scholarly journals Estimation of Soil Electrical Properties in a Multilayer Earth Model with Boundary Element Formulation

2012 ◽  
Vol 2012 ◽  
pp. 1-13 ◽  
Author(s):  
T. Islam ◽  
Z. Chik ◽  
M. M. Mustafa ◽  
H. Sanusi
Keyword(s):  
Boundary Conditions ◽  
Boundary Element ◽  
Earth Model ◽  
Element Formulation ◽  
Soil Resistivity ◽  
Resistivity Ratio ◽  
Soil Medium ◽  
Near Surface ◽  
Soil Model ◽  
Geotechnical Investigations

This paper presents an efficient model for estimation of soil electric resistivity with depth and layer thickness in a multilayer earth structure. This model is the improvement of conventional two-layer earth model including Wenner resistivity formulations with boundary conditions. Two-layer soil model shows the limitations in specific soil characterizations of different layers with the interrelationships between soil apparent electrical resistivity (ρ) and several soil physical or chemical properties. In the multilayer soil model, the soil resistivity and electric potential at any points in multilayer anisotropic soil medium are expressed according to the variation of electric field intensity for geotechnical investigations. For most soils with varying layers, multilayer soil resistivity profile is therefore more suitable to get soil type, bulk density of compacted soil and to detect anomalous materials in soil. A boundary element formulation is implemented to show the multilayer soil model with boundary conditions in soil resistivity estimations. Numerical results of soil resistivity ratio and potential differences for different layers are presented to illustrate the application, accuracy, and efficiency of the proposed model. The nobility of the research is obtaining multilayer soil characterizations through soil electric properties in near surface soil profile.

Performance of Multi-Layer Soil Electric Resistivity Model Comparing with Two-Layer Characterizations in Geotechnical Investigations

2013 ◽  
Vol 655-657 ◽  
pp. 1857-1863
Author(s):  
Zamri Chik ◽  
Taohidul Islam
Keyword(s):  
Apparent Resistivity ◽  
Soil Characteristics ◽  
Electric Resistivity ◽  
Layer Model ◽  
Soil Resistivity ◽  
Near Surface ◽  
Resistivity Profile ◽  
Geotechnical Investigations ◽  
Resistivity Model ◽  
Two Layer Model

This paper shows the performance of multi-layer soil electric resistivity model comparing with two-layer characterizations in geotechnical investigations. In conventional model, there are inter-relationships between soil apparent electrical resistivity (ρ) and several soil physical or chemical properties. These empirical relationships show limitations to obtain specific soil characterizations of different layers with. Multi-layer true resistivity model is the improvement of conventional two-layer earth model including the criteria of four points probe method. Multi-layer soil resistivity profile shows more accuracy to obtain near surface soil characteristics including the types of soil and rocks, and to detect anomalous materials in soil profile. Alternatively, apparent resistivity in two-layer model can be used to obtain deeper profile of soil characteristics. In this multi-layer soil model, the soil resistivity and resistivity ratio corresponding to the depth in soil medium are considered for geotechnical investigations. Two-layer model includes soil apparent resistivity according to probe distances in depth corresponding resistivity profile. This paper is important for including criteria and performance of multi-layer soil resistivity model and conventional two-layer model for geotechnical characterizations.

A Computational Acoustic Field Reconstruction Process Based on an Indirect Variational Boundary Element Formulation

1999 ◽  
Author(s):  
Zhidong Zhang ◽  
Nickolas Vlahopoulos ◽  
S. T. Raveendra ◽  
T. Allen ◽  
K. Y. Zhang
Keyword(s):  
Boundary Conditions ◽  
Boundary Element ◽  
Acoustic Field ◽  
Acoustic Pressure ◽  
Transfer Functions ◽  
Element Formulation ◽  
Reconstruction Process ◽  
Field Reconstruction ◽  
Original Field ◽  
New Formulation

Abstract The objective of the work presented in this paper is to develop a computational capability based on the indirect variational boundary element method (IVBEM) to evaluate appropriate velocity boundary conditions on an assembly of piston type sources such that they can recreate a prescribed acoustic field. Information for the acoustic pressure of the original acoustic field at certain field points constitutes the input to the developed process. Several new developments associated with the IVBEM are completed within the field reconstruction process. A new formulation for treating irregular frequencies in the IVBEM is developed and implemented in the field reconstruction process. The velocities on the piston type sources are computed from transfer functions between the field points, where the acoustic pressure of the original field is prescribed, and the velocity boundary condition on each element of the generic source. The IVBEM is employed for computing the transfer functions. A singular value decomposition solver is integrated with the IVBEM computations in order to evaluate the velocity boundary conditions from the transfer functions. Finally, an algorithm is developed that identifies the optimum field points where the acoustic pressure of the original field must be prescribed. The optimum field points are selected from a set of prescribed candidate points. The selection of the optimum points is based on the geometric characteristics of the generic source, the frequency of analysis, and the properties of the medium. Several validation and application cases are presented.

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