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CONTENTS
Volume 32, Number 2, January25 2023
 

Abstract
Nonlinear vibration analysis of composite beam reinforced by carbon nanotubes resting on the nonlinear viscoelastic foundation is investigated in this study. The material properties of the composite beam is considered as a polymeric matrix by reinforced carbon nanotubes according to different distributions. With using Hamilton's principle, the governing nonlinear partial differential equations are derived based on the Euler-Bernoulli beam theory. In the nonlinear kinematic assumption, the Von Kármán nonlinearity is used. The Galerkin' s decomposition technique is utilized to discretize the governing nonlinear partial differential equation to nonlinear ordinary differential equation and then is solved by using of multiple time scale method. The nonlinear natural frequency and the nonlinear free response of the system is obtained. In addition, the effects of different patterns of reinforcement, linear and nonlinear damping coefficients of the viscoelastic foundation on the nonlinear vibration responses and phase trajectory of the carbon nanotube reinforced composite beam are investigated.

Key Words
carbon nanotubes; composite beams; nonlinear foundation; nonlinear vibration

Address
M. Alimoradzadeh: Department of Mechanical Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran
S.D. Akbas: Department of Civil Engineering, Bursa Technical University, 16330, Bursa, Turkey

Abstract
The current article studied wave propagation in a nonlocal porous thermoelastic half-space with temperature-dependent properties. The problem is solved in the context of the Green-Lindsay theory (G˗L) and the Lord˗ Shulman theory (L˗S) based on thermoelasticity with memory-dependent derivatives. The governing equations of the porous thermoelastic solid are solved using normal mode analysis with an eigenvalue approach. In order to illustrate the analytical developments, the numerical solution is carried out, and the effect of local parameter and temperature-dependent properties on the physical fields are presented graphically.

Key Words
eigenvalue approach; memory-dependent derivative; nonlocal porous thermoelastic solid; temperature-dependent properties

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

Abstract
This paper aims at investigating the face stability of large-diameter underwater shield tunnels considering seepage in soft-hard uneven strata. Using the kinematic approach of limit upper-bound analysis, the analytical solution of limit supporting pressure on the tunnel face considering seepage was obtained based on a logarithmic spiral collapsed body in uneven strata. The stability analysis method of the excavation face with different soft- and hard-stratum ratios was explored and validated. Moreover, the effects of water level and burial depth on tunnel face stability were discussed. The results show the effect of seepage on the excavation face stability can be accounted as the seepage force on the excavation face and the seepage force of pore water in instability body. When the thickness ratio of hard soil layer within the excavation face exceeds 1/6D, the interface of the soft and hard soil layer can be placed at tunnel axis during stability analysis. The reliability of the analytical solution of the limit supporting pressure is validated by numerical method and literature methods. The increase of water level causes the instability of upper soft soil layer firstly due to the higher seepage force. With the rise of burial depth, the horizontal displacement of the upper soft soil decreases and the limit supporting pressure changes little because of soil arching effect.

Key Words
arching effect; face stability; limit analysis; numerical analysis; seepage; soil underwater tunnel; upper-soft and lower-hard strata

Address
Shanglong Zhang, Xinhai Zhou and Yue Sun: Key Laboratory of Disaster Prevention and Mitigation in Civil Engineering of Gansu Province,
Lanzhou University of Technology, No. 287, Langongping Road, Lanzhou 730050, China
Xuansheng Cheng: Key Laboratory of Disaster Prevention and Mitigation in Civil Engineering of Gansu Province,
Lanzhou University of Technology, No. 287, Langongping Road, Lanzhou 730050, China;
Western Engineering Research Center of Disaster Mitigation in Civil Engineering of Ministry of Education,
Lanzhou University of Technology, No. 287, Langongping Road, Lanzhou 730050, China

Abstract
In the present work, a simple and refined shear deformation theory is used to analyze the effect of visco-elastic foundation on the buckling response of exponentially-gradient sandwich plates under various boundary conditions. The proposed theory includes indeterminate integral variables kinematic with only four generalized parameters, in which no shear correction factor is used. The visco-Pasternak's foundation is taken into account by adding the influence of damping to the usual foundation model which characterized by the linear Winkler's modulus and Pasternak's foundation modulus. The four governing equations for FGM sandwich plates are derived by employing principle of virtual work. To solve the buckling problem, Galerkin' s approach is utilized for FGM sandwich plates for various boundary conditions. The analytical solutions for critical buckling loads of several types of powerly graded sandwich plates resting on visco-Pasternak foundations under various boundary conditions are presented. Some numerical results are presented to indicate the effects of inhomogeneity parameter, elastic foundation type, and damping coefficient of the foundation, on the critical buckling loads.

Key Words
buckling; functionally graded materials; Galerkin's approach; refined shear deformation theory; sandwich plates; various boundary conditions; visco-Pasternak foundations

Address
Mimoun Bennedjadi: Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria
Salem Mohammed Aldosari: Enhanced Composite and Structures Centre, School of Aerospace, Transport, and Manufacturing,
Cranfield University, Cranfield MK43 0AL, UK;
National Center for Aviation Technology, King Abdulaziz City for Science and Technology (KACST), Riyadh 11442, Saudi Arabia
Abdelbaki Chikh: Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria;
Ibn Khaldoun University, BP 78 Zaaroura, 14000 Tiaret, Algeria
Abdelhakim Kaci:Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria;
5Université Dr. Tahar Moulay, Faculté de Technologie, Département de Génie Civil et Hydraulique,
BP 138 Cité En-Nasr 20000 Saida, Algérie
Abdelmoumen Anis Bousahla: Laboratoire de Modélisation et Simulation Multi-échelle, Université de Sidi Bel Abbés, Algeria
Fouad Bourada: Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria;
Département des Sciences et de la Technologie, université de Tissemsilt, BP 38004 Ben Hamouda, Algérie
Abdeldjebbar Tounsi: Industrial Engineering and Sustainable Development Laboratory, University of Rélizane,
Faculty of Science & Technology, Mechanical Engineering Department, Algeria
Kouider Halim Benrahou: Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria;
Department of Physics, College of Sciences, Princess Nourah bint Abdulrahman University (PNU),
P.O. Box 84428, Riyadh 11671, Saudi Arabia
Abdelouahed Tounsi:Material and Hydrology Laboratory, University of Sidi Bel Abbes, Faculty of Technology, Civil Engineering Department, Algeria;
YFL (Yonsei Frontier Lab), Yonsei University, Seoul, Korea;
Department of Civil and Environmental Engineering, King Fahd University of Petroleum &Minerals, 31261 Dhahran,
Eastern Province, Saudi Arabia





Abstract
To study the influences of tunneling on the earth pressure and ground settlement when the tunnel passes through the adjacent underground retaining structure, 30 two-dimensional model tests were carried out taking into account the ratios of tunnel excavation depth (H) to lateral width (w), excavation width (B), and excavation distance using a custom-made test device and an analogical soil. Tunnel crossing adjacent existing retaining structure (TCE) and tunnel crossing adjacent newly-built retaining structure (TCN) were simulated and the earth pressure variations and ground settlement distribution during excavation were analyzed. For TCE condition, the earth pressure increments, maximum ground settlement and the curvature of the ground settlement curve are negatively related to H/B, but positively related to H/s and H/w. For TCN condition, most trends are consistent with TCE except that the earth pressure increments and the curvature of ground settlement curve are negatively related to H/w. The maximum ground settlement is larger than that observed in tunnel crossing the existing underground structure. This study provides an assessment basis for the design and construction under confined space conditions.

Key Words
analogical soil; earth pressure; ground settlement; model test; retaining wall; tunneling

Address
Jinyuan Wang and Rui Rui: School of Civil Engineering and Architecture, Wuhan University of Technology, 122 Luoshi Rd., Wuhan 430070, China
Wenjun Li: China Harbour Engineering Company Ltd., 9 Chunxiu Rd., Dongzhi gate, Dongcheng District, Beijing 100027, China
Yuxin Zhai: China Railway Construction Group Co., Ltd., No. 69 Fuxing Road, Haidian District, Beijing 100040, China
Qing He: China Fortune Land Development Co., Ltd., No. 18 Xiaguangli, Dongsanhuan North Road, Chaoyang District, Beijing 100027, China

Abstract
In general, the numerous classical approaches available in the literature can anticipate the settlement of shallow foundations. As long as the footings are not in close proximity to other subsurface buildings, the findings achieved using these methods are legitimate and acceptable. However, due to increased urbanisation and land scarcity, footings are frequently built close together. As a result, these footings' settlement behaviour differs from those of isolated footings. A simpler approach for assessing the settlement behaviour of two square or rectangular footings placed in close proximity is presented in this work. A Parametric study has been carried out to examine the interference effect on the settlement of these footings placed in close vicinity on the surface of a homogeneous, isotropic and elastic soil medium. The interaction factors are examined by varying the different aspect ratios (L/B), clear spacing ratio (S/B) and intensity of loading on the right footing with respect to the left footing. Further, variation of the settlement ratio (s/B) with respect to embedment depth ratio Df/B is examined. For square and rectangular footings, the interference settlement profile is also investigated by varying the clear spacing ratio (S/B) and the degree of loading. The results were compared to 3D finite element analysis and experimental data that were available.

Key Words
interference effect; intensity of loading; interaction factor; settlement; square and rectangular footings

Address
R. Sarvesh, V. Srinivasan and Anjan Patel: Department of Civil Engineering, Visvesvaraya National Institute of Technology, Nagpur – 440 010, India

Abstract
A comprehensive study was conducted to design economical foundations for a number of buildings on soft cohesive soil in the southern coastal regions of Iran. Both static and seismic loads were considered in the design process. Cyclic experiments indicated that the cohesive soil of the area has potential for softening. Consequently, the major challenge in the design stages was relatively high dimensions of settlement, under both static and seismic loadings. Routine soil-improvement methods were too costly for the vast area of the project. After detailed numerical modeling of different scenarios, we concluded that, in following a performance-based design approach and applying a special time schedule of construction, most of the settlement would dissipate during the construction of the buildings. Making the foundation as rigid as possible was another way to prevent any probable differential settlement. Stiff subgrade of stone and lime mortar under the grid foundation and a reinforced concrete slab on the foundation were considered as appropriate to this effect. In favor of an economical design, in case the design earthquake strikes the site, the estimations indicate no collapse of the buildings even if considerable uniform settlements may occur. This is a considerable alternative design to costly soil-improvement methods.

Key Words
compressible soil; cyclic softening; dynamic numerical analysis; grid foundation; performance-based design; rigid foundation; soil improvement

Address
Javad Jalili, Farajdollah Askari, Ebrahim Haghshenas and Azadeh Marghaiezadeh: International Institute of Earthquake Engineering and Seismology, No.21, Arghavan St.,
Northern Dibaji St., Lavasani Ave., Tehran 19395/3913, Iran

Abstract
With the increasing amount of resources required by the society development, mining operations go deeper, which raises the requirements of studying the effects of temperature on the physical and mechanical properties of coal and adjacent rock. For now, these effects are yet to be fully revealed. In this paper, a mechanical-electromagnetic radiation (EMR) test system was established to understand the mechanical deterioration characteristics of coal by the effect of thermal treatment and its deformation and fracture characteristics under thermo-mechanical coupling conditions. The mechanical properties of high-temperature-treated coal were analyzed and recorded, based on which, reasons of coal mechanical deterioration as well as the damage parameters were obtained. Changes of the EMR time series under unconstrained conditions were further analyzed before characteristics of EMR signals under different damage conditions were obtained. The evolution process of thermal damage and deformation of coal was then analyzed through the frequency spectrum of EMR. In the end, based on the time-frequency variation characteristics of EMR, a method of determining combustion zones within the underground gasification area and combustion zones's stability level was proposed.

Key Words
coal; EMR; mechanical deterioration; stability evaluation; temperature

Address
Biao Kong: College of Safety and Environmental Engineering, Shandong University of Science and Technology, Qingdao 266590, China;
Engineering Technology Research Centre for Safe and Efficient Coal Mining (Anhui University of Science and Technology),
Huainan, 232001, China;
State Key Laboratory of Coal Mine Safety Technology, China Coal Technology & Engineering Group Shenyang Research Institute, Shenyang, 113122, China
Sixiang Zhu and Xiaolei Sun: College of Safety and Environmental Engineering, Shandong University of Science and Technology, Qingdao 266590, China
Wenrui Zhang and Wei Lu: College of Safety and Environmental Engineering, Shandong University of Science and Technology, Qingdao 266590, China;
Engineering Technology Research Centre for Safe and Efficient Coal Mining (Anhui University of Science and Technology),
Huainan, 232001, China
Yankun Ma: Engineering Technology Research Centre for Safe and Efficient Coal Mining (Anhui University of Science and Technology),
Huainan, 232001, China

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