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CONTENTS
Volume 25, Number 5, June10 2021
 


Abstract
The EPS geofoam as a lightweight material has been widely used in recent years to boost the performance of geotechnical structures. Both the internal and external stability of the fills made by the EPS blocks should be met. Overlying concrete slabs and thick pavements or applying denser EPS blocks provide internal stability of EPS geofoam lightweight fills by reducing the internal vertical stress within the EPS blocks. As an alternative way, in this study, new composite material is introduced by using the polypropylene fiber to reinforce the EPS geofoam in the factory as an attempt to improve the mechanical properties of the EPS geofoam. The composite material was fabricated in different fiber contents by solidifying the mixture of fiber and geofoam beads using controlled heat and temperature. Then, the behavior of the composite was studied using a series of direct shear tests. The results show that including fiber leads to a rise in the shear strength and a significant decline in the compressibility of the reinforced EPS geofoam. For the geofoam reinforced with 80% fiber content, up to 23.3% increase in the shear strength and 57.6% reduction in the vertical displacement (Δz) were observed in the laboratory. In addition, while the change in the composite's cohesion is largely decreased, the friction angle of the composite shows an increasing trend with fiber content increase. A maximum of 12.6% reduction in the cohesion and 100% increase in the internal friction angle of the reinforced material were observed in the laboratory.

Key Words
EPS geofoam; polypropylene fiber; reinforcement; shear behavior; fiber content

Address
Mohammad Reza Arvin, Gholam Reza Ghafary and Ali Reza Ghafary: Department of Civil Engineering, Fasa University, Fasa, Iran

Nader Hataf: Department of Civil and Environmental Engineering, Faculty of Engineering, Shiraz University, Shiraz, Iran


Abstract
Polymer strip (PS) reinforced soil retaining walls (RSRW) are in common use due to the associated construction speed, ease of use, aesthetic appeal and low cost. It is quite significant to estimate the deformation behavior of this types of walls before construction. In this study, firstly, a full-scale field model of PS-RSRW was constructed and instrumented. According to the experimental result, the maximum measured displacements occurred at 30% of the height down from the top of the wall. The maximum tensile loads in the reinforcements were measured at a distance of 40% of the wall height from the face of the wall. Then, a two-dimensional (2D) finite element method (FEM) model was established and calibrated with experimental data from the field model. The predicted displacements of the wall facing showed reasonable agreement with the measured deformations. The reinforcement loads calculated from the validated FEM model were also compared with theoretical methods. Finally, RSRW having different heights were numerically modeled with various combinations of materials utilized for filling and reinforcement. The effects of parameters such as wall height (H), reinforcement length (L) and reinforcement interval (Sv) on the horizontal wall displacement and on the reinforcement loads are investigated through parametric analyses.

Key Words
geosynthetics; reinforced soil; retaining wall; instrumentation and monitoring; numerical analyses; earth pressure

Address
Mehmet R. Kahyaoglu: Department of Civil Engineering, Faculty of Engineering, Mugla Sitki Kocman University, Mugla, Turkey

Mehmet Sahin: Ministry of Youth and Sports– General Directorate of Investment and Enterprises, Ankara, Turkey

Abstract
Pile foundations are very important elements in the design of railways and bridges. In many projects, piles are under the combination of vertical and horizontal loads. In this regard, the maximum moment which is applied to the piles is a key factor for designers. Therefore, in this study, experimental investigations on loaded single piles in sandy soils with different energies in various conditions of loading and relative densities were performed. Nine physical modeling tests were created to evaluate the load-deflection response, bending moment and strain along with the driven aluminum model pile. The single piles were subjected under both horizontal and combination of horizontal and vertical loads. The dimensions of soil tank and model pile were designed by considering chamber size effects and internal scale effects. The results showed a significant difference in magnitude and shapes of bending when the mole pile was subjected to combined loads with a relative density of 30% (loose) and 75% (dense). Additionally, the combined load test results demonstrated that the bending moments and lateral deflection of the pile head increase substantially in the presence of vertical loads. Finally, two computational models were proposed to estimate the maximum moment on the piles.

Key Words
physical modeling; combined load; lateral load; single pile; bending moment; layered sandy soil

Address
Mahdy Khari: Department of Civil Engineering, East Tehran Branch, Islamic Azad University, Tehran, Iran

Ali Dehghanbandaki: Department of Civil Engineering, Damavand Branch, Islamic Azad University, Damavand, Iran

Danial Jahed Armaghani: Department of Urban Planning, Engineering Networks and Systems, Institute of Architecture and Construction, South Ural State University, 76, Lenin Prospect, Chelyabinsk 454080, Russia

Abstract
In the present study, the free vibration of bidirectional functionally graded (FG) beams resting on variable elastic foundation are comprehensively investigated. The beam's behavior is modeled using 2D displacement field that contain undetermined integral terms and involves a reduced unknown functions. The material properties of the FG beam are assumed to be graded in both the thickness and longitudinal directions according to a power law. The beams are considered simply supported and resting on variable elastic foundation. The differential equation system governing the free vibration behavior of bidirectional beams is derived based on the Hamilton principle. The problem is then solved using the Navier solution for a simply supported beam. The accuracy of the used model can be noticed by comparing it with other solutions available in the literature where a good conformance was obtained. A detailed parametric study is conducted to explore the influences of material composition and variable elastic parameters on the vibration characteristics of the beams. The results reveal that the grading indexes in one or both directions as well as the parameters of the elastic foundation strongly impact the fundamental frequencies.

Key Words
BDFG beams; 2D theory; variable elastic foundation; free vibration

Address
Ismail Benaberrahmane, Samir Benyoucef and Mohamed Sekkal:Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Algeria

Mohamed Mekerbi: 1.) Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Algeria
2.) Department of Civil Engineering, University of Ferhat Abbas Setif 1, Algeria

Rabbab Bachir Bouiadjra: 1.)Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Algeria
2.) Department of Civil Engineering, University Mustapha Stambouli of Mascara, Algeria

Mahmoud M.Selim: Department of Mathematics, Al-Aflaj College of Science and Humanities, Prince Sattam bin Abdulaziz University, Al-Aflaj 710-11912, Saudi Arabia

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

Muzamal Hussain: Department of Mathematics, Government College University Faisalabad, 38000, Faisalabad, Pakistan


Abstract
Vibrations induced by the operation of underground trains result in certain changes in the flow characteristics of the underground soft soil, which may lead to problems like ground settlement and damages of subway tunnels. In this study, an improved drag-sphere device is implemented to investigate the flow ability of soft soil subjected to vibrations, and the experimental results indicate that vibrations with high frequencies and low confining pressure enhanced the flow ability of soil samples. Then an artificial neural network (ANN) model is developed based on the obtained experimental data to predict the soil viscosity, where the genetic algorithm (GA) is implemented to optimize the weights and biases in the network. Specifically, by comparing the simulated results with experimental data, the optimal topology, training algorithm, and transfer functions are selected for the proposed model, and the model predictions are in high agreement with the experimental data, which denotes the proposed ANN model is accurate and reliable. Moreover, an analysis on the contributions of each input reveals that the water content affects the soil viscosity most while the frequency has the least impact for a single factor, which is in correspondence with the fact that the flow ability of soft soil is mainly affected by the geological conditions and its natural properties.

Key Words
flow ability; artificial neural network; soft soil; genetic algorithm

Address
Guangjian Xiang, Deshun Yin and Chenxi Cao: College of Mechanics and Materials, Hohai University, Nanjing 211100, China

Lili Yuan: Shenzhen Guoyi Park Construction Co., LTD, Shenzhen 518000, China

Abstract
The reliability of reinforced concrete structures is frequently compromised by the deterioration caused by reinforcement corrosion. Evaluating the effect caused by reinforcement corrosion on structural behaviour of corrosion damaged concrete structures is essential for effective and reliable infrastructure management. In lifecycle management of corrosion affected reinforced concrete structures, it is difficult to correctly assess the lifecycle performance due to the uncertainties associated with structural resistance deterioration. This paper presents a stochastic deterioration modelling approach to evaluate the performance deterioration of corroded concrete structures during their service life. The flexural strength deterioration is analytically predicted on the basis of bond strength evolution caused by reinforcement corrosion, which is examined by the experimental and field data available. An assessment criterion is defined to evaluate the flexural strength deterioration for the time-dependent reliability analysis. The results from the worked examples show that the proposed approach is capable of evaluating the structural reliability of corrosion damaged concrete structures.

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

Address
Xiaofei Guo, Chen Li and Tianhong Huo: School of Energy and Mining Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China

Abstract
To investigate the effects of soil structrue and dry density on water retention behavior of lateritic clay over a wide suction range, the axial translation technique (ATT), filter paper technique (FPT) and vapour equilibrium technique (VET) were combined to obtain soil-water retention curves (SWRCs) of specimens with different structures and dry densities. Measured SWRCs indicate that the air-entry value (AEV) and descent gradient in terms of saturation degree versus suction relationship are smallest for undisturbed specimens, and are largest for pre-consolidated specimens. The SWRCs obtained from compacted specimens with different dry densities illustrate that the AEV and descent gradient of saturation degree versus suction relationship increase with increasing the dry density. However, the effects of soil structure and dry density on the water retention behavior can be negligible at high suctions, which are verified by the curves of gravimetric water content (w) verusus suction (s) coincided after a limiting suction for specimens with different structures and dry densities. In addition, the water retention behavior can be well illustrated by pore size distributions (PSDs), obtained from mercury intrusion porosimetry (MIP). The AEVs depend on the diameters that corresponding to dramatically increase in differential intruded void ratio. And the descent gradients in the saturation degree versus suction relationship depend on their distinct PSD ranges and incremental peaks in the dominant pore sizes. Furthermore, the consistences of the AEVs and limiting suctions, deduced from the PSDs and SWRCs, demonstrate that the water retention behavior is highly dependent on the PSDs, and the SWRC features can be captured well by the PSDs.

Key Words
lateritic clay; soil water retention curve; soil structure; dry density; pore size distribution

Address
Pan Jin and Bo Chen: College of Civil Engineering and Architecture, Quzhou University,78 Jiuhua Road, Kecheng District, Quzhou, Zhejiang, 324000, P. R. China

Wenzhan Zhen: China Railway Eryuan Engineering Group Co. LTD, Chengdu, 610031, P. R. China

De'an Sun: Department of Civil Engineering, Shanghai University, 99 Shangda Road, Baoshan District, Shanghai, 200444, P. R. China

You Gao and Yonglin Xiong: School of Civil and Environmental Engineering, Ningbo University, Ningbo, Zhejiang, 315211, P. R. China

Abstract
Stone columns are one of the best-suited methods of ground improvement for sites consisting of soft clays, silts and silty sands. Stone columns need to be supported against bulging failure as the main reason that reduces their bearing capacity. Disposal of scrap tires is one of the principal environmental problems around the world. Therefore, the reuse of scrap tires has grown globally. This paper investigates the behavior of stone columns encased by scrap tires which has the potential of replacing other encasements. Stone columns with diameters of 66, 80 and 92 mm which are one-tenth of original tire sizes have been tested in a large box, and the load-carrying characteristics of them are analyzed. Based on the results, by increasing the diameter of the encasement stone column, the benefit of the encasement increases. In addition, tests on the groups of stone columns with a diameter of 66 mm were carried out to investigate the presence effects of neighboring columns on the reference load. Furthermore, a comparison has been made with the results of ordinary stone columns and encased stone columns with geotextile to obtain the benefits of scrap tire columns. The bearing capacity of both single and group of stone columns encased with the scrap tire increases more than the ordinary stone columns. However, the bearing capacity of geotextile encased stone column is more than the other groups. Further, numerical analysis has been conducted to implement full-scale reinforced columns. The results illustrate that using scrap tires reduces bulging failure and increases the bearing capacity of stone columns. Accordingly, scrap tires replace the geotextile (as usual encasement) because their amount of bearing capacities are similar to each other especially in columns with larger diameters.

Key Words
laboratory tests; stone column; scrap tires; geotextile; ground improvement

Address
Seyed Hamid Lajevardi and Saeed Enami: Department of Civil Engineering, Arak Branch, Islamic Azad University, Arak, Iran, Khomein Road, Imam Khomeini Square, Arak, Iran



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