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CONTENTS
Volume 14, Number 6, April30 2018
 

Abstract
This paper proposes a numerical methodology for capturing the complete curve of a pressuremeter test including initial or disturbed parts and loops through a stiffness-based approach adopted in three dimensional finite difference code, FLAC3D. In order to enable this, a new hyperbolic model was used to replace the conventional linear elastic model prior to peak strength of Mohr-Coulomb soil model and update or degradation of shear modulus was considered. Presented modeling approach and implemented constitutive model are impressively successful. It leads to obtain the whole set of parameters for characterizing sands and seems promising for modeling the most of geotechnical structures.

Key Words
pressuremeter test; modified hyperbolic model; modulus evolution; small strain

Address
Sadik Oztoprak, Sinan Sargin, Hidayet K. Uyar and Ilknur Bozbey: Faculty of Engineering, Department of Civil Engineering, Istanbul University, Avcilar 34320, Istanbul, Turkey

Abstract
In this work, two dimensional (2D) and quasi three-dimensional (quasi-3D) HSDTs are proposed for bending and free vibration investigation of functionally graded (FG) plates using hyperbolic shape function. Unlike the existing HSDT, the proposed theories have a novel displacement field which include undetermined integral terms and contains fewer unknowns. The material properties of the plate is inhomogeneous and are considered to vary continuously in the thickness direction by three different distributions; power-law, exponential and Mori-Tanaka model, in terms of the volume fractions of the constituents. The governing equations which consider the effects of both transverse shear and thickness stretching are determined through the Hamilton\'s principle. The closed form solutions are deduced by employing Navier method and then fundamental frequencies are obtained by solving the results of eigenvalue problems. In-plane stress components have been determined by the constitutive equations of composite plates. The transverse stress components have been determined by integrating the 3D stress equilibrium equations in the thickness direction of the FG plate. The accuracy of the present formulation is demonstrated by comparisons with the different 2D, 3D and quasi-3D solutions available in the literature.

Key Words
bending; vibration; functionally graded plate; shear deformation theory; stretching effect

Address
Abderahman Younsi: Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria

Abdelouahed Tounsi and Abdelmoumen Anis Bousahla: 1.)Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria
2.)Laboratory of Structures and Advanced Materials in Civil Engineering and Public Works, Department of Civil Engineering,
Faculty of Technology, University of Sidi Bel Abbes, Algeria
3.)Multi-scale Modeling and Simulation Laboratory, Department of Physics, Faculty of Exact Sciences, University of Sidi Bel Abbés, Algeria

Fatima Zohra Zaoui: Laboratory for Numerical and Experimental Modeling of Mechanical Phenomena, Faculty of Sciences and Technology, Department of Mechanical Engineering, University Abdelhamid Ibn Badis of Mostaganem, 27000, Algeria

S.R. Mahmoud: Department of Mathematics, Faculty of Science, King Abdulaziz University, Saudi Arabia

Abstract
The importance of using materials cost effectively to enhance the strength and reduce the cost, and weight of earth fill materials in geotechnical engineering led researchers to seek for modifying the soil properties by adding proper additives. Lightweight fill materials made of soil, binder, water, and Expanded polystyrene (EPS) beads are increasingly being used in geotechnical practices. This paper primarily investigates the behavior of sandy soil, modified by EPS particles. Besides, the mechanical properties of blending sand, EPS and the binder material such as fly ash and cement were examined in different mixing ratios using a number of various laboratory studies including the Modified Standard Proctor (MSP) test, the Unconfined Compressive Strength (UCS) test, the California Bearing Ratio (CBR) test and the Direct Shear test (DST). According to the results, an increase of 0.1% of EPS results in a reduction of the density of the mixture for 10%, as well as making the mixture more ductile rather than brittle. Moreover, the compressive strength, CBR value and shear strength parameters of the mixture decreases by an increase of the EPS beads, a trend on the contrary to the increase of cement and fly ash content.

Key Words
sand; EPS; fly ash; cement; unconfined compression strength; California bearing ratio; direct shear test

Address
Reza Jamshidi Chenari, Ali Ghorbani and Mohsen Nasiri Alamoti: Faculty of Engineering, University of Guilan, Rasht, Guilan, Iran

Behzad Fatahi:School of Civil and Environmental Engineering, Faculty of Engineering and Information Technology, University of Technology, Sydney (UTS), City Campus PO Box 123 Broadway NSW 2007, Australia

Abstract
Blast-induced ground vibrations by a significant amount of explosives may cause many problems for mining slope stability. Geological discontinuities have a significant influence on the transmission of dynamic pressure of detonation and according to their position relative to the slope face may have damaging or useful impacts on the slope stability. In this study, the effect of geological discontinuities was investigated by modelling a slope with geological discontinuities through applying the dynamic pressure in three-dimensional discrete element code (3DEC). The geological discontinuities in four states that generally apperceived in mine slopes are considered. Given the advantages of the pressure decay function defined by some researcher, this type of function was used to develop the pressure-time profile. The peak particle velocities (PPV) values were monitored along an axis by utilization of Fish programming language and the results were used as an indicator to measure the effects. As shown in the discontinuity-free model, PPV empirical models are reliable in rocks lacking discontinuities or tightly jointed rock masses. According to the other results, the empirical models cannot be used for the case where the rock mass contains discontinuities with any direction or dip. With regard to PPVs, when the direction of discontinuities is opposite to that of the slope face, the dynamic pressure of detonation is significantly damped toward the slope direction at the surface of discontinuities. On the other hand, when the discontinuities are horizontal, the dynamic pressure of detonation affects the rock mass to a large distance.

Key Words
geological discontinuities; detonation pressure; PPV; slope stability; 3DEC

Address
Ali Haghnejad and Kaveh Ahangari: Department of Mining Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran

Parviz Moarefvand: Department of Mining and Metallurgical Engineering, Amirkabir University of Technology, Tehran, Iran

Kamran Goshtasbi: Department of Mining Engineering, Tarbiat Modares University, Tehran, Iran University Square, End of North Sattari Highway, Tehran, Iran


Abstract
Road construction is becoming increasingly important in marine and desert areas due to population growth and economic development. However, the load carrying capacity of pavement is of gear concern to design and geotechnical engineers because of the poor engineering properties of the soils in these areas. Therefore, stabilization of the soils is regarded as an important issue. Besides, due to the fuels combustion and carbonate decomposition, cement industry generates around 5% of global CO2 emission. Thus, using bentonite as a natural pozzolan in soil stabilization is more eco-friendly than using cement. The aim of this research is to experimentally study of the stabilized marine and desert sands using deep mixing method by ordinary Portland cement and sodium bentonite. Different partial percentages of cement along with different weight percentages of sodium bentonite were added to the sands. Unconfined compression test (UCS), Energy Dispersive X-ray (EDX), and Scanning Electron Microscope (SEM) were conducted on the specimens. Moreover, a mathematical model was developed for predicting the strength of the treated soils.

Key Words
marine and desert sandy soils; deep mixing method; cement; sodium bentonite; unconfined compressive strength; mathematical model

Address
Mohammad Saberian:School of Engineering, RMIT University, 376-392 Swanston Street, Melbourne, Victoria, Australia

Mojtaba Moradi: Department of Civil Engineering, Yazd University, Yazd, Iran

Ramin Vali: Department of Civil Engineering, Mohajer Technical and Vocational College of Isfahan, Isfahan, Iran

Jie Li: School of Engineering, RMIT University, 376-392 Swanston Street Melbourne, Victoria, Australia

Abstract
Ballast layer has an important role in vertical stiffness and stability of railway track. In most of the Middle East countries and some of the Asian ones, significant parts of railway lines pass through desert areas where the track (particularly ballast layer) is contaminated with sands. Despite considerable number of derailments reported in the sand contaminated tracks, there is a lack of sufficient studies on the influences of sand contamination on the ballast vertical stiffness as the main indicator of track stability. Addressing this limitation, the effects of sand contamination on the mechanical behavior of ballast were experimentally investigated. For this purpose, laboratory tests (plate load test) on ballast samples with different levels of sand contamination were carried out. The results obtained were analyzed leading to derive mathematical expressions for the strain modulus (EV) as a function of the ballast level of contamination. The EV was used as an index for evaluation of the load-deformation characteristics and bearing capacity of track substructure. The critical limit of sand contamination, after which the EV of the ballast reduces drastically, was obtained. It was shown that the obtained research results improve the current track maintenance approach by providing key guides for the optimization of ballast maintenance planning (the timing of ballast cleaning or renewal).

Key Words
railway ballast; sand; contamination; strain modulus; maintenance; laboratory test

Address
Ali R. Tolou Kian, Jabbar A. Zakeri and Javad Sadeghi: School of Railway Engineering, Iran University of Science and Technology, Narmak, Tehran, Islamic Republic of Iran

Abstract
The failure mechanism of tunnel roof is investigated with upper bound theorem of limit analysis. The stochastic settlement and nonlinear failure criterion are considered in the present analysis. For the collapse of tunnel roof, the surface settlement is estimated by the simplified stochastic medium theory. The failure curve expressions of collapse blocks in homogeneous and in layered soils are derived, and the effects of material parameters on the potential range of failure mechanisms are discussed. The results show that the material parameters of initial cohesion, nonlinear coefficient and unit weight have significant influences on the potential range of collapse block in homogeneous media. The proportion of collapse block increases as the initial cohesion increases, while decreases as the nonlinear coefficient and the unit weight increase. The ground surface settlement increases with the tunnel radius increasing, while the possible collapse proportion decreases with increase of the tunnel radius. In layered stratum, the study is investigated to analyze the effects of material parameters of different layered media on the proportion of possible collapse block.

Key Words
nonlinear failure; roof collapse; stochastic medium theory; settlement; layered soils

Address
Xiaolin Huang and Zhigang Zhou:School of Traffic and Transportation Engineering, Changsha University of Science and Technology, Hunan, China

X.L. Yang: School of Civil Engineering, Central South University, Hunan 410075, China

Abstract
In order to explore the comprehensive evaluation means of the extent of hydraulic fracturing region in coal seams, we analyzed the feasibility of detecting the response of coal rock direct current (DC) apparent resistivity to hydraulic-fracturing using Archie\'s theory, and conducted experimental researches on the response of DC resistivity in the hydraulic fracturing process using small-scale coal rock samples. The results show that porosity and water saturation are the two factors affecting the apparent resistivity of coal rock while hydraulic fracturing. Water has a dominant effect on the apparent resistivity of coal rock samples. The apparent resistivity in the area where water flows through is reduced more than 50%, which can be considered as a core affect region of hydraulic fracturing. Stress indirectly impacts the apparent resistivity by changing porosity. Before hydraulic fracturing, the greater axial load applied, the more serious the rupture in the samples, resulting in the greater apparent resistivity. Apparent resistivity testing is a potential regional method to evaluate the influence range of hydraulic fracturing in coal seams.

Key Words
coal rock mass; hydraulic fracturing; DC resistivity response; apparent resistivity

Address
Dazhao Song and Menghan Wei: School of Civil and Resource Engineering, University of Science and Technology Beijing, Beijing 100083, China

Enyuan Wang, Liming Qiu and Haishan Jia: 1.) Key Laboratory of Gas and Fire Control for Coal Mines, China University of Mining and Technology, Xuzhou 221116, China
2.)School of Safety Engineering, China University of Mining and Technology, Xuzhou 221116, China

Peng Chen: Safety Engineering College of NCIST & Center, North China Institute of Science and Technology, Yanjiao 065201, China

Abstract
For foundations in permafrost regions, the displacement characteristics are uncertain because of the randomness of temperature characteristics and mechanical parameters, which make the structural system have an unexpected deviation and unpredictability. It will affect the safety of design and construction. In this paper, we consider the randomness of temperature characteristics and mechanical parameters. A stochastic analysis model for the uncertain displacement characteristic of foundations is presented, and the stochastic coupling program is compiled by Matrix Laboratory (MATLAB) software. The stochastic displacement fields of an embankment in a permafrost region are obtained and analyzed by Neumann stochastic finite element method (NSFEM). The results provide a new way to predict the deformation characteristics of foundations in permafrost regions, and it shows that the stochastic temperature has a different influence on the stochastic lateral displacement and vertical displacement. Construction disturbance and climate warming lead to three different stages for the mean settlement of characteristic points. For the stochastic settlement characteristic, the standard deviation increases with time, which imply that the results of conventional deterministic analysis may be far from the true value. These results can improve our understanding of the stochastic deformation fields of embankments and provide a theoretical basis for engineering reliability analysis and design in permafrost regions.

Key Words
stochastic analysis; uncertain deformation; foundations; permafrost regions; random field

Address
Tao Wang, Guoqing Zhou, Jianzhou Wang, Xiaodong Zhao and Leijian Yin: State Key Laboratory for Geomechanics and Deep Underground Engineering, School of Mechanics and Civil Engineering, China University of Mining and Technology, Xuzhou, Jiangsu, 221116, China

Abstract
This study presents structural and parametric analyses on the behavior of an integrated and pile-bent abutment with mechanically stabilized earth wall (IPM) bridge. The IPM bridge is an integral abutment bridge (IAB) with partially protruded piles, which excludes earth pressure by means of a mechanically stabilized earth wall developed by the authors. The results of the analysis indicate that the IPM bridge, as any other IAB, is influenced to a large extent by temperature and time-dependent loads. When these loads are applied, the stress on a pile in the IPM bridge decreases as the displacement of the pile top increases, because the piles protrude from the ground surface and no soil reaction is generated on the protruded pile. Because the length of an IAB is restricted by the forces acting on its piles, the IPM bridge is an effective alternative to extend its length.

Key Words
IPM bridge; structural analysis; protruded pile; pile behavior; seasonal behavior

Address
Min-Cheol Park: Department of Civil Engineering, Kumoh National Institute of Technology, 208 Global-gwan, 61, Daehak-ro, Gumi-si, Gyeongsangbuk-do, Republic of Korea

Moon S. Nam: Structure Research Division, Research Institute of Korea Expressway Corporation, 208-96, Dongbu-daero 922beon-gil, Dongtan-myeon, Hwaseong-si, Gyeonggi-do, Republic of Korea


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