Gravimetric terrain corrections by triangular‐element method

Geophysics ◽  
1990 ◽  
Vol 55 (2) ◽  
pp. 232-238 ◽  
Author(s):  
X. Zhou ◽  
B. Zhong ◽  
X. Li
Keyword(s):  
Simple Formula ◽  
Gravity Data ◽  
High Accuracy ◽  
Rectangular Prism ◽  
Triangular Element ◽  
Volume Integral ◽  
Correction Process ◽  
Rugged Topography ◽  
Terrain Corrections ◽  
Element Method

Terrain corrections for gravity data are a critical concern in rugged topography, because the magnitude of the corrections may be large relative to the anomalies of interest. The terrain‐correction process, however, is very tedious. At present, rectangular prism and fan‐shaped prism methods are commonly used for the corrections; but these methods assume elements have horizontal tops, an assumption which does not reflect true topography, especially near the station. A triangular‐element method which allows dipping surfaces has been developed using a Gaussian formulation to improve the correction process. This method involves a simple formula employing a surface rather than a volume integral for computing the terrain corrections with high accuracy.

scholarly journals Gravity terrain correction for mainland territory of Vietnam

2017 ◽  
Vol 17 (4B) ◽  
pp. 145-150
Author(s):  
Pham Nam Hung ◽  
Cao Dinh Trieu ◽  
Le Van Dung ◽  
Phan Thanh Quang ◽  
Nguyen Dac Cuong
Keyword(s):  
Gravity Data ◽  
Computing Time ◽  
Terrain Correction ◽  
Bouguer Gravity ◽  
Mountainous Region ◽  
Terrain Effect ◽  
Rugged Topography ◽  
Terrain Corrections ◽  
Gravity Map

Terrain corrections for gravity data are a critical concern in rugged topography, because the magnitude of the corrections may be largely relative to the anomalies of interest. That is also important to determine the inner and outer radii beyond which the terrain effect can be neglected. Classical methods such as Lucaptrenco, Beriozkin and Prisivanco are indeed too slow with radius correction and are not extended while methods based on the Nagy’s and Kane’s are usually too approximate for the required accuracy. In order to achieve 0.1 mGal accuracy in terrain correction for mainland territory of Vietnam and reduce the computing time, the best inner and outer radii for terrain correction computation are 2 km and 70 km respectively. The results show that in nearly a half of the Vietnam territory, the terrain correction values ≥ 10 mGal, the corrections are smaller in the plain areas (less than 2 mGal) and higher in the mountainous region, in particular the correction reaches approximately 21 mGal in some locations of northern mountainous region. The complete Bouguer gravity map of mainland territory of Vietnam is reproduced based on the full terrain correction introduced in this paper.

scholarly journals Thermal Stress Analysis of 3D Anisotropic Materials Involving Domain Heat Source by the Boundary Element Method

2019 ◽  
Vol 35 (6) ◽  
pp. 839-850
Author(s):  
Y. C. Shiah ◽  
Nguyen Anh Tuan ◽  
M.R. Hematiyan
Keyword(s):  
Boundary Element Method ◽  
Heat Source ◽  
Boundary Element ◽  
Thermal Stresses ◽  
Quadratic Function ◽  
Boundary Integral ◽  
Volume Integral ◽  
Direct Evaluation ◽  
Volume Heat ◽  
Element Method

ABSTRACTIn engineering applications, it is pretty often to have domain heat source involved inside. This article proposes an approach using the boundary element method to study thermal stresses in 3D anisotropic solids when internal domain heat source is involved. As has been well noticed, thermal effect will give rise to a volume integral, where its direct evaluation will need domain discretization. This shall definitely destroy the most distinctive notion of the boundary element method that only boundary discretization is required. The present work presents an analytical transformation of the volume integral in the boundary integral equation due to the presence of internal volume heat source. For simplicity, distribution of the heat source is modeled by a quadratic function. When needed, the formulations can be further extended to treat higher-ordered volume heat sources. Indeed, the present work has completely restored the boundary discretization feature of the boundary element method for treating 3D anisotropic thermoelasticity involving volume heat source.

scholarly journals Dynamic Analysis of Functionally Graded Porous Plates Resting on Elastic Foundation Taking into Mass subjected to Moving Loads Using an Edge-Based Smoothed Finite Element Method

2020 ◽  
Vol 2020 ◽  
pp. 1-19
Author(s):  
Trung Thanh Tran ◽  
Quoc-Hoa Pham ◽  
Trung Nguyen-Thoi
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Dynamic Analysis ◽  
Elastic Foundation ◽  
Functionally Graded ◽  
Triangular Element ◽  
Moving Loads ◽  
Smoothed Finite Element Method ◽  
Edge Based ◽  
Element Method

The paper presents the extension of an edge-based smoothed finite element method using three-node triangular elements for dynamic analysis of the functionally graded porous (FGP) plates subjected to moving loads resting on the elastic foundation taking into mass (EFTIM). In this study, the edge-based smoothed technique is integrated with the mixed interpolation of the tensorial component technique for the three-node triangular element (MITC3) to give so-called ES-MITC3, which helps improve significantly the accuracy for the standard MITC3 element. The EFTIM model is formed by adding a mass parameter of foundation into the Winkler–Pasternak foundation model. Two parameters of the FGP materials, the power-law index (k) and the maximum porosity distributions (Ω), take forms of cosine functions. Some numerical results of the proposed method are compared with those of published works to verify the accuracy and reliability. Furthermore, the effects of geometric parameters and materials on forced vibration of the FGP plates resting on the EFTIM are also studied in detail.

Application of the particle finite element method for large deformation consolidation analysis

2019 ◽  
Vol 36 (9) ◽  
pp. 3138-3163 ◽  
Author(s):  
Wei-Hai Yuan ◽  
Wei Zhang ◽  
Beibing Dai ◽  
Yuan Wang
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Large Deformation ◽  
Excess Pore Pressure ◽  
Triangular Element ◽  
Particle Finite Element Method ◽  
Content Type ◽  
Modified Cam Clay ◽  
Large Deformation Problems ◽  
Element Method

Purpose Large deformation problems are frequently encountered in various fields of geotechnical engineering. The particle finite element method (PFEM) has been proven to be a promising method to solve large deformation problems. This study aims to develop a computational framework for modelling the hydro-mechanical coupled porous media at large deformation based on the PFEM. Design/methodology/approach The PFEM is extended by adopting the linear and quadratic triangular elements for pore water pressure and displacements. A six-node triangular element is used for modelling two-dimensional problems instead of the low-order three-node triangular element. Thus, the numerical instability induced by volumetric locking is avoided. The Modified Cam Clay (MCC) model is used to describe the elasto-plastic soil behaviour. Findings The proposed approach is used for analysing several consolidation problems. The numerical results have demonstrated that large deformation consolidation problems with the proposed approach can be accomplished without numerical difficulties and loss of accuracy. The coupled PFEM provides a stable and robust numerical tool in solving large deformation consolidation problems. It is demonstrated that the proposed approach is intrinsically stable. Originality/value The PFEM is extended to consider large deformation-coupled hydro-mechanical problem. PFEM is enhanced by using a six-node quadratic triangular element for displacement and this is coupled with a four-node quadrilateral element for modelling excess pore pressure.

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