非饱和压实黄土渗气特性及细观渗气机制研究

doi:10.3724/100-6915.jrme.2024.0318

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摘要为探究非饱和土透气性能及其细观机制，采用自制渗气设备，测试压实黄土在不同初始状态、增减湿路径及等应力比压缩路径下的渗气系数，并结合压汞法(MIP)测试土体细观孔隙结构，分析渗气细观机制。试验结果表明：渗气系数keff随着压实饱和度Sr0的增大在10－12～10－15 m2范围变化，低干密度下keff随Sr0的增大先增后减，而高干密度下呈非线性减小；增湿可以使渗气系数降低达3个数量级，且增湿饱和度0.65以后降低迅速，而减湿可以提高渗气性，但影响远不及增湿明显；等应力比压缩下，keff随应力增大呈指数关系降低，且应力比越低降低越明显。MIP试验发现：随着Sr0增大，压实黄土中大孔隙先增多后减少，增湿对于孔隙密度分布曲线(PSD)影响较小，但减湿可以提高大孔隙度，且压实土较等状态下增减湿后土体表现出更多大孔隙结构；等应力比压缩会造成大孔隙减少，且应力比越低，大孔隙减少越多。结合渗气系数变化规律，非饱和压实土渗气性取决于其联通大孔隙结构，大孔隙结构越多，孔隙联通越好，渗气性则越好。提出孔隙结构参数，建立考虑孔隙结构的细观渗气模型，并结合试验数据对模型进行验证。

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	葛苗苗1
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	朱才辉3
	盛岱超4
	PINEDA Jubert5
	李宁3

关键词 ：土力学, 压实黄土, 渗气系数, 孔隙结构, 增减湿路径, 渗气模型

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 words： soil mechanics compacted loess gas permeability pore structure wetting/drying path air permeation model

引用本文:

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.

链接本文:

https://rockmech.whrsm.ac.cn/CN/10.3724/100-6915.jrme.2024.0318 或 https://rockmech.whrsm.ac.cn/CN/Y2025/V44/I1/221

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