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CONTENTS
Volume 31, Number 6, December25 2022
 

Abstract
Evaluation and optimization of tunnel wall convergence (TWC) plays a vital role in preventing potential problems during tunnel construction and utilization stage. When convergence occurs at a high rate, it can lead to significant problems such as reducing the advance rate and safety, which in turn increases operating costs. In order to design an effective solution, it is important to accurately predict the degree of TWC; this can reduce the level of concern and have a positive effect on the design. With the development of soft computing methods, the use of deep learning algorithms and neural networks in tunnel construction has expanded in recent years. The current study aims to employ the long-short-term memory (LSTM) deep neural network predictor model to predict the TWC, based on 550 data points of observed parameters developed by collecting required data from different tunnelling projects. Among the data collected during the pre-construction and construction phases of the project, 80% is randomly used to train the model and the rest is used to test the model. Several loss functions including root mean square error (RMSE) and coefficient of determination (R2) were used to assess the performance and precision of the applied method. The results of the proposed models indicate an acceptable and reliable accuracy. In fact, the results show that the predicted values are in good agreement with the observed actual data. The proposed model can be considered for use in similar ground and tunneling conditions. It is important to note that this work has the potential to reduce the tunneling uncertainties significantly and make deep learning a valuable tool for planning tunnels.

Key Words
convergence estimation; deep neural network; LSTM; optimization; tunnel wall convergence

Address
Arsalan Mahmoodzadeh: Rock Mechanics Division, School of Engineering, Tarbiat Modares University, Tehran, Iran
Mohammadreza Taghizadeh: Department of Civil engineering, Faculty of engineering, University of Kashan, Kashan, Iran
Adil Hussein Mohammed: Department of Communication and Computer Engineering, Faculty of Engineering, Cihan University-Erbil, Kurdistan Region, Iraq
Hawkar Hashim Ibrahim: Department of Civil Engineering, College of Engineering, Salahaddin University-Erbil, 44002 Erbil, Kurdistan Region, Iraq
Hanan Samadi: School of Geology, College of Science, University of Tehran, Tehran, Iran
Mokhtar Mohammadi: Department of Information Technology, College of Engineering and Computer Science,
Lebanese French University, Kurdistan Region, Iraq
Shima Rashidi: Department of Computer Science, College of Science and Technology, University of Human Development,
Sulaymaniyah, Kurdistan Region, Iraq

Abstract
Landslides are often triggered by weak interlayers initiated in tailings dam foundations, and hazards gradually occur. This is serious for landslides in high tailings dams due to their high potential energy. Tailing samples with a fine-grained interlayer at a set dip angle were prepared. Consolidated undrained (CU) triaxial shear tests were carried out by using a high-pressure triaxial apparatus. The results were compared with the results under a low confining pressure. Four reasons were summarized for high tailings dams more prone to instability than low dams. The shear strength of the samples with dipping interlayers decreases with increasing dip angle. An obvious straight drop in the stress path after the peak occurs in samples with dipping interlayers at an angle of 60. The effect of the interlayer on the mechanical behaviour of tailings is very sensitive, especially for the sample with a dipping interlayer at an angle of 60. Shear slipping along the interlayer should be given more attention in tailings dams. Compared with the results under low confining pressure, the stress decreases continuously for the samples with dipping interlayers at large angles under high confining pressure. The positive pore pressure, which reduces the effective stress, occurred in tailings samples under high confining pressure. The residual strength of tailings under high confining pressure is smaller than that under low confining pressure. These factors increase the dam break risk and the disaster impact for high tailings dams.

Key Words
critical state; deformation patterns; fine-grained interlayer; high confining pressure; tailings

Address
Qinglin Chen, Zugui Li, Zeyu Dai, Xiaojun Wang and Chao Zhang: School of Resources and Environmental Engineering, Jiangxi University of Science and Technology,
Ganzhou, Jiangxi 341000, China;
State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics,
Chinese Academy of Sciences, Wuhan, Hubei 430071, China

Abstract
The geometry of the gravity-type anchorage changes depends on various factors such as the installation location, ground type, and relationship with the upper structure. In particular, the anchorage geometry embedded in the ground is an important design factor because it affects the pull-out resistance of the anchorage. This study examined the effect of four parameters, related to anchorage geometry and embedded ground conditions, on the pull-out resistance in the gravity-type anchorage through two-dimensional finite element analysis, and presented a guide for major design variables. The four parameters include the 1) flight length of the stepped anchorage (m), 2) flight height of the stepped anchorage (n), 3) the anchorage heel height (b), and 4) the thickness of the soil (e). It was found that as the values of m increased and the values of n decreased, the pull-out resistance of the gravity-type anchorage increased. This trend is related to the size of the contact surface between the anchorage and the rock, and it was confirmed that the value of n, which has the largest change rate of the contact surface between the anchorage and the rock, has the greatest effect on the pull-out resistance of the anchorage. Additionally, the most effective design was achieved when the ratio of the step to the bottom of the anchorage (m) was greater than 0.7, and m was found to be an important factor in the pull-out resistance behavior of the anchorage.

Key Words
finite element analysis; geometric condition; gravity-type anchorage; pull-out resistance; suspension bridge

Address
Hyunsung Lim: Department of Wind Power Business, Hanwha Corporation/E&C, Seoul 04541, Republic of Korea
Seunghwan Seo and Moonkyung Chung: Department of Geotechnical Engineering Research, Korea Institute of Civil Engineering and Building Technology,
Goyang-si, Gyeonggi-do 10223, Republic of Korea
Junyoung Ko: Department of Civil Engineering, Chungnam National University, Daejeon 34134, Republic of Korea

Abstract
Frost heave can cause uneven ground uplift that may damage geo-infrastructure. To assist damage-prevention strategies, standard frost heave testing methods and frost susceptibility criteria have been established and used in various countries. ASTM International standard testing method is potentially the most useful standard, as abundant experimental data have been acquired through its use. ASTM International provides detailed recommendations, but the method is expensive and laborious because of the complex testing procedure requiring a freezing chamber. A simple frost heave testing method using a temperature-controllable cell has been proposed to overcome these difficulties, but it has not yet been established whether a temperature-controllable cell can adequately replace the ASTM International recommended apparatus. This paper reviews the applicability of the ASTM International testing method using the temperature-controllable cell. Freezing tests are compared using various soil mixtures with and without delivering blow to depress the freezing point (as recommended by ASTM International), and it is established that delivering blow does not affect heave rate, which is the key parameter in successful characterization of frost susceptibility. As the freezing temperature decreases, the duration of supercooling of pore water shortens or is eliminated; i.e., thermal shock with a sufficiently low freezing temperature can minimize or possibly eliminate supercooling.

Key Words
freezing temperature; frost heave; heave rate; standard testing method; supercooling

Address
Hyunwoo Jin, Jangguen Lee and Byung-Hyun Ryu: Department of Future and Smart Construction Research, KICT, 283, Goyang-daero, Ilsanseo-gu,
Goyang-si, Gyeonggi-do, Republic of Korea

Abstract
One of the methods of stabilizing retaining walls, embankments, and deep excavations is the implementation of plate anchors (like the Geolock wall anchor systems). Back-to-back Mechanically Stabilized Earth (BBMSE) walls are common stabilized earth structures that can be used for bridge ramps. But so far, the analysis of the interactive behavior of two back-to-back anchored walls (BBAW) by double-plates anchors (constructed closely from each other and subjected to the limited-breadth vertical loading) including interference of their failure and sliding surfaces has not been the subject of comprehensive studies. Indeed, in this compound system, the interaction of sliding wedges of these two back-to-back walls considering the shear failure wedge of the foundation, significantly impresses on the foundation bearing capacity, adjacent walls displacements and deformations, and their stability. In this study, the effect of horizontal distance between two walls (W), breadth of loading plate (B), and position of vertical loading was investigated experimentally. In addition, the comparison of using single and equivalent double-plate anchors was evaluated. The loading plate bearing capacity and displacements, and deformations of BBAW were measured and the results are presented. To evaluate the shape, form, and how the critical failure surfaces of the soil behind the walls and beneath the foundation intersect with one another, the Particle Image Velocimetry (PIV) technique was applied. The experimental tests results showed that in this composite system (two adjacent-loaded BBAW) the effective distance of walls is about W = 2.5*H (H: height of walls) and the foundation effective breadth is about B = H, concerning foundation bearing capacity, walls horizontal displacements and their deformations. For more amounts of W and B, the foundation and walls can be designed and analyzed individually. Besides, in this compound system, the foundation bearing capacity is an exponential function of the System Geometry Variable (SGV) whereas walls displacements are a quadratic function of it. Finally, as an important achievement, doubling the plates of anchors can facilitate using concrete walls, which have limitations in tolerating curvature.

Key Words
back-to-back walls; BBAW walls; bearing capacity; failure surface; interaction; Particle Image Velocimetry (PIV); retaining walls; shallow foundation; sliding surface; system geometry

Address
Amir Najafizadeh and AmirAli Zad: Department of Civil Engineering, Faculty of Civil & Earth Resources Engineering,
Islamic Azad University, Central Tehran Branch, Tehran, Iran

Abstract
In this paper, considering the temperature dependence of material physical parameters as well as the effects of thermal effect and shear deformation, we have conducted an in-depth study on the wave propagation of functionally graded (FG) materials circular plate in thermal environment based on the physical neutral surface concept. The dynamic governing equations of functionally graded plates are established, and the dispersion relation of wave propagation is derived. The influence of different temperature fields on the propagation characteristics of flexural waves in FG circular plates is discussed in detail. It can be found that the phase velocity and group velocity of wave propagation in the plate decrease with the increase of temperature.

Key Words
circular plate; FG materials; physical neutral surface concept; porosities; wave propagation

Address
Gui-Lin She and Yin-Ping Li: College of Mechanical and Vehicle Engineering, Chongqing University, Chongqing 400044, China

Abstract
This paper presents the re-evaluation of existing piezocone penetration test (CPTu)-based shear wave velocity (Vs) equations through their application into well-documented data obtained at nine sites in six countries. The re-evaluation indicates that the existing equations are appropriate to use for any specific soil, but not for various types of clays. Existing equations were adjusted to suit all nine clays and show that the correlations between the measured and predicted Vs values tend to improve with an increasing number of parameters in the equations. An adjusted equation, which comprises a CPTu parameter and two soil properties (i.e., effective overburden stress and void ratio) with the best correlation, can be converted into a CPTu-based equation that has two CPTu parameters and depth by considering the effect of soil cementation. Then, the developed equation was verified by application to each of the nine soils and nine other worldwide clays, in which the predicted Vs values are comparable with the measured and the stochastically simulated values. Accordingly, the newly developed CPTu-based equation, which is a time-saving and economical method and can estimate Vs indirectly for any type of naturally deposited clay, is recommended for practical applications.

Key Words
clay; correlations; CPTu; empirical methods; shear wave velocity

Address
Vinod K. Singh and Hyeog-Jun Kweon: Soft Clay Engineering Laboratory, Industry-Academy Cooperation, Dong-A University, Republic of Korea
Sung-Gyo Chung: Department of Civil Engineering, Dong-A University,
37, #550 Street, Nakdong-ro, Busan, 49315, Republic of Korea

Abstract
The seismic design of embankment dams requires more comprehensive studies to understand the behaviour of dams. Deformations primarily control this behaviour occur during or after earthquake loading. Dam failures and incidents show that the impacts of deformations should be reviewed for existing and new embankment dams. Overtopping erosion failure can occur if crest deformations exceed the freeboard at the time of the deformations. Therefore, crest settlement is one of the most critical deformations. This study developed empirical formulas using Gene Expression Programming (GEP) based on 88 cases. In the analyses, dam height (Hd), alluvium thickness (Ha), the magnitude-acceleration-factor (MAF) values developed based on earthquake magnitude (Mw) and peak ground acceleration (PGA) within this study have been chosen as variables. Results show that GEP models developed in the paper are remarkably robust and accessible tools to predict earthquake-induced crest settlement of embankment dams and perform superior to the existing formulation. Also, dam engineering professionals can use them practically because the variables of prediction equations are easily accessible after the earthquake.

Key Words
crest settlement; earthquake; embankment dam; freeboard; GEP

Address
Evren Seyrek: Civil Engineering Department, Engineering Faculty,Kütahya Dumlupinar University, Evliya Çelebi Campus, Kütahya, Turkey
Sadettin Topçu: Department of Construction Technology, Vocational School of Technical Science, Kütahya Dumlupinar University,
Campus of Germiyan, Kütahya, Turkey

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