Impact of hydraulic suction history on crack growth mechanics in soil
Impact of hydraulic suction history on crack growth mechanics in soil
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DOI：
10.1029/2007wr006055
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发表时间：
2008-05
影响因子：
5.4
通讯作者：
S. Yoshida;Paul D. Hallett
中科院分区：
文献类型：
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作者：
S. Yoshida;Paul D. Hallett
利用断口分析法测量的裂纹尖端张开角（CTOA）描述了裂纹形成的机理和土应力历史的影响。研究了两种土壤：由40%钙膨润土和60%细硅砂组成的模型土壤和具有相似粘土含量和矿物学的重塑水稻土。断裂试验使用深切口弯曲试样，该试样通过将液限土壤成型为矩形棒，平衡5 kPa至50 kPa范围内的土壤水吸力（某些50 kPa试样润湿至5 kPa），并插入0.4×试样厚度的裂缝而形成。在1 mm min−1的恒定位移速率下进行的弯曲试验提供了所施加的力和载荷点位移的数据。从一系列图像中量化裂纹的生长和几何形状，以确定CTOA。从峰值力评价的断裂模量随着水吸力的增加而增加。然而，再湿并没有改变峰值应力从50 kPa的值，这表明收缩诱导的固结是更重要的比土壤水吸力在测试开始。在稳定裂纹扩展过程中测得的CTOA随干燥而降低。当最初平衡至50 kPa的试样再润湿至5 kPa时，CTOA甚至进一步降低。这些结果表明，CTOA主要是由刚度，虽然再润湿可能会改变裂纹尖端之前的毛细应力。我们未来的工作将结合联合收割机CTOA与耦合水文和机械过程的模型，考虑到依赖CTOA对土壤水分状况，使裂缝在土壤中的传播可以预测。
The mechanics of crack formation and the influence of soil stress history were described using the crack tip opening angle (CTOA) measured with fractography. Two soils were studied: a model soil consisting of 40% Ca‐bentonite and 60% fine silica sand and a remolded paddy soil with similar clay content and mineralogy. Fracture testing used deep‐notch bend specimens formed by molding soils at the liquid limit into rectangular bars, equilibrating to soil water suction ranging from 5 kPa to 50 kPa (with some 50 kPa specimens wetted to 5 kPa), and inserting a crack 0.4× specimen thickness. Bend tests at a constant displacement rate of 1 mm min−1 provided data on applied force and load point displacement. The growth and geometry of the cracks were quantified from a series of images to determine the CTOA. Modulus of rupture, evaluated from the peak force, increased as water suction increased. However, rewetting did not alter the peak stress from the 50 kPa value, indicating that shrinkage‐induced consolidation was more important than the soil water suction at the onset of testing. CTOA measured during stable crack growth decreased with drying. CTOA decreased even further when specimens equilibrated initially to 50 kPa were rewetted to 5 kPa. These results suggested that CTOA was primarily governed by the stiffness, although rewetting probably altered the capillary stresses in advance of the crack tip. Our future work will combine CTOA with a model that couples hydrological and mechanical processes to take into account the dependency of CTOA on the soil water regime so that crack propagation in soil can be predicted.