Dynamic Response Of Single Pile Research Articles

Scour effects on the vertical dynamic response of single piles in transversely isotropic soils

Pile foundations in ocean engineering are often simultaneously subjected to dynamic loads and scour activity. A coupled finite element method (FEM) - analytical layer element method (ALEM) is provided in this paper for investigating the vertical dynamic impedances of piles in layered soils under scour conditions. The pile modeled as a one-dimensional vibration bar is solved using the FEM. The dynamic responses for a layered soil are derived from the ALEM. Based on the force equilibrium and the displacement compatibility at the pile-soil interface, the pile-soil interaction equations under scour conditions are established and solved. Finally, several numerical examples are performed to verify the correctness of the proposed method, and to explore the effects of scour type, scour depth and slenderness ratio on the vertical impedances of single piles, which show that these factors significantly affect the vertical pile-head impedances, and the optimal pile slenderness ratio is mainly associated with the excitation frequency.

Dynamic Responses of the Pile-Saturated-Soil System to a Moving Load

According to the basic solution of viscoelastic and saturated soil subjected to moving load on the surface and circular uniform harmonic load on the inside, the integral equation of soil-pile interaction under moving load in frequency domain is established by using Muki virtual pile method, and then the time-space dynamic response characteristics of a single pile in viscoelastic saturated soil to moving load vibration source are analyzed by using inverse Fourier transform. The factors that affect the dynamic response of single pile, such as load speed, length of single pile, saturated soil parameters, vibration source properties, etc., are analyzed and compared with the known results in related literature.

Dynamic Lateral Response of the Partially-Embedded Single Piles in Layered Soil

Scouring can reduce the strength and rigidity of the pile–soil system and become one of the major causes for the failure of the structure of the partially-embedded single pile. The stratification of the soil fields has a significant influence on the internal force and deformation of laterally-loaded piles. A dynamic model of the laterally-loaded single pile in layered soil is established employing Hamilton’s principle based on the modified Vlasov foundation model. Then, the finite difference method is used to obtain the numerical matrix containing the control equations of the single pile to achieve accurate modeling of the soil–structure interaction (SSI) system affected by scouring, so as to solve the natural frequencies of the single pile. Green’s function method obtains the analytical solution of the forced vibration of the single pile. The effects of scouring and the layered soil on the dynamic response of the single pile are studied by numerical calculation and parameter analysis. It is shown that the dynamic model of the partially-embedded single pile in layered soil based on the modified Vlasov foundation model can accurately predict the dynamic characteristics of pile foundation affected by scouring. As the scouring degree intensifies, the first-order natural frequencies of the single pile in layered soil decrease significantly. The subgrade reaction coefficient of each layer of soil in the modified Vlasov foundation model decreases, and the shear coefficient increases. The first-order natural frequencies of the single pile at each scour level increase with the increase in the thickness of the underlying soil. When the elastic modulus of the first layer of soil is increased by one time, the first-order natural frequencies of the single pile are increased by about 20%.

Dynamic Response of Single Pile Subjected to Different Frequencies in Gypseous Soil

This paper exhibits an experimental study on dynamic response of a single pile under dynamic load which comes from motor placed on cap pile called a vibration source. This study used the effect of the dynamic movement of vibration on one pile, collapsible soil (gypseous soil) used in this study with 30% gypsum content. The experiment is performed in a dry and soak state. A solid steel pile with a slenderness ratio of 27 was inserted into the soil after preparing it in layers in a steel container (30 * 30 * 60) cm. The test was performed under a dynamic response to the different frequencies 10, 15, 20, and 25 Hz. The results showed that the speed, acceleration and displacement increase with increasing frequency of the vibration source in addition to that the values of speed, acceleration and displacement amplitude are less in the case of soaking compared to their values in the dry state.

Vertical Vibration of Full-Scale Pile—Analytical and Experimental Study

This paper presents the results of vertical vibration tests on two full-scale single piles. The diameter of pile and embedded depth were 0.45 and 22 m, respectively. The soil samples were collected from three boreholes located at the site of investigation and it was explored to a depth up to 30.45 m below the ground level. The vertical vibration tests were conducted for different eccentricities to determine the frequency-amplitude response of the pile. Static load tests were also carried out on two single piles. A simple axisymmetric two-dimensional finite-element model was developed to predict the dynamic pile response. Novak’s plane strain model was also used for the prediction of the dynamic response of single pile. It was observed that the finite-element model predicted the natural frequency and peak displacement amplitude of pile reasonably well. However, prediction of dynamic response of the pile was found unsatisfactory by Novak’s plane strain model. Possible reasons for unsatisfactory performance of Novak’s model were investigated and presented.

Torsional vibrations of single piles embedded in saturated medium

From the axisymmetrical point of view, the dynamic response of single piles vertically embedded in the saturated half space and subjected to harmonic torsional loadings is investigated by means of integral transform and Muki’s methods for the first time. By treating the pile as a one-dimensional bar and the half space as a three-dimensional poroelastic continuum, the dynamic interaction between the pile and poroelastic medium is formulated in a Fredholm integral equation of the second kind. Numerical results are presented to illustrate the influence of pile flexibility, geometrical properties of pile–saturated soil system and frequency of excitation on the pile’s torque, torsional angle and coupled impedances. The conclusions obtained can serve as guidelines for the design and dynamic pile testing of practical engineering.

SOME EXPERIENCES ON PROGRAMMING OF TIME DOMAIN BOUNDARY ELEMENT IN PARALLEL PROCESSING ENVIRONMENT

Numerical simulations of the transient dynamic response of single piles in homogenous soil under vertical loads are carried out by using the time domain boundary element method. The availability of parallel processing machine allows the programme for such analysis to be parallelized. The real time taken for computing can thus be very much reduced. This paper presents the experience gained in parallelizing the programme for the IBM 9076 Scalable Powerparallel (SP2) System. Two coarse gain and one fine grain parallelisms based on various strategies are discussed. Parallel performance results obtained in terms of speed-up and efficiency are presented to demonstrate the high level of parallelism inherent in the time domain BEM.

Dynamic response of single piles and soil-pile interaction : Huaren Dou & P. M. Byrne, Canadian Geotechnical Journal, 33(1), 1996, pp 80–96

Dynamic response of single piles and soil-pile interaction : Huaren Dou & P. M. Byrne, Canadian Geotechnical Journal, 33(1), 1996, pp 80–96

Dynamic response of single piles and soil–pile interaction

Pile reponse to earthquake loading and soil–pile interaction behaviour were investigated experimentally using the hydraulic gradient similitude technique. The unique feature of this method is the application of a very high hydraulic gradient to increase the effective stresses in the model, simulating full-scale stress conditions in the field. The dynamic loading was applied to model piles using a conventional shake table. Tests on model piles embedded in dense sands are described herein. Both free vibration and forced vibration simulating earthquake loading were carried out. Pile bending moment, deflection, and acceleration were measured during testing. Dynamic p–y curves were derived from the measurements and were found to be highly nonlinear and hysteretic at shallow depths under strong shaking. The p–y curves for low-level shaking showed essentially linear elastic behaviour. The experimental p–y curves were compared with the backbone p–y curves for sand recommended by the American Petroleum Institute, and the agreement was reasonable except at shallow depths. Key words: pile, hydraulic gradient, modelling, vibration, shaking, p–y curve.

Analysis of the transient response of vertically loaded single piles by time-domain BEM

A quasi-linear time marching time domain boundary element method is developed for the analysis of the transient dynamic response of single piles in a layered soil under a time-dependent vertical force. The pile and the layered soil are modelled by finite elements (beam elements) and cylindrical coordinate time-domain boundary elements, respectively. The field quantities of the soil such as the displacements and tractions are assumed to vary linearly along the depth. In the time domain, the field quantities for both the soil and pile are interpolated by quadratic functions in terms of corresponding values at time ( n − 1)Δ t, ( n − 1 2 )Δ t and nΔ t. Expressing the field quantities at ( n − 1 2 )Δ t as the average of the values at ( n − 1)Δ t and nΔ t, a quasi-linear scheme has been developed for the time-marching process. Numerical examples of response of pile due to different types of dynamic loadings are reported to demonstrate the accuracy and stability of the proposed method.

Dynamic response of single piles embedded in transversely isotropic layered media: Weiming Liu & M. Novak, Earthquake Engineering & Structural Dynamics, 23(11), 1994, pp 1239–1257

Dynamic response of single piles embedded in transversely isotropic layered media: Weiming Liu & M. Novak, Earthquake Engineering & Structural Dynamics, 23(11), 1994, pp 1239–1257

Dynamic response of single piles embedded in transversely isotropic layered media

AbstractDynamic response of single piles embedded in transversely isotropic layered media is investigated using the finite element method combined with dynamic stiffness matrices of the soil derived from Green's functions for ring loads. The influence of soil anisotropy on the dynamic behaviour of piles is examined through a series of parametric studies.

Torsional Dynamic Analysis Of Single Piles By Time-Domain BEM

The transient dynamic response of single piles in a layered half-space under a time-dependent torque is analyzed by a coupled FEM-BEM approach in which the pile is modelled by FEM and the half-space by a general cylindrical co-ordinates time-domain BEM. By virtue of the Fourier theory, only one-dimensional discretization is necessary for the boundaries of the three-dimensional layered half-space, while the pile shaft can be discretized as a one-dimensional elastic column member. The compatibility and equilibrium conditions between pile shaft and soil layers are employed to assemble the respective equations into one set. A comparison is carried out to demonstrate the accuracy of the approach. The influence of several parameters on the transient behavior of single piles is investigated through numerical examples. Of all the parameters, the shear modulus ratio Gp /Gs is found to be the most important governing factor. The other effective factors are the pile slenderness ratio l/r0 , the soil layering and so on.

Vertical response of single piles: transient analysis by time-domain BEM

The transient dynamic response of single piles in a layered half-space under a time-dependent vertical force is analyzed by an FEM-BEM coupling approach. The pile is modeled by FEM and the layered half-space is modeled by a general cylindrical coordinates time-domain BEM. Only one-dimensional discretization is necessary on the boundaries of the three-dimensional layered half-space by virtue of the Fourier theory, while the pile shaft can be discretized as a one-dimensional elastic beam. The compatibility and equilibrium conditions between pile shaft and soil layers are employed to assemble respective equations into one. Fairly good agreement between two unknown solutions and the current approach is found. Parametric studies reveal the influences of several dimensionless factors, such as E p/ E s, l/ r 0, ϱ p/ ϱ s and ν s. The effect of soil layering and the support condition of the pile tip is also reported by numerical examples.

Dynamic response of pile groups with different configurations

A general methodology is outlined for a complete seismic soil—pile-foundation—structure interaction analysis. A Beam-on-Dynamic-Winkler-Foundation (BDWF) simplified model and a Green's-function-based rigorous method are utilized in determining the dynamic response of single piles and pile groups. The simplified model is validated through comparisons with the rigorous method. A comprehensive parameter study is then performed on the effect of pile group configuration on the dynamic impedances of pile foundations. Insight is gained into the nature of dynamic pile—soil—pile interaction. The results presented herein may be used in practice as a guide in obtaining the dynamic stiffness and damping of foundations with a large number of piles.

Time Domain Axial Response of Dynamically Loaded Single Piles

Adopting a Winkler assumption, a simple mechanical soil model is developed for the flexural response analysis of dynamically loaded piles. The model is defined by examining a frequency-domain analytical expression of the dynamic response of a massless cylinder in an infinite previously developed medium. The expression is based on the plane strain assumption. Using this soil model, the time-domain transfer matrix is developed for the flexural response of a single pile. The steady-state harmonic response of a single pile is computed by both the present approach and a previously developed frequency-domain solution. Good agreement between the two computed results validates the present approach. The dynamic response of single piles subjected to the lateral impulse load is computed for piles in both homogeneous and inhomogeneous soil, in order to demonstrate the capability of the present approach. It is confirmed that the developed soil model and pile response formulation are very efficient in numerical computation.