UH model for ideal expansive unsaturated soils
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摘要: 膨胀性非饱和土具有吸水膨胀和浸水强度降低的特点，容易引发地基不均匀沉降导致建筑物开裂破坏。构建了与土体干密度和超固结度相关的膨胀式，并将其融入已有的非饱和土UH模型，从而能够合理地描述理想膨胀土湿化过程中体积膨胀与强度降低的特性。与已有模型相比，提出的模型所需参数少，可以更合理地考虑超固结度和初始干密度对膨胀土应力应变关系的影响，同时可以体现膨胀土在超固结状态下的应力软化特性和剪胀特性。该模型在不考虑土体膨胀式时可以退化成已有的非饱和土UH模型。通过与已有膨胀性非饱和土的试验结果对比分析，验证了模型在定量描述膨胀性超固结非饱和土应力应变特性上的合理性。Abstract: The expansive unsaturated soils are characterised by the behaviour of volume increase and strength reduction during wetting, which may cause nonuniform foundation settlement and further result in cracking of overlaying buildings. A factor accounting for the plastic volumetric expansion is developed, which is associated with the dry density and overconsolidation ratio. This factor is subsequently introduced to the framework of the existing unified hardening (UH) model for the overconsolidated unsaturated soils to properly describe the characteristics of volume expansion and strength reduction during wetting. Compared with other existing models, the model requires fewer parameters, and can adequately account for the influences of the overconsolidation ratio and initial dry density on the stress-strain relationship of the expansive unsaturated soils. Meanwhile, the proposed model can describe the strain-softening behaviour of the expansive soils in the overconsolidated state. This model can be reduced to the existing UH model for the overconsolidated unsaturated soils when the factor accounting for the plastic volumetric expansion becomes zero. The capability of the proposed model in quantitatively describing the stress-strain characteristics of the expansive overconsolidated unsaturated soils is verified by comparing with the existing experimental results.
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Keywords:
- unsaturated expansive soil /
- overconsolidated soil /
- elasto-plastic model /
- wetting
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图 1 饱和土和非饱和土的等向压缩线
Figure 1. Normal compression lines for saturated and unsaturated soils
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图 3 不同C值等向回弹湿化应力路径
Figure 3. Stress paths of isotropic unloading-wetting with different values of C
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图 4 等向回弹湿化中不同C值下体应变
Figure 4. Variation of volumetric strain under stress path of isotropic unloading-wetting with different values of C
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图 5 不同超固结度等向回弹湿化路径
Figure 5. Stress paths of isotropic unloading-wetting with different overconsolidation ratios
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图 6 等向回弹湿化不同超固结度下体应变
Figure 6. Variation of volumetric strain under stress path of isotropic unloading-wetting with different overconsolidation ratios
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图 7 等p剪切中湿化不同C值下体应变
Figure 7. Variation of volumetric strain under stress path of shearing- wetting-shearing with different values of C and constant mean effective stress
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图 8 等p剪切中湿化不同超固结度下体应变
Figure 8. Variation of volumetric strain under stress path of shearing- wetting-shearing with different overconsolidation ratios and constant mean effective stress
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图 9 等体积湿化不同C值膨胀力变化
Figure 9. Variation of swelling pressure during wetting under constant volume with different values of C
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图 10 等体积湿化不同超固结度膨胀力变化
Figure 10. Variation of swelling pressure during wetting under constant volume with different overconsolidation ratios
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图 11 三轴压缩中湿化不同C值下体应变
Figure 11. Variation of volumetric strain under stress path of triaxial compression-wetting-triaxial compression with different values of C
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图 12 三轴压缩中湿化不同超固结度体应变
Figure 12. Variation of volumetric strain under stress path of triaxial compression-wetting-triaxial compression with different overconsolidation ratios
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