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In this study, a series of numerical calculations were performed to investigate the lateral behavior of piles in slopes and in horizontal ground. First, a numerical model is created and then verified by comparing the numerical results with the results of model tests. The numerical results agree well with the results of model tests. Second, numerical calculations of different slopes were conducted to explore the effect of slope angle on the horizontal displacement of pile and bending moment. Then, the effect of slope angle on the foundation stiffness proportional coefficient m is investigated. The stress distribution of soil around the pile and the deformation of pile at different slope angles are also compared. Finally, the p–y curves of the different slope angles are compared. An improved p–y method is proposed to consider the effect of slope angle based on the numerical results. The results show that the bearing capacity of piles decreases with an increase in slope angle. The horizontal displacement of pile nonlinearly decreases along the pile body with the depth of pile. The bending moment of piles increases along the pile body with an increase in pile depth, and until 0.5 times of the pile length, the bending moment reaches the maximum value. As the slope angle increases, the maximum of bending moment tends to decrease. The distance from the slope toe to the pile section has a little influence on the pile bending moment and horizontal displacement. With an increase in slope angle, the horizontal foundation coefficient m gradually decreases. [ABSTRACT FROM AUTHOR]

The p–y method as a simplified analysis tool has been widely used to analyze the behavior of laterally loaded piles. This paper develops a novel cyclic p–y elastoplastic model within the framework of the single-surface bounding surface theory. The model can capture the soil stiffness degradation during cyclic loading by incorporating the cumulative plastic displacement to an interpolation function of the elastoplastic resistance coefficient. The model is relatively simple with only four parameters that can be determined from standard soil properties and stress–strain responses measured in direct simple shear tests. The performance of developed model is validated by predicting the cyclic lateral response of piles installed in soft clay during field and centrifuge tests published in the literature. The model can reliably simulate monotonic and cyclic responses of piles under different lateral loading patterns, and capture main characteristics of the pile-head load–displacement curve, such as nonlinearity, hysteresis, displacement accumulation, and stiffness degradation. It can also predict the evolution of the lateral deflection and sectional bending moment along the pile during cyclic loading. [ABSTRACT FROM AUTHOR]

In order to ease consequences of spudcan-footprint interactions during jack-up rigs reinstalling in the vicinity of an existing seabed footprint, three new types of spudcan shapes, that is, a lotus-shaped spudcan with six circular holes, a flat-bottomed spudcan, and a concave-shaped spudcan, were proposed to perform an optimizing study of the spudcan structures, and the effectiveness of them were analyzed comparatively with other different measures. Firstly, 3D Large Deformation Finite Element (LDFE) analyses were carried out using the Coupled Eulerian-Lagrangian (CEL) method in the commercial finite element package ABAQUS. After calibrating the validity of the numerical calculation model against existing centrifuge test data and LDFE results, the differences in interaction mechanism between the novel spudcans and the generic spindle-shaped spudcan were studied when penetrating near an existing footprint with an eccentric distance of 0.5D, and the horizontal range of plastic deformation of the disturbed soils, the inclination angle of the spudcan and the offset distance of the pile legs were analyzed comparatively as well. The results show that the proposed novel spudcans can mitigate the maximum horizontal sliding force and the maximum bending moment at the top of the pile leg obviously, compared with those of the generic one, which were reduced by 32.59%, 22.47%, 28.18%, and 26.32%, 12.88%, 18.02%, respectively. It also can be seen that all novel structures can ease the adverse consequences of spudcan-footprint interactions effectively, and can improve the in -place stability of the spudcan as well. Finally, three possible measures in mitigating interactions of the spudcan-footprint were contrasted, that is, the novel spudcan (represented by the lotus-shaped spudcan with six holes), stomping method, and perforation drilling method. The results show that all of them can reduce adverse impacts induced by interactions of the spudcan-footprint, and also can improve the in-place stability of the spudcan during reinstallation. In addition, among them, according to the effect of reducing the additional stress of the spudcan, the effectiveness of them can be listed as follows: perforation drilling near an existing footprint > the lotus-shaped spudcan with six holes > stomping method. In terms of the vertical bearing capacity of the spudcan, the lotus-shaped spudcan with six holes can improve it as much as 16.33% compared with the spindle-shaped structure due to the particularity of the structure. While reducing the continuity and strength of soil foundations, the perforation drilling measure leads to the decrease of the vertical bearing capacity of the spudcan by 13.07%. It can be concluded that all the three measures have merits and demerits, so the relevant construction environment conditions and engineering practice should be fully considered when selecting measures to deal with interactions of the spudcan-footprint. [ABSTRACT FROM AUTHOR]

Combined with the soft clay layer of Foshan metro, a back-analysis method combining model test and numerical simulation is developed. First, the similitude criterion for the model used in this study was derived from similarity theory and elasticity mechanics equations. Artificial clay is prepared by mixing kaolin, bentonite, loess, and river sand in proportions of 4 : 2: 3 : 1. Gypsum, water, and borax are mixed in proportions of 1 : 0.7 : 0.015 to simulate the tunnel lining. The model tests were carried out based on four load modes: the combination of mode 1, vertical load distribution and horizontal load linear distribution, mode 2, vertical load distribution and horizontal load parabolic distribution, mode 3, vertical load parabolic distribution and horizontal load linear distribution, and mode 4, vertical and horizontal load parabolic distribution. Then, the calculation model corresponding to the four load modes is established using ABAQUS, and the measured data is back-analyzed as the known quantity. The specific load values obtained were 359 kPa, 380 kPa, 361 kPa, and 368 kPa by the load-internal force curve. The bending moment and axial force are calculated by substituting the back-analysis load values back into the model and comparing the results with the measured values; it was found that the internal forces under the back-calculation load still deviated by varying degrees. By using the comprehensive error function E to evaluate the advantages and disadvantages of the four distribution modes, the comprehensive errors are 4.3%, 1.7%, 6.5%, and 5.9%, respectively. That is, the error of load distribution of mode 2 (the combination of vertical load distribution and horizontal load parabolic distribution) is the lowest and is highly consistent with the measured value, which is the closest to the characteristics of the load pattern of the stratum. [ABSTRACT FROM AUTHOR]

Inverse analysis procedures are used to update project parameters and applied to predict future performance in the later stages. However, the inverse analysis procedure of earth pressure of excavation has received less attention. This paper proposes an improved inverse analysis method and the modified apparent earth pressure model for braced excavations in soft clay. A new procedure for inverse analysis of excavation is suggested based on the quintic spline interpolation function, and a trial algorithm is used to eliminate the errors generated in the inverse process. The proposed inverse solutions are validated by numerical simulations and reported engineering examples and show good agreements. Based on the inverse data and empirical apparent pressure diagram (APD), a modified apparent earth pressure method for braced excavations in soft clay is further suggested. And the relationship between the degree of anisotropy of soft clay and apparent earth pressure coefficients is discussed. The study results provide a reference for dynamic feedback design and adaptive management of the excavation. [ABSTRACT FROM AUTHOR]

Investigations of earthquakes have shown that piles in soft or liquefiable soils are more susceptible to problems arising from ground amplification or excessive soil movements. However, because of the complexity of dynamic pile-soil interaction during seismic shaking, the seismic response of piles embedded in soft soils has yet to be fully understood. Based on a series of centrifuge tests and three-dimensional (3D) finite-element analyses, a relevant study has provided a framework for the prediction of seismic pile bending moment response for piles embedded in clays in an average (i.e., mean value) sense. In this paper, this relevant study was extended by considering seismic ground motion as a nonstationary Gaussian stochastic process. By doing so, the coefficient of variation and probability distribution of the pile bending moment were examined through 3D finite-element analyses incorporated with Monte Carlo simulations. The findings from this study likely will provide some useful guidance for practical reliability-based design of piles embedded in soft clays subjected to seismic shaking. [ABSTRACT FROM AUTHOR]

The safe and stable operation of monopile offshore wind turbines (MOWTs) under seismic and environmental loading is a major challenge facing designers. A numerical method was developed for simulating the dynamic interaction of the soil-pile-structure system by employing an elastoplastic bounding surface constitutive model that can capture the cyclic degradation of clay stiffness well. Then, the suitability of the method was validated by comparison with the existing simulation results in the literature. The dynamic responses of MOWTs to seismic and environmental loading were simulated by employing the above numerical method. The effects of soil plasticity and stiffness degradation on the dynamic responses of MOWTs were investigated. The influence of environmental loads on the seismic responses of MOWTs was also analysed. It was found that the monopile experienced significant rotation and settlement, and the soil plasticity and stiffness degradation significantly increased the peak response of the lateral deflection, rotation angle and bending moment of the MOWT under combined seismic and environmental loads. The input bedrock peak acceleration was amplified to varying degrees from the monopile bottom to the tower top, and the acceleration amplification along the height was the most significant overall when considering the soil stiffness degradation. Environmental loads such as winds and waves significantly increased the absolute values of the seismic response profile, including the deflection, rotation angle and bending moment, as well as the acceleration amplification factor. The research results can support the seismic design of MOWTs. [ABSTRACT FROM AUTHOR]

Based on advanced clay-monopile-OWT numerical model, the wind-wave coupling effect was investigated. Compared to the case of wind load only, both the nacelle top displacement and the maximum monopile's bending moment are smaller when the wind-wave load coupling is considered. The monopile-head displacement cumulation can cause the drift of the nacelle top displacements. Moreover, the wind and wave loads may cause opposite accumulative direction of the monopile-head displacement due to the difference in load nature. The displacement cumulative magnitude is positively correlated to the load magnitude. Hence, the monopile possesses better energy-dissipating capacity in the coupled load case. The equivalent damping ratio of the soil is about 3.2 ∼ 4.9% under the wind-wave combination, 1.2 ∼ 1.4% under the wind only and 2.3 ∼ 3.5% under the wave only, which agrees with superposition principle. Under the wind-wave loads, noticeable accumulation of excess pore pressure exists in the seabed soil. Compared to the separate load cases, the excess pore pressure in the coupling case may be smaller. Analysis also showed that mean effective stress of soil decreases with loading time due to pore pressure buildup, although the soil mean stress may increase when total stress method is considered. [ABSTRACT FROM AUTHOR]

The discusser is correct that the construction of the cyclic contour diagrams for a new soil without any prior knowledge or experience would have required more cyclic soil element tests than those indicated in Fig. These diagrams can also be used to inform the shape of diagrams for other clays, when test results are limited. This procedure is based on the use of cyclic contour diagrams, which are fundamentally based on observed soil responses at the element level. [Extracted from the article]

• The horizontal bearing capacity of CBF can be enhanced by existing vertical load. • The effect of horizontal load and bending moment on the CBF is similar. • The influence of aspect ratio on the capacity envelopes is analyzed. Failure of offshore wind power structural system is an important research topic in many countries. Most previous researches focus on the tower failures and blade failures rather than foundation failure. Taking the 3 MW of the composite bucket foundation (CBF) in China as a case study, a comprehensive study of the horizontal bearing response of CBF were carried out by a centrifuge model test and a series of numerical simulations. Results show that the horizontal bearing capacity of CBF increase at first and then decrease with the increase of the existing vertical load in two-dimensional loading space. The relationship between bending moment and horizontal load in two-dimensional loading space is approximate linear. The aspect ratio has influence on the capacity envelopes peak in horizontal-vertical load loading space. Three-dimensional envelope surface is obtained, the results provide a basis for the design of CBF of offshore wind turbine. [ABSTRACT FROM AUTHOR]

This paper presents the results of static lateral load tests carried out on 1×2, 2×2, 1×4, and 3×3 model pile groups embedded in soft clay. Tests were carried out on piles with length to diameter ratios of 15, 30, and 40 and three to nine pile diameter spacing. The effects of pile spacing, number of piles, embedment length, and configuration on pile-group interaction were investigated. Group efficiency, critical spacing, and p multipliers were evaluated from the experimental study. The experimental results have been compared with those obtained from the program GROUP. It has been found that the lateral capacity of piles in 3×3 group at three diameter spacing is about 40% less than that of the single pile. Group interaction causes 20% increase in the maximum bending moment in piles of the groups with three diameter spacing in comparison to the single pile. Results indicate substantial difference in p multipliers of the corresponding rows of the linear and square pile groups. The predicted field group behavior is in good agreement with the actual field test results reported in the literature. [ABSTRACT FROM AUTHOR]

Pile foundations are frequently used in very loose and weak deposits, in particular soft marine clays deposits to support various industrial structures, power plants, petrochemical complexes, compressor stations and residential multi-storeyed buildings. Under these circumstances, piles are predominantly subjected to horizontal dynamic loads and the pile response to horizontal vibration is very critical due to its low stiffness. Though many analytical methods have been developed to estimate the horizontal vibration response, but they are not well validated with the experimental studies. This paper presents the results of horizontal vibration tests carried out on model aluminium single piles embedded in a simulated Elastic Half Space filled with clay. The influence of various soil and pile parameters such as pile length, modulus of clay, magnitude of dynamic load and frequency of excitation on the horizontal vibration response of single piles was examined. Measurement of various response quantities, such as the load transferred to the pile, pile head displacement and the strain variation along the pile length were done using a Data Acquisition System. It is found that the pile length, modulus of clay and dynamic load, significantly influences the natural frequency and peak amplitude of the soil-pile system. The maximum bending moment occurs at the fundamental frequency of the soil-pile system. The maximum bending moment of long piles is about 2 to 4 times higher than that of short piles and it increases drastically with the increase in the shear modulus of clay for both short and long piles. The active or effective pile length is found to be increasing under dynamic load and empirical equations are proposed to estimate the active pile length under dynamic loads. [ABSTRACT FROM AUTHOR]

Using the results from three full-scale lateral pile group load tests in stiff clay with spacing ranging from 3.3 to 5.65, computer analyses were performed to back-calculate p multipliers. The p multipliers, which account for reduced resistance due to pile–soil–pile interaction, increased as pile spacing increased from 3.3 to 5.65 diameters. Extrapolation of the test results suggests that group reduction effects can be neglected for spacings greater than about 6.5 for leading row piles and 7–8 diameters for trailing row piles. Based on analysis of the full-scale test results, pile behavior can be grouped into three general categories, namely: (1) first or front row piles; (2) second row piles; and (3) third and higher row piles. p multiplier versus normalized pile spacing curves were developed for each category. The proposed curves yield p multipliers which are higher than those previously recommended by AASHTO in 2000, the US Army in 1993, and the US Navy in 1982 based on limited test data, but lower values than those proposed by Reese et al. in 1996 and Reese and Van Impe in 2001. The response (load versus deflection, maximum moment versus load, and bending moment versus depth) for each row of the pile groups computed using GROUP and Florida Pier generally correlated very well with measurements from the full-scale tests when the p multipliers developed from this test program were employed. [ABSTRACT FROM AUTHOR]

A series of centrifuge model tests has been conducted to investigate the behavior of a single pile subjected to excavation-induced soil movements behind a stable retaining wall in clay. The results reveal that after the completion of soil excavation, the wall and the soil continue to move and such movement induces further bending moment and deflection on an adjacent pile. For a pile located within 3 m behind the wall where the soil experiences large shear strain (>2%) due to stress relief as a result of the excavation, the induced pile bending moment and deflection reach their maximum values sometime after soil excavation and thereafter decrease slightly with time. For a pile located 3 m beyond the wall, the induced pile bending moment and deflection continue to increase slightly with time after excavation until the end of the test. A numerical model developed at the National University of Singapore is used to back-analyze the centrifuge test data. The method gives a reasonably good prediction of the induced bending moment and deflection on a pile located at 3 m or beyond the wall. For a pile located at 1 m behind the wall where the soil experiences large shear strain (>2%) due to stress relief resulting from the excavation, the calculated pile response is in good agreement with the measured data if the correct soil shear strength obtained from postexcavation is used in the analysis. However, if the original soil shear strength prior to excavation is used in the analysis, this leads to an overestimation of the maximum bending moment of about 25%. The practical implications of the findings are also discussed in this paper. [ABSTRACT FROM AUTHOR]

It is very important to analyze the lateral cyclic response of monopiles for the design of offshore wind turbines (OWTs). A three-dimensional finite element method for lateral cyclic responses of large-diameter monopiles is developed based on a simplified constitutive model of clays that has been successfully encoded into the ABAQUS software package. The applicability of this method is validated by simulating the existing centrifugal model test. The method can predict the nonlinear hysteresis responses of monopiles in clays during cyclic loading, and the evolution of bending moment and lateral deflection profile of monopile with loading cycles. Various lateral cyclic loads with different loading patterns including one-way and two-way loading, symmetric and asymmetric loading, variable-amplitude and constant-amplitude loading are applied to monopiles. The impact of different cyclic loading patterns on lateral responses of large-diameter monopiles is systematically investigated. The research results can provide some reference for the engineering design of large-diameter monopiles under lateral cyclic loads. [ABSTRACT FROM AUTHOR]

Pile's excessive internal forces and displacements induced by adjacent tunnelling can cause serious serviceability problems for infrastructure aboveground, emphasizing the necessity for predicting the pile responses during the preliminary tunnel design. This study present extensive finite element (FE) analysis to investigate the passive pile's lateral stress and deformation development using a centrifuge test study as model validation. An anisotropic soil constitutive model NGI-ADP is employed to simulate the clay's behaviour, filling the gap of capturing soil's stress-induced anisotropy characteristics in exploring tunnel-soil-pile interaction problem. For further exploration of construction factors' effects, the parametric analysis for tunnelling locations, pile service situations and the anisotropic degree are conducted, assessing their influences on tunnelling-induced pile deflection, bending moment, and shaft resistance. The results show despite the conventional ignorance of the soil's intrinsic anisotropy, it stands as a contributing factor in determining the pile behaviour since the soil displacement field is inevitably dependent on this inherent characteristic. For various pile properties and tunneling locations, some useful suggestions for constructions are drawn to avoid severe damage within the pile body. Moreover, the effect of the pile's vertical working is revealed to be not critical to its stability when the pile was subject to surrounding disturbance. [ABSTRACT FROM AUTHOR]

Quantifying the lateral displacement and bending moment of the existing pile caused by the penetration of the adjacent pile are of great engineering significance to ensure the safety and stability of the buildings. In this paper, a two-stage analysis approach for predicting the response of the existing pile due to the penetration of the adjacent pile is presented. First, a simplified model is proposed to determine the free-field lateral soil displacement induced by the pile penetration. This model assumes that the pile penetration process can be regarded as a series of displacement-controlled spherical cavity expansion in semi-infinite soil, and considers the large deformation effect of soil as well as the influence of the existence of the ground surface. The validity and accuracy of the proposed model are verified by comparing with the published results. Subsequently, the p-y curve method is adopted to analyze the nonlinear pile-soil interaction for solving the response of the existing pile induced by the lateral displacement of soil obtained in the first stage. Through a series of parametric investigations, it is indicated that the impact of the penetration of adjacent pile on the response of the existing pile rests with some factors. Finally, some design charts are presented by parametric analysis, which can be used to assess the response of the existing pile caused by the penetration of the adjacent pile in practical engineering. [ABSTRACT FROM AUTHOR]