Coupled Effect of Wet-Dry Cycles and Rainfall on Highway Slope Made of Yazoo Clay
Coupled Effect of Wet-Dry Cycles and Rainfall on Highway Slope Made of Yazoo Clay
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DOI：
10.3390/geosciences9080341
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发表时间：
2019-08-01
期刊：
影响因子：
2.7
通讯作者：
Nobahar, Masoud
中科院分区：
文献类型：
--
作者：
Khan, Sadik;Ivoke, John;Nobahar, Masoud
膨胀性亚祖粘土易受体积变形的影响，主要分布在密西西比中部和美国南部其他相邻各州。反复出现的收缩-膨胀行为对该地区的基础设施造成了严重的问题。虽然Yazoo粘土在南部各州造成了严重的问题，但对Yazoo粘土的行为进行了有限的研究，特别是在降雨的情况下。本研究的目的是调查由于干湿循环和降雨对Yazoo粘土公路边坡稳定性的孔隙比变化的耦合效应。利用Bentley System（https：//www.plaxis.com/）的Plaxis 2D中的有限元方法，通过流动变形和稳定性分析，研究了力学性能变化和降雨的耦合效应。采用重塑膨胀粘土土样进行室内试验。将重构的Yazoo粘土样品在封闭室中进行3、5和7次润湿和干燥循环，持续24小时。密切监测样品的轴向变形和每个循环次数下空隙比的变化。在每个干湿循环的强度变化也进行了研究，并用于边坡稳定性分析在降雨的存在。试验结果表明，孔隙比随着干湿循环次数的增加而增加。孔隙比的连续增量从0.99在一个未受干扰的状态下，没有干湿循环到1.49在第7干湿循环，表明增加了48.9%，作为润湿和干燥循环的增加记录;反过来，减少77%的土壤的凝聚力。考虑到第7次干湿循环的影响，考虑Rv = 126.2mm（2 h）和Rv = 271.7mm（3d）两个总降雨期的影响，安全系数分别从1.7降低到1.2和1.68降低到1.02。由于Yazoo粘土的干湿循环，孔隙比的变化降低了剪切强度到完全软化的状态，增加了边坡破坏的可能性。由于雨水的渗透，这种情况进一步恶化了栖息水条件的存在。
Expansive Yazoo clay soil is susceptible to volumetric deformation and is dominant in central Mississippi and other neighboring southern states of the United States. Recurring shrink-swell behavior causes a significant problem to infrastructures in the area. Although Yazoo clay causes a significant problem in the deep southern states, limited study has been conducted on the behavior of Yazoo clay, especially in the presence of rainfall. The objective of this current study is to investigate the coupled effect of changes in void ratio due to wet-dry cycles and rainfall on the stability of highway slopes made of Yazoo clay. The finite element method in Plaxis 2D by Bentley System (https://www.plaxis.com/) has been utilized to investigate the coupled effect of changes in mechanical properties and rainfall using flow-deformation and stability analysis. Reconstituted expansive clay soil samples were used for the laboratory experiment. The reconstituted Yazoo clay samples were subjected to 3, 5, and 7 wetting and drying cycles in an enclosed chamber for a 24-h period. The axial deformation of the samples and the change in void ratios at each number of the cycle was closely monitored. The strength change at each wet and dry cycle was also investigated and used for slope stability analysis in the presence of rainfall. The test results indicate that the void ratio increases with the increasing number of wet-dry cycles. A continuous increment in void ratios from 0.99 in an undisturbed state with no wet-dry cycle to 1.49 at the 7th wet-dry cycle, indicating a 48.9% increase, as the wetting and drying cycle increases was recorded; in turn, decreasing the cohesion of the soil by 77%. The factor of safety considering the effect of two total rainfall periods of Rv = 126.2 mm (2 h) and Rv = 271.7 mm (3 days) reduced from 1.7 to 1.2 and 1.68 to 1.02, considering the effect of the 7th wet-dry cycle at the topsoil. The changes in the void ratio due to the wetting and drying cycle of Yazoo clay soil reduces the shear strength to a fully softened condition, increasing the possibility of slope failure. This condition further worsens in the presence of a perched water condition due to the infiltration of rain water.