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CONTENTS
Volume 25, Number 4, May25 2021
 

Abstract
In this work, we compare the analytical solutions with the numerical solutions for photothermal interactions in semiconductor medium containing cylindrical cavity. This paper is devoted to a study of the photothermal interactions in semiconductor medium in the context of the coupled photo-thermal model. The basic equations are formulated in the domain of Laplace transform and the eigenvalue scheme are used to get the analytical solutions. The numerical solution is obtained by using the implicit finite difference method (IFDM). A comparison between the analytical solution and the numerical solutions are obtained. It is found that the implicit finite difference method (IFDM) is applicable, simple and efficient for such problems.

Key Words
Laplace transforms; finite difference method; semi-conductor mediums; cylindrical cavity; eigenvalue method

Address
Ibrahim A. Abbas: Department of mathematics, Faculty of Science, Sohag University, Sohag, Egypt

Abstract
Failure mechanism which can affect geotechnical infrastructures (shallow foundations, retaining walls, and piles) constitutes one of the most encountered problems during the design process. In this respect, the shear behavior of interfaces between grained soils and solid building materials, as well as those between cohesive soils should be investigated. Therefore, a range of ring shear tests with different cohesive soils and stainless-steel interfaces have been carried out through the Bromhead apparatus that allows simulating large displacements along a failure surface. The effects of steel rings roughness and soil type on the residual friction coefficient and the shear zone features (structure, thickness, and texture orientation angle) have been investigated using the Scanning Electron Microscopy. The obtained results indicate that the residual friction coefficient and the structural characteristics of the shear zone vary according to the surface roughness and the soil type. Scanning electron microscopy reveals that the particles inside the shear zone tend to be re-oriented. Also, the shear failure mechanism can be identified along with the interface, within the soil, or simultaneously at the interface and within the soil specimen.

Key Words
failure mechanism; Bromhead apparatus; large displacements; cohesive soils; shear zone features; surface roughness

Address
Belgacem Mamen: Department of Civil Engineering, Faculty of Science and Technology, University Abbés Laghrour of Khenchela, Algeria

Farid Hammoud: Department of Civil Engineering, Faculty of Technology, University Mustapha Ben Boulaid of Batna, Algeria

Abstract
This paper presents a rigorous solution for spherical cavity expansion in unsaturated soils under constant suction condition. The hydraulic behavior that describes the saturation-suction relationship is modeled by a void ratio-dependent soil-water characteristic curve, which allows the hydraulic behavior to fully couple with the mechanical behavior that is described by an extended critical state soil model for unsaturated soil through the specific volume. Considering the boundary condition and introducing an auxiliary coordinate, the problem is formulated to a system of first-order differential equations with three principal stress components and suction as basic unknowns, which is solved as an initial value problem. Parameter analyses are conducted to investigate the effects of suction and the overconsolidation ratio on the overall expansion responses, including the pressure-expansion response, the distribution of the stress components around the cavity, and the stress path of the soil during cavity expansion. The results reveal that the expansion pressures and the distribution of the stress components in unsaturated soils are generally higher than those in saturated soils due to the existence of suction.

Key Words
spherical cavity; suction; hydraulic behaviour; mechanical behavior; expansion responses

Address
Jianhua Tang, Hui Wang and Jingpei Li: Department of Civil Engineering, Tongji University, Shanghai 200092, China

Abstract
Cross-borehole electrical resistivity tomography (ERT) is an effective groundwater detection tool in geophysical investigations. In this paper, an artificial water injection test was conducted on a small clay sample, where the high-resolution cross-borehole ERT was used to investigate the moisture migration law over time. The moisture migration path can be two-dimensionally imaged based on the relationship between resistivity and saturation. The hydraulic conductivity was estimated, and the magnitude ranged from 10-11 m/s to 10-9 m/s according to the comparison between the simulation flow and the saturation distribution inferred from ERT. The results indicate that cross-borehole ERT could help determine the resistivity distribution of small size clay samples. Finally, the cross-borehole ERT technique has been applied to investigate the self-sealing characteristics of clay.

Key Words
cross-borehole electrical resistivity tomography; unsaturated clay; moisture migration, fracture self-sealing

Address
Jiang Lei: 1.) State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan, Hubei 430071, China
2.) Shaanxi Provincial Expressway Construction Group Co., Xian, Shaanxi 710065, China

Weizhong Chen, Fanfan Li, Hongdan Yu, Yongshang Ma and Yun Tian: State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics,
Chinese Academy of Sciences, Wuhan, Hubei 430071, China

Abstract
A rigorous and generic similarity solution is developed for assessment of the undrained expansion responses of a cylindrical cavity expansion in K₀-consolidated anisotropic soils. A K₀-consolidated anisotropic modified Cam-clay (K₀-AMCC) model that can represent the initial stress anisotropy and the effects of stress-induced anisotropy is used to model the soil behaviors during cavity expansion. All the seven basic unknowns, the three stress components, the pore water pressure, the particle velocity, the specific volume and the hardening parameter, are reduced to the functions of a dimensionless radial coordinate and are taken as coupled variables to formulate the problem. The governing equations are formulated by making use of the equilibrium equation, the constitutive equation, the consistency condition, the continuity condition and the undrained condition, which are then solved as an initial value problem. The proposed rigorous similarity solution is compared with some well-documented rigorous solutions to validate the solution and to highlight the special expansion responses in anisotropic soils. The results reveal that the present solution can yield more predictions for cavity expansion problems in soils with initial anisotropic stresses.

Key Words
similarity solution; cavity expansion; undrained condition; anisotropy

Address
You Wang and Jingpei Li: Department of Civil Engineering, Tongji University, Shanghai 200092, China

Lin Li: School of Highway, Chang'an University, Xi'an 710064, China

Abstract
This paper reports the results of advanced data analysis involving artificial neural networks for the prediction of the unconfined compressive strength of granite using only two non-destructive test indexes. A data-independent site-independent unbiased database comprising 182 datasets from non-destructive tests reported in the literature was compiled and used to train and develop artificial neural networks for the prediction of the unconfined compressive strength of granite. The results show that the optimum artificial network developed in this research predicts the unconfined compressive strength of weak to very strong granites (20.3-198.15MPa) with less than ±20% deviation from the experimental data for 70% of the specimen and significantly outperforms a number of available models available in the literature. The results also raise interesting questions with regards to the suitability of the Pearson correlation coefficient in assessing the prediction accuracy of models.

Key Words
unconfined compressive strength; rocks; non-destructive testing; effective porosity, pulse velocity, artificial neural networks; machine learning

Address
Danial J. Armaghani: Department of Civil Engineering, Faculty of Engineering, University of Malaya, 50603, Kuala Lumpur, Malaysia

Anna Mamou,Vassilis G. Siorikis, Athanasia D. Skentou and Panagiotis G. Asteris: Computational Mechanics Laboratory, School of Pedagogical and Technological Education, 15122 Marousi, Greece

Chrysanthos Maraveas: Department of Civil Engineering, University of Patras, Greece

Panayiotis C. Roussis: Department of Civil and Environmental Engineering, University of Cyprus, 1678 Nicosia, Cyprus

Abstract
In this work, an analytical solution is provided for the dynamical response of an orthotropic non-homogeneous elastic material. The present study has engineering applications in the fields of geophysical physics, structural elements, plasma physics, and the corresponding measurement techniques of magneto-elasticity. The analytical performances for the elastodynamic equations has been solved regarding displacements. The influences of the rotation, the magnetic field, the non-homogeneity based radial displacement and the corresponding stresses in an orthotropic material are investigated. The variations of the stresses, the displacement, and the perturbation magnetic field have been illustrated. The comparisons is performed using the previous solutions in the magnetic field absence, the non-homogeneity and the rotation.

Key Words
non-homogeneous; the rotation; orthotropic material; magnetic field; dynamical behavior

Address
Mohammed Balubaid: Department of Industrial Engineering, Faculty of Engineering, King Abdulaziz University, Jeddah, Saudi Arabia

H. Abdo: Faculty of Science, Mathematics Dept, Computer Science Branch, South Valley University, Aswan, Egypt

E. Ghandourah: Department of Nuclear Engineering, Faculty of Engineering, King Abdulaziz University, Jeddah, Saudi

S. R. Mahmoud: GRC Department, Jeddah Community College, King Abdulaziz University. Jeddah 21589, Saudi Arabia

Abstract
1D sand compression response to ko-loading experiences volume contraction from low to high effective stress regimes. Previous study suggested compressibility model with physically correct asymptotic void ratios at low and high stress levels and examined only for both remolded clays and natural clays. This study extends the validity of Enhanced Terzaghi model for different sand types complied from 1D compression data. The model involved with four parameters can adequately fit 1D sand compression data for a wide stress range. The low stress obtained from fitting parameters helps to identify the initial fabric conditions. In addition, strong correlation between compressibility and the void ratio at low stress facilitates determination of self-consistent fitting parameters. The computed tangent constrained modulus can capture monotonic stiffening effect induced by an increase in effective stress. The magnitude of tangent stiffness during large strain test should not be associated with small strain stiffness values. The use of a single continuous function to capture 1D stress-strain sand response to ko-loading can improve numerical efficiency and systematically quantify the yield stress instead of ad hoc methods.

Key Words
1D sand compression response; enhanced Terzaghi model; monotonic stiffening effect; tangential stiffness; small strain stiffness; yield stress

Address
Song-Hun Chong: Department of Civil Engineering, Sunchon National University, 255 Jungang-ro, Sunchon, Jeollanam-do 57922, Republic of Korea

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