Describing soil crack formation using elastic–plastic fracture mechanics
Describing soil crack formation using elastic–plastic fracture mechanics
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DOI：
10.1111/j.1365-2389.2004.00652.x
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发表时间：
2005-02
影响因子：
4.2
通讯作者：
Paul D. Hallett;T. A. Newson
中科院分区：
文献类型：
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作者：
Paul D. Hallett;T. A. Newson
裂缝发育在土体结构形成中占主导地位。许多断裂力学模型已经被应用于描述土的开裂，但大多数都不适用于土的湿塑性状态。我们通过应用一种新的弹塑性断裂力学方法来描述塑性土中的裂缝形成，从而解决了这一弱点。使用深缺口（改进的四点）弯曲试验对样品进行断裂，收集载荷传输、样品弯曲、裂纹扩展和裂纹口张开的数据，以评估裂纹尖端张开角（CTOA）。CTOA为描述土壤开裂提供了一个强有力的参数，因为它可以由土壤收缩（一个容易测量的参数）引起，并且可以用于描述数值近似中的弹塑性断裂，例如有限元模型。我们研究的试验变量是施加固结应力的方向、粘土含量和孔隙水矿化度。所有样品均采用垂直有效应力120 kPa的一维固结土浆形成。在纯高岭石上进行的试验表明，固结应力方向对试样的CTOA没有影响，水平方向和垂直方向的CTOA均为0.23±0.02 m m−1。然而，土壤粘土含量有显著影响，硅砂：高岭石混合物的质量比为20:80和40:60，CTOA分别降低至0.14±0.02 m m - 1和0.12±0.01 m m - 1。这些较小的CTOA值表明，当粘土用量较少时，诱发断裂所需的应变较小。盐度（0.5 m NaCl）使纯高岭石的CTOA从0.23±0.02 m m−1降低到0.17±0.03 m m−1。
Crack development is predominant in soil structure formation. A number of fracture mechanics models have been applied to soil to describe cracking, but most are not applicable for soil in a wet, plastic state. We address this weakness by applying a new elastic–plastic fracture mechanics approach to describe crack formation in plastic soil. Samples are fractured using a deep‐notch (modified four‐point) bend test, with data on load transmission, sample bending, crack growth, and crack‐mouth opening collected to assess the crack‐tip opening angle (CTOA). CTOA provides a powerful parameter for describing soil cracking since it can be induced by soil shrinkage (an easily measured parameter) and can be used to describe elastic–plastic fracture in numerical approximations, such as finite element modelling. The test variables we studied were the direction of the applied consolidation stress, clay content, and pore water salinity. All samples were formed by consolidating soil slurry one‐dimensionally with a 120‐kPa vertical effective stress. Tests on pure kaolinite showed that the direction of the consolidation stress did not affect CTOA, which was 0.23 ± 0.02 m m−1 for specimens cut both in a horizontal and in a vertical direction to the applied stress. Soil clay content had a marked influence, however, with silica sand:kaolinite mixtures by weight of 20:80 and 40:60 reducing CTOA to 0.14 ± 0.02 m m−1 and 0.12 ± 0.01 m m−1, respectively. These smaller values of CTOA indicate that less strain is required to induce fracture when the amount of clay is less. Salinity (0.5 m NaCl) caused a reduction in the CTOA of pure kaolinite from 0.23 ± 0.02 m m−1 to 0.17 ± 0.03 m m−1.