Pile In Saturated Soil Research Articles

Horizontal dynamic response of an offshore pile in saturated soil considering radial inhomogeneity

Horizontal dynamic response of an offshore pile in saturated soil considering radial inhomogeneity

Seismic response of end-bearing piles in saturated soil to P-waves

Seismic response of end-bearing piles in saturated soil to P-waves

Kinematic response of end-bearing piles in saturated soil to seismic SH-waves

This paper presents a mathematical model for the seismic analysis of end-bearing piles founded in a homogeneous saturated soil of finite thickness. Seismic loading is modelled as harmonic horizontal strong motion of the rigid bedrock, that generates vertically-propagating shear SH-waves. The transfer function of the soil layer is first established, considering soil as uniform isotropic poroelastic medium that obeys Biot’s governing equations. Accordingly, free-field and scattered soil displacements are co-evaluated, to establish a series-form expression that provides the dynamic lateral force acting on an Euler-Bernoulli elastic beam representing the pile. We employ the model to show that energy dissipation due to relative movement between the pore fluid and the solid matrix may have a noteworthy effect on the amplitude of high-frequency components of the strong motion in high permeability soils, and this in turn affects the kinematic response of piles. Finally, we use arithmetic examples to identify the soil permeability threshold, beyond which simpler single-phase soil models will produce reliable results for piles embedded in saturated two-phase soil.

Torsional vibration of open-ended pipe piles in saturated soil considering the construction disturbance

A soil-pipe pile-inner soil torsional dynamic interaction model is developed accounting for the radial inhomogeneity of the outer saturated soil as well as the soil plug (inner soil) due to the construction disturbance. Both the outer and inner saturated soils are divided into a series of annular zones in the radial direction with linearly varying soil properties from zone to zone. The governing equation of motion for each soil zone is established based on the Biot's two-phase linear theory and is solved to derive the circumferential shear stress at the pipe pile-soil interface in conjunction with the continuous conditions at the interface of adjacent soil zones. Further, the governing equation for the open-ended pipe pile is established and is solved to derive an analytical solution for the torsional vibration of the pile in the frequency domain. The developed solution is validated against the results of available analytical solutions. The validated solution is then used to examine the torsional vibration characteristics of the open-ended pipe pile under different saturated soil parameters and construction disturbance conditions. The results show that: (1) The pile resistance to torsional dynamic load is enhanced as the soil strengthening range or degree increases, while is reduced as the soil porosity, soil weakening range or degree increases; (2) The inner soil contributes a lot to the enhancement of pile torsional resistance.

Vertical dynamic impedance of a sand-filled nodular pile in saturated soil

A new type of composite pile called a sand-filled nodular (SFN) pile has been increasingly used as a foundation element in the southeast coastal region of China. This paper derives an analytical solution of the vertical dynamic impedance of a SFN pile in saturated soil. The accuracy of the derived solution was verified by degenerating the SFN pile into a general pipe pile. The feasibility of incorporating the thin-layer assumption in Biot theory was then examined and the results suggested that for soft soils with shear modulus less than 5 MPa, the thin-layer solution is sufficiently accurate to estimate the vertical dynamic impedance of a pile in saturated soil. A parametric study was further conducted to provide insight into the influences of pile geometries and sand fill properties on the vertical dynamic impedance of the pile. The results indicated that the pile geometries have considerable influence on the vertical dynamic impedance of SFN piles where pile rib length plays a most significant role.

Analytical solution for longitudinal vibration of a floating pile in saturated porous media based on a fictitious saturated soil pile model

Based on Biot’s theory of wave propagation in saturated porous media, a new analytical approach for the vertical vibration of a floating pile in saturated viscoelastic soil is proposed, by combining the differential operator method with a fictitious saturated soil pile (FSSP) model. As an extended fictitious soil pile model, the FSSP model can fully consider the wave propagation in saturated soil with limit thickness beneath pile toe. The analytical solution for the velocity admittance of pile head is derived by introducing the completely coupled conditions at the pile-soil interface. The accuracy of the proposed approach and relevant solutions are degenerated and subsequently verified via comparisons with previous solutions. In addition, comparative analyses are further carried out to examine the effects of the porosity and shear modulus of soil as well as the layer thickness of the saturated soil layer beneath pile toe on the dynamic behavior of the floating pile. It is indicated that the presented approach and relevant solutions provide a more wide-ranging application for vertical vibration problems of a floating pile in saturated soil, which can be degenerated for the vertical vibration problems of a floating pile in single-phase soil or an end-bearing pile in saturated soil.

Model Studies on Load Sharing for Shaft and Tip of Pile Groups in Saturated and Unsaturated Soils

The behavior of pile foundation is dictated by its structural properties and stiffness and strength of the soil supporting the pile. This complexity is further increased when the soil is in partially saturated condition. In this work, an attempt has been done to investigate the influence of matric suction on the behavior of single pile and pile group, and the amount of increase in the bearing capacity due to the influence of this suction. The load transfer for shaft and tip of pile groups embedded in soil with different properties (saturated and unsaturated) is investigated. First, the stresses below the center of piles are measured by a soil pressure transducer located at a depth of 0.25 L, (L = length of pile). These stresses are transferred directly to pile tip according to approximate 2 V:1 H method and then converted to load at the tip and shaft of pile. The general trend is that in a single pile, at the start of load applying, the percentage of distributed load is 70% for shaft and 30% for tip, then as the applied load increases, the pile settles and a differential movement between the soil and pile occurs, creating more adhesion between the soil resulting in increase in shaft capacity. For pile groups, the same trend is obtained, but the percentage of load transferred to the shaft increases as the number of piles increases, in contrast to the load transferred to the tip. The results showed that the sharing of load between shaft and end resistance for single pile in saturated soil is halved when the pile reaches its ultimate resistance, while this response is different for unsaturated soil where the load is transferred as a whole to the pile tip at approximately the intermediate stages of loading according to the analysis criteria adopted.

Vertical dynamic response of an end-bearing pile considering the nonlocal effect of saturated soil

Although the classical Biot theory has been widely used in geotechnics, the simplifying assumption that the wavelength is much larger than the pore size may not conform to practical circumstances. Therefore, the nonlocal Biot theory, in which the effects of pore size and porosity dynamics are lumped into a nonlocal parameter, was proposed by others. In this paper, the nonlocal Biot theory is extended to investigate the vertical dynamic response of an end-bearing pile in saturated soil. The analytical solution for the vertical vibration of the pile in the frequency domain is obtained using Helmholtz decomposition and Laplace transform. The corresponding semi-analytical solution in the time domain for the pile under a semi-sinusoidal excitation is derived by inverse Fourier transform. The convergence and accuracy of the present solution is examined by degrading the nonlocal Biot theory into the classical Biot theory. The validation of the present solution is verified by comparing the results of the local theory with the nonlocal theory with a small nonlocal parameter. A parametric study is implemented to investigate the influence of the nonlocal parameter on the vertical dynamic response of a pile and the interplay between the soil properties and nonlocal effects.

Lateral Vibration of Offshore Piles Considering Pile-Water Interaction

The dynamic response of an offshore pile in saturated soil subjected to lateral harmonic loading is theoretically investigated by considering the dynamic pile-water interaction. The governing equation of water is solved based on the separation of variable method, and the analytical expression of the hydrodynamic force applied on the pile is then obtained. Based on the continuous conditions at the pile-soil interface and pile-water interface, the analytical solution of the dynamic impedance of the offshore pile is derived by using transfer matrix method. To verify this solution, the dynamic impedance obtained for a cylinder in water is compared with that of a partially embedded pile. Based on this solution, the effect of hydrodynamic pressure and other parameters on the dynamic response of offshore piles is investigated. The results show that the analytical model ignoring the hydrodynamic force applied on the pile misestimates the impedance of the pile in the high frequency range.

An improved model for the horizontal dynamic response of piles in saturated soil

An improved model is developed to analyze the horizontal dynamic response of piles in saturated soil. The proposed model retains the simplicity of the plane strain model while accounting for 3-D effects. The vertical coordinate is suppressed by integrating the governing equations over the length of the pile. The three-dimensional model is reduced to a simpler model that is similar to the plane strain model. Explicit closed-form solutions are obtained by introducing potential functions. The proposed model is verified by comparison with more rigorous solutions. Finally, the influence of pile slenderness, permeability of soil, and other parameters on dynamic soil reaction and dynamic response of pile is investigated. It is revealed that the proposed model avoids the drawbacks of the earlier model and is effective in predicting the horizontal dynamic response of the pile.

Dynamic characteristics of a large‐diameter pile in saturated soil and its application

SummaryThis study theoretically investigates the dynamic response of an end‐bearing pile embedded in saturated soil considering the transverse inertial effect of the pile. The saturated soil surrounding the pile is described by Biot poroelastic theory, and the pile is represented by a Rayleigh‐Love rod because both the vertical and radial displacements at the soil‐pile interface are considered. The potential function decomposition method and variable separation method are introduced to solve the governing equations of the soil, in which the vertical and radial displacement components are coupled. The governing equation of the pile is solved using the continuity conditions at the pile‐soil interface. Next, the velocity admittance in the frequency domain and the velocity response in the time domain at the pile top are presented based on the Laplace transform and inverse Fourier transform, respectively. Subsequently, the reduced solution is compared with a 1‐dimensional model solution to verify the validity, and the influences of the slenderness ratio of the pile on the transverse inertial effect of the pile are analyzed. Moreover, Poisson ratio, the slenderness ratio of the pile, and the pile‐soil modulus ratio are studied. Finally, the theoretical and measured curves in the engineering project are compared, and the results demonstrate the good application prospects of the solution presented in this article.

Experimental Study on the Dynamic Response of PHC Pipe-Piles in Liquefiable Soil

Abstract Shaking-table testing of seismic performance and dynamic interaction of prestressed high-strength concrete (PHC) pipe-piles in saturated soils and unsaturated soils was conducted using a series of sine waves, typical earthquake waves, as well as artificial ground motions based on in situ measurements. The presented test results, involving the time history of water pore pressure ratio and the responding displacement related to soil liquefaction, indicated that the natural frequency of soil-pile system decreased because of gradual degradation of soil and pile shift. Moreover, the peak displacement responses of piles in saturated soil were larger than the peak displacements in unsaturated soil. In addition, prestressing in pile was beneficial to the resistance of pile damage or degradation. These experimental results were able to calibrate FE models and to provide a database for seismic design of PHC pipe-piles.

Computer simulation of underground blast response of pile in saturated soil

This paper treats the blast response of a pile foundation in saturated sand using explicit nonlinear finite element analysis, considering complex material behavior of soil and soil–pile interaction. Blast wave propagation in the soil is studied and the horizontal deformation of pile and effective stresses in the pile are presented. Results indicate that the upper part of the pile to be vulnerable and the pile response decays with distance from the explosive. The findings of this research provide valuable information on the effects of underground explosions on pile foundation and will guide future development, validation and application of computer models.