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CONTENTS
Volume 31, Number 2, October25 2022
 


Abstract
The properties of soil are naturally highly variable and thus, to ensure proper safety and reliability, we need to test a large number of samples across the length and depth. In pile foundations, conducting field tests are highly expensive and the traditional empirical relations too have been proven to be poor in performance. The study proposes a state-of-art Particle Swarm Optimization (PSO) hybridized Artificial Neural Network (ANN), Extreme Learning Machine (ELM) and Adaptive Neuro Fuzzy Inference System (ANFIS); and comparative analysis of metaheuristic models (ANN-PSO, ELM-PSO, ANFIS-PSO) for prediction of bearing capacity of pile foundation trained and tested on dataset of nearly 300 dynamic pile tests from the literature. A novel ensemble model of three hybrid models is constructed to combine and enhance the predictions of the individual models effectively. The authenticity of the dataset is confirmed using descriptive statistics, correlation matrix and sensitivity analysis. Ram weight and diameter of pile are found to be most influential input parameter. The comparative analysis reveals that ANFIS-PSO is the best performing model in testing phase (R2 = 0.85, RMSE = 0.01) while ELM-PSO performs best in training phase (R2 = 0.88, RMSE = 0.08); while the ensemble provided overall best performance based on the rank score. The performance of ANN-PSO is least satisfactory compared to the other two models. The findings were confirmed using Taylor diagram, error matri X and uncertainty analysis. Based on the results ELM-PSO and ANFIS-PSO is proposed to be used for the prediction of bearing capacity of piles and ensemble learning method of joining the outputs of individual models should be encouraged. The study possesses the potential to assist geotechnical engineers in the design phase of civil engineering projects.

Key Words
dynamic pile load tests; meta-heuristic optimization; pile foundations; rank analysis; reliability analysis

Address
Manish Kumar: Department of Civil Engineering, SRM Institute of Science and Technology (SRMIST),
Deemed to be University, Tiruchirappalli, Tamil Nadu, India
Rahul Biswas: Department of Applied Mechanics, Visvesvaraya National Institute of Technology Nagpur, India
Divesh Ranjan Kumar, Pradeep T. and Pijush Samui: Department of Civil Engineering, National Institute of Technology Patna, Bihar, India

Abstract
Ladle furnace (LF) slag, waste from the steel-making process, was incorporated to improve the compressive strength of soil cement. LF slag was mixed to replace the cement in the soil-cement samples with wt% ratio 20:0, 15:5, and 10:10 of cement and slag, respectively. LF slag in the range of 5, 10, and 20 wt% was also separately added to the 20-wt% cement-treated soil samples. The soil-cement mixed LF slag samples were incubated in a plastic wrapping for 7, 14, and 28 days. The strength of soil cement was highly developed to be higher than the standard acceptable value (0.6 MPa) after incorporating slag into soil cement. The mixing of LF slag resulted in more hydration products for bonding soil particles, and hence improved the strength of soil cement. With the LF slag mixing either a replacement or additive materials in soil cement, the LF slag to cement ratio is considered to be less than 1, while the cement content should be more than 10 wt%. This is to promote a predominant effect of cement hydration by preventing the partially absorbed water on slag particles and keeping sufficient water content for the cement hydration in soil cement.

Key Words
LF slag; soil cement; soft clay; soil stabilization; strength

Address
Jiratchaya Ayawanna and Namthip Kingnoi: School of Ceramic Engineering, Institute of Engineering, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand
Ochakkraphat Sukchaisit and Salisa Chaiyaput: Department of Civil Engineering, School of Engineering, King Mongkut' s Institute of Technology Ladkrabang, Bangkok 10520, Thailand

Abstract
The model of two-dimensional plane waves is analyzed in a micropolar-thermoelastic solid with microtemperatures in the context of the three-phase-lag model, dual-phase-lag model, and the Green-Naghdi theory of type III. Harmonic wave analysis is used to hold the solution to the problem. Numerical results of the physical fields are visualized to show the effects of the gravity field, magnetic field, and viscosity. The expression for the field variables is obtained generally and represented graphically for a particular medium.

Key Words
micropolar; initial stress; microtemperatures; viscoelastic-thermoelastic

Address
Samia M. Said: Department of Mathematics, Faculty of Science, Zagazig University, P.O. Box 44519, Zagazig, Egypt

Abstract
Soil liquefaction has been one of the most important concerns in geotechnical earthquake engineering in recent years, due to its damages to structures and its destructive effects. The cyclic liquefaction of silty sands, in particular, remains of great interest for both research and application. Although many factors are known that affect the liquefaction resistance of sands, the effect of fine grain content is perhaps one of the most studied and still controversial. In this study, 48 deformation-controlled cyclic simple shear tests were performed on BS and CS silt samples mixed with 5%, 15% and 30% by weight of Krk085, Krk042 and Krk025 sands in constant–volume conditions to determine the liquefaction potential of silty sands. The tests were carried out at 30% and 50% relative density and under 100 kPa effective stress. The results revealed that the liquefaction potential of silty sand increases with increasing average particle size ratio (D50sand / d50silt) of the mixture for a fixed silt content. Furthermore, for identical base sand, the liquefaction potentials of coarse grained sands increase with increasing silt content, while the respective potentials of fine grained sands generally decrease. However, this situation may vary depending on the silt grain structure and is affected by the nature of the fine grains. In addition, the variation of the void ratio interval was shown to provide a good intuition in determining the liquefaction potentials of silty sands, while the intergranular void ratio alone does not constitute a criterion for determining the liquefaction potentials of silty sands.

Key Words
cyclic simple shear; fines content; liquefaction; sand; silt

Address
Yetis Bulent Sonmezer: Department of Civil Engineering, Faculty of Engineering, Kirikkale University, 71450 Kirikkale, Turkiye
Kamil Kayabali and Mustafa Fener: Department of Geological Engineering, Faculty of Engineering, Ankara University, 06100 Ankara, Turkiye
Turgay Beyaz: Department of Geological Engineering, Faculty of Engineering, Pamukkale University, 20160 Denizli, Turkiye


Abstract
Under the effects of the near-field earthquakes, the incident angle of the incoming wave could be different. In this study, the influences of some parameters such as incident angle, basin edge, peak ground acceleration level of the bedrock motion as well as different clay types with different consistency on the amplification behavior of the shallow basins are investigated. To attain this goal, the numerical analyses of the basins filled with three different clay types are performed using a fully nonlinear method. The two dimensional models of the basins are subjected to a set of strong ground motions with different peak ground acceleration levels and three different incident angles of 30, 45 and 90 with respect to the horizontal axes. The results show the dominant effect of the obliquely subjected waves at most cases. The higher effect of the 45◦ incident angle on the basin response was concluded. In the other part of this study, the spectral amplification curves of the surface points were compared. It was seen that the maximum spectral amplification of different surface points occurs at different periods. Also, it is affected by the increase in the peak acceleration level of the incoming motions.

Key Words
basin edge effect; dynamic behavior; incident angle; numerical modeling; site effects

Address
Hadi Khanbabazadeh: Department of Engineering Gebze Technical University, Kocaeli, Turkey
Recep Iyisan and Bilal Ozaslan: Department of Civil Engineering, Istanbul Technical University, Istanbul, Turkey

Abstract
Micropiles consisting of steel bars and grouts are commonly used in underpinning methods to reinforce supports or to suppress the subsidence of existing structures. Recently, applications in the field of geotechnical engineering have expanded. Despite the increasing use of micropiles are used, the PHC or steel pile formula is still applied for the settlement amount of micropiles. Compared with field test results, the amount of micropile subsidence obtained from the existing method may result in a very large error in the displacement of the micropile. Therefore, it is difficult to utilize micropiles effectively. Hence, to solve this problem, this study evaluated the behaviors and support characteristics of micropiles through field compression and tensile tests, and proposed a method for predicting the amounts of their subsidence. To confirm the appropriateness of the proposed method, field test results and the results obtained using the proposed method were compared. It was found that the settlement amounts of the micropiles as predicted through the existing method were significantly overestimated (error ≈ 50–80%) relative to the field test results, whereas the settlement errors of the piles predicted through the proposed method decreased (error ≈6–32%). Thus, it is possible to reduce the previously overestimated amount of settlement, and the modified method of this study allows more efficient design than the conventional method.

Key Words
behavior and bearing characteristic of pile; estimating method of micropile settlement; field test; micropile

Address
TaeHyun Hwang, JungMin Cho and YeongSaeng Lee: Department of Civil Engineering, Kyonggi University,
154-42, Gwanggyosan-ro, Yeongtong-gu, Suwon-si, Gyeonggi-do, Republic of Korea

Abstract
Finite element analyses using coupled Eulerian-Lagrangian technique are performed to investigate the effect of soil conditions on plugging of open-ended piles in sands. Results from numerical simulations are compared against the data from field load tests on three open-ended piles and show very good agreement. A parametric study focusing on determination of the coefficient of lateral earth pressure (K) in soil plug after pile driving are then performed for various soil densities, end-bearing conditions, and layering conditions. Results from the parametric study suggest that the K value in the soil plug ‒ and hence the degree of soil plugging ‒ increases with increasing soil densities. The analysis results further show that the K value within the soil plug can reach about 63 to 71% of the coefficient of passive earth pressure after pile driving. For layered soil profiles, the greater K values are achieved after pile driving when the denser soil layer is present near the pile base regardless of number of soil layers. This study provides comprehensive numerical and experimental data that can be used to develop advanced theory for analysis and design of open-ended pipe piles, especially for estimation of inner shaft resistance after pile driving.

Key Words
coefficient of lateral earth pressure; coupled Eulerian-Lagrangian technique; degree of soil plugging; end-bearing conditions; open-ended piles; soil conditions

Address
Junyoung Ko:1Department of Civil Engineering, Chungnam National University, 99 Daehak-ro, Yuseong-gu, Daejeon 34134, Republic of Korea
Sangseom Jeong: School of Civil and Environmental Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea
Hoyoung Seo: Department of Civil, Environmental and Construction Engineering, Texas Tech University, 911 Boston Ave., Lubbock, TX 79409, USA


Abstract
Bearing capacity of shallow foundations is often determined for either dry or saturated soils. In some occasions, foundations may be subjected to external loading which is inclined and/or eccentric. In this study, the ultimate bearing capacity of shallow foundations resting on partially saturated coarse-grained cohesionless and fine-grained cohesive soils subjected to a wide range of combined vertical (V) - horizontal (H) - moment (M) loadings is rigorously evaluated using the well-established limit equilibrium method. The unified effective stress approach as well as the suction stress concept is effectively adopted so as to simulate the behaviour of the underlying unsaturated soil medium. In order to obtain the bearing capacity, four equilibrium equations are solved by adopting Coulomb failure mechanism and Bishop effective stress concept and also considering a linear variation of the induced matric suction beneath the foundation. The general failure loci of the shallow foundations resting on unsaturated soils at different hydraulic conditions are presented in V− H − M spaces. The results indicate that the matric suction has a marked influence on the bearing capacity of shallow foundations. In addition, the effect of induced suction on the ultimate bearing capacity of obliquely-loaded foundations is more pronounced than that of the eccentrically-loaded footings.

Key Words
bearing capacity; combined loading; limit equilibrium method; suction stress; unsaturated soil

Address
Siavash Afsharpour, Meghdad Payan, Reza Jamshidi Chenari, Hadi Ahmadi and Hessam Fathipour: Department of Civil Engineering, Faculty of Engineering, University of Guilan, Rasht, Iran


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