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Experiment study on the strength and microstructure of bentonite-lime improved loess
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摘要: 黄土工程性能较差，必须经过处理才能作为路基填料使用。为了提高黄土路基的承载力，更好地解决黄土路基的工程病害问题，在黄土路基填料中加入膨润土和石灰，通过不同组合掺量的膨润土-石灰-黄土的无侧限抗压强度试验与核磁共振试验，分别从土体强度和孔隙结构的角度出发，研究各掺量膨润土-石灰对黄土路基填料强度及孔隙结构的改良效果。试验结果表明：膨润土可以有效填充黄土的孔隙，石灰能使土体内分散的颗粒连成整体，并使土体无侧限抗压强度提高4.01倍；改良黄土的无侧限抗压强度随着养护龄期的增大而增大；与素黄土相比，改良黄土的孔隙度降低，大孔隙占比显著减少。通过微观电镜扫描发现土颗粒之间连成整体，且颗粒间的大孔隙也基本被填充。因此，膨润土和石灰对黄土填料的改良效果较为显著。Abstract: Loess has poor engineering performance and must be treated before it can be used as a roadbed filler. In order to improve the bearing capacity of the loess subgrade, and better solve the engineering disease problem of the loess subgrade, bentonite and lime are added to the loess roadbed filler, and the unconfined compressive strength test and nuclear magnetic resonance test of different combinations of bentonite-lime-loess are carried out. From the perspective of soil strength and pore structure, each content is studied. Bentonite-lime improves the strength and pore structure of loess roadbed fillers. The test results show that bentonite can effectively fill the pores of loess, lime can make the dispersed particles in the soil form a whole, and increase the unconfined compressive strength of the soil by 4.01 times; the unconfined compressive strength of the improved loess increases with the maintenance. Compared with plain loess, the porosity of modified loess decreases, and the proportion of large pores decreases significantly. Scanning through a microscopic electron microscope found that the soil particles were connected as a whole, and the large pores between the particles were basically filled. Therefore, the improvement effect of bentonite and lime on loess filler is more significant.
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Key words:
- bentonite /
- lime /
- unconfined compressive strength /
- microstructure; improved loess
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图 2 膨润土及石灰改良黄土应力-应变曲线
Figure 2. Stress-strain curves of bentonite and lime modified loess
图 3 膨润土-石灰掺量与黄土无侧限抗压强度关系
Figure 3. Relationship between bentonite and lime content and unconfined loess compressive strength
图 4 龄期14 d膨润土和石灰掺量与无侧限抗压强度关系
Figure 4. Relationship between bentonite and lime content at 14 d and unconfined compressive strength
图 5 养护龄期对改良土无侧限抗压强度的影响
Figure 5. Influence of curing age on unconfined compressive strength of improved soil
表 1 黄土试样基本物理性质
Table 1. Basic physical properties of loess soil samples
土粒相对
密度最优含水率/
%最大干密度 /
（g·cm−3)液限/
%塑限/
%塑性
指数2.68 16.61 1.72 29.70 19.46 10.23 
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表 2 试验工况
Table 2. Test conditions
试验工况 膨润土掺量/% 石灰掺量/% 最优含水量/% 最大干密度/(g·cm−3) 液限/% 塑限/% 塑性指数 1 3 3 18.17 1.60 40.32 21.69 18.63 2 3 5 19.39 1.58 41.58 20.30 21.28 3 3 7 20.58 1.55 38.85 25.12 13.73 4 5 3 19.36 1.63 36.54 17.42 19.12 5 5 5 21.29 1.61 40.21 25.10 15.11 6 5 7 23.40 1.58 35.67 17.15 18.53 7 7 3 21.47 1.66 41.10 27.26 13.84 8 7 5 23.91 1.65 42.06 27.19 14.88 9 7 7 24.58 1.60 38.63 19.77 18.85
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表 3 不同膨润土-石灰掺量的孔隙度
Table 3. Porosity of different bentonite and lime contents
膨润土
掺量/%孔隙度/% 石灰掺量0 石灰掺量3% 石灰掺量5% 石灰掺量7% 0 32.00 / / / 3 / 29.91 28.79 28.20 5 / 28.26 27.68 28.71 7 / 29.32 29.45 30.51
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表 4 最大孔隙值及占比
Table 4. Maximum pore value and proportion
膨润土掺量/% 石灰掺量/% 最大孔径值/μm 所占百分比/% 0 0 70.594 15 1.09 3 3 61.442 26 0.53 3 5 61.442 26 0.10 3 7 61.442 26 9×10−4 5 3 70.594 15 0.12 5 5 61.442 26 0.29 5 7 70.594 15 0.15 7 3 75.669 25 1×10−4 7 5 65.859 43 0.35 7 7 65.859 43 0.39
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