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)
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.
葛苗苗1，2，朱才辉3，盛岱超4，PINEDA Jubert5，李 宁3. 非饱和压实黄土渗气特性及细观渗气机制研究[J]. 岩石力学与工程学报, 2025, 44(1): 221-235.
GE Miaomiao1，2，ZHU Caihui3，SHENG Daichao4，PINEDA Jubert5，LI Ning3. Study on the gas permeability of unsaturated compacted loess and its underlying micro-mechanism. , 2025, 44(1): 221-235.
[1] 罗 汀，陈 含，姚仰平，等. 锅盖效应水分迁移规律分析[J]. 工业建筑，2016，46(9)：6–9.(LUO Ting，CHEN Han，YAO Yangping，et al. Analysis of water migration characteristics of pot-cover effect[J]. Industrial Construction，2016，46(9)：6–9.(in Chinese))
[2] 陈云敏. 环境土工基本理论及工程应用[J]. 岩土工程学报，2014，36(1)：1–46.(CHEN Yunmin. A fundamental theory of environmental geotechnics and its application[J]. Chinese Journal of Geotechnical Engineering，2014，36(1)：1–46.(in Chinese))
[3] 魏海云，詹良通，陈云敏. 城市生活垃圾的气体渗透性试验研究[J]. 岩石力学与工程学报，2007，26(7)：1 408–1 415.(WEI Haiyun，ZHAN Liangtong，CHEN Yunmin. Experimental study on the gas permeability of municipal solid waste[J]. Chinese Journal of Rock Mechanics and Engineering，2007，26(7)：1 408–1 415.(in Chinese))
[4] 李明玉，孙文静. 生物炭改性填埋场覆盖层土的渗气特性研究[J]. 岩石力学与工程学报，2022，41(增2)：3 543–3 550.(LI Mingyu，SUN Wenjing. Gas permeability characteristics of biochar-amended landfill cover soil[J]. Chinese Journal of Rock Mechanics and Engineering，2022，41(Supp.2)：3 543–3 550.(in Chinese))
[5] 包 含，尹晓晴，兰恒星，等. 基于微结构量化的含渐变带天然黄土渗透各向异性研究——以延安新区Q1黄土为例[J]. 岩土工程学报，2023，45(4)：730–738.(BAO Han，YIN Xiaoqing，LAN Hengxing，et al. Permeability anisotropy of natural loess with gradation zone：case study of Q1 loess in Yan?an New District[J]. Chinese Journal of Geotechnical Engineering，2023，45(4)：730–738.(in Chinese))
[6] 钱文见，尚岳全，朱森俊，等. 粉质黏土透水性与透气性模型试验研究[J]. 水文地质工程地质，2016，43(5)：94–99.(QIAN Wenjian，SHANG Yuequan，ZHU Senjun，et al. An experimental study of water permeability and air permeability of silty clay[J]. Hydrogeology and Engineering Geology，2016，43(5)：94–99.(in Chinese))
[7] 陈正汉，谢定义，王永胜. 非饱和土的水气运动规律及其工程性质研究[J]. 岩土工程学报，1993，15(3)：9–20.(CHEN Zhenghan，XIE Dingyi，WANG Yongsheng. Experimental studies of laws of fluid motion，suction and pore pressure in unsaturated soil[J]. Chinese Journal of Geotechnical Engineering，1993，15(3)：9–20.(in Chinese))
[8] 张 昭，刘奉银，李荣建，等. 基于持水曲线预测非饱和土相对渗气系数的新方法[J]. 岩土工程学报，2016，38(增2)：280–285.(ZHANG Zhao，LIU Fengyin，LI Rongjian，et al. New approach to predict relative air permeability based on water retention curve for unsaturated soils[J]. Chinese Journal of Geotechnical Engineering，2016，38(Supp.2)：280–285.(in Chinese))
[9] 彭尔兴，孙文博，章定文，等. 非饱和含砂细粒土的气体渗透特性研究[J]. 岩土力学，2016，37(5)：1 301–1 306.(PENG Erxing，SUN Wenbo，ZHANG Dingwen，et al. Air permeability of unsaturated fine sandy soil[J]. Rock and Soil Mechanics，2016，37(5)：1 301–1 306.(in Chinese))
[10] JUCA J F T，MACIEL F J. Air permeability of a compacted soil used in a landfill cover layer[C]// Geotechnical Special Publication. [S. l.]：[s. n.]，2006：1 536–1 546.
[11] 汪 龙，方祥位，申春妮，等. 膨润土–砂混合型缓冲/回填材料渗气规律试验研究[J]. 岩石力学与工程学报，2015，34(增1)：3 381–3 388.(WANG Long，FANG Xiangwei，SHEN Chunni，et al. Experimental study of gas permeability of bentonite-sand mixtures as buffer/backfilling materials[J]. Chinese Journal of Rock Mechanics and Engineering，2015，34(Supp.1)：3 381–3 388.(in Chinese))
[12] 刘奉银，张 昭，周 冬. 湿度和密度双变化条件下的非饱和黄土渗气渗水函数[J]. 岩石力学与工程学报，2010，29(9)：1 907–1 914. (LIU Fengyin，ZHANG Zhao，ZHOU Dong. Density-saturation-dependent air-water permeability function of unsaturated loess[J]. Chinese Journal of Rock Mechanics and Engineering，2010，29(9)：1 907–1 914.(in Chinese))
[13] HE Y，CUI Y J，YE W M，et al. Effects of wetting-drying cycles on the air permeability of compacted Téguline clay[J]. Engineering Geology，2017，228：173–179.
[14] LIU J F，SKOCZYLAS F，TALANDIER J. Air permeability of a compacted bentonite-sand mixture：coupled effects of water content，dry density and confining pressure[J]. Canadian Geotechnical Journal，2015，52：1 159–1 167.
[15] 陈存礼，张登飞，张 洁，等. 等向应力条件下原状Q3黄土的渗气特性研究[J]. 岩土工程学报，2017，39(2)：287–294.(CHEN Cunli，ZHANG Dengfei，ZHANG Jie，et al. Gas permeability of intact Q3 loess under isotropic stresses[J]. Chinese Journal of Geotechnical Engineering，2017，39(2)：287–294.(in Chinese))
[16] CHEN C L，ZHANG D F，ZHANG J. Influence of stress and water content on air permeability of intact loess[J]. Canadian Geotechnical Journal，2017，54(9)：1 221–1 230.
[17] 张登飞，陈存礼，陈 惠，等. 三轴应力条件下原状黄土的渗气特性[J]. 岩土工程学报，2018，40(增1)：93–99.(ZHANG Dengfei，CHEN Cunli，CHEN Hui，et al. Gas permeability of intact loess under traixial stress conditions[J]. Chinese Journal of Geotechnical Engineering，2018，40(Supp.1)：93–99.(in Chinese))
[18] 张登飞，陈存礼，舒迎涛，等. 原状黄土的结构性与渗气特性的关联性初探[J]. 岩土工程学报，2021，43(7)：1 345–1 351.(ZHANG Dengfei，CHEN Cunli，SHU Yingtao，et al. Correlation between structure of intact loess and gas permeability[J]. Chinese Journal of Geotechnical Engineering，2021，43(7)：1 345–1 351.(in Chinese))
[19] 杨 博，张虎元，赵天宇，等. 改性黄土渗透性与孔隙结构的依存关系[J]. 水文地质工程地质，2011，38(6)：96–101.(YANG Bo，ZHANG Huayan，ZHAO Tianyu，et al. Responsibility of permeability of modified loess soil on microstructure[J]. Hydrogeology and Engineering Geology，2011，38(6)：96–101.(in Chinese))
[20] 赵枝艳，张常亮，沈 伟，等. 黄土–古土壤饱和渗透性与孔隙分布特征关系研究[J]. 水文地质工程地质，2024，51(1)：47–56.(ZHAO Zhiyan，ZHANG Changliang，SHEN Wei，et al. Research on the relationship between saturated permeability and pore distribution characteristics of loess-paleosol[J]. Hydrogeology and Engineering Geology，2024，51(1)：47–56.(in Chinese))
[21] 董 辉，罗 潇，李智飞. 堆积碎石土细观孔隙空间特征对其渗透特性的定量影响[J]. 中南大学学报：自然科学版，2017，48(5)：1 367–1 375.(DONG Hui，LUO Xiao，LI Zhifei. Quantitative influence of meso-porosity space features of aggregate gravel soil on its permeability characteristics[J]. Journal of Central South University：Science and Technology，2017，48(5)：1 367–1 375.(in Chinese))
[22] 刘锦阳，李喜安，郭泽泽，等. 含水率对黄土渗气性影响及其微观机制[J]. 中南大学学报：自然科学版，2019，50(8)：1 930–1 940. (LIU Jinyang，LI Xi?an，GUO Zeze，et al. Influence of water content on loess air permeability and its microcosmic mechanism[J]. Journal of Central South University：Science and Technology，2019，50(8)：1 930–1 940.(in Chinese))
[23] 李喜安，刘锦阳，郭泽泽，等. 马兰黄土孔隙结构参数与渗透性关系研究[J]. 工程地质学报，2018，26(6)：1 415–1 423.(LI Xi?an，LIU Jinyang，GUO Zeze，et al. Study on relationship between pore structure parameters and permeability of malan loess[J]. Journal of Engineering Geology，2018，26(6)：1 415–1 423.(in Chinese))
[24] NGUYEN V，PINEDA A J，ROMERO E，et al. Influence of soil microstructure on air permeability in compacted clay[J]. Géotechnique，2020，71(5)：373–391.
[25] ZHAN T L T，YANG Y B，CHEN R，et al. Influence of clod size and water content on air permeability of a compacted loess[J]. Canadian Geotechnical Journal，2014，51(12)：1 468–1 474.
[26] 葛苗苗，李 宁，盛岱超，等. 水力耦合作用下非饱和压实黄土细观变形机制试验研究[J]. 岩土力学，2021，42(9)：2 437–2 448.(GE Miaomiao，LI Ning，SHENG Daichao，et al. 2021. Experimental investigation of microscopic deformation mechanism of unsaturated compacted loess under hydraulic coupling conditions [J]. Rock and Soil Mechanics，2021，42(9)：2 437–2 448(in Chinese))
[27] PINEDA A J，ROMERO E，ALONSO E E，et al. A new high-pressure triaxial apparatus for inducing and tracking hydro-mechanical degradation of clayey rocks[J]. Geotechnical Testing Journal，2014，37(6)：933–947.
[28] YOSHIMI J，OSTERBERG J O. Compression of partially saturated cohesive soils[J]. Journal of the Soil Mechanics and Foundations Division，ASCE，1963，89(4)：1–24.
[29] 葛苗苗，何 璇，谷 川，等. 压缩及增减湿作用下非饱和黄土细观结构演化规律研究[J]. 工程地质学报，2024，32(2)：397–409.(GE Miaomiao，HE Xuan，GU Chuan，et al. Study on the microstructure evolution of a compacted loess along compression，wetting and drying[J]. Journal of Engineering Geology，2024，32(2)：397–409.(in Chinese))
[30] ROMERO E，GENS A，LORET A. Water permeability，water retention and microstructure of unsaturated compacted Boom clay[J]. Engineering Geology，1999，54：117–127.
[31] 孙德安. 非饱和土力学特性及本构模型[J]. 岩土工程学报，2023，45(1)：1–23.(SUN De'an. Mechanical behaviors and constitutive model for unsaturated soils[J]. Chinese Journal of Geotechnical Engineering，2023，45(1)：1–23.(in Chinese))
[32] 周凤玺，周志雄，邵生俊. 非饱和黄土的增湿湿陷变形特性分析[J]. 岩土工程学报，2021，43(增1)：36–40.(ZHOU Fengxi， ZHOU Zhixiong，SHAO Shengjun. Wetting deformation properties of unsaturated collapsible loess[J]. Chinese Journal of Geotechnical Engineering，2021，43(Supp.1)：36–40.(in Chinese))
[33] 王继成，俞建霖，龚晓南，等. 大降雨条件下气压力对边坡稳定的影响研究[J]. 岩土力学，2014，35(11)：3 157–3 162.(WANG Jicheng，YU Jianlin，GONG Xiaonan，et al. Research on effect of closed air pressure on slope stability under intense rainfall [J]. Rock and Soil Mechanics，2014，35(11)：3 157–3 162.(in Chinese))
[34] 何玲丽，田东方. 考虑封闭气体影响的边坡稳定系数计算[J]. 水利水运工程学报，2022，(1)：104–110.(HE Lingli，TIAN Dongfang. Calculation of safety factor of slope stability considering the effect of closed air[J]. Journal of Hydraulic Engineering，2022，(1)：104–110.(in Chinese))
[35] 舒 实，施建勇. 气压和温度变化共同作用下垃圾填埋场边坡稳定性研究[J]. 岩土工程学报，2022，44(1)：82–89.(SHU Shi，SHI Jianyong. Slope stability of municipal solid waste landfills under combined effects of gas pressure and temperature changes[J]. Chinese Journal of Geotechnical Engineering，2022，44(1)：82–89.(in Chinese))
[36] 王 帆，徐啸川. 不同条件下非饱和土中孔隙气压变化特征研究[J]. 有色金属(矿山部分)，2023，75(5)：98–106.(WANG Fan，XU Xiaochuan. Variation characteristics of pore pressure in unsaturated soil under different considtions[J]. Nonferrous Material(Mining Seciton)，2023，75(5)：98–106.(in Chinese))
2025, Vol. 44 
