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CONTENTS
Volume 38, Number 4, August25 2024
 

Abstract
Low carbon energy demand in South Korea is increasing, hence leading to an increasing usage of wood pellets and the amount of its combustion by-product called wood pellet fly ash (WA). In an effort to develop recycling technology, this research investigates the use of WA as a new sustainable binder for backfill soil materials. The influence of WA on weathered granite soils (WS) is investigated by mixing 5%, 15%, and 25% of WA dosage, compacted at optimum moisture content, then cured for 3, 7, 14, and 28 days. After curing, the compacted specimens were investigated through unconfined compressive tests, pH tests, total suction tests, and microstructural analysis. The findings suggest that the higher the dosage rate, the higher strength and modulus. Additionally, the alkali ions of WA aid in the cementation of WS particles, and newly cementitious minerals are confirmed after 28 curing days. The refinement of pore microstructures led to a denser WS matrix and stiffness improvements. The results validate the binding potential of wood pellet fly ash on weathered granite soils in terms of strength, modulus, and microstructures.

Key Words
microstructural analysis; sustainable binder; unconfined compressive tests; weathered granite soils; wood pellet fly ash

Address
Jebie A. Balagosa, Min Jy Lee and Yun Wook Choo: Department of Civil and Environmental Engineering, Kongju National University, 1223-24,
Cheonan-daero, Seobuk-gu, Cheonan-si 31080, Republic of Korea
Ha Seog Kim and Jin Man Kim: Department of Architectural Engineering, Kongju National University, 1223-24, Cheonan-daero,
Seobuk-gu, Cheonan-si 31080, Republic of Korea

Abstract
Organic soils pose significant challenges in geotechnical engineering due to their high compressibility and low stability, which can result in issues like differential settlement, rutting, and pavement deformation. This study explores effective methods for stabilizing organic soils. Rather than conventional ordinary Portland cement (OPC), the focus is on using environmentally friendly calcium sulfoaluminate (CSA) cement, known for its rapid setting, high early strength development, and environmental benefits. Mechanical behavior is analyzed through 1-D free swell, unconfined compressive strength (UCS), and bender element (BE) tests. Microstructural analyses, including Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), characterize the soil mixed with CSA cement. Experimental results demonstrate improved soil properties with increasing cement dosage and curing periods. A notable strength increase is observed in soil samples with 15% cement content, with UCS doubling after 7 days. This trend aligns with shear wave velocity results from the BE test. SEM and FTIR spectroscopy reveal how CSA cement hydration forms hydrated calcium silicate gel and ettringite, enhancing soil properties. CSA cement is recommended for reinforcing organic subgrade soil due to its eco-friendly nature and rapid strength gain, contributing to improved durability.

Key Words
calcium sulfoaluminate cement; compressive strength; free swell; organic soil; shear wave velocity; soil stabilization; unconfined

Address
Nazerke Sagidullina, Jong Kim, Alfrendo Satyanaga and Sung-Woo Moon: Department of Civil and Environmental Engineering, Nazarbayev University, Astana, 010000, Kazakhstan
Taeseo Ku: Department of Civil and Environmental Engineering, Konkuk University, Seoul, 05029, Korea

Abstract
In this study, a prediction model for the cutting force evolution in brittle rocks was developed. This model is based on indentation tests using a conical pick at a cutting depth of 9 mm. The behavior of the indentation mechanism was analyzed in three phases by using Evans'cutting mode. The peak values in the force history identified these phases. The variation in the local strength of the rock caused a large offset in the model prediction of chipping. Regression analyses showed that there is a strong power relationship between the upper bound of the cutting force along with chipping and depth of cut. The slope of the three crushing phases has been found to increase sequentially (a1,a2,a3). In addition, a positive correlation existed between the Schmidt hardness and brittleness index that affects the lower and upper bounds of chipping. Consequently, the results clearly demonstrate that the new model can reasonably predict the evolution of the cutting force based on experimental data. These results would be beneficial for engineers to design and select the optimum excavation machine to reduce mechanical vibration and enhance cutting efficiency.

Key Words
conical pick; Evans' cutting mode; indentation test; rock cutting

Address
Xiang Wang: School of Mechanical Engineering, Chongqing University of Technology, Chongqing 400054, China;
Institute of Mining Engineering, Beijing General Research Inst. of Min. and Metall., Beijing 102628, China
Ming S. Gao: School of Mechanical Engineering, Chongqing University of Technology, Chongqing 400054, China
Okan Su: Department of Mining and Mineral Extraction, Zonguldak Bülent Ecevit University, Zonguldak 67600, Türkiye
Dan Huang: Institute of Mining Engineering, Beijing General Research Inst. of Min. and Metall., Beijing 102628, China

Abstract
With the wide application of urban subway tunnels, the foundation pits of new stations and existing subway tunnels are becoming increasingly close, and even zero-distance close-fitting construction has taken place. To optimize the construction support scheme, the existing tunnel's vertical displacement is theoretically analyzed using the two-stage analysis method to understand the action mechanism of the construction of zero-distance deep large foundation pits on both sides of the existing stations; a three-dimensional numerical calculation is also performed for further analysis. First, the additional stress field on the existing tunnel caused by the unloading of zero-distance foundation pits on both sides of the tunnel is derived based on the Mindlin stress solution of a semi-infinite elastic body under internal load. Then, considering the existing subway tunnel' s joints, shear stiffness, and shear soil deformation effect, the tunnel is regarded as a Timoshenko beam placed on the Kerr foundation; a sixth-order differential control equation of the tunnel under the action of additional stress is subsequently established for solving the vertical displacement of the tunnel. These theoretical calculation results are then compared with the numerical simulation results and monitoring data. Finally, an optimized foundation pit support scheme is obtained considering the pit corner effect and external corner failure mode. The research shows a high consistency between the monitoring data,analytical and numerical solution, and the closer the tunnel is to the foundation pit, the more uplift deformation will occur. The internal corner of the foundation pit can restrain the deformation of the tunnel and the retaining structure, while the external corner can cause local stress concentration on the diaphragm wall. The proposed optimization scheme can effectively reduce construction costs while meeting the safety requirements of foundation pit support structures.

Key Words
deep and large foundation pit; external corner of foundation pit; Kerr foundation model; pit corner effectsupport optimization; zero-distance construction

Address
Tonghua Ling, Xing Wu, Fu Huang and Jian Xiao: Changsha University of Science & Technology, Changsha, China
Yiwei Sun: Shanghai Geoharbor Construction Group Co., Ltd., Shanghai, China
Wei Fenng: China Construction Fifth Engineering Division Corp, Ltd, China

Abstract
Buried box culverts are crucial elements of transportation infrastructure. However, their behavior under foundation loads is not well understood, indicating a significant gap in existing research. This study aims to bridge this gap by conducting a detailed numerical analysis using the Finite Element Method and Abaqus software. The research evaluates the behavior of buried box culverts by examining their interaction with surrounding soil and the pressures from surface foundation loads. Key variables such as embedment depth, culvert wall thickness, concrete material properties, foundation pressure, foundation width, soil elastic modulus, and friction angle are altered to understand their combined effects on structural response. The methodology employs a validated 2D numerical model under plane strain conditions. Parametric studies highlight the critical role of culvert depth (H) in influencing earth pressure and bending moments. Foundation pressure and width demonstrate complex interdependencies affecting culvert behavior. Variations in culvert materials' elastic modulus show minimal impact. It was found that the lower wall of the buried culvert experiences higher average pressure compared to the other two walls, due to the combined effects of the culvert's weight and down drag forces on the side walls. Furthermore, while the pressure distribution on the top and bottom walls is parabolic, the pressure on the side walls follows a different pattern, differing from that of the other two walls.

Key Words
bending moment; box culvert; earth Pressure; foundation loading; numerical analysis

Address
Bin Du: Civil & Architecture Engineering Xi'an Technological University, Xi'an, Shaanxi 710062, China
Bo Hao and Wanjiong Wang: School of Mechanical Engineering and Automation, Northeastern University; Shenyang, Liaoning, 110819 China
Xuejing Duan: Marine Engineering Department, Weihai Marine Vocational College; Rongcheng Shandong, 264300 China
Mohammad Roohani: Faculty of Geotechnical Engineering, Civil Engineering Department, University of Zanjan, Zanjan, Iran



Abstract
In this research the hygro-thermo-mechanical loading and micromechanical model effects on bending behavior of functionally graded material plates resting on Winkler and Pasternak elastic foundations, the higher order shear deformation theory is used here. The material properties of the plate: young's modulus, thermal coefficient and moisture expansion coefficient are assumed to be graded in the thickness direction according to various micromechanical models starting with the Voigt's model which is commonly used in most functionally graded plates studies to the Reuss' LRVE's and Mori-Tanaka's models. The principle of virtual displacement is used to determine the equilibrium equations and the a several numerical results are given to validate the precision of the present method for bending behavior of FGM plates subjected to hygro-thermo-mechanical loading resting on elastic foundations. Afterwards, a parametric study is conducted to determine the effect of different parameters on the deflection of the FGM plates like micromechanical models, type of loading and plate geometry. In the lights of the present research, it can be concluded that the present theory is accurate and simple in predicting the deflection behavior of functionally graded plates under hygro-thermo-mechanical effects and micromechanical models.

Key Words
deflection; elastic foundations; functionally graded plates; hygro-thermo-mechanical loading; micromechanical models

Address
Belkacem Adim: Department of Sciences and technology, Tissemsilt University, Tissemsilt, Algeria;
Geomatics and Sustainable Development Laboratory, Ibn Khaldoun University, Tiaret, Algeria
Tahar Hassaine Daouadji: Geomatics and Sustainable Development Laboratory, Ibn Khaldoun University, Tiaret, Algeria;
3Department of Civil engineering, Ibn Khaldoun University, Tiaret, Algeria

Abstract
The soil nailing method entails the utilisation of nails to reinforce and stabilise a zone of soil mass. This is widely used for various applications due to its effective performance under various loading conditions. The seismic response of 6m high vertical soil-nailed cut in various site classes under dynamic excitations has been investigated in this study considering various lengths and inclinations of nails. The influence of frequency content of dynamic excitation on the response of structure has been assessed through finite element analysis using time history data of three different earthquakes. The seismic stability of the nailed cut in retaining soil in various sites under El Centro, Kobe and Trinidad earthquake ground motion is evaluated based on maximum acceleration response, maximum horizontal deformation, earth pressure distribution on the wall and maximum axial force mobilised in nails. The optimum nail inclination is identified as 15 and a minimum nail length ratio of 0.7 is essential for a stable vertical cut under dynamic excitations.

Key Words
dynamic excitation; finite element analyses; nail length ratio; soil nailing; vertical cuts

Address
Amrita, B.R. Jayalekshmi and R. Shivashankar: Department of Civil Engineering, National Institute of Technology Karnataka (NITK), Surathkal, Karnataka - 575025, India

Abstract
The research findings of two nonlinear machine learning and soft computing models- the Cuckoo optimization algorithm (COA) and the Teaching-learning-based optimization (TLBO) in combination with artificial neural network (ANN)- are presented in this article. Detailed finite element modeling (FEM) of a shallow footing on two layers of cohesionless soil provided the data sets. The models are trained and tested using the FEM outputs. Additionally, various statistical indices are used to compare and evaluate the predicted and calculated models, and the most precise model is then introduced. The most precise model is recommended to estimate the solution after the model assessment process. When the anticipated findings are compared to the FEM data, there is an excellent agreement, which indicates that the TLBO-MLP solutions in this research are reliable (R2=0.9816 for training and 0.99366 for testing). Additionally, the optimized COA-MLP network with a swarm size of 500 was observed to have R2 and RMSE values of (0.9613 and 0.11459) and (0.98017 and 0.09717) for both the normalized training and testing datasets, respectively. Moreover, a straightforward formula for the soft computing model is provided, and an excellent consensus is attained, indicating a high level of dependability for the suggested model.

Key Words
artificial neural network; bearing capacity; cohesionless soil; limit equilibrium; shallow foundation

Address
Hossein Moayedi and Binh Nguyen Le: Institude of Research and Development, Duy Tan University, Da Nang, Vietnam;
School of Engineering & Technology, Duy Tan University, Da Nang, Vietnam
Mesut Gör: Department of Civil Engineering, Division of Geotechnical Engineering, Firat University, 23119 Elazig, Turkey
Mansour Mosallanezhad: Department of Civil and Environmental Engineering, Shiraz University, Shiraz, Iran
Soheil Ghareh: Department of Civil Engineering, Payame Noor University, Tehran, Iran

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