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  2025, Vol. 44 Issue (1): 221-235    DOI: 10.3724/1000-6915.jrme.2024.0318
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Study on the gas permeability of unsaturated compacted loess and its underlying micro-mechanism
GE Miaomiao1,2,ZHU Caihui3,SHENG Daichao4,PINEDA Jubert5,LI Ning3
(1. College of Civil Engineering and Architecture,Wenzhou University,Wenzhou,Zhejiang 325035,China;2. Key Laboratory of Engineering and Technology for Soft Soil Foundation and Tideland Reclamation of Zhejiang Province,Wenzhou,Zhejiang 325035,China;3. Institute of Geotechnical Engineering,Xi?an University of Technology,Xi?an,Shaanxi 710048,China;4. School of Civil and Environmental Engineering,University of Technology Sydney,Sydney,NSW 2007,Australia;
5. School of Engineering,The University of Newcastle,Newcastle,NSW 2308,Australia)
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Abstract  Aiming to investigate the gas permeability of unsaturated soil and its underlying micro-mechanism,the gas permeability coefficients of compacted loess under various initial states,along wetting/drying,and constant stress ratio compression paths were examined in this study by utilizing a modified gas permeation device. The Mercury Intrusion Porosimetry(MIP) technique was employed to further examine the microstructure changes of compacted losses,thereby analyzing the micro-mechanism of air permeation. The test results indicate that the gas permeability coefficient(keff) of compacted loess varies within the range of 10-12 to10-15 m2 in response to the increasing compaction saturation degree(Sr0). At low dry densities,keff exhibits an initial rise followed by a decline as Sr0 increases,whereas at high dry densities,a nonlinear decrement is observed. Wetting significantly reduces keff of compacted loess by up to three orders of magnitude,with a rapid decrease after the wetting saturation degree reaches 0.65. Conversely,drying improves gas permeability,but its impact is much less significant than that of wetting. Under constant stress ratio compression,keff decreases exponentially with increasing stress,and the decrease is more pronounced at lower stress ratios. The MIP test results reveal that the macro porosity first increases and then decreases with the increase of Sr0. Wetting has a minor effect on the pore size distribution curve(PSD),while drying can increase macro porosity. Under similar state,the as-compacted soil exhibits more macropore structures compared to the after-wetting soil,while less macropore structures compared to the after-drying soil. The constant stress ratio compression results in a reduction of macropores,with a greater reduction at lower stress ratio. According to the variation of keff,the gas permeability of unsaturated compacted loess depends on the amount of the interconnected macropores,the more macropore structures,the better pore connectivity,and the better gas permeability. A pore structure paramesed,and a micro-scale air permeation model considering the pore structure parameter is established. The applicability of the proposed model is then verified through experimental data.
Key wordssoil mechanics      compacted loess      gas permeability      pore structure      wetting/drying path      air permeation model     
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GE Miaomiao1
2
ZHU Caihui3
SHENG Daichao4
PINEDA Jubert5
LI Ning3
Cite this article:   
GE Miaomiao1,2,ZHU Caihui3, et al. Study on the gas permeability of unsaturated compacted loess and its underlying micro-mechanism[J]. , 2025, 44(1): 221-235.
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https://rockmech.whrsm.ac.cn/EN/10.3724/1000-6915.jrme.2024.0318      OR      https://rockmech.whrsm.ac.cn/EN/Y2025/V44/I1/221
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