Abstract
The widely used approach of mesoscale finite element modeling for permeability analysis is to simulate the matrix and cracks with continuum elements (CE), whereas this process brings technical difficulties in generating a satisfying mesh conformity at the interface. In this work, an alternative method based on embedded element (EE) technique is developed for the prediction of water pressure field and effective permeability in the numerical simulation. Based on the mathematical similarity between elasticity and seepage problems, water pressure can derive from the corresponding displacement through “elastic analogy.” To assess the capability of the EE technique, different cases are simulated and compared with the CE model. The results show that there is a satisfactory agreement in water pressures and velocities between the CE and EE modeling. In the CE model, different factors, such as permeability contrast between matrix and cracks (Kcrack/Kmatrix) and mesh size, are considered. It is obvious to find that results will become stable when Kcrack/Kmatrix reaches 104, and the mesh size has little impact. The effective permeability of 3D porous media with random cracks is evaluated and the results show that the differential method is accurate for 3D permeability analysis when the crack density is not large.
Highlights
During the period of services, porous media like concrete and rocks are often subjected to various loads caused by mechanical, thermal, or physicochemical factors; the damage process generates new microcracks [1,2,3]
The two main categories of models used in permeability analysis are the equivalent continuum model (ECM) and the discrete fracture model (DFM) [9, 10]
We have developed a novel numerical method to calculate permeability of cracked porous media
Summary
During the period of services, porous media like concrete and rocks are often subjected to various loads caused by mechanical, thermal, or physicochemical factors; the damage process generates new microcracks [1,2,3]. In small-scale studies, the influence of the individual cracks cannot be neglected, the DFM are quite suitable on this condition In this approach cracks are represented by line elements or surface elements for 2D problems, and for 3D problems cracks are simulated with surface elements or body elements [5, 16,17,18]. Some noncontinuous methods like s-version FE model are developed and implemented by some authors, which makes it difficult for other researchers to use and develop them further In this case, this paper adopts the EE technique to simulate pressure fields of cracked porous media. The results of meso-FE simulations of different cases using the CE and EE models are investigated and discussed to verify the EE technique Some factors such as permeability ratio between matrix and cracks and mesh size which could influence results are taken into consideration. Effective permeability of 3D porous media with random distributed cracks are evaluated
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