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CONTENTS
Volume 27, Number 5, December10 2021
 

Abstract
Construction of retaining walls with geocell has been gaining in popularity because of its easy and fast installation compared to conventional methods. In this study, model tests were conducted by constructing the geocell retaining wall (GRW) at a constant height (i.e., 90 cm) and using aggregate as an infill material at four different configurations and two different surface angles. In these tests, a circular footing was placed behind the walls at different lateral distances from the wall surface and loaded monotonically. Subsequent to this vertical loading being applied to the footing, horizontal displacements on the GRW surface were measured at three different points. The performance of Type 4 GRW exceeded the other three types of GRW, with the highest lateral displacement occurring in Type 4 GRW at approximately 0.67 % of wall height. In addition, the results of these tests were compared with theoretical approaches widely accepted in the literature. The stress levels reached beneath the footing were found to be compatible with theoretical results.

Key Words
geocell; granular soil; model test; monotonic loading; retaining walls

Address
Gokhan Altay:Department of Civil Engineering, Osmaniye Korkut Ata University, Karacaoğlan Campus, Merkez/Osmaniye, Turkey

Cafer Kayadelen:Department of Civil Engineering, Osmaniye Korkut Ata University, Karacaoğlan Campus, Merkez/Osmaniye, Turkey

Hanifi Canakci:Department of Civil Engineering, Hasan Kalyoncu University, Havaalan

Baki Bagriacik:Department of Civil Engineering, Çukurova University, Balcali Campus Saricam/Adana, Turkey

Abstract
Artificial ground freezing (AGF) is a commonly used geotechnical support technique that can be applied in any soil type and has low environmental impact. Experimental and numerical investigations have been conducted to optimize AGF for application in diverse scenarios. Precise simulation of groundwater flow is crucial to improving the reliability these investigations' results. Previous experimental research has mostly considered horizontal seepage flow, which does not allow accurate calculation of the groundwater flow velocity due to spatial variation of the piezometric head. This study adopted vertical seepage flow-which can maintain a constant cross-sectional area-to eliminate the limitations of using horizontal seepage flow. The closure time is a measure of the time taken for an impermeable layer to begin to form, this being the time for a frozen soil-ice wall to start forming adjacent to the freeze pipes; this is of great importance to applied AGF. This study reports verification of the reliability of our experimental apparatus and measurement system using only water, because temperature data could be measured while freezing was observed visually. Subsequent experimental AFG tests with saturated sandy soil were also performed. From the experimental results, a method of estimating closure time is proposed using the inflection point in the thermal conductivity difference between pore water and pore ice. It is expected that this estimation method will be highly applicable in the field. A further parametric study assessed factors influencing the closure time using a two-dimensional coupled thermo-hydraulic numerical analysis model that can simulate the AGF of saturated sandy soil considering groundwater flow. It shows that the closure time is affected by factors such as hydraulic gradient, unfrozen permeability, particle thermal conductivity, and freezing temperature. Among these factors, changes in the unfrozen permeability and particle thermal conductivity have less effect on the formation of frozen soil–ice walls when the freezing temperature is sufficiently low.

Key Words
artificial ground freezing; closure time; groundwater; model test; parametric study; vertical flow

Address
Hyunwoo Jin:Department of Future and Smart Construction Research, KICT, 283, Goyang daero, Ilsanseo gu, Goyang si, Gyeonggi do, Republic of Korea

Gyu-Hyun Go:Department of Civil Engineering, Kumoh National Institute of Tech., 61, Daehak-ro, Gumi-si, Gyeongsangbuk-do, Republic of Korea

Byung Hyun Ryu:Department of Future and Smart Construction Research, KICT, 283, Goyang daero, Ilsanseo gu, Goyang si, Gyeonggi do, Republic of Korea

Jangguen Lee:1Department of Future and Smart Construction Research, KICT, 283, Goyang daero, Ilsanseo gu, Goyang si, Gyeonggi do, Republic of Korea

Abstract
Caisson-type structures are widely used as quay walls in coastal areas. In Korea, for a long time, many caisson-type quay walls have been constructed with a low front water depth. These facilities can no longer meet the requirements of current development. This study developed a new technology for deepening existing caisson-type quay walls using grouting and rubble mound excavation to economically reuse them. With this technology, quay walls could be renovated by injecting grout into the rubble mound beneath the front toe of the caisson to secure its structure. Subsequently, a portion of the rubble mound was excavated to increase the front water depth. This paper reports the results of an investigation of the seismic behavior of a renovated quay wall in comparison to that of an existing quay wall using centrifuge tests and numerical simulations. Two centrifuge model tests at a scale of 1/120 were conducted on the quay walls before and after renovation. During the experiments, the displacements, accelerations, and earth pressures were measured under five consecutive earthquake input motions with increasing magnitudes. In addition, systematic numerical analyses of the centrifuge model tests were also conducted with the PLAXIS 2D finite element (FE) program using a nonlinear elastoplastic constitutive model. The displacements of the caisson, response accelerations, deformed shape of the quay wall, and earth pressures were investigated in detail based on a comparison of the numerical and experimental results. The results demonstrated that the motion of the caisson changed after renovation, and its displacement decreased significantly. The comparison between the FE models and centrifuge test results showed good agreement. This indicated that renovation was technically feasible, and it could be considered to study further by testbed before applying in practice.

Key Words
caisson-type gravity quay wall; centrifuge model test; deepening; numerical simulation; renovated quay wall

Address
Young-Sang Kim:Department of Civil Engineering, Chonnam National University, Gwangju, South Korea

Anh-Dan Nguyen:Department of Architecture and Civil Engineering, Graduate school, Chonnam National University, Gwangju, South Korea

Gyeong-O Kang:Department of Civil Engineering, Gwangju University, Gwangju, South Korea

Abstract
One of the important causes of building and infrastructure failure, such as bridges on pile foundations, is the placement of the piles in liquefiable soil that can become unstable under seismic loads. Therefore, the overarching aim of this study is to investigate the seismic behavior of a soil-pile system in liquefiable soil using three-dimensional numerical FEM analysis, including soil-pile interaction. Effective parameters on concrete pile response, involving the pile diameter, pile length, soil type, and base acceleration, were considered in the framework of finite element non-linear dynamic analysis. The constitutive model of soil was considered as elasto-plastic kinematic-isotropic hardening. First, the finite element model was verified by comparing the variations on the pile response with the measured data from the centrifuge tests, and there was a strong agreement between the numerical and experimental results. Totally 64 non-linear time-history analyses were conducted, and the responses were investigated in terms of the lateral displacement of the pile, the effect of the base acceleration in the pile behavior, the bending moment distribution in the pile body, and the pore pressure. The numerical analysis results demonstrated that the relationship between the pile lateral displacement and the maximum base acceleration is non-linear. Furthermore, increasing the pile diameter results in an increase in the passive pressure of the soil. Also, piles with small and big diameters are subjected to yielding under bending and shear states, respectively. It is concluded that an effective stress-based ground response analysis should be conducted when there is a liquefaction condition in order to determine the maximum bending moment and shear force generated within the pile.

Key Words
earthquake loading; FEM; liquefaction; numerical modeling; pile; reinforced concrete; soil-pile interaction

Address
Mehdi Ebadi-Jamkhaneh:Department of Civil Engineering, School of Engineering, Damghan University, Damghan, Iran

Amir Homaioon-Ebrahimi:Department of Civil Engineering, School of Engineering, University of Birmingham, Birmingham, UK

Denise-Penelope N. Kontoni:Department of Civil Engineering, School of Engineering, University of the Peloponnese, GR-26334 Patras, Greece/ School of Science and Technology, Hellenic Open University, GR-26335 Patras, Greece

Maedeh Shokri-Amiri:School of Literature, Humanities and Social Sciences, Science and Research Branch, Islamic Azad University, Tehran, Iran

Abstract
This article assesses and estimates the progressive failure mechanism of complex pit-rest secondary toppling of slopes that are located within the vicinity of the Gas Flare Site of Refinery No. 4 in South Pars Special Zone (SPSZ), southwest Iran. The finite element numerical procedure based on the Shear Strength Reduction (SSR) technique has been employed for the stability analysis. In this regard, several step modelling stages that were conducted to evaluate the slope stability status revealed that the main instability was situated on the left-hand side (western) slope in the Flare Site. The toppling was related to the rock column-overburden system in relation to the overburden pressure on the rock columns which led to the progressive instability of the slope. This load transfer from the overburden has most probably led to the separation of the rock column and to its rotation downstream of the slope in the form of a complex pit-rest secondary toppling. According to the numerical modelling, it was determined that the Strength Reduction Factor (SRF) decreased substantially from 5.68 to less than 0.320 upon progressive failure. The estimated shear and normal stresses in the block columns ranged from 1.74 MPa to 8.46 MPa, and from 1.47 MPa to 16.8 MPa, respectively. In addition, the normal and shear displacements in the block columns ranged from 0.00609 m to 0.173 m and from 0.0109 m to 0.793 m, respectively.

Key Words
finite element method; Iran; rock slope stability; secondary toppling

Address
Mohammad Azarafza:Department of Civil Engineering, University of Tabriz, Tabriz, Iran

Masoud Hajialilue Bonab:Department of Civil Engineering, University of Tabriz, Tabriz, Iran

Haluk Akgun:Geotechnology Unit, Department of Geological Engineering, Middle East Technical University (METU), Ankara, Turkey

Abstract
A large deformation FEM (Finite Element Method) based numerical analysis has been performed to study the behaviour of the bell-shaped anchor embedded in undrained saturated (cohesive) soil with the help of finite element based software ABAQUS. A typical model anchor with bell-diameter of 0.125m, embedded in undrained saturated soil with varying cohesive strength (from 5 kN/m2 to 200 kN/m2) has been chosen for studying the characteristic behaviour of the bell-shaped anchor installed in cohesive soil. Breakout factors have been evaluated for each case and verified with the results of experimental model tests for three different types of soil samples. The maximum value of breakout factor was found as about 8.5 within a range of critical embedment ratio of 2.5 to 3. An explicit model has been developed to estimate the breakout factor (Fc) for uplift capacity of bell-shaped anchor within clay mass in terms of H/D ratio (embedment ratio). It was also found that, the ultimate uplift capacity of the anchor increases with the increase of the value of cohesive strength of the soil and H/D ratio. The empirical equation developed in the present investigation is usable within the range of cohesion value and H/D ratio from 5 kN/m2 to 200 kN /m2 and 0.5 to 3.0 respectively. The proposed model has been validated against data obtained from a series of model tests carried out in the present investigation. From the stress-profile analysis of the soil mass surrounding the anchor, occurrence of stress concentration is found to be generated at the joint of anchor shaft and bell. It was also found that the vertical and horizontal stresses surrounding the anchor diminish at about a distance of 0.3 m and 0.15 m respectively.

Key Words
anchor; axisymmetric; breakout factor; critical H/D ratio; FEM; uplift capacity

Address
Arya Das:Department of Civil Engineering, Indian Institute of Engineering Science and Technology, Shibpur, Howrah-711 103, India

Ashis Kumar Bera:Civil Engineering, Department of Civil Engineering, Indian Institute of Engineering Science and Technology, Shibpur, Howrah-711 103, India

Abstract
In the design of underground excavation, the shear strength (SS) is a key characteristic. It describes the way the rock material resists the shear stress-induced deformations. In general, the measurement of the parameters related to rock shear strength is done through laboratory experiments, which are costly, damaging, and time-consuming. Add to this the difficulty of preparing core samples of acceptable quality, particularly in case of highly weathered and fractured rock. This study applies rock index test to the indirect measurement of the SS parameters of shale. For this aim, two efficient artificial intelligence methods, namely (1) adaptive neuro-fuzzy inference system (ANFIS) implemented by subtractive clustering method (SCM) and (2) support vector regression (SVR) optimized by Harmony Search (HS) algorithm, are proposed. Note that, it is the first work that predicts the SS parameters of shale through ANFIS-SCM and SVR-HS hybrid models. In modeling processes of ANFIS-SCM and SVR-HS, the results obtained from the rock index tests were set as inputs, while the SS parameters were set as outputs. By reviewing the obtained results, it was found that both ANFIS-SCM and SVR-HS models can provide acceptable predictions for interlocking and friction angle parameters, however, ANFIS-SCM showed a better generalization capability.

Key Words
ANFIS; hybrid models; shear strength; SVR

Address
Hadi Fattahi: Faculty of Earth Sciences Engineering, Arak University of Technology, Arak, Iran

Mahdi Hasanipanah:Institute of Research and Development, Duy Tan University, Da Nang 550000, Vietnam/ Department of Mining Engineering, University of Kashan, Kashan, Iran

Abstract
The creep characteristics of rock is of great significance for the study of long-term stability of engineering, so it is necessary to carry out indoor creep test and creep model of rock. First of all, in different water-bearing state and different positive pressure conditions, the granite is graded loaded to conduct indoor shear creep test. Through the test, the shear creep characteristics of granite are obtained. According to the test results, the stress-strain isochronous curve is obtained, and then the long-term strength of granite under different conditions is determined. Then, the fractional-order calculus software element is introduced, and it is connected in series with the spring element and the nonlinear viscoplastic body considering the creep acceleration start time to form a nonlinear viscoplastic creep model with fewer elements and fewer parameters. Finally, based on the shear creep test data of granite, using the nonlinear curve fitting of Origin software and Levenberg-Marquardt optimization algorithm, the parameter fitting and comparative analysis of the nonlinear creep model are carried out. The results show that the test data and the model curve have a high degree of fitting, which further explains the rationality and applicability of the established nonlinear visco-elastoplastic creep model. The research in this paper can provide certain reference significance and reference value for the study of nonlinear creep model of rock in the future.

Key Words
accelerating creep starting element; fractional calculus; nonlinear creep model; shear creep test

Address
Bin Hu:School of Resources and Environmental Engineering, Wuhan University of Science and Technology, 947 Heping Avenue,Qingshan District, Wuhan, China/ Hubei Key Laboratory for Efficient Utilization and Agglomeration of Metallurgic Mineral Resources, 947 Heping Avenue,Qingshan District, Wuhan, China

Er-Jian Wei:School of Resources and Environmental Engineering, Wuhan University of Science and Technology, 947 Heping Avenue,Qingshan District, Wuhan, China/ Hubei Key Laboratory for Efficient Utilization and Agglomeration of Metallurgic Mineral Resources, 947 Heping Avenue,Qingshan District, Wuhan, China

Jing Li:School of Resources and Environmental Engineering, Wuhan University of Science and Technology, 947 Heping Avenue,Qingshan District, Wuhan, China/ Hubei Key Laboratory for Efficient Utilization and Agglomeration of Metallurgic Mineral Resources, 947 Heping Avenue,Qingshan District, Wuhan, China

Xin Zhu:School of Resources and Environmental Engineering, Wuhan University of Science and Technology, 947 Heping Avenue,Qingshan District, Wuhan, China/ Hubei Key Laboratory for Efficient Utilization and Agglomeration of Metallurgic Mineral Resources, 947 Heping Avenue,Qingshan District, Wuhan, China

Kun-Yun Tian:School of Resources and Safety Engineering, Henan University of Engineering, 1 Xianghe Road, Xinzheng District, Zhengzhou, China

Kai Cui:School of Resources and Environmental Engineering, Wuhan University of Science and Technology, 947 Heping Avenue,Qingshan District, Wuhan, China/ Hubei Key Laboratory for Efficient Utilization and Agglomeration of Metallurgic Mineral Resources, 947 Heping Avenue,Qingshan District, Wuhan, China

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