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CONTENTS
Volume 16, Number 3, October30 2018
 
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Abstract
Clayey soils with swelling and shrinkage characteristics have been major causes for many problems in roads, buildings and other civil engineering infrastructure in various areas of Pakistan, particularly where there are several patches of such soils on either side of Indus River. As the consistency characteristics are directly related with the variation of moisture content; therefore, this study was explicitly focused to investigate the effect of lime and wheat straw on the consistency characteristics of clayey soils with relatively high swelling and shrinkage characteristics. The consistency test results indicate that by the increase in lime content there is a decrease in the plasticity index of soil; for instance, 10% lime content resulted to 59% decrease in the plasticity index value. On the other hand; the addition of wheat straw resulted in a significant increase in the plasticity index; for instance, 10% wheat straw content resulted to a 120% increase in the plasticity index. This study has further shown that the shrinkage and swelling of clayey soils which resulting to several problems in the civil engineering infrastructures may adequately be managed through mixing an appropriate amount of lime and wheat straw as soil stabilizing agent for both immediate and long-term effects.

Key Words
consistency; wheat straw; lime; clayey soil; shrinkage

Address
Gul Muhammad and Amanullah Marri: Department of Civil Engineering, NED University of Engineering and Technology, Karachi-75270, Pakistan

Abstract
Interest to basal reinforced piled embankments is increasing recently due to their rapid construction and reliability. A comprehensive parametric study is conducted to determine effects of pile properties, reinforcement stiffness, embankment properties and soft soil properties into settlements, pressures and excess pore water pressure development and dissipations. Results which are obtained by using one-layer reinforcement during construction are compared with the results obtained by using two-layer reinforcement during construction. Finite element method is used during the parametric study. Second layer of reinforcement is placed

Key Words
consolidation; settlement; geosynthetics; pile; embankment

Address
Eren Balaban: Department of Transport Structures, University of Pardubice, Studentska 95, 532 10, Pardubice, Czech Republic

Mehmet İ. Onur:Department of Civil Engineering, Eskişehir Technical University, İki Eylül Kampüsü 26470 Tepebaşi/Eskişehir, Turkey

Abstract
Organic-sandy soils that contain abundant organic matters are widely encountered in estuarine cities. Due to the existence of organic matters, the strength and stiffness of this type of soil are significantly low. As a result, various geotechnical engineering problems such as difficulties in piling and constructing embankments and a lack of strength in poured concrete may occur in many estuarine sites; ground improvement such as cement treatment to this type of soils is needed. In this study, laboratory tests were performed to investigate the compressive strength of organic-sandy soil reinforced with primarily cement, in which the influences of several factors, namely types of cement and additional stabilizing agent, cement content, and water-cement ratio, were investigated and the orthogonal experimental design scheme was adopted. Based on the test results, an optimal permutation of these influencing factors is suggested for the reinforcement of organic-sandy soils, which can provide a useful reference for the relevant engineering practice.

Key Words
organic-sandy soil; chemical reinforcement; cement; orthogonal experimental design; compressive strength

Address
Jun Hu, Hong Wei and Juan Du: College of Civil Engineering and Architecture, Hainan University, Haikou 570228, P. R. China

Lei Zhang: School of Civil Engineering and Architecture, Wuhan University of Technology, Wuhan 430070, P. R. China

Abstract
In this paper, the effect of the homogenization models on buckling and free vibration is presented for simply supported functionally graded plates (FGM) resting on elastic foundation. The majority of investigations developed in the last decade, explored the Voigt homogenization model to predict the effective proprieties of functionally graded materials at the macroscopic-scale for FGM mechanical behavior. For this reason, various models have been used to derive the effective proprieties of FGMs and simulate thereby their effects on the buckling and free vibration of FGM plates based on comparative studies that may differ in terms of several parameters. The refined plate theory, as used in this paper, is based on dividing the transverse displacement into both bending and shear components. This leads to a reduction in the number of unknowns and governing equations. Furthermore the present formulation utilizes a sinusoidal variation of displacement field across the thickness, and satisfies the stress-free boundary conditions on the upper and lower surfaces of the plate without requiring any shear correction factor. Equations of motion are derived from Hamilton\'s principle. Analytical solutions for the buckling and free vibration analysis are obtained for simply supported plates. The obtained results are compared with those predicted by other plate theories. This study shows the sensitivity of the obtained results to different homogenization models and that the results generated may vary considerably from one theory to another. Comprehensive visualization of results is provided. The analysis is relevant to aerospace, nuclear, civil and other structures.

Key Words
buckling; vibration; FGM; plate theory; elastic foundation; homogenization models

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

Zakaria Belabed: 1.) Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department, University of Sidi Bel Abbes, Algeria
2.) Department of Technology, Institute of Science and Technology, Center University of Naama, Algeria

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

O. Anwar Bég: Aeronautical and Mechanical Engineering, University of Salford, Newton Building, G77, The Crescent, Salford, M54WT, England, U.K.


Abstract
A detailed understanding of the mechanical behaviors for crushed coal rocks after grouting is a key for construction in the broken zones of mining engineering. In this research, experiments of grouting into the crushed coal rock using independently developed test equipment for solving the problem of sampling of crushed coal rocks have been carried out. The application of uniaxial compression was used to approximately simulate the ground stress in real engineering. In combination with the analysis of crack evolution and failure modes for the grouted specimens, the influences of different crushed degrees of coal rock (CDCR) and solidified grout strength (SGS) on the mechanical behavior of grouted specimens under uniaxial compression were investigated. The research demonstrated that first, the UCS of grouted specimens decreased with the decrease in the CDCR at constant SGS (except for the SGS of 12.3 MPa). However, the UCS of grouted specimens for constant CDCR increased when the SGS increased; optimum solidification strengths for grouts between 19.3 and 23.0 MPa were obtained. The elastic moduli of the grouted specimens with different CDCR generally increased with increasing SGS, and the peak axial strain showed a slightly nonlinear decrease with increasing SGS. The supporting effect of the skeleton structure produced by the solidified grouts was increasingly obvious with increasing CDCR and SGS. The possible evolution of internal cracks for the grouted specimens was classified into three stages: (1) cracks initiating along the interfaces between the coal blocks and solidified grouts; (2) cracks initiating and propagating in coal blocks; and (3) cracks continually propagating successively in the interfaces, the coal blocks, and the solidified grouts near the coal blocks. Finally, after the propagation and coalescence of internal cracks through the entire specimens, there were two main failure modes for the failed grouted specimens. These modes included the inclined shear failure occurring in the more crushed coal rock and the splitting failure occurring in the less crushed coal rock. Both modes were different from the single failure mode along the fissure for the fractured coal rock after grouting solidification. However, compared to the brittle failure of intact coal rock, grouting into the different crushed degree coal rocks resulted in ductile deformation after the peak strength for the grouted specimens was attained.

Key Words
experimental investigation; mechanical behaviors; crushed coal rocks; grouting solidification

Address
Yuhao Jin: 1.) School of Mechanics and Civil Engineering, China University of Mining and Technology, Xuzhou, Jiangsu 221116, China
2.)State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining and Technology, Xuzhou, Jiangsu 221116, China
3.) GeoEnergy Research Centre (GERC), University of Nottingham, Nottingham, NG7 2RD, U.K.

Lijun Han: 1.) School of Mechanics and Civil Engineering, China University of Mining and Technology, Xuzhou, Jiangsu 221116, China
2.)State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining and Technology, Xuzhou, Jiangsu 221116, China

Qingbin Meng: State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining and Technology, Xuzhou, Jiangsu 221116, China

Dan Ma: School of Resources & Safety Engineering, Central South University, Changsha, Hunan 410083, China

Shengyong Wen: School of Mechanics and Civil Engineering, China University of Mining and Technology, Xuzhou, Jiangsu 221116, China

Shuai Wang: State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining and Technology, Xuzhou, Jiangsu 221116, China



Abstract
In densely populated urban areas with a large amount of infrastructure, ground subsidence events can result in massive casualties and economic losses. In South Korea, the incidence of ground subsidence in urban areas has increased in recent years and the number of underground cavities suspected of causing such events has significantly increased. Therefore, it is essential to develop techniques to prevent the occurrence of underground and ground subsidence. In this study, a field test, laboratory test, and numerical analysis were conducted to determine the optimal compaction degree of the upper support layer of any underground cavity below the level of sewer pipes in order to prevent such cavities from collapsing and leading to ground subsidence accidents. During the field test, an underground cavity was simulated using ice, and the generation of the cavity was confirmed using ground penetrating radar. The ground investigation was performed using a cone penetration test, and the compaction of the ground where ground subsidence occurred was evaluated with a laboratory test. The behaviour of the ground under various conditions was predicted using a numerical analysis based on the data obtained from the field test and previous studies. Based on these results, the optimal compaction degree of the ground required to prevent the underground cavity from causing ground subsidence was predicted and presented.

Key Words
ground subsidence; compaction; CPT; field test; laboratory test; numerical analysis

Address
Suk-Min Kong and Yong-Joo Lee: Department of Civil Engineering, Seoul National University of Science and Technology, 232 Gongneung-ro, Nowon-gu, Seoul 01811, Korea

Dong-Min Kim and Dae-Young Lee: Geotechnical Engineering Research Division, Korea Institute of Civil Engineering and Building Technology, 283, Goyang-daero, Ilsanseo-gu, Goyang-si, Gyeonggi-do, 10223, Korea

Hyuk-Sang Jung: Department of Railroad Construction and Safety Engineering, Dongyang University, 145 Dongyangdaero, Punggi, Yeongju, Gyeongbuk, 750-711, Korea

Abstract
The excavation of twin tunnels is a process that destabilizes the ground. The stability of the tunnel lining, the control of ground displacements around the tunnel resulting from each excavation and the interaction between them must be controlled. This paper provides a new approach for replacing the costly 3D analyses with the equivalent 2D analyses that closely reflects the in-situ measurements when excavating twin tunnels. The modeling was performed in two dimensions using the FLAC2D finite difference code. The three-dimensional effect of excavation is taken into account through the deconfinement rate l of the soil surrounding the excavation by applying the convergence-confinement method. A comparison between settlements derived by the proposed 2D analysis and the settlements measured in a real project in Algeria shows an acceptable agreement. Also, this paper reports the investigation into the changes in deformations on tunnel linings and surface settlements which may be expected if the twin tunnels of T4 El-Harouche Skikda were constructed with a tunneling machine. Special attention was paid to the influence of the excavation phase shift distance between the two mechanized tunnel faces. It is revealed that the ground movements and the lining deformations during tunnel excavation depend on the distance between the tunnels\' axis and the excavation phase shift.

Key Words
tunnel; interaction; numerical-simulation; convergence-confinement; excavation phase shift

Address
Chafia Djelloul: 1.) Department of Civil Engineering, Faculty of Technology, Batna 2 University, 53 Street of Constantine, Fésdis, CP 05078 Batna, Algeria
2.) Department of Civil Engineering, Mohamed El Bachir El Ibrahimi University, 34030 Bordj Bou Arreridj El-Anasser, Algeria

Toufik Karech and Rafik Demagh: Department of Civil Engineering, Mohamed El Bachir El Ibrahimi University, 34030 Bordj Bou Arreridj El-Anasser, Algeria

Oualid Limam: Laboratory of Civil Engineering, University of Tunis El Manar, National Engineers School of Tunis, BP 37, 1002 Tunis Le Belvédère, Tunisia

Juan Martinez: Laboratoire GCGM, National Institute of Applied Sciences, 20 avenue Buttes de Coësmes CS 70839 - 35 708 RENNES Cedex 7, France

Abstract
In this paper, a numerical study using finite element method with considering soil-structure interaction was conducted to investigate the stress and deformation behavior of a sheet pile wall structure. In numerical model, one of the nonlinear elastic material constitutive models, Duncan-Chang E-v model, is used for describing soil behavior. The hard contact constitutive model is used for simulating the behavior of interface between the sheet pile wall and soil. The construction process of excavation and backfill is simulated by the way of step loading. We also compare the present numerical method with the in-situ test results for verifying the numerical methods. The numerical analysis showed that the soil excavation in the lock chamber has a huge effect on the wall deflection and stress, pile deflection, and anchor force. With the increase of distance between anchored bars, the maximum wall deflection and anchor force increase, while the maximum wall stress decreases. At a low elevation of anchored bar, the maximum wall bending moment decreases, but the maximum wall deflection, pile deflection, and anchor force both increase. The construction procedure with first excavation and then backfill is quite favorable for decreasing pile deflection, wall deflection and stress, and anchor forces.

Key Words
anchored sheet pile wall; anchorage pile; anchored bar; soil-structure interaction; finite element analysis

Address
Shouyan Jiang, Chengbin Du and Liguo Sun: Department of Engineering Mechanics, Hohai University, Nanjing 210098, China

Abstract
Classic braced walls use struts and wales to minimize ground movements induced by deep excavation. However, the installation of struts and wales is a time-consuming process and confines the work space. To secure a work space around the retaining structure, an anchoring system works in conjunction with a braced wall. However, anchoring cannot perform well when the shear strength of soil is low. In such a case, innovative retaining systems are required in excavation. This study proposes an innovative earth-retaining wall that uses in situ soil confined in dual sheet piles as a structural component. A numerical study was conducted to evaluate the stability of the proposed structure in cohesionless dry soil and establish a design chart. The displacement and factor of safety of the structural member were monitored and evaluated. According to the results, an increase in the clearance distance increases the depth of safe excavation. For a conservative design to secure the stability of the earth-retaining structure in cohesionless dry soil, the clearance distance should exceed 2 m, and the embedded depth should exceed 40% of the wall height. The results suggest that the proposed method can be used for 14 m of excavation without any internal support structure. The design chart can be used for the preliminary design of an earth-retaining structure using in situ soil with dual steel sheet piles in cohesionless dry soil.

Key Words
Earth-retaining structure using in situ soil; dual steel sheet pile; numerical analysis; cohesionless dry soil; preliminary design chart

Address
Joon-Sang An, Yeo-Won Yoon and Ki-Il Song: Deptartment of Civil Engineering, Inha University, 100 Inha-ro, Nam-gu, Incheon, 22212, Republic of Korea

Abstract
Worldwide growth in hydrocarbon and energy demand is driving the oil and gas companies to drill more wells in complex situations such as areas with high-pressure, high-temperature conditions. As a result, in recent years the number of wells in these conditions have been increased significantly. Wellbore instability is one of the main issues during the drilling operation especially for directional and horizontal wells. Many researchers have studied the wellbore stability in complex situations and developed mathematical models to mitigate the instability problems before drilling operation. In this work, a fully coupled thermoporoelastic model is developed to study the well stability in high-pressure, high-temperature conditions. The results show that the performance of the model is highly dependent on the truly evaluated rock mechanical properties. It is noted that the rock mechanical properties should be evaluated at elevated pressures and temperatures. However, in many works, this is skipped and the mechanical properties, which are evaluated at room conditions, are entered into the model. Therefore, an accurate stability analysis of high-pressure, high-temperature wells is achieved by measuring the rock mechanical properties at elevated pressures and temperatures, as the difference between the model outputs is significant.

Key Words
well drilling; borehole instability; wellbore collapse failure; geomechanical model; HPHT

Address
Seyyed Shahab Tabatabaee Moradi, Nikolay I. Nikolaev, Inna V. Chudinova and Aleksander S. Martel: Well Drilling Department, Saint-Petersburg Mining University, 199106, Saint Petersburg, Russian Federation


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