scholarly journals Development of Embedded Element Technique for Permeability Analysis of Cracked Porous Media

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Peng Qian ◽  
Qianjun Xu
Keyword(s):  
Porous Media ◽  
Effective Permeability ◽  
Water Pressure ◽  
Crack Density ◽  
Mesh Size ◽  
Differential Method ◽  
Simulation Based ◽  
The Matrix ◽  
Element Technique ◽  
Cracked Porous Media

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.

An Overall Approach for Microcrack and Inhomogeneity Toughening in Brittle Solids

1999 ◽  
Vol 15 (2) ◽  
pp. 57-68
Author(s):  
Huang Hsing Pan
Keyword(s):  
Poisson Ratio ◽  
Crack Density ◽  
Mean Field ◽  
Analytic Form ◽  
Density Parameter ◽  
Brittle Solids ◽  
The Matrix ◽  
Microcrack Toughening ◽  
Average Quantity ◽  
The Mean

ABSTRACTBased on the weight function theory and Hutchinson's technique, the analytic form of the toughness change near a crack-tip is derived. The inhomogeneity toughening is treated as an average quantity calculated from the mean-field approach. The solutions are suitable for the composite materials with moderate concentration as compared with Hutchinson's lowest order formula. The composite has the more toughened property if the matrix owns the higher value of the Poisson ratio. The composite with thin-disc inclusions obtains the highest toughening and that with spheres always provides the least effective one. For the microcrack toughening, the variations of the crack shape do not significantly affect the toughness change if the Budiansky and O'Connell crack density parameter is used. The explicit forms for three types of the void toughening and two types of the microcrack toughening are also shown.

Experiment and Simulation Analysis of the Pressure Carrying Capacity of X80 Pipe with Metal Loss Defect on the Girth Weld

2021 ◽  
Vol 1035 ◽  
pp. 813-818
Author(s):  
Zheng Long Li ◽  
Lin Chen ◽  
Zhi Hong Li ◽  
Guo Shuai Yan ◽  
Wei Li
Keyword(s):  
Sensitivity Analysis ◽  
Carrying Capacity ◽  
Simulation Analysis ◽  
Water Pressure ◽  
Metal Loss ◽  
Factors Affecting ◽  
Element Simulation ◽  
Simulation Based ◽  
Blasting Test ◽  
Water Pressure Blasting

In order to study the pressure carrying capacity of X80 pipe with metal loss defect on the girth weld the water-pressure blasting test of the pipe with metal loss defect was analyzed by experiment and finite element simulation. Based on this, the sensitivity analysis of the factors affecting the pressure carrying of the pipeline, such as the circular size, the axial size, and the depth of the metal loss defect, was carried out. The research results show that the circular size of the metal loss defect on the girth weld had little impact to the pressure carrying capacity of the pipe while it reduced with the increasing of the axial size and the depth of the metal loss defect.

Pore-morphology-based simulations of drainage and wetting processes in porous media

2011 ◽  
Vol 42 (2-3) ◽  
pp. 128-149 ◽  
Author(s):  
T. P. Chan ◽  
Rao S. Govindaraju
Keyword(s):  
Porous Media ◽  
Hydraulic Properties ◽  
Pore Space ◽  
Water Pressure ◽  
Theoretical Models ◽  
Hysteretic Behavior ◽  
Water Retention Curve ◽  
Pore Morphology ◽  
Soil Hydraulic Properties ◽  
Soil Hydraulic

Soil hydraulic properties relating saturation, water pressure, and hydraulic conductivity are known to exhibit hysteresis. In this paper, we focus on the determination of the water retention curve for a porous medium through a novel pore-scale simulation technique that is based on mathematical morphology. We develop an algorithm that allows for the representation of three-dimensional randomly packed porous media of any geometry (i.e. not restricted to idealized geometries such as spherical or ellipsoidal particles/pore space) so that the connectivity-, tortuosity-, and hysteresis-causing mechanisms are represented in both drainage and wetting processes, and their role in determining macroscopic fluid behavior is made explicit. Using this method, we present simulation results that demonstrate hysteretic behavior of wetting and non-wetting phases during both drainage and wetting cycles. A new method for computing interfacial surface areas is developed. The pore-morphology-based method is critically evaluated for accuracy, sample size effects, and resolution effects. It is found that the method computes interfacial areas more accurately than existing methods and allows for (i) examination of relationships between water pressure, saturation and interfacial area for hysteretic soils, and (ii) comparisons with previously developed theoretical models of soil hydraulic properties. The pore-morphology-based method shows promise for applications in vadose zone hydrology.

scholarly journals Stability of saprolitic slopes: nature and role of field scale heterogeneities

2006 ◽  
Vol 6 (1) ◽  
pp. 89-96 ◽  
Author(s):  
A. Aydin
Keyword(s):  
Pore Water Pressure ◽  
Water Pressure ◽  
Cost Effective ◽  
Field Scale ◽  
Instability Modes ◽  
Effective Manner ◽  
Ground Investigation ◽  
The Matrix ◽  
Chaotic Distribution ◽  
Horizontal Drains

Abstract. Heterogeneities in various forms and scales often control the mechanisms and locations of failure and deformation, and the factor of safety of saprolitic slopes. This paper presents a critical review of field scale heterogeneities and their roles in controlling the stability of saprolitic slopes. In particular corestones and relict joints are analysed, with emphasis on characterization and possible instability modes. Abnormal flow patterns, fast build-up and/or chaotic distribution of pore water pressure are the most common causative factors of landslides. As heterogeneities are often responsible for the occurrence of such localized abnormalities, realistic models incorporating effects of these features can help predict how and where abnormal flow/pressure patterns may develop. Potential pitfalls during ground investigation in landslide prone slopes are elucidated and effective investigation strategies to avoid these pitfalls are recommended. The uncertainties, for example, in distribution and volumetric percentage of corestones and in delineating zonal boundaries, require continuous upgrading of the engineering geological model during the construction stage of site investigations. Such uncertainties can be reduced in a cost-effective manner by recording drill penetration rates during installation of soil nails and horizontal drains. A better understanding of the interactions among the heterogeneities, the matrix and the engineering geological environment as a whole should enable the significance of discrete features in stability to be more consistently assessed, thereby providing a more rational basis for investigation and design practice in saprolitic profiles.

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