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THE PERMEABILITY CHARACTERISTICS OF LOESS AND RED CLAY INTERFACE IN HEIFANGTAI AREA
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摘要: 黄土与红黏土这一地层结构组合在黑方台地区普遍存在，黄土与红黏土之间存在渗透差，在持续灌溉条件下红黏土层会出现滞水效应，从而发生层带软化现象，最终诱发滑坡。本文分别开展室内土工试验、核磁共振试验(NMR)以及颗分试验，进而研究增湿条件下黄土-红黏土界面处非饱和入渗情况以及充水孔隙变化规律。得出以下结论：(1)在入渗过程中充水孔隙体积分布曲线中峰值不断向右迁移，充水孔隙半径不断增大且分布范围逐渐变广。黄土-红黏土组合样与纯黄土相比，充水孔隙体积分布曲线中最大峰值向右迁移较慢且分布范围较窄，入渗结束后红黏土层富含水分。(2)在相同流量条件下，黄土-红黏土组合样初始含水率越高，充水孔隙体积分布曲线中最大峰值向右迁移得越慢，所对应的充水孔隙半径变化越小且在界面处滞水效应越不明显。在相同初始含水率条件下，流量越大，充水孔隙体积分布曲线中峰值向右迁移得越快，水分进入中大孔隙越多且在界面处滞水现象越明显。(3)黄土-红黏土组合样在增湿过程中发生颗粒运移，导致颗粒间接触方式发生改变，最终试样底部细颗粒含量较多，界面处粗颗粒含量较多。Abstract: The stratum structure combination of loess and red clay is common in Heifangtai area. Loess and red clay have penetration differences. Under continuous irrigation conditions,the red clay layer will have a water stagnation effect,which can cause layer softening and eventually induce landslides. In this paper,indoor geotechnical tests,NMR and particle fractionation tests were carried out respectively to study the unsaturated infiltration situation and pore change law at the interface between loess and red clay. The analysis of the test results show the following findings. (1)During the infiltration process,the peak value of the water-filled pore volume distribution map keeps moving to the right. The radius of the water-filled pore increases and the distribution range gradually becomes wider. Compared with pure loess,the maximum peak value in the water-filled pore volume distribution curve of the loess-red clay composite sample migrates more slowly to the right and has a narrower distribution range. The red clay layer is rich in water after the end of infiltration. (2)Under the same flow conditions,the higher the initial water content of the loess-red clay composite sample,the slower the peak value in the water-filled pore volume distribution curve shifts to the right,the smaller the change of the corresponding water-filled pore radius,and the water entering the medium and large. The fewer the pores,the less obvious the water stagnation effect at the interface. Under the condition of the same initial water content,the larger the flow rate,the faster the peak value in the water-filled pore volume distribution curve shifts to the right,and the corresponding water-filled pore radius is larger. The more water enters the medium and large pores,and the more obvious the phenomenon of water stagnation at the interface. (3)Particle migration occurs during the humidification process of the loess and red clay composite samples,which leads to changes in the contact mode between particles and the pore structure. The final sample contains more fine particles at the bottom and more coarse particles at the interface.
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Key words:
- NMR /
- Permeability /
- Particle migration /
- Reshape soil
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图 1 黑方台地区地层组合图
a. 黑方台某滑坡坡脚处; b. 黑方台区域典型地质剖面图
Figure 1. Stratigraphic assemblage map of Heifangtai area
图 4 不同初始含水率纯黄土充水孔隙分布图
a. 15%纯黄土充水孔隙体积分布；b. 15%纯黄土不同充水孔隙体积分布柱状图; c. 17%纯黄土充水孔隙体积分布; d. 17%纯黄土不同充水孔隙体积分布柱状图
Figure 4. The infiltration pore distribution map of pure loess with different initial water content
图 5 不同初始含水率黄土-红黏土组合样充水孔隙分布图
a. 15%黄土-红黏土组合样充水孔隙体积分布; b. 15%黄土-红黏土组合样不同充水孔隙体积分布柱状图; c. 17%黄土-红黏土组合样充水孔隙体积分布; d. 17%黄土-红黏土组合样不同充水孔隙体积分布柱状图
Figure 5. The infiltration pore distribution map of loess and red clay combined sample with different initial water content
图 6 流量0.74 mL·min-1初始含水率15%试样充水孔隙分布图
a. 0.74 mL·min-1纯黄土充水孔隙体积分布; b. 0.74 mL·min-1纯黄土充水不同充水孔隙体积分布柱状图; c. 0.74 mL·min-1黄土-红黏土组合样充水孔隙体积分布; d. 0.74 mL·min-1黄土-红黏土组合样不同充水孔隙体积分布柱状图
Figure 6. The infiltration pore distribution map of flow 0.74 mL·min-1 initial water content 15% sample
图 7 纯黄土入渗核磁共振成像图
a. 流量0.45 mL·min-1—初始含水率15%入渗图; b. 流量0.45 mL·min-1—初始含水率17%入渗图; c. 流量0.74 mL·min-1—初始含水率15%入渗图; d. 纯黄土T2谱总面积图
Figure 7. The infiltration MRI image of pure loess
图 8 黄土与红黏土组合样入渗核磁共振成像图
a. 流量0.45 mL·min-1—初始含水率15%入渗图; b. 流量0.45 mL·min-1—初始含水率17%入渗图; c. 流量0.74 mL·min-1—初始含水率15%入渗图; d. 黄土与红黏土组合样T2谱总面积图
Figure 8. The infiltration MRI image of loess and red clay combined samples
图 9 黄土与红黏土组合样颗粒运移情况图
a. 黄土与红黏土组合样底部颗分图；b. 黄土与红黏土组合样界面处颗分图
Figure 9. The diagram of particle migration of loess and red clay combined samples
表 1 入渗试验工况表
Table 1. Infiltration test condition table
序号 初始含水率/% 流量/mL·min-1 土样高度/cm N1 15 0.45 6(黄土) N2 4(黄土)+2(红黏土) N3 17 0.45 6(黄土) N4 4(黄土)+2(红黏土) N5 15 0.74 6(黄土) N6 4(黄土)+2(红黏土) 
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表 2 流量0.45 mL·min-1初始含水率15%纯黄土充水孔隙分布表
Table 2. The infiltration pore distribution table of flow 0.45 mL·min-1 initial water content 15% pure loess
时间T/min 第1个峰值对应的孔径R/μm 积分面积所占比例/% 第2个峰值对应的孔径R/μm 积分面积所占比例/% 第3个峰值对应的孔径R/μm 积分面积所占比例/% 0 0.105 99.4 9.117 0.6 — — 15 0.121 95.3 2.597 3.9 48.668 0.8 30 0.159 96.2 2.597 3.0 48.688 0.8 45 0.242 96.8 3.433 2.5 55.956 0.7 60 0.423 97.8 3.947 2.2 — — 75 0.643 97.5 6 0.9 18.323 1.6 表中“—”代表无数据
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表 3 流量0.45 mL·min-1初始含水率17%纯黄土充水孔隙分布表
Table 3. The infiltration pore distribution table of flow 0.45 mL·min-1 initial water content 17% pure loess
时间T/min 第1个峰值对应的孔径R/μm 积分面积所占比例/% 第2个峰值对应的孔径R/μm 积分面积所占比例/% 第3个峰值对应的孔径R/μm 积分面积所占比例/% 0 0.069 99.6 4.539 0.4 — — 15 0.079 95.8 1.709 3.4 42.329 0.9 30 0.105 97.5 1.709 1.7 36.815 0.9 45 0.278 97.8 3.947 2.2 — — 60 0.423 97.0 6 3.0 — — 75 0.486 94.6 6 2.0 15.936 3.4 表中“—”代表无数据
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表 4 流量0.45 mL·min-1初始含水率15%黄土-红黏土组合样充水孔隙分布表
Table 4. The infiltration pore distribution table of flow rate 0.45 mL·min-1 initial water content 15% loess and red clay combined sample
时间T/min 第1个峰值对应的孔径R/μm 积分面积所占比例/% 第2个峰值对应的孔径R/μm 积分面积所占比例/% 第3个峰值对应的孔径R/μm 积分面积所占比例/% 0 0.091 98.8 6 0.9 18.323 0.3 15 0.105 93.0 2.259 4.3 27.849 2.6 30 0.121 95.6 2.259 2.0 27.849 2.5 45 0.278 95.2 3.947 1.9 21.067 2.9 60 0.559 96.1 5.218 0.7 24.222 3.2 75 0.739 95.3 6 0.4 24.222 4.3
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表 5 流量0.45 mL·min-1初始含水率17%黄土-红黏土组合样充水孔隙分布表
Table 5. The infiltration pore distribution table of flow rate 0.45 mL·min-1 initial water content 17% loess and red clay combined sample
时间T/min 第1个峰值对应的孔径R/μm 积分面积所占比例/% 第2个峰值对应的孔径R/μm 积分面积所占比例/% 第3个峰值对应的孔径R/μm 积分面积所占比例/% 0 0.079 98.8 4.539 0.9 18.323 0.3 15 0.079 95.8 2.259 2.9 36.815 1.3 30 0.139 95.4 2.597 3.5 42.329 1.1 45 0.242 96.7 3.433 2.7 64.336 0.6 60 0.32 97.7 3.947 1.7 73.971 0.6 75 0.423 96.0 18.323 2.8 84.971 1.2
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表 6 流量0.74 mL·min-1初始含水率15%纯黄土充水孔隙分布表
Table 6. The infiltration pore distribution table of flow 0.74 mL·min-1 initial water content 15% pure loess
时间T/min 第1个峰值对应的孔径R/μm 积分面积所占比例/% 第2个峰值对应的孔径R/μm 积分面积所占比例/% 第3个峰值对应的孔径R/μm 积分面积所占比例/% 0 0.105 95.1 6.900 1.2 13.86 3.7 15 0.211 83.8 3.433 16.2 — — 30 0.487 91.7 6.898 1.4 24.22 6.9 45 1.292 95.2 36.815 4.8 — — 60 2.597 96.3 36.815 3.7 — — 表中“—”代表无数据
下载: 导出CSV
表 7 流量0.74 mL·min-1初始含水率15%黄土-红黏土组合样充水孔隙分布表
Table 7. The infiltration pore distribution table of flow rate 0.74 mL·min-1 initial water content 15% loess and red clay combined sample
时间T/min 第1个峰值对应的孔径R/μm 积分面积所占比例/% 第2个峰值对应的孔径R/μm 积分面积所占比例/% 第3个峰值对应的孔径R/μm 积分面积所占比例/% 0 0.105 0.992 24.220 0.8 — — 15 0.159 93.500 3.433 4.5 48.668 2.0 30 0.320 95.900 4.539 2.0 18.323 2.1 45 0.851 0.972 27.849 2.8 — — 60 1.486 91.900 32.020 8.1 — — 表中“—”代表无数据
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