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CONTENTS
Volume 21, Number 5, June10 2020
 

Abstract
The paper describes the influence of pile reinforcement on the stability of the slope behaviour, and the exploitation of the results of in situ measurements will be conducted. In the second part, a 2D numerical modelling will be conducted by using the finite element code PLAXIS2D; in order to validate the proposed modelling approach by comparing the numerical results with the measurements results carried out on the slides studied; to study the effect of positioning of piles as a function of the shear parameters of the supported soil on the behaviour of the soil. For various shear strength of the soil a row of pile position is found, at which the piles offer the maximum contribution to slope stability. The position of piles is found to influence the safety factor in granular soil whereas it shows a slight influence on the safety factor in coherent soil. The results also indicate that the ideal position for such stabilizing piles is in the middle height of the slope. Comparison of results of present study with literature from publication: indicated that to reach the maximum stability of slope, the pile must be installed with Lx/L ratio (0.37 to 0.62) and the inclination must be between 30o to 60o. Even, after a certain length of the pile, the increasing will be useless. The application of the present approach to such a problem is located at the section of PK 210+480 to 210+800 of the Algerian East-West Highway.

Key Words
landslide; reinforcement; numerical model; shear strength reduction finite element method; pile; safety factor

Address
Khalifa Boulfoul and Farid Hammoud: Department of Civil Engineering, Faculty of Science, Mustapha Ben Boulaid, Batna2 University, Batna, Algeria

Khelifa Abbeche: Research Laboratory of Applied Hydraulics RLAHYA, Department of Civil Engineering,Faculty of Science, Mustapha Ben Boulaid, Batna2 University, Batna, Algeria

Abstract
The choice of eco-friendly materials for ground improvement is a necessary way forward for sustainable development. Adapting naturally available biopolymers will render the process of soil stabilization carbon neutral. An attempt has been made to use β-glucan a natural biopolymer for the stabilization of lean clay as a sustainable alternative with specific emphasis on comprehending the effect of confining stresses on lean clay through triaxial compression tests. A sequence of laboratory experiments was performed to examine the various physical and mechanical characteristics of β-glucan treated soil (BGTS). Micro-analysis through micrographs were used to understand the strengthening mechanism. Results of the study show that the deviatoric stress of 2% BGTS is 12 times higher than untreated soil (UTS). The micrographs from Scanning Electron Microscopy (SEM) and the results of the Nitrogen-based Brunauer Emmett Teller (N2-BET) analysis confirm the formation of new cementitious fibres and hydrogels within the soil matrix that tends to weld soil particles and reduce the pore spaces leading to an increase in strength. Hydraulic conductivity (HC) and compressibility reduced significantly with the biopolymer content and curing period. Results emphases that β-glucan is an efficient and sustainable alternative to the traditional stabilizers like cement, lime or bitumen.

Key Words
biopolymer; β-glucan; shear strength; hydraulic conductivity; compressibility

Address
S. Anandha Kumar and Evangelin Ramani Sujatha:Centre for Advanced Research on Environment, School of Civil Engineering, SASTRA Deemed University, Thanjavur 613401, Tamil Nadu, India


Abstract
Hydraulic conductivity is one of the engineering properties of soil. This study focusses on the influence of cement content on the hydraulic conductivity of cemented sand, which is investigated based on the results from numerical analysis and laboratory testing. For numerical analysis the cemented samples were scanned using X-ray Computed Tomography (CT) while laboratory testing was carried out using a triaxial setup. Numerical analysis enables us to simulate flow through the sample and provides insight to the microstructure. It quantifies the pore volume, proportion of interconnected voids and pore size distribution in both cemented and uncemented samples, which could be computed only through empirical equations in case of laboratory testing. With reduction in global voids, the interconnecting voids within the samples also reduce with cement content. Gamma cumulative distribution function is used to predict the percentage of voids lesser than a given pore volume. Finally, the results obtained from both numerical analysis and laboratory testing are compared.

Key Words
lifecycle performance; stochastic deterioration modelling; structural reliability; reinforcement corrosion; residual strength

Address
Sathya Subramanian, Yi Zhang and Taeseo Ku: Department of Civil and Environmental Engineering, National University of Singapore, 1 Engineering Drive 2, 117576 Singapore

Ganapathiraman Vinoth: Department of Civil Engineering, The University of British Columbia, 6250 Applied Science Ln #2002, Vancouver, BC V6T 1Z4, Canada

Juhyuk Moon: Department of Civil and Environmental Engineering, Seoul National University, Kwanak-gu Kwanak-ro 1, 35-412, Seoul 08826, Korea

Abstract
The weakening and softening behavior of soft clay subjected to cyclic loading due to the build-up of excess pore water pressure is well-known. During the design stage of the foundation of highways and coastal high-rise buildings, it is important to study the mechanical behavior of marine soils under cyclic loading as they undergo greater settlement during cyclic loading than under static loading. Therefore, this research evaluates the cyclic stress-strain and shear strength of untreated and treated marine clay under the effects of wind, earthquake, and traffic loadings. A series of laboratory stress-controlled cyclic triaxial tests have been conducted on both untreated and treated marine clay using different effective confining pressures and a frequency of 0.5 and 1.0 Hz. In addition, treated samples were cured for 28 and 90 days and tested under a frequency of 2.0 Hz. The results revealed significant differences in the performance of treated marine clay samples than that of untreated samples under cyclic loading. The treated marine clay samples were able to stand up to 2000 loading cycles before failure, while untreated marine clay samples could not stand few loading cycles. The untreated marine clay displayed a higher permanent axial strain rate under cyclic loading than the treated clay due to the existence of new cementing compounds after the treatment with recycled tiles and low amount (2%) of cement. The effect of the effective confining pressure was found to be significant on untreated marine clay while its effect was not crucial for the treated samples cured for 90 days. Treated samples cured for 90 days performed better under cyclic loading than the ones cured for 28 days and this is due to the higher amount of cementitious compounds formed with time. The highest deformation was found at 0.5 Hz, which cannot be considered as a critical frequency since smaller frequencies were not used. Therefore, it is recommended to consider testing the treated marine clay using smaller frequencies than 0.5 Hz.

Key Words
marine clay; cyclic triaxial test; loading frequency; curing time; confining pressure

Address
Mohammed A. M. Al-Bared, Indra S. H. Harahap, Hisham Mohamad and Zahiraniza Mustaffa: Department of Civil and Environmental Engineering, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 32610, Malaysia

Aminaton Marto: Malaysia-Japan International Institute of Technology, Universiti Teknologi Malaysia (UTM) Kuala Lumpur, 54100 Kulala Lumpur, Malaysia

Seyed Vahid Alavi Nezhad Khalil Abad: Department of Civil Engineering, Birjand University of Technology, Birjand, Iran


Abstract
This paper aims to investigate the effect of rotation on a micropolar thermoelastic medium with voids problem. The problem is assessed according to three-phase-lag model. The normal mode analysis used to obtain the analytical expressions of the considered variables. The non-dimensional displacement, temperature, Micro rotation, the change in the volume fraction field, and stress of the material are obtained and illustrated graphically. Comparisons are made with the results predicted by two theories; namely three- phase-lag model (3PHL) and Green-Naghdi theory of type III (G-N III). The considered variables were plotted for different values of the rotation parameter, the phase-lag of heat flux and the phase-lag of temperature. The numerical results reveal that the rotation and the phase-lag times significantly influence the distribution of the field quantities. Some particular cases of interest are deduced from the present investigation.

Key Words
micropolar; voids; rotation; Green-Naghdi theory; three-phase-lag

Address
Mohamed I. A. Othman: Department of Mathematics, Faculty of Science, Zagazig University,P.O. Box 44519, Zagazig, Egypt

Amnah M. Alharbi and Al-Anoud M. Kh. Al-Autabi: Department of Mathematics, Faculty of Science, Taif University, Taif, Saudi Arabia

Abstract
The objective of this paper is to study the deformation in a homogeneous isotropic modified couple stress thermoelastic medium with and without energy dissipation and with two temperatures due to thermal source and mechanical force. Laplace and Fourier transform techniques are applied to obtain the solutions of the governing equations. The displacement components, stress components, conductive temperature and couple stress are obtained in the transformed domain. Isothermal boundary and insulated boundary conditions are used to investigate the problem.The effect of two temperature and GN theory of type–II and type–III has been depicted graphically on the various components. Numerical inversion technique has been used to obtain the solutions in the physical domain. Some special cases of interest are also deduced.

Key Words
isotropic medium; two temperatures; Laplace and Fourier transform technique; modified couple stress; thermoelastic

Address
Parveen Lata and Harpreet Kaur: Department of Basic and Applied Sciences, Punjabi University, Patiala, Punjab, India

Abstract
In this work, the buckling analysis of material sandwich plates based on a two-parameter elastic foundation under various boundary conditions is investigated on the basis of a new theory of refined trigonometric shear deformation. This theory includes indeterminate integral variables and contains only four unknowns in which any shear correction factor not used, with even less than the conventional theory of first shear strain (FSDT). Applying the principle of virtual displacements, the governing equations and boundary conditions are obtained. To solve the buckling problem for different boundary conditions, Galerkin\'s approach is utilized for symmetric EGM sandwich plates with six different boundary conditions. A detailed numerical study is carried out to examine the influence of plate aspect ratio, elastic foundation coefficients, ratio, side-to-thickness ratio and boundary conditions on the buckling response of FGM sandwich plates. A good agreement between the results obtained and the available solutions of existing shear deformation theories that have a greater number of unknowns proves to demonstrate the precision of the proposed theory.

Key Words
buckling sandwich plates; functionally graded materials; new four-unknown refined shear deformation theory and various boundary conditions

Address
Sara Chelahi Chikr: 1.) Department of Civil and Hydraulic Engineering, Dr Tahar Moulay University, Faculty of
Technology, BP 138 Cité En-Nasr 20000, Saida, Algeria
2.) Water Resources and Environment Laboratory, Dr Tahar Moulay University, BP 138 Cité En-Nasr 20000, Saida, Algeria

Abdelhakim Kaci: 1.) Department of Civil and Hydraulic Engineering, Dr Tahar Moulay University, Faculty of Technology, BP 138 Cité En-Nasr 20000, Saida, Algeria
2.) Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria

Abdelmoumen Anis Bousahla: 1.) Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia
2.) Multi-scale Modeling and Simulation Laboratory, University of Sidi Bel Abbés, Algeria

Fouad Bourada: 1.) Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria
2.) Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia
3.) Department of Science and Technology, Tissemsilt University Center, BP 38004 Ben Hamouda, Algeria

Abdeldjebbar Tounsi, Kouider Halim Benrahou and Abdelouahed Tounsi: 1.) Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria
2.) Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia

E.A. Adda Bedia: Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia

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

Abstract
This paper conducts a complicated coupled effective stress analysis of X-section-in-place concrete (XCC) pile installation and consolidation processes using the dual-stage Eulerian-Lagrangian (DSEL) technique incorporating the modified Cam-clay model. The numerical model is verified by centrifuge data and field test results. The main objective of this study is to investigate the shape effect of XCC pile cross-section on radial total stress, excess pore pressure and time-dependent strength. The discrepancies of the penetration mechanism and set-up effects on pile shaft resistance between the XCC pile and circular pile are discussed. Particular attention is placed on the time-dependent strength around the XCC pile shaft. The results show that soil strength improved more significantly close to the flat side compared with the concave side. Additionally, the computed ultimate shaft resistance of XCC pile incorporating set-up effects is 1.45 times that of the circular pile. The present findings are likely helpful in facilitating the incorporation of set-up effects into XCC pile design practices.

Key Words
XCC pile; coupled effective stress analysis; large deformation; time-dependent strength; pile shaft resistance

Address
Fei Liu, Jiangtao Yi and Po Cheng: School of Civil Engineering, Chongqing University, No.83 Shabei Street, Chongqing, 400045, China

Kai Yao: 1.) School of Qilu Transportation, Shandong University, 12550 East Second Ring Road, Jinan, 250002, China
2.) Department of Civil and Environmental Engineering, National University of Singapore, 1 Engineering Drive 2, Singapore, 117576, Singapore


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