Search

Soil liquefaction is considered as one of the most significant issues that leads to failure of shallow and deep foundations. However, the effect of liquefaction on the seismic response of piles still poorly understood. Therefore, this research examines the seismic response of a pile embedded in soil stratum of saturated fine-grained soils. Midas GTS/NX is used to carry out the number assessment. In addition, the modified UBCSAND soil constitutive model is used to depict the nonlinear features of saturated sand during earthquake waves. The developed three-dimensional model is first validated using the results of a shaking table test of a pile embedded in coarse-grained soil, where good agreement is obtained between the finite element model and the experimental results for the displacement, acceleration, and liquefaction ratio demonstrated good agreement. Furthermore, the orientations of the vectors produced by the numerical study, that matched a global circular flow characteristic, reflected the movement of the liquefied soil all around pile. The findings showed a considerable decrease in the pile frictional resistance during the seismic events as a consequence of increasing the pore water pressure and subsequent liquefaction. Regarding this, before the soil was entirely softened, resistance due to friction was observed near the ground, in correspondence with the loose sand layer. In addition, the pile showed excessive settling, which is due to the decrease of the soil stiffness caused by the increase of the pore water pressure. The results of this research provide an insight into the mechanism of the behavior of pile in saturated coarse-grained soils and thus, it helps to improve future research on the topic and also achieve better design of piles embedded in saturated coarse-grained soils. [ABSTRACT FROM AUTHOR]

In the present paper, an experimental study was conducted to determine the factors affecting the point bearing capacity of pile foundations constructed in dry and saturated sandy soils. Model piles were installed as reinforced concrete bored piles cast-in-situ. Model pile foundations of various geometries resting at different depths in homogeneous sand of different saturation degrees (%0-100) were loaded statically to failure. The test results showed that the bearing capacity of piles did not significantly affect by the loading rate. At most 10% difference was observed in pile bearing capacity when the loading rate was between 0.7 and 2.5 mm/min. Subsequently, the load bearing capacities of the piles were determined at a specified constant loading rate. The point and total capacities of the piles were measured separately in the experiments, then test results were compared with theoretical values. Pile point capacities provided from pile load tests are smaller than the theoretical values. The differences between experimental and theoretical results have been attributed to the Nq values. The Nq values not only dependent on the internal friction angle of the soil but also the saturation degree of the soil, the pile diameter, and the effective stress. Nq values decrease since the pile length/pile diameter ratio increases. [ABSTRACT FROM AUTHOR]

The scouring effect is widely acknowledged as a primary contributor to the weakening in the bearing performance of offshore piles; it often results in asymmetric scour patterns around the pile. To meticulously examine the impact of three-dimensional asymmetric local scour on the lateral bearing performance of a single pile, the Boussinesq solution is employed to determine the effective stress within the soil encompassing the pile, considering the presence of a three-dimensional asymmetric local scour hole. Utilizing the strain wedge model, the calculation method for the lateral bearing performance of a single pile under the condition of three-dimensional asymmetric local scour is established. The validity of this approach is established, and parameter analysis unveils the effect of varying sizes of three-dimensional asymmetric scour holes on the mechanical properties and displacement performance of a single pile. The analysis reveals that, as scouring dimensions around the pile escalate, the impact of scouring on single-pile lateral displacement and internal forces intensifies, leading to a decrease in the lateral bearing performance of a single pile. At a constant scour depth, the bottom area of the upstream scour hole significantly influences the displacement performance of a single pile. When the bottom length Swb1 of the upstream scour hole grows by 1 time, 4 times, and 8 times, the lateral displacement of a single pile at a buried depth of 6 m is augmented by approximately 0.41%, 1.65%, and 2.06%, respectively. The simplified model obtained via the modified strain wedge model and Boussinesq solution can provide a theoretical basis for the preliminary design of a single pile under asymmetric scour hole conditions. [ABSTRACT FROM AUTHOR]

Introduction. Modelling of pile foundations in modern software packages (PC) is often carried out in a linear formulation of the problem and with the use of coefficients that overestimate the results of pile foundations by several times. This approach leads to significant overconsumption of materials and overestimation of the estimated cost of the object under construction. In modern realities, designers are faced with the problem of modelling the design situation, which is closest to the real operation of the pile in the ground, and since the foundation soil is a heterogeneous medium, the calculation must be carried out non–linearly, which is quite time-consuming in software packages. A numerical comparison of full-scale tests of a single pile under static load and calculation in a software package, taking into account the nonlinearity of the foundation soils, is carried out.Materials and methods. The calculations are carried out in the finite element software package LIRA-CAD by modelling the design scheme with volumetric finite elements. The change in the settlement of piles in different soils under step load is analyzed.Results. Numerical experiment of change in the settlement of a single pile using a volumetric finite element model with a given physical nonlinearity of the soil was performed. The obtained results of the numerical experiment are compared with the results of the full-scale experiment.Conclusions. The results of the study show a large discrepancy between the settlements of piles according to field tests and the results of calculations according to SP 24.13330.2021. With the help of modern software packages, it is possible to carry out more accurate calculations. However, the introduction of correction coefficients can bring the calculated situation according to regulatory documents closer to more real conditions of deformation of the foundation soils in the process of preliminary selection.

Earthquakes are sudden and unpredictable natural activity that causes severe damage. As a result of the increasing seismic activity in Iraq, it has become necessary to conduct a study on the impact of earthquakes and methods of damping them. Since traditional seismic damping methods for construction are very expensive, alternative solutions are necessary. Therefore, this research proposes a new damping method that depends on surrounding the piles with rubber crumbs, as the rubber works to dampen the seismic force before it reaches the piles before moving to the structure. This method is considered a type of sustainability. The study included a set of variables, including (the thickness of the rubber that surrounds the piles, and the position of placing the rubber that sleeved the piles). The tests were carried out using the shaking table device. The results showed that surrounding the piles with rubber gave distinct results in damping the seismic force and it is considered an easy damping method due to its ease of implementation, as well as its economic feasibility. The results showed for the models that surround the rubber in the upper part of the pile, an increase in the values of the acceleration of the structure and a decrease in the values of the movement speed of the structure, the values of the lateral displacement of the structure. The models in which the rubber surrounds the middle and bottom part of the pile, the results were close to the reference model.

The scouring effect is widely acknowledged as a primary contributor to the weakening in the bearing performance of offshore piles; it often results in asymmetric scour patterns around the pile. To meticulously examine the impact of three-dimensional asymmetric local scour on the lateral bearing performance of a single pile, the Boussinesq solution is employed to determine the effective stress within the soil encompassing the pile, considering the presence of a three-dimensional asymmetric local scour hole. Utilizing the strain wedge model, the calculation method for the lateral bearing performance of a single pile under the condition of three-dimensional asymmetric local scour is established. The validity of this approach is established, and parameter analysis unveils the effect of varying sizes of three-dimensional asymmetric scour holes on the mechanical properties and displacement performance of a single pile. The analysis reveals that, as scouring dimensions around the pile escalate, the impact of scouring on single-pile lateral displacement and internal forces intensifies, leading to a decrease in the lateral bearing performance of a single pile. At a constant scour depth, the bottom area of the upstream scour hole significantly influences the displacement performance of a single pile. When the bottom length Swb1 of the upstream scour hole grows by 1 time, 4 times, and 8 times, the lateral displacement of a single pile at a buried depth of 6 m is augmented by approximately 0.41%, 1.65%, and 2.06%, respectively. The simplified model obtained via the modified strain wedge model and Boussinesq solution can provide a theoretical basis for the preliminary design of a single pile under asymmetric scour hole conditions.

In this study, a unified p–y curve model is developed for clays in undrained conditions using the results of 3D finite element (FE) modeling. The p–y curves are primarily used in the analysis of laterally loaded piles. Formulas for the ultimate lateral bearing capacity factor (Np), and the reference deflection in the p–y curve (y50), were obtained using the results of parametric studies and regression analysis. The tangent hyperbolic function was used to model the p–y curve shape. In the FE models, the clay soil material was modeled as elastic-perfectly plastic material using Mohr–Coulomb criteria, and the pile material was modeled as elastic only. The parametric study results show that Np varies nonlinearly with depth. The proposed model for Np is composed of two regions: a nonlinear zone and a linear zone. The model for Np used the undrained shear strength (su), effective unit weight of soil (γ′), and pile width (D) as parameters. Further, the proposed model for y50 was found to be dependent on the soil stiffness (Es), D, and Np. The dependency of y50 on Np was often overlooked in previous studies. Finally, the proposed model was imported in LPILE program and the results from previous case studies were compared with the proposed model predictions. [ABSTRACT FROM AUTHOR]

Steel pipe piles have been increasingly used as deep foundations for offshore or onshore structures in weak soil formations. These piles are usually open-ended and installed to their final level using suitable hammers or vibrators relying on the subsurface conditions. Simultaneously, the soil plug (SP) forms inside the employed pipe pile during driving or installation. Moreover, it affects bearing behavior and total pile resistance. The experimental tests have been performed on a single tube pile. All tube piles were tested using the well-graded sand collected from the Egyptian desert, and the sand was prepared at medium density using a raining technique. The outcomes of the model pile tests showed that the value of plug resistance in open-ended pipe pile (OEPP) is typically on the order of 50% to 70% of the total pile load of OEPP, and it is influenced by pile thickness, pile diameter, pile length, and submerged state. Simultaneously, the plugging influence of OEPP increased with increasing pile thickness and embedded pile length. However, the plugging influence decreased with increasing pile diameter. The total pile load of OEPP increased with increasing the embedded pile length. It must be noted that the influence of pile length on the total pile load is greater than the influence of pile diameter; this refers to the pile length having a significant effect on the total pile load. This is due to an increase in the influence of SP.

To reasonably analyze the bearing characteristics of curved beam bridge pile foundation under the combined action of vertical force (V) and torque (T) in expansive soil, a method of determining Tu (limit torque) under the action of V is proposed. Considering the effects of expansive force and ground heave after immersion, the load transfer function at the pile–soil interface with positive and negative friction resistance is established. The nonlinear solution of a single pile under vertical load is achieved by the finite difference method. Subsequently, the circumferential limit friction resistance is modified, and a loop iteration program is compiled through MATLAB. Thus, the bearing capacity of single pile under the loading path of V→T is obtained. The corresponding failure envelope curve is drawn and verified by laboratory model tests. Based on the verified solution, the bearing capacity envelope curve and deformation characteristics of single pile are analyzed. The influence of the expansion rate on the bearing capacity envelope curve is discussed, and reasonable engineering suggestions are put forward. [ABSTRACT FROM AUTHOR]

Pile foundations in liquefied ground may be subjected to a substantial force induced by lateral soil movement, which is crucial in the seismic design of pile-supported structures. Thus, this study aims to investigate the liquefaction-induced lateral force to piles by conducting centrifuge tests. Pile–deck systems installed in liquefiable finite slope with an angle of 27° were constructed and tested with different base motions. Results show that the liquefied slope pushes the piles toward the downslope, causing a large bending moment. The linear and uniform distributions of lateral soil pressure, which have been previously suggested for pile analysis in liquefied ground, were examined and compared with the measured maximum bending moment. The linear soil pressure profile reasonably predicted the bending moment compared to the results of the uniform profile. The empirical gradient factor of the linear profile was calibrated for the single piles and then implemented in the pile group analysis. The calibrated factor improved conventional methods for predicting the bending moment profile of group piles. [ABSTRACT FROM AUTHOR]

The influence of deep excavation on adjacent pile behaviour is an important issue to ensure its serviceability and stability. In this paper, the effect of deep excavation on an adjacent loaded single pile in saturated cohesionless soil was investigated by 3D finite element method. After verification of finite element model using centrifuge test results found in literature, a parametric study was conducted by varying the most influence factors on the pile behaviour such as excavation depth, distance from the pile to the excavation and pile head type. It was concluded that the excavation depth (He) with respect to pile length (Lp) has a significant effect on pile response. Among the three cases of He/Lp, the case of He/Lp=0.5 induced the maximum bending moment while the case of He/Lp= 1.5 induced the maximum pile lateral deflection. Moreover, the distance from the pile to the excavation site has also a significant influence on pile response and the induced bending moment in pile is inconsiderable after 9 m distance. Also, it is observed that the pile head type has an important effect on the pile behaviour especially in case of rigid head case.

The present study discusses the effect of hydraulic loading in terms of water infiltration caused by rainfall on load-mobilization mechanism of single-pile (SP) and monopile–raft foundation (MPRF) embedded in unsaturated sand by means of the finite element-based computer program Plaxis3D. Soil was modeled using the conventional Mohr–Coulomb model incorporating Bishop's effective stress, and the hydromechanical behavior was incorporated using the van Genuchten model. A fully coupled flow deformation analysis based on Biot's theory of consolidation was employed to model the behavior of soil during water infiltration. Water infiltration at different rates ranging from 5 to 864 mm/day was simulated using the time-dependent flow boundary condition at the ground surface. After successful validation of the developed numerical model using the experimental study available in literature, the evolution of suction, effective saturation, and suction stress during the different rates of infiltration was investigated and the responses of SP and MPRF in terms of settlement and axial forces were obtained. The results indicated the contribution of suction stress in increasing the stiffness of soil to an infiltration rate of 240 mm/day, thereby increasing the capacities of both SP and MPRF. The mobilization of shaft resistance was greatly dependent on the suction stress, and a reduction in the suction stress upon infiltration led to a lesser mobilization of shaft resistances (reduced around 6%). This caused a higher pile deformation, leading to further mobilization of pile base resistance. The rate of infiltration and the raft dimension has significant effect on mobilization of raft and pile resistance within MPRF due to raft–soil and pile–raft interactions. A higher rate of infiltration led to a greater mobilization of pile resistance due to positive pile–raft interaction brought by reduction in the contribution of raft base resistance that was associated with reduction in Bishop's stress. The outcome of the present study would help in better understanding the effect of hydraulic loading on the behavior of SP and MPRF and can be extended to pile group and combined pile–raft foundation. [ABSTRACT FROM AUTHOR]

Based on disturbed state concept (DSC) theory, this paper reports an analysis of the progressive failure mechanism of a pile–soil system from a new perspective. Assuming that the strengths of the pile–soil interface elements and the soil elements at the pile end follow an exponential distribution, the load transfer models of skin friction and end resistance based on DSC theory are established, and the significance and value method of the parameters in the models are clarified. The analysis of the relevant parameters shows that the proposed DSC load transfer models can simulate the nonlinear hardening or softening behavior of skin friction and end resistance. Based on the proposed DSC load transfer models, a simple and efficient iterative calculation method for the analysis of the bearing behavior of a single pile is established. It is demonstrated from case studies that, compared with calculated results using other methods, the load–settlement curves at the pile head obtained from the method proposed in this paper are in better agreement with the measured values, and could reflect the skin friction and end resistance softening characteristics of the tested piles in a more realistic manner. Furthermore, a parametric study is carried out to analyze the influence of the relevant model parameters on the response of a single pile. [ABSTRACT FROM AUTHOR]

In order to facily determine the ultimate lateral bearing capacity of single flexible pile, the theoretical formulas of coefficient of earth pressure and the friction coefficient of horizontal differential enements and the improved calculation method of ultimate lateral bearing capacity of single flexible pile were established on the basis of the soil arching effect of wedge failure, major principal stress arching, Mohr-Coulomb strength criterion, and horizontal differential enements, by replacing flexible long pile with rigid short pile. The results obtained by the calculation method show great aggrement with the test results, with an average error of only 2.9%. The method develoged in this work has a certain reference significance for the determination of the bearing capacity of single flexible pile.

The Dynamic Penetration Test (DPT) is one of the simplest and least expensive in-situ tests, used in geotechnical projects. However, in the literature, there is no available practical method for constructing the P–Y curves based on the DPT test (P is the soil-pile reaction and Y is the pile deflection). This paper is aimed at suggesting a new practical method of constructing the P–Y curves on the basis on the DPT data in sandy soils. This method was derived from the interpretation of five full-scale lateral loading tests on fully instrumented piles in sandy soils. Simple analytical formulation of the P–Y curves parameters, as well as design practical charts were proposed as function of the number of blows Nd of the DPT test. The results predicted by the proposed DPT based P–Y curve agreed relatively well with measured results within the margin of small to medium deflection. [ABSTRACT FROM AUTHOR]

Pile foundations are widely used in regions with expansive soils to transfer the loads from superstructures to a rigid soil stratum, thereby alleviating stability and deformation problems. However, current design procedures for pile foundations are typically based on saturated soil mechanics principles assuming drained conditions, despite the fact expansive soils surrounding the piles are typically in an unsaturated state. Volume changes of expansive soil induced by matric suction changes upon seasonal wetting and drying can significantly influence the pile load-transfer mechanisms. In this paper, using unsaturated soil mechanics as a tool, theoretical models are introduced for estimations of pile shaft friction and pile base resistance considering both the influences of matric suction changes and matric suction variation-induced volume changes of expansive soil around the pile. The commonly used shear displacement method for interpreting the pile mechanical behaviors is modified by including these models to extend their application to piles in unsaturated expansive soils. The proposed modified shear displacement method (MSDM) is interpreted and successfully validated using a pile infiltration test conducted in the laboratory along with another case study from published literature. The results of investigation studies using the proposed MSDM suggest that it can be a valuable tool for practicing engineers to make reasonable predictions of mechanical behaviors of piles in unsaturated expansive soils. [ABSTRACT FROM AUTHOR]

It is nowadays recognized the P-Y curves-based methods are the most commonly used methods for the analysis and design of pile foundations under lateral loads. Such methods have the advantage to account for the non-homogeneity of soil properties and the non-linear pile/soil interface behavior as well. The paper aims at presenting a practical method to define a hyperbolic function describing the P-Y curves along the pile whose parameters, namely the initial reaction modulus and the limit lateral soil resistance, are correlated with the SPT N-value. The study is based on an extensive interpretation of several full-scale pile loading tests; the test piles being fully instrumented by strain gauges to derive the bending moment profiles along the pile. Finally, the predictive capability of the proposed method was demonstrated by comparing the predicted load-deflection curves by the software SPULL to the experimental ones obtained from lateral loading tests on simply instrumented full-scale piles.

To reasonably analyze the bearing characteristics of curved beam bridge pile foundation under the combined action of vertical force (V) and torque (T) in expansive soil, a method of determining Tu (limit torque) under the action of V is proposed. Considering the effects of expansive force and ground heave after immersion, the load transfer function at the pile–soil interface with positive and negative friction resistance is established. The nonlinear solution of a single pile under vertical load is achieved by the finite difference method. Subsequently, the circumferential limit friction resistance is modified, and a loop iteration program is compiled through MATLAB. Thus, the bearing capacity of single pile under the loading path of V→T is obtained. The corresponding failure envelope curve is drawn and verified by laboratory model tests. Based on the verified solution, the bearing capacity envelope curve and deformation characteristics of single pile are analyzed. The influence of the expansion rate on the bearing capacity envelope curve is discussed, and reasonable engineering suggestions are put forward.

The single pile is a structural element that has an important role in supporting any part of the superstructure. This paper adopted three dimensional finite element modelling by using ANSYS to discover the influence of soil size domain on pile diameter, pile length, load eccentricity and torsion magnitude. One type of soil was used and described by Drucker-Prager model. The numerical analysis has been performed to show how the variation in soil size domain effects on the behaviour of single pile under torsion load. The procedure which is adopted in the investigation depends on fixing all variables and changing one variable to show the impact of this variable on the pile response considering soil domain variation. From the investigation, it is obvious that the pile diameter, eccentricity and torsion load have a major influence on the pile response, while the pile length has a minor influence on the pile response. Here, the increase in pile diameter reduces the load transfer to the soil; also the increase in eccentricity increases the load transfer to the soil while the increase in soil domain reduces the pile response. When the torsion load increases the pile response increases too. The pile response refers to displacement, rotation, shear force and bending moment. [ABSTRACT FROM AUTHOR]

In most reconstructions, existing old pile foundations are removed to construct new foundations. After removing the existing pile, the hole is backfilled, but there are issues such as different conditions from the surrounding ground. We report axial compressive loading model tests to investigate the shaft resistance of piles close to backfilled sand. In these model tests, the sandy ground is prepared in a chamber and a backfilling process is simulated, with varied backfilled sand density. The tests reveal that the maximum shaft resistance of the pile depends on the density of the backfilled sand. A numerical finite element method analysis is also performed to examine shear failure in the soil near the pile, which contributes to the shaft resistance mechanism of the pile. When the conditions of the backfilled sand are different from those of the soil, the shear stress of the soil near the pile is affected in both the backfilled sand area and the soil opposite the backfilled sand, and the shape and thickness of the shear band that occurs near the pile changes. [ABSTRACT FROM AUTHOR]

Pile foundations in calcareous sand are often applied to bear vertical cyclic loads. Model tests of a single pile bearing vertical cyclic loads were performed in calcareous sand, and the accumulated settlement and bearing capacity were measured via sensors using a self-designed experimental device. The influences of the dynamic load and number of cycles on the accumulated settlement and bearing capacity of the pile were analyzed. The results revealed that the accumulated settlement of the pile increased with the number of cycles, it was categorized as either stable, progressive, or destructive. The "threshold effect" was observed once a critical number of cycles had been achieved, the particles breakage hindering the settlement tendency lead to the accumulated settlement rate of the pile gradually decreased and stabilized. During cyclic loading, the proportions of the upper load shared by the pile end and side constantly changed, the pile-side frictional resistance gradually decreased, while the average resistance of pile end slowly increased. After cyclic loading, the bearing capacity of the pile was improved slightly, but the pile-side frictional resistance was greatly reduced, two formulas were presented. The test results can be used for the design of pile foundations in calcareous sand. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Architecture & Civil Engineering is the property of Chang'an Daxue Zazhishe and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper proposes a semianalytical solution to analyze the long-term settlement of a single pile embedded in fractional derivative viscoelastic soils under time-dependent loading. In this paper, a three-dimensional (3D) fractional derivative viscoelastic model will be introduced to describe the rheological behavior of soils around the pile. Based on the shear deformation compatibility between the pile and soils, the semianalytical solution will be strictly derived using the correspondence principle and the Laplace transform technique. Three well-documented cases will be used to verify the correctness and reliability of the proposed semianalytical solution, all of which show a very close agreement. Furthermore, worked examples that include instantaneous and ramp loadings will be carried out to capture the influence of six dimensionless parameters, that is, a, b, c, d, κ, and α, on the long-term settlement of a single pile. The results indicate that: the dimensionless settlement for fractional derivative viscoelastic models is larger in the early stage and smaller in the later stage than those for conventional viscoelastic models; the dimensionless settlement capacity of the pile is controlled by the parameters a and d, and the dimensionless settlement rate is controlled by the parameters b and α, which means the selection of these four parameters has a great influence on the long-term settlement; and the parameter c causes little variation in the results. [ABSTRACT FROM AUTHOR]

This paper investigates the frequency-dependent pile-head impedance characteristics of a model soil-pile foundation system under large amplitude loads, inducing soil yielding. Testing was conducted on a scaled single pile embedded in sand under a 1 g condition. A laminar shear box mounted on a unidirectional shaking table was used to house the soil-pile foundation system. Quasi-static loads and dynamic loads were applied to obtain the force–displacement relationships and pile-head impedance functions, respectively, through the pile head connected to a loading actuator providing fixity to the pile head in all directions, except horizontal. In the quasi-static case, loads with three different velocities were applied to study the rate-dependent characteristics of the lateral bearing capacity of the pile. The Stereo-PIV system was employed to measure the surface soil displacement around the pile. The lateral bearing capacity changed with the loading velocity, but the soil near the pile showed a consistent failure pattern despite a significant change in velocity. Lateral pile-head dynamic impedance functions were obtained for low-to-high amplitude harmonic loading for a wide range of frequencies. The dynamic stiffness was seen to converge to that of the secant static stiffness with an increase in the amplitude of the dynamic loading for all the excitation frequencies. [ABSTRACT FROM AUTHOR]

In this paper, we analyze the behavior of a monopile under lateral loading. Specifically, this work focuses on the examination of the static stiffness coefficients of a monopile vertically embedded in a homogeneous or multilayer soil of random geometry and random mechanical properties. To solve the problem, a semi-analytical, closed form solution is developed, based on Winkler's theory. In this model, simulation of the mechanical behavior of the soil is achieved via non-linear "p-y" springs positioned along the axis of the pile, in conjunction with shape functions which describe the lateral movement of the pile. By iterative application of the proposed method the lateral stiffness coefficients at the pile head are calculated with satisfactory accuracy. The results of the proposed method converge satisfactory enough with real data and other theoretical results coming from sophisticated numerical analysis methods. [ABSTRACT FROM AUTHOR]

Copyright of International Architecture is the property of Omniscient Pte. Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study presents a series of model experiments conducted on single pile embedded in saturated and unsaturated expansive soil. A soil composed of 70% bentonite and 30% sand which represents a very high expansive soil is employed in this study. Soil suction (total and matric) was measured using the filter paper technique and calibrated electrical resistance gauges to study the behavior of the soil water retention curve (SWRC) and initial suction and their influence on the results. The results showed that the ultimate skin resistance is increased about 49% when the initial degree of saturation decreases from 90 to 70%. However, the adhesion factor (α, used in calculating the skin friction) increases as the unconsolidated undrained cohesion decreases and as the initial matric suction decreases. The adhesion factor reached a value of 1.3 when the undrained cohesion is 36 kPa, initial degree of saturation of 100% and initial matric suction of 10 kPa. The sharing ratio of the ultimate shaft capacity to the ultimate pile capacity of a single pile changes from 91 to 81% when the degree of saturation decreases from 100 to 70%. [ABSTRACT FROM AUTHOR]

Summary: Pile serves as an essential component for transferring loads from superstructures to the soil ground. Proper consideration of soil‐structure interaction (SSI) responses is crucial in evaluating the pile capacity and deflections under external loads. In the current design practices, semi‐empirical or linear‐elastic analyses are utilized, which are often overly conservative and unable to properly consider the nonlinear SSI responses. Thus, this paper presents a new Euler‐Bernoulli pile element for robustly and efficiently simulating the piles considering the SSI responses. The nonlinear springs distributed continuously along with the pile are directly integrated into the element formulations. A quasi‐analytical solution based on the Gauss‐Legendre method is utilized in the summation processes of the total potential energy to significantly simplify the mathematical expressions and ease difficulties in programming. The element tangent stiffness matrix and secant relations are respectively formulated for predicting the displacement and eliminating the accumulative errors in a Newton‐Raphson incremental‐iterative numerical procedure. Because a pile might exhibit large deflections in soft soils, the kinematic motion description using the Updated Lagrangian (UL) approach is developed where the equilibrium conditions are determined by referring to the last configurations. Finally, several examples are provided to validate the accuracy and efficiency of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, responses of a single pile embedded in sand soil (loose and dense) under dynamic loading (sinusoidal dynamic vibrations of 0.1 g to 0.5 g) have been investigated by two-dimensional analysis using the finite element method (FEM). Viscous (dashpot) boundaries have been used for taking the boundary effects of far-field into account. The applicability and accuracy of site responses of two-dimensional analysis due to the FEM modelling have been well verified with one-dimensional site responses. The results indicate that the relative density of sand (loose, dense) becomes prominent for the displacements of the pile, specifically under the frequency effects of resonance. While the pile in loose sand causes the displacements of 0.1 m to 0.5 m, the pile in dense sand leads to the displacements of 0.05 m to 0.25 m, proportionally with the dynamic loads from 0.1 g to 0.5 g. Moreover, the displacements reach their peak value at the frequency ratio of the resonance case. Viscous boundaries are found sufficient for modelling excessive displacements due to dynamic loading. However, the displacements reveal that high vibrations (> 0.1 g for loose sand, > 0.2 g for dense sand) influencing the pile deformations are critical for the issues of settlements. This is more significant for the resonance case in order for ensuring sufficient design. Consequently, the findings from the study are promising good contributions for pile design under the dynamic effect. [ABSTRACT FROM AUTHOR]

The offshore construction environment is harsh, and the single pile stabilization technology is the key technology to control the verticality of offshore wind power single piles. Aiming at the jack-up stable pile platform developed in this paper, the construction technology of single pile sinking pile was studied and applied to Guohua Dongtai Offshore Wind Power Project. The application results show that the construction quality of the single pile construction technology of the jack-up stable pile platform meets the design and specification requirements, and the construction efficiency is higher, the number of ship machines is less, and the economy is better. [ABSTRACT FROM AUTHOR]

The pile–soil interaction in expansive foundation is complicated. The expansive action affects the performance of the pile foundation. To explore impact of the expansive action on the bearing capacity of a single pile, an analytical solution to the elastic theory of the load-transfer of a single pile is put forward by using the shear displacement method and considering the law of soil shear modulus changing with depth. On this basis, via combination with the load transfer matrix, a nonlinear analysis method for calculating the bearing capacity of a single pile in expansive soil after immersion is put forward. The validities of the suggested methods are confirmed through comparisons with the test results. Then, the influence of various parameters on the performance of a single pile are analyzed. It is determined that an increase in the pile length can effectively reduce the uplift of the pile top and improve the bearing capacity of the pile when part of the pile is under expansive action. However, the effect is not obvious when the pile length is approximately 3 times that of the affected depth. Compared to the pile length, the pile diameter exerts less of an effect on the performance of single pile, and when the entire pile is under expansive action, the increase in the pile length will augment the uplift of the pile top. Additionally, the bearing capacity first increases and then decreases with an increase in the pile length. [ABSTRACT FROM AUTHOR]

The dynamic response of a single pile embedded in dry and saturated sandy soil excited by two opposite rotary machines was considered experimentally. A small-scale physical model was manufactured. It consists of: two small motors supplied with eccentric mass (.012 kg) and eccentric distance (20 mm) representing two opposite rotary machines, aluminium shaft with 20 mm in diameter as pile, and a steel plate with dimensions of (160 × 160 × 20 mm) as a pile cap. The experimental work was achieved taking the following parameters into considerations: pile embedment depth ratio (L/d) and operating frequency of the rotary machines. Twenty-four tests were conducted in medium dense sandy soil with 60% relative density. Half of these tests were performed in dry soil and the other was conducted in saturated soil. In all these tests, the strain along pile's length and the amplitude of vertical vibration for the pile cap were measured. It was found that the axial strain along the pile becomes frequency-dependent, which means that it increases with increasing the operating frequency, as well as its oscillation increases too. The amplitude of vibration at pile head also be frequency-dependent, it increases with increasing the operating frequency. [ABSTRACT FROM AUTHOR]