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CONTENTS
Volume 36, Number 2, January25 2024
 

Abstract
Studying the dynamic behavior of axially moving cylindrical shells in hygro-thermal environments has important theoretical and engineering value for aircraft design. Therefore, in this paper, considering hygro-thermal effect, the nonlinear forced vibration of an axially moving cylindrical shell made of functionally graded materials (FGM) is studied. It is assumed that the material properties vary continuously along the thickness and contain pores. The Donnell thin shell theory is used to derive the motion equations of FGM cylindrical shells with hygro-thermal loads. Under the four sides clamped (CCCC) boundary conditions, the Gallekin method and multi-scale method are used for nonlinear analysis. The effects of power law index, porosity coefficient, temperature rise, moisture concentration, axial velocity, prestress, damping and external excitation amplitude on nonlinear forced vibration are explored through parametric research. It can be found that, the changes in temperature and humidity have a significant effect. Increasing in temperature and humidity will cause the resonance position to shift to the left and increase the resonance amplitude.

Key Words
axial motion; FGM cylindrical shell; Hygro-thermal load; nonlinear forced vibration; the multi-scale method

Address
Jin-Peng Song, Gui-Lin She and Yu-Jie He: College of Mechanical and Vehicle Engineering, Chongqing University, Chongqing 400044, China

Abstract
In the realm of rock excavation projects, precise estimation of the drilling rate index stands as a pivotal factor in strategic planning and cost assessment. This study introduces and evaluates two pioneering computational intelligence models designed for the prognostication of the drilling rate index, a pivotal parameter with direct implications for cost estimation in rock excavation projects. These models, denoted as the Relevance Vector Regression (RVR) optimized with the Invasive Weed Optimization algorithm (IWO) (RVR-IWO model) and the RVR integrated with the Shuffled Frog Leaping algorithm (SFL) (RVR-SFL model), represent a groundbreaking approach to forecasting drilling rate index. The RVR-IWO and RVR-SFL models were meticulously devised to harness the capabilities of computational intelligence and optimization techniques for drilling rate index estimation. This research pioneers the integration of IWO and SFL with RVR, constituting an unprecedented effort in forecasting drilling rate index. The primary objective of this study was to gauge the precision and dependability of these models in forecasting the drilling rate index, revealing significant distinctions between the two. In terms of predictive precision, the RVR-IWO model emerged as the superior choice when compared to the RVR-SFL model, underscoring the remarkable efficacy of the Invasive Weed Optimization algorithm. The RVR-IWO model delivered noteworthy results, boasting a Variance Account for (VAF) of 0.8406, a Mean Squared Error (MSE) of 0.0114, and a Squared Correlation Coefficient (R2) of 0.9315. On the contrary, the RVR-SFL model exhibited slightly lower precision, yielding an MSE of 0.0160, a VAF of 0.8205, and an R2 of 0.9120. These findings serve to highlight the potential of the RVR-IWO model as a formidable instrument for drilling rate index prediction, particularly within the framework of rock excavation projects. This research not only makes a significant contribution to the realm of drilling engineering but also underscores the broader adaptability of the RVR-IWO model in tackling an array of challenges within the domain of rock engineering. Ultimately, this study advances the comprehension of drilling rate index estimation and imparts valuable insights into the practical implementation of computational intelligence methodologies within the realm of engineering projects.

Key Words
drilling rate index; invasive weed optimization algorithm; relevance vector regression; rock geomechanical properties; shuffled frog leaping algorithm

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

Abstract
Many foundation projects are built on red-bed soft rocks, and the damage evolution of this kind of rocks affects the safety of these projects. At present, there is insufficient research on the damage evolution of red-bed soft rocks, especially the progressive process from mesoscopic texture change to macroscopic elastoplastic deformation. Therefore, based on the dual-porosity characteristics of pores and fissures in soft rock, we adopted a cellular automata model to simulate the propagation of these voids in soft rocks under an external load. Further, we established a macro–mesoscopic damage model of red-bed soft rocks, and its reliability was verified by tests. The results indicate that the relationship between the number and voids size conformed to a quartic polynomial, whereas the relationship between the damage variable and damage porosity conformed to a logistic curve. The damage porosity was affected by dual-porosity parameters such as the fractal dimension of pores and fissures. We verified the reliability of the model by comparing the test results with an established damage model. Our research results described the progressive process from mesoscopic texture change to macroscopic elastoplastic deformation and provided a theoretical basis for the damage evolution of these rocks.

Key Words
damage evolution; elastoplastic deformation; fissures; pores; red-bed soft rocks

Address
Guangjun Cui: Institute of Estuarine and Coastal Research/Guangdong Provincial Engineering Research Center of Coasts, Islands and Reefs,
School of Ocean Engineering and Technology, Sun Yat-sen University, Guangzhou 510275, China;
Guangdong Engineering Research Centre for Major Infrastructure Safety, Sun Yat-sen University, Guangzhou 510275, China
Cuiying Zhou and Zhen Liu: Guangdong Engineering Research Centre for Major Infrastructure Safety, Sun Yat-sen University, Guangzhou 510275, China
Lihai Zhang: Department of Infrastructure Engineering, The University of Melbourne, Melbourne VIC 3010, Australia

Abstract
Shield tunneling construction commonly crosses underground pipelines in urban areas, resulting in soil loss and followed deformation of grounds and pipelines nearby, which may threaten the safe operation of shield tunneling. This paper investigated the pipeline deformation caused by double curved shield tunnels in soil-rock composite stratum in Nanjing, China. The stratum settlement equation was modified to consider the double shield tunneling. Moreover, a three dimensional finite element model was established to explore the effects of hard-layer ratio, tunnel curvature radius, pipeline buried depth and other influencing factors. The results indicate the subsequent shield tunnel would cause secondary disturbance to the soil around the preceding tunnel, resulting in increased pipeline and ground surface settlement above the preceding tunnel. The settlement and stress of the pipeline increased gradually as buried depth of the pipeline increased or the hard-layer ratio (the ratio of hard-rock layer thickness to shield tunnel diameter within the range of the tunnel face) decreased. The modified settlement calculation equation was consistent with the measured data, which can be applied to the settlement calculation of ground surface and pipeline settlement. The modified coefficients a and b ranged from 0.45 to 0.95 and 0.90 to 1.25, respectively. Moreover, the hard-layer ratio had the most significant influence on the pipeline settlement, but the tunnel curvature radius and the included angle between pipeline and tunnel axis played a dominant role in the scope of the pipeline settlement deformation.

Key Words
double curved shield tunneling; field monitoring; numerical simulation; pipeline deformation; soil-rock composite stratum

Address
Ning Jiao, Xing Wan, Jianwen Ding, Sai Zhang and Jinyu Liu: Institute of Geotechnical Engineering, School of Transportation, Southeast University,
No.2, Southeast Road, Jiangning District, Nanjing, 211189, China

Abstract
The mechanical properties of the concrete-frozen soil interface play a significant role in the stability and service performance of construction projects in cold regions. Current research mainly focuses on the precast concrete-frozen soil interface, with limited consideration for the more realistic cast-in-place concrete-frozen soil interface. The two construction methods result in completely different contact surface morphologies and exhibit significant differences in mechanical properties. Therefore, this study selects silty clay as the research object and conducts direct shear tests on the concrete-frozen soil interface under conditions of initial water content ranging from 12% to 24%, normal stress from 50 kPa to 300 kPa, and freezing temperature of -3C. The results indicate that (1) both interface shear stress-displacement curves can be divided into three stages: rapid growth of shear stress, softening of shear stress after peak, and residual stability; (2) the peak strength of both interfaces increases initially and then decreases with an increase in water content, while residual strength is relatively less affected by water content; (3) peak strength and residual strength are linearly positively correlated with normal stress, and the strength of ice bonding is less affected by normal stress; (4) the mechanical properties of the cast-in-place concrete-frozen soil interface are significantly better than those of the precast concrete-frozen soil interface. However, when the water content is high, the former's mechanical performance deteriorates much more than the latter, leading to severe strength loss. Therefore, in practical engineering, cast-in-place concrete construction is preferred in cases of higher negative temperatures and lower water content, while precast concrete construction is considered in cases of lower negative temperatures and higher water content. This study provides reference for the construction of frozen soil-structure interface in cold regions and basic data support for improving the stability and service performance of cold region engineering.

Key Words
cold region engineering; concrete-frozen soil interface; frozen soil; interface bond strength; mechanical properties; peak strength; residual strength; silty clay

Address
Guo Zheng, Ke Xue, Jian Hu, Ping Yang and Jun Xie: College of Water Conservancy and Hydropower, Sichuan Agricultural University, 46 Xinkang Road, Yucheng District, Ya'an, China
Mingli Zhang: School of Civil Engineering, Lanzhou University of Technology, 287 Langongping Road, Qilihe District, Lanzhou, China
Desheng Li: School of Science, Nanjing University of Science and Technology, 200 Xiaoling Wei Street, Xuanwu District, Nanjing, China

Abstract
Generally, the rubble mound installed on the slope embankment of the open-type wharf is designed based on the impact of wave force, with no consideration for the impact of seismic force. Therefore, in this study, dynamic centrifuge model test results were analyzed to examine the acceleration amplification of embankment reinforced with rubble mound under seismic conditions. The experimental results show that when rubble mounds were installed on the ground surface of the embankment, acceleration response of embankment decreased by approximately 22%, and imbalance in ground settlement decreased significantly from eight to two times. Furthermore, based on the experimental results, one-dimensional site response (1DSR) analyses were conducted. The analysis results indicated that reinforcing the embankment with rubble mound can decrease the peak ground acceleration (PGA) and short period response (below 0.6 seconds) of the ground surface by approximately 28%. However, no significant impact on the long period response (above 0.6 seconds) was observed. Additionally, in ground with lower relative density, a significant decrease in response and wide range of reduced periods were observed. Considering that the reduced short period range corresponds to the critical periods in the design response spectrum, reinforcing the loose ground with rubble mound can effectively decrease the acceleration response of the ground surface.

Key Words
amplification; centrifuge model test; embankment; one-dimension site response analysis; rubble mound

Address
Jung-Won Yun: Department of Civil Engineering, Korea Army Academy at Yeongcheon, Yeongcheon, South Korea
Jin-Tae Han: Department of Geotechnical Engineering Research, Korea Institute of Civil Engineering and Building Technology, Gyeonggi, South Korea
Jae-Kwang Ahn: Earthquake and Volcano Technology Team, Korea Meteorological Administration, Seoul, South Korea

Abstract
The soil-structure relative stiffness is a key factor affecting the seismic response of underground structures. It is of great significance to study the soil-structure relative stiffness for the soil-structure interaction and the seismic disaster reduction of subway stations. In this paper, the dynamic shear modulus ratio and damping ratio of an inhomogeneous soft soil site under different buried depths which were obtained by a one-dimensional equivalent linearization site response analysis were used as the input parameters in a 2D finite element model. A visco-elasto-plastic constitutive model based on the Mohr-Coulomb shear failure criterion combined with stiffness degradation was used to describe the plastic behavior of soil. The damage plasticity model was used to simulate the plastic behavior of concrete. The horizontal and vertical relative stiffness ratios of soil and structure were defined to study the influence of relative stiffness on the seismic response of subway stations in inhomogeneous soft soil. It is found that the compression damage to the middle columns of a subway station with a higher relative stiffness ratio is more serious while the tensile damage is slighter under the same earthquake motion. The relative stiffness has a significant influence on ground surface deformation, ground acceleration, and station structure deformation. However, the effect of the relative stiffness on the deformation of the bottom slab of the subway station is small. The research results can provide a reference for seismic fortification of subway stations in the soft soil area.

Key Words
layered soft soil foundation; seismic response; soil-structure interaction; soil-structure relative stiffness; subway station

Address
Min-Zhe Xu, Zhen-Dong Cui and Li Yuan: State Key Laboratory of Intelligent Construction and Healthy Operation & Maintenance of Deep Underground Engineering, School of Mechanics and Civil Engineering, China University of Mining and Technology, Xuzhou, Jiangsu, 221116, P.R. China

Abstract
In current investigation, a novel beam finite element model is formulated to analyze the buckling and free vibration responses of functionally graded porous beams resting on Winkler-Pasternak elastic foundations. The novelty lies in the formulation of a simplified finite element model with only three degrees of freedom per node, integrating both C0 and C1 continuity requirements according to Lagrange and Hermite interpolations, respectively, in isoparametric coordinate while emphasizing the impact of z-coordinate-dependent porosity on vibration and buckling responses. The proposed model has been validated and demonstrating high accuracy when compared to previously published solutions. A detailed parametric examination is performed, highlighting the influence of porosity distribution, foundation parameters, slenderness ratio, and boundary conditions. Unlike existing numerical techniques, the proposed element achieves a high rate of convergence with reduced computational complexity. Additionally, the model's adaptability to various mechanical problems and structural geometries is showcased through the numerical evaluation of elastic foundations, with results in strong agreement with the theoretical formulation. In light of the findings, porosity significantly affects the mechanical integrity of FGP beams on elastic foundations, with the advanced beam element offering a stable, efficient model for future research and this in-depth investigation enriches porous structure simulations in a field with limited current research, necessitating additional exploration and investigation.

Key Words
beam finite element model; elastic stability; free vibration; porous functionally graded beam; Winkler-Pasternak elastic foundations

Address
Zakaria Belabed: Artificial Intelligence Laboratory for Mechanical and Civil Structures, and Soil, Institute of Technology,
University Center of Naama, BP 66, 45000 Naama, Algeria;
Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria
Mohammed A. Al-Osta: Department of Civil and Environmental Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran,
Eastern Province, Saudi Arabia;
Interdisciplinary Research Center for Construction and Building Materials, KFUPM, 31261 Dhahran, Saudi Arabia
Abdeldjebbar Tounsi: Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria
Abdelouahed Tounsi and Hoang-Le Minh: Center for Engineering Application & Technology Solutions, Ho Chi Minh City Open University, Ho Chi Minh City, Vietnam

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