基于CT连用与模拟退火理论的土壤结构及渗流模拟研究

In this Fund Program, we aim at establishing the soil pore structure three-dimensional model by using the multilevel CT scanning technology and the theory of simulated annealing algorithm（SAA）.The program mainly studies following three parts: 1. Obtain the two-dimensional images on the geometric and topological properties of different specifications soil pore by separately using the microscopic CT equipment and medical CT instrument to scanning two sizes undisturbed soil column samples. 2. Performing integration on multi-resolution CT images by using image pre-processing, digital image processing techniques and ternary segmentation, etc. Then, describing the soil pore spatial variation characters and the geometric and topological properties at different levels with mathematical functions.3. Based on the theory of simulated annealing to build soil pore 3d model. Combine the soil pore model with lattice Boltzmann (LBM) model, we try to quantitatively describe the evolution and the development of the process of the microcosmic porous flow, single-phase flow and other physical phenomenon, which exist widely in real soil. . Finally, in this program, we attempt to reveal the constitutive relation between the soil pore microstructure and the soil moisture and solute movement in microscale from the viewpoint of model simulation, and put forward a new method on acquiring the soil physical parameters (mainly refer to the properties on soil hydraulic) in macroscale, which is hard to solve well by relying on traditional soil investigation.

现实土壤具有强烈的空间变异性，土壤学家普遍基于“黑箱原理”—即通过体积平均意义上的有效（或等价）参数开展结构研究，据此构建的结构体系难以准确反映土壤孔隙空间的几何与拓扑特征，也无法精细地刻画流体在其中的具体运移途径和行为。因此本项目拟借助于孔隙模型来定量描述孔隙空间的结构，模拟流体运移过程，从而预测难以用实验方法获得的宏观连续体尺度下的函数关系。.主要研究内容如下：两级CT扫描典型褐土原状土柱，采用三维成像技术获取真实土壤孔隙结构并将其作为参考模型；然后，采用随机堆积球方法，基于模拟退火理论构建与参考模型有相同孔隙率，不同结构特征的重构体系，通过计算特征函数定量表征重构体系与参考模型间的结构差异；最后采用晶格波尔兹曼法模拟单相流在土壤孔隙中的渗流过程。分析孔隙体系统计特征函数与渗透率之间的函数关系。定量解析微观尺度上土壤孔隙结构与宏观尺度上土壤连续体复杂水力学性质间的本构关系。

现实土壤具有强烈的空间变异性，土壤学家普遍基于“黑箱原理”—即通过体积平均意义上的有效（或等价）参数开展结构研究，据此构建的结构体系难以准确反映土壤孔隙空间的几何与拓扑特征，也无法精细地刻画流体在其中的具体运移途径和行为。因此本项目拟借助于孔隙模型来定量描述孔隙空间的结构，模拟流体运移过程，从而预测难以用实验方法获得的宏观连续体尺度下的函数关系。主要研究内容如下：两级CT扫描典型褐土原状土柱，采用三维成像技术获取真实土壤孔隙结构并将其作为参考模型；然后，采用随机堆积球方法，基于模拟退火理论构建与参考模型有相同孔隙率，不同结构特征的重构体系，通过计算特征函数定量表征重构体系与参考模型间的结构差异；最后采用晶格波尔兹曼法模拟单相流在土壤孔隙中的渗流过程。分析孔隙体系统计特征函数与渗透率之间的函数关系。定量解析微观尺度上土壤孔隙结构与宏观尺度上土壤连续体复杂水力学性质间的本构关系

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