scholarly journals Theoretical and Numerical Analysis of Soil-Pipe Pile Horizontal Vibration Based on the Fractional Derivative Viscoelastic Model

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Hao Zhang ◽  
Jienan Niu ◽  
Ningning Huang ◽  
Qifang Yan
Keyword(s):  
Fractional Derivative ◽  
Soil Layer ◽  
Viscoelastic Model ◽  
Dynamic Resistance ◽  
Elastic Model ◽  
Soil Layers ◽  
Pipe Pile ◽  
Function Decomposition ◽  
Dynamic Impedance ◽  
Core Soil

To describe the mechanical properties of the system of pipe pile-soil reasonably and accurately, the constitutive relations of the soil around pile and pile core soil are characterized by the fractional derivative viscoelastic model. We assume that the radial and circumferential displacements of the soil around the pile and pile core soil are the functions of r, θ, and z. The horizontal dynamic control equations of soil layers are derived by using the fractional derivative viscoelastic model. Considering the fractional derivative properties, soil layer boundary condition, and contact condition of pile and soil, the potential function decomposition method is used to solve the radial and circumferential displacements of the soil layer. Then, the force of unit thickness soil layer on the pipe pile and the impedance factor of the soil layer are obtained. The horizontal dynamic equations of pipe pile are established considering the effect of soil layers. The horizontal dynamic impedance and horizontal-swaying dynamic resistance at the pile top are obtained by combining the pipe pile-soil boundary conditions and the orthogonal operation of trigonometric function. Numerical solutions are used to analyze the influence of pile and soil parameters on the soil impedance factor and horizontal dynamic impedance at pile top. The results show that the horizontal impedance factors of the soil layer and horizontal dynamic impedance of pipe pile by using the fractional derivative viscoelastic model can be degraded to those of the classical viscoelastic model and the elastic model. For the fractional derivative viscoelastic model of soil layer, the influence of soil around pile on the dynamic impedance is greater than that of pile core soil. The model parameter TOa, the inner radius of pipe pile, and the pile length have obvious effects on the horizontal impedance of the soil layer and pipe pile, while the influence of the pile core soil on the pile impedance is smaller.

Vertical Vibration of Pile Groups in Soil Described by Fractional Derivative Viscoelastic Model

2011 ◽  
Vol 189-193 ◽  
pp. 3492-3497
Author(s):  
Jiu Min Sun ◽  
Lin Chao Liu ◽  
Qi Fang Yan
Keyword(s):  
Fractional Derivative ◽  
Soil Layer ◽  
Viscoelastic Model ◽  
Dynamic Interaction ◽  
Vertical Vibration ◽  
Pile Groups ◽  
Pile Spacing ◽  
Dynamic Impedance ◽  
Stiffness And Damping ◽  
Relationship Of

The stress-strain relationship of soil is described by fractional derivative viscoelastic model, and established the vertical governing equations of viscoelastic soil. The stiffness and damping of the soil layer described by fractional viscoelastic model are obtained based on the method of layer. The pile-soil dynamic interaction is modeled by Winkler dynamic elastic-damping model, the pile to pile dynamic interaction and vertical vibration of the pile groups in the soil described by fractional derivative viscoelastic model is solved. The influence of the pile spacing, order of fractional derivative and model parameter of soil on the vertical dynamic impedance of pile groups is also investigated. The result indicated that the curves of the dynamic impedance varying with frequency were more complex with the increase of pile spacing, the influence of the order of fractional derivative on vertical dynamic impedance of pile groups is different at lower frequency and high frequency, and the selection of the constitutive model of viscoelastic soil had great effect on the vertical dynamic impedance of pile groups.

scholarly journals Ultimate capacity of piles penetrating in weak soil layers

2018 ◽  
Vol 162 ◽  
pp. 01025
Author(s):  
Ahmed Al-Obaidi ◽  
Pinar Mahmood
Keyword(s):  
Soft Soil ◽  
Soil Layer ◽  
Vertical Direction ◽  
Deep Foundations ◽  
Elastic Model ◽  
Ultimate Capacity ◽  
Weak Soil ◽  
Soil Layers ◽  
Dense Sand ◽  
Pass Through

A pile foundation is one of the most popular forms of deep foundations. They are routinely employed to transfer axial structure loads through the soft soil to stronger bearing strata. Piles generally used to increase the load carrying capacity of the foundation and reduce the settlement of the foundation. On the other hand, many cases in practice where piles pass through different layers of soil that contain weak layers located at different depths and extension, also some time cavities with a different shape, size, and depth are found. In this study, a total of 96 cases is considered and simulated in PLAXIS 2D program aiming to understand the influence of weak soil on the ultimate pile capacity. The piles embedded in the dense sand with a layer of weak soil at different extension and location. The cross section of the geometry used in this study was designed as an axisymmetric model with the 15-node element; the boundary condition recommended at least 5D in the horizontal direction, and (L+5D) in the vertical direction where D and L are the diameter and length of pile, respectively. The soil is modeled as Mohr-Coulomb, with five input parameters and the behavior of pile material represented by the linear elastic model. The results of the above cases are compared with the results found in a pile embedded in dense soil without weak layers or cavities. The results indicated that the existence of weak soil layer within the surrounding soil around the pile decreases the ultimate capacity. Furthermore, it has been found that increase in the weak soil width (extension) leads to reduction in the ultimate capacity of the pile. This phenomenon is applicable to all depth of weak soil. The influence of weak layer extension on the ultimate capacity is less when it is presentin the upper soil layers.

The Parameters Research on Considering the Influence of Dynamic Torsion Impedance of the Radial Inhomogeneous Viscoelastic Soil

2011 ◽  
Vol 105-107 ◽  
pp. 1400-1405
Author(s):  
Ji Min Wu ◽  
Shu Zhen Feng ◽  
Hai Cui
Keyword(s):  
Contact Surface ◽  
Axial Symmetry ◽  
Soil Layer ◽  
Viscoelastic Model ◽  
Basic Solution ◽  
Linear Variation ◽  
Recursion Method ◽  
Soil Layers ◽  
Dynamic Damping ◽  
Dynamic Torsion

Based on the recursion method of shearing ragidity of soil layer, dynamic torsional impedance of the radial inhomogeneous viscoelastic soil is studied.Under the certain fundamental assumption,combined with displacement basic solution of the plane axial symmetry strain question,the displacement the continuous and boundary of the soil layers, the formula of dynamic torsional impedance of the pile-soil contact surface is deduced.Degenerated into homogeneous viscoelastic model,the model is further confirmed accurate.Finally, the conclusion is obtained:(1) The bigger is G2/G1,the larger the soil body actual stiffness is. The dynamic damping presents the trend of increase;(2)In the area of the radial disturbance soil,as ‘d’increases, the soil body actual stiffness is increasing. When G2/G1 is smaller than 1,the dynamic damping is reducing along with increases of ‘d’,when G2/G1 is bigger than 1,the dynamic damping is increasing along with increases of ‘d’.(3)Actual stiffness and dynamic damping assumes the linear variation along with increasing of material damping.

IDENTIFICATION OF VISCOELASTIC MODEL OF FOUR-WIRE SUSPENSION SYSTEM IN OPTICAL PICKUP ACTUATOR

2017 ◽  
Vol 41 (5) ◽  
pp. 731-744
Author(s):  
Ren J. Chang ◽  
Zheng Y. Liu
Keyword(s):  
Transfer Function ◽  
Fractional Derivative ◽  
Dynamic Model ◽  
Classical Model ◽  
Viscoelastic Model ◽  
Optical Pickup ◽  
Static Tests ◽  
Wire Suspension ◽  
Suspension Structure ◽  
Sinusoidal Excitation

A novel viscoelastic model of four-wire suspension structure with damping gel in an optical pickup actuator was identified and validated. A two-stage method was developed for the identification of inertia, damping, and spring parameters in the dynamic model. The inertia and spring parameters were identified from static tests. With the identified parameters in the dynamic model, the damping parameters were identified through sinusoidal excitation tests. The accuracy of utilizing fractional derivative to model the damping of polymer damper was validated by carrying out error analysis. The fractional transfer function with voltage input was identified and compared with the transfer function of classical model.

scholarly journals Viscosity and elasticity: a model intercomparison of ice-shelf bending in an Antarctic grounding zone

2017 ◽  
Vol 63 (240) ◽  
pp. 573-580 ◽  
Author(s):  
CHRISTIAN T. WILD ◽  
OLIVER J. MARSH ◽  
WOLFGANG RACK
Keyword(s):  
Young’S Modulus ◽  
Ocean Circulation ◽  
Young's Modulus ◽  
Viscoelastic Model ◽  
Ice Sheet ◽  
Global Ocean ◽  
Elastic Model ◽  
Ice Shelf ◽  
Bending Stresses ◽  
Global Ocean Circulation

ABSTRACTGrounding zones are vital to ice-sheet mass balance and its coupling to the global ocean circulation. Processes here determine the mass discharge from the grounded ice sheet, to the floating ice shelves. The response of this transition zone to tidal forcing has been described by both elastic and viscoelastic models. Here we examine the validity of these models for grounding zone flexure over tidal timescales using field data from the Southern McMurdo Ice Shelf (78° 15′S, 167° 7′E). Observations of tidal movement were carried out by simultaneous tiltmeter and GPS measurements along a profile across the grounding zone. Finite-element simulations covering a 64 d period reveal that the viscoelastic model fits best the observations using a Young's modulus of 1.6 GPa and a viscosity of 1013.7 Pa s (≈ 50.1 TPa s). We conclude that the elastic model is only well-constrained for tidal displacements >35% of the spring-tidal amplitude using a Young's modulus of 1.62 ± 0.69 GPa, but that a viscoelastic model is necessary to adequately capture tidal bending at amplitudes below this threshold. In grounding zones where bending stresses are greater than at the Southern McMurdo Ice Shelf or ice viscosity is lower, the threshold would be even higher.

A Method of Calculating the Dynamic Characteristics of Rubber Isolator

2013 ◽  
Vol 395-396 ◽  
pp. 1170-1173 ◽  
Author(s):  
Xiao Yan Guo ◽  
Jin Zhi Zhou ◽  
Da Peng Feng ◽  
Hou Min Li
Keyword(s):  
Dynamic Characteristics ◽  
Dynamic Property ◽  
Excitation Frequency ◽  
Viscoelastic Model ◽  
Elastic Model ◽  
Frequency Dependency ◽  
Plastic Model ◽  
Filled Rubber ◽  
Relative Errors ◽  
Rubber Isolator

The dynamic property of carbon filled rubber materials is related to pre-load, excitation frequency and amplitude etc. A model by superimposing an elastic model, a viscoelastic model and an elastic-plastic model is presented to model the dynamic property of a rubber isolator. In this paper, this approach is adopted to calculate the dynamic property of a rubber isolator. It is shown that the presented model can predict the amplitude and frequency dependency of a rubber isolator with small relative errors. The validity of this model is verified by experiment. The approach described in this paper can be used in the design and calculation for rubber isolators.

scholarly journals Depth-Dependent C-N-P Stocks and Stoichiometry in Ultisols Resulting from Conversion of Secondary Forests to Plantations and Driving Forces

Forests ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1300
Author(s):  
Xiaogang Ding ◽  
Xiaochuan Li ◽  
Ye Qi ◽  
Zhengyong Zhao ◽  
Dongxiao Sun ◽  
...  
Keyword(s):  
Soil Depth ◽  
Soil Layer ◽  
Pinus Elliottii ◽  
Slash Pine ◽  
Pine Plantations ◽  
Secondary Forests ◽  
Masson Pine ◽  
Soil Layers ◽  
Soil C ◽  
Significant Difference

Stocks and stoichiometry of carbon (C), nitrogen (N), and phosphorus (P) in ultisols are not well documented for converted forests. In this study, Ultisols were sampled in 175 plots from one type of secondary forest and four plantations of Masson pine (Pinus massoniana Lamb.), Slash pine (Pinus elliottii Engelm.), Eucalypt (Eucalyptus obliqua L’Hér.), and Litchi (Litchi chinensis Sonn., 1782) in Yunfu, Guangdong province, South China. Five layers of soil were sampled with a distance of 20 cm between two adjacent layers up to a depth of 100 cm. We did not find interactive effects between forest type and soil layer depth on soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) concentrations and storages. Storage of SOC was not different between secondary forests and Eucalypt plantations, but SOC of these two forest types were lower than that in Litchi, Masson pine, and Slash pine plantations. Soil C:P was higher in Slash pine plantations than in secondary forests. Soil CNP showed a decreasing trend with the increase of soil depth. Soil TP did not show any significant difference among soil layers. Soil bulk density had a negative contribution to soil C and P stocks, and longitude and elevation were positive drivers for soil C, N, and P stocks. Overall, Litchi plantations are the only type of plantation that obtained enhanced C storage in 0–100 cm soils and diverse N concentrations among soil layers during the conversion from secondary forests to plantations over ultisols.

scholarly journals Grazing and Cultivated Grasslands Cause Different Spatial Redistributions of Soil Particles

2019 ◽  
Vol 16 (15) ◽  
pp. 2639 ◽  
Author(s):  
Jinsheng Li ◽  
Jianying Shang ◽  
Ding Huang ◽  
Shiming Tang ◽  
Tianci Zhao ◽  
...  
Keyword(s):  
Soil Layer ◽  
Soil Health ◽  
Grazing Intensity ◽  
Health Condition ◽  
Soil Particle ◽  
Particle Sizes ◽  
Soil Layers ◽  
Soil Particles ◽  
Heavy Grazing ◽  
Grazing Intensities

The distribution of soil particle sizes is closely related to soil health condition. In this study, grasslands under different grazing intensities and different cultivation ages grasslands were selected to evaluate the dynamics of soil particle size redistribution in different soil layers. When the grazing intensity increased, the percentage of 2000~150-μm soil particles in the 0–10-cm soil layer decreased; 150~53-μm soil particles remained relatively stable among the grazing intensities—approximately 28.52%~35.39%. However, the percentage of less than 53-μm soil particles increased. In cultivated grasslands, the larger sizes (>53 μm) of soil particles increased and the smaller sizes (<53 μm) decreased significantly (p < 0.05) in the 0–10 cm-soil layer with increasing cultivation ages. The increase in small soil particles (<53 μm) in topsoil associated with grazing intensity increased the potential risk of further degradation by wind erosion. The increase in big soil particles (>53 μm) in topsoil associated with cultivation ages decreased the soil capacity of holding water and nutrient. Therefore, to maintain the sustainability of grassland uses, grazing grasslands need to avoid heavy grazing, and cultivated grasslands need to change current cultivation practices.

scholarly journals Plasmon-Enhanced Photothermal and Optomechanical Deformations of a Gold Nanoparticle

Nanomaterials ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1881
Author(s):  
Jiunn-Woei Liaw ◽  
Guanting Liu ◽  
Yun-Cheng Ku ◽  
Mao-Kuen Kuo
Keyword(s):  
Gold Nanoparticle ◽  
Liquid Layer ◽  
Viscoelastic Model ◽  
Dynamics Simulation ◽  
Photothermal Effect ◽  
Continuous Heating ◽  
Heating Process ◽  
Elastic Model ◽  
Linearly Polarized ◽  
Quasi Liquid Layer

Plasmon-enhanced photothermal and optomechanical effects on deforming and reshaping a gold nanoparticle (NP) are studied theoretically. A previous paper (Wang and Ding, ACS Nano 13, 32–37, 2019) has shown that a spherical gold nanoparticle (NP) irradiated by a tightly focused laser beam can be deformed into an elongated nanorod (NR) and even chopped in half (a dimer). The mechanism is supposed to be caused by photothermal heating for softening NP associated with optical traction for follow-up deformation. In this paper, our study focuses on deformation induced by Maxwell’s stress provided by a linearly polarized Gaussian beam upon the surface of a thermal-softened NP/NR. We use an elastic model to numerically calculate deformation according to optical traction and a viscoelastic model to theoretically estimate the following creep (elongation) as temperature nears the melting point. Our results indicate that a stretching traction at the two ends of the NP/NR causes elongation and a pinching traction at the middle causes a dent. Hence, a bigger NP can be elongated and then cut into two pieces (a dimer) at the dent due to the optomechanical effect. As the continuous heating process induces premelting of NPs, a quasi-liquid layer is formed first and then an outer liquid layer is induced due to reduction of surface energy, which was predicted by previous works of molecular dynamics simulation. Subsequently, we use the Young–Laplace model to investigate the surface tension effect on the following deformation. This study may provide an insight into utilizing the photothermal effect associated with optomechanical manipulation to tailor gold nanostructures.

scholarly journals Rooting patterns of Rumex species under drained conditions

1987 ◽  
Vol 65 (8) ◽  
pp. 1638-1642 ◽  
Author(s):  
L. A. C. J. Voesenek ◽  
C. W. P. M. Blom
Keyword(s):  
Growth Rate ◽  
Root Distribution ◽  
Soil Layer ◽  
The Other ◽  
Rumex Acetosa ◽  
Soil System ◽  
Relative Growth ◽  
Soil Layers ◽  
Vertical Root Distribution ◽  
Rooting Patterns

Root development and architecture were studied in three Rumex species growing in a perforated soil system in the greenhouse. Distinct differences in vertical root distribution under drained conditions were found among the three species. Rumex acetosa and R. palustris had a relatively superficial root pattern, whereas in R. crispus much of the root growth was concentrated in lower soil layers. In the upper soil layer the relative growth rate of the roots of R. palustris was significantly larger than that of the other species. A relation between the characteristic rooting patterns under drained conditions and the Rumex zonation in the field is discussed.

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