| 基于CT扫描的黄土孔隙结构特征研究 |
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| 引用本文： | 郑佳,庄建琦,孔嘉旭,付玉婷,牟家琦,王杰.基于CT扫描的黄土孔隙结构特征研究[J].地质科技通报,2022,41(6):211-222. |
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| 作者姓名： | 郑佳 庄建琦 孔嘉旭 付玉婷 牟家琦 王杰 |
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| 作者单位： | a.长安大学地质工程与测绘学院, 西安 710054 |
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| 基金项目： | 国家自然科学基金项目42090053国家自然科学基金项目41922054 |
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| 摘 要： | 孔隙特征作为反映黄土微观结构的重要特征之一, 直接影响黄土的水敏性、渗透性和强度等物理力学性质。为了研究水力耦合作用下黄土微观孔隙结构特征, 使用CT技术对天然原状、原状饱和与重塑黄土的初始结构以及不固结不排水剪切试验后的土体结构进行了扫描, 通过建立黄土三维结构模型, 分析了剪切试验前后孔隙结构的演变特征。结果表明: 饱和与重塑作用使天然原状黄土的大孔隙减少, 剪切作用使天然原状黄土和重塑黄土发生剪切破坏, 原状饱和黄土发生压缩破坏, 局部孔隙率增加。天然原状黄土与原状饱和黄土在剪切前后均表现为微孔和小孔数量较多, 其孔隙倾角主要分布在50°~90°之间, 解释了黄土亚稳态结构形成的主要原因。扰动作用使重塑黄土的孔隙尺寸分布均匀, 且重塑黄土与原状饱和黄土在水力作用下更易失稳屈服。揭示了黄土剪切变形破坏的微观结构主要表现为粒间胶结物的溶解、孔隙的坍塌与填充以及颗粒旋转、破碎和滑移。试验结果可为黄土剪切强度降低和湿陷机理研究提供依据。
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| 关 键 词： | 黄土剪切 孔隙结构 CT扫描试验 孔隙三维模型 |
| 收稿时间： | 2022-05-09 |
Study of loess pore structure characteristics based on CT scanning |
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| Affiliation: | a.School of Geological Engineering and Geomatics, Chang'an University, Xi'an 710054, Chinab.Key Laboratory of Western China's Mineral Resources and Geological Engineering, Chang'an University, Xi'an 710054, China |
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| Abstract: | Porosity is one of the important characteristics reflecting the microstructure of loess and directly affects the physical and mechanical properties of loess, such as water sensitivity, permeability and strength. To study the micropore structure characteristics of loess under hydraulic coupling, micro CT technology was used to scan the initial structure of natural undisturbed, undisturbed saturated and remolded loess and the soil structure after unconsolidated-undrained shear tests. The evolution characteristics of the pore structure before and after shear tests are analyzed through the three-dimensional structure model of loess. The results show that the pore structures of the natural undisturbed loess, the saturated undisturbed loess and the remolded loess are significantly different, and the pore structures of the samples have a significant impact on the shear failure process. The process of saturation and remodeling can reduce the macropores of undisturbed soil.Shear stress can cause shear failure of natural undisturbed and remolded loess, compression failure of undisturbed saturated loess, and the increases of local porosity. The natural undisturbed and undisturbed saturated loess show a large number of micropores and small pores before and after shear, and the pore dip angle is mainly distributed between 50°-90°, which explains the main reason for the formation of the metastable structure of loess. The remodeled loess has a uniform pore size distribution due to the disturbance effect, and the remodeled and saturated loess is more prone to buckling and yielding under hydraulic action. It is revealed that the microstructure of shear deformation and failure of loess is mainly manifested in the dissolution of intergranular cement, the collapse and filling of pores, and the rotation, fragmentation and slip of particles. The test results can provide a basis for the mechanism of shear strength reduction and collapsibility of loess. |
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