mtext>n</mtext> </msub> </math></EquationSource> </InlineEquation>) and anisotropy coefficient (<InlineEquation ID="IEq2"> <EquationSource Format="TEX">$A_{{\text{c}}}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>A</mi> <mtext>c</mtext> </msub> </math></EquationSource> </InlineEquation>), demonstrating that low-frequency, high-impact ramming promotes denser and more ordered microstructures. Over time, environmental factors become dominant drivers of microfabric evolution: both the frequency of wet-dry alternation (<InlineEquation ID="IEq3"> <EquationSource Format="TEX">$F_{{{\text{dw}}}}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>F</mi> <mtext>dw</mtext> </msub> </math></EquationSource> </InlineEquation>) and the cumulative disturbance intensity (<InlineEquation ID="IEq4"> <EquationSource Format="TEX">$D_{{\text{L}}}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>D</mi> <mtext>L</mtext> </msub> </math></EquationSource> </InlineEquation>) exhibit strong power-law correlations with structural organization, highlighting the long-term role of climatic alternation in promoting microstructural densification and orientation. These findings reveal a threefold mechanism: materials define potential boundaries, ramming techniques determine initial configuration, and environment governs long-term transformation, providing a quantitative framework for interpreting and conserving the structural integrity of heritage rammed earth.</p>

Synergistic mechanisms of material provenance, ramming technique, and environmental factors on the microfabric of heritage rammed earth in northwestern China

期刊论文
发表日期：

2026年4月18日

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Kai Cui,
Chengrui Ge,
Pengfei Xu,
Xiangyu Wen,
Hongke Liu,
Zijuan Dong,
Hua Xia,
Yang Yang

摘要

Heritage rammed earth represents a unique geomaterial shaped through the interaction of local material sourcing, manual ramming, and long-term environmental processes. Understanding how its microfabric forms and transforms is fundamental to the conservation of earthen heritage. This study investigates 35 representative sites across northwestern China, encompassing five climatic zones and five historical periods from the Han to Qing dynasties. By integrating 3D surface scanning, scanning electron microscopy, and high-resolution paleoclimate reconstruction, the research systematically explores the synergistic mechanisms linking material provenance, ramming techniques, and environmental weathering. Results indicate that the aspect ratio of constituent particles decreases progressively from west to east (approximately 1.54 → 1.42), reflecting a transition from elongated, angular grains derived from proximal alluvial-diluvial sources to rounded, equant particles produced by long-distance fluvial transport. The Compaction Index (CI), derived from 3D roughness, pit area ratio and rhythmicity, shows a consistent negative correlation with structural parameters such as coordination number ( $C_{{\text{n}}}$ $C_{n}$ ) and anisotropy coefficient ( $A_{{\text{c}}}$ $A_{c}$ ), demonstrating that low-frequency, high-impact ramming promotes denser and more ordered microstructures. Over time, environmental factors become dominant drivers of microfabric evolution: both the frequency of wet-dry alternation ( $F_{{{\text{dw}}}}$ $F_{dw}$ ) and the cumulative disturbance intensity ( $D_{{\text{L}}}$ $D_{L}$ ) exhibit strong power-law correlations with structural organization, highlighting the long-term role of climatic alternation in promoting microstructural densification and orientation. These findings reveal a threefold mechanism: materials define potential boundaries, ramming techniques determine initial configuration, and environment governs long-term transformation, providing a quantitative framework for interpreting and conserving the structural integrity of heritage rammed earth.