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While the effects of tunnel construction on vertical loaded piled foundations have been extensively explored, the impact of side-by-side twin tunnel excavation on laterally loaded pile groups remains less understood in existing literature. This study investigates the repercussions of twin tunnel excavation at various depths on a laterally loaded (2 × 2) pile group, utilizing a combination of three-dimensional centrifuge model tests and back-analyses employing a sophisticated hypoplastic model. The test IDs CD1.5_1.5, CD2.7_2.7, and CD3.7_3.7 represent tunnelling activities near the pile shaft, pile toe, and beneath the pile toe in a side-by-side twin configuration. Twin tunnelling in test CD1.5_1.5 resulted in the most significant lateral movement of the pile cap due to reduced horizontal stress near the pile group shaft. Furthermore, twin tunnelling in test CD2.7_2.7 led to a substantial transverse tilt of 0.5 % for the pile cap, surpassing the recommended 0.2 % limit per Eurocode 7. During the second tunnelling in tests CD2.7_2.7, and CD3.7_3.7, a shift in load direction from upward to downward occurred in pile P2, potentially compromising its integrity. In test CD1.5_1.5, stress reduction near the pile shaft led to pile P1 enduring a bending moment of 1050 kNm at its midpoint, exceeding its capacity of 850 kNm. [ABSTRACT FROM AUTHOR]

This study presents the impact of tunnelling on a battered and vertical pile groups when subjected to lateral loads. A comprehensive investigation was undertaken to examine the effects of varying the tunnel depth in relation to the length of the pile group, as well as the direction of the lateral load (i.e., towards and away from the tunnel). A sophisticated hypoplastic model, which has the ability to accurately represent the small strains stiffness was used to capture clay behaviour. As compared to the battered pile group, the vertical pile group exhibited the largest pile cap lateral displacement due to tunnelling adjacent to pile shaft. The tunnel below the battered pile group toe exhibited the most significant pile cap lateral displacement and tilting of the pile group. The stress release caused by tunnelling in the vicinity of the pile shaft induced the largest bending moment in both battered and vertical pile groups, regardless of direction of the applied lateral load. The pile cap experiences linearly increasing lateral movement with tunnel volume loss. Moreover, the lateral movement and tilting are greater in the presence of lateral loads compared to vertical loads on the battered pile group. [ABSTRACT FROM AUTHOR]

Offshore wind turbines (OWTs) are affected by wind, wave, and current during their service life, which lead to the substructures undergoing combined effects of complex lateral loads and local scour. This phenomenon poses a significant challenge to the bearing capacity and cyclic responses of the widely used rigid monopiles for OWTs. This study develops three-dimensional numerical model to investigate the behavior of a rigid monopile subjected to lateral monotonic and cyclic loads, considering the stress history alteration induced by local scour. The hysteresis and plasticity accumulation of soils are captured by a bounding surface model. An accurate and concise semi-implicit stress integration scheme is creatively proposed to effectively incorporate this advanced constitutive model into the finite element (FE) software. The numerical model is verified by comparing FE results with centrifuge test results. Subsequently, the key factors such as cumulative deformation characteristics and bending moments distribution are investigated under different scour and cyclic loading conditions. The results indicate that with the facilitation of proposed semi-implicit scheme, the bounding surface model is capable of capturing the deformation pattern and cumulative deformation behavior of laterally loaded rigid monopile, and the cyclic responses of the monopile are significantly affected by the local scour. [ABSTRACT FROM AUTHOR]

Chalk's sensitive, variable nature poses difficulties for foundation designers. It can present as weak rock and yet be de-structured to very weak putty by dynamic or high-pressure loading. The development of multiple offshore wind farms at north European chalk sites led to the recent ALPACA Joint Industry Programme, which undertook intensive material characterisation and large-scale field testing at St Nicholas at Wade (SNW), Kent, UK to capture and better understand the behaviour of piles driven in fractured low-to-medium density chalk. Noting that lateral loading response is a vital design concern for monopile and jacket supported structures, this paper focuses on 3D Finite Element (FE) modelling of ALPACA's monotonic lateral loading field tests on open-ended driven tubular steel piles. The brittle chalk is modelled with a strain-softening Mohr-Coulomb model combined with nonlocal regularisation, calibrated meticulously against the ALPACA characterisation dataset. A second, simpler modelling approach, adopting a perfectly-plastic Mohr-Coulomb model, is also explored as a simplified practical alternative. Both approaches can match field lateral capacity and bending moment distributions, after taking due account of pile installation and chalk fracturing effects. The analyses indicate how robust, accurate and cost-effective lateral loading design may be approached for low-to-medium density fractured chalks. [ABSTRACT FROM AUTHOR]

This paper addresses the effect of particle gradation on the lateral response of pile in coral sand foundation through numerical method. Firstly, the parameters of Hypoplastic (HP) constitutive model were calibrated by a series of laboratory tests and show obvious difference in value between fine and coarse coral sand. Subsequently, a 50 g centrifuge test and 1g model pile test were carried out to verify the numerical model and calibrated parameters. Afterward, numerical analyses were systematically conducted to investigate the influence of particle gradation, buried depth, and relative density on the lateral response of pile. The lateral load–displacement response, deflection and bending moment of pile, and soil resistance were analyzed and discussed in detail. Numerical results show that the bearing capacity of pile and soil resistance in coarse sand are greater than those in fine coral sand when the relative density is 25 % or 50 %. However, when the relative density is 75 %, the bearing capacity of pile and soil resistance in fine sand present significantly greater values than those in coarse sand under higher lateral displacement level. Moreover, the difference in lateral response of pile between coarse and fine coral sand is more significant in looser sand or shorter pile. [ABSTRACT FROM AUTHOR]

A new p–y curve of the lateral static loading of large diameter piles in cohesive slopes is proposed in this paper, which considers both the size effect and slope inclination. A series of pile size and slope inclination varied three–dimensional finite difference analyses are used to study the behavior of large–diameter pile foundations under lateral loading on cohesive sloping ground. Based on the results of numerical calculations, the pile–soil failure mechanism is discussed for large–diameter piles. Combined with the failure mechanism, nonlinear analytical formulations are derived for the ultimate lateral load and initial stiffness of hyperbolic p–y curves at different depths, which considers both the size effect and slope inclination. The proposed p–y curve is compiled into a program for parametric analysis of pile displacement and bending moment. To verify the proposed p–y curve, it is compared with large–scale foundation lateral loading field test and centrifuge test data to obtain a remarkable result. [ABSTRACT FROM AUTHOR]

• Eccentric and/or inclined loads induce nonlinear roto-translational displacements of pile groups. • Simplified modelling (beams, elastic half-space, localised yielding) compared with advanced analyses. • Vertical eccentric loads mobilise the lateral soil resistance at large cap displacements. • Charts for the reduction in vertical capacity, at prescribed cap displacements, due to load eccentricity and inclination. This paper presents a numerical study of 3 × 3 pile groups embedded in clay under vertical and inclined eccentric loads. Simplified modelling, based on elastic beams embedded in a soil continuum, is used to explore the soil-pile-cap response. This simple model allows rigorous treatment of the 3D foundation geometry and local soil plasticity, demonstrated through validation with 3D finite element analysis. The numerical results reveal that complex roto-translational displacements of the pile group are induced by eccentric or inclined loads, with highly nonlinear relationships when soil plasticity is considered. Interestingly, vertical eccentric loads mobilise the lateral soil resistance at large cap displacements. Thus, while existing t-z type models are shown to be adequate for serviceability predictions, they could provide overly-conservative estimates of the ultimate load capacity. Also, foundation internal forces can exceed allowable bending moments of reinforced concrete piles under multi-directional loads. For performance based design of pile groups under inclined eccentric actions, engineers should estimate the impact of soil yielding on both displacements and rotations of the cap, to satisfy limit state requirements. Dimensionless charts are presented, which describe the reduction in vertical capacity, for a prescribed cap displacement, as a function of load eccentricity and inclination. [ABSTRACT FROM AUTHOR]

In this paper, a thorough numerical study is conducted to rigorously evaluate the lateral earth pressures exerted on the retaining walls backfilled with geosynthetic-reinforced soil strata. With this aim, the lower bound theorem of limit analysis is exploited in conjunction with the finite element discretization method. The computational programming adopting second-order cone optimization is employed to model the Mohr-Coulomb yield criterion in its respective nonlinear form. The reinforcement layers are assumed to bear solely axial tension; but not bending moment, which is the common characteristic of all geosynthetic materials. Results show that the horizontal stress field behind retaining structures is heavily disturbed by placing geosynthetic layers, especially in close proximity to the retaining structure. Accordingly, the failure zone shrinks in size and the lateral earth pressure decreases by either adding more reinforcement layers or increasing their relative lengths. Through a comprehensive parametric survey, the influence of several parameters, including internal friction angle, soil-wall and soil-reinforcement interface friction angles, length and number of reinforcements, soil inherent anisotropy and surface loading on the lateral earth pressure is meticulously examined. The employed formulations are rigorously compared with results published in the literature. A design table is also provided so as to effectively estimate the active earth pressure coefficient of geosynthetic-reinforced walls accounting for all contributing parameters. [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]

A concrete cut-off wall has been recently used in a landslide dam as an anti-seepage measure. Due to it is under a complex loading condition, the wall may undergo inelastic straining and have a potential of cracking. Several centrifuge model tests and numerical simulation are conducted to investigate the damage behavior of the cut-off wall. The numerical method of concurrently modelling small cracks in the cut-off wall and the overall landslide dam based on the finite element method (FEM)-Peridynamics (PD) multiscale coupling method is confirmed to be effective by the centrifuge model tests. The cut-off wall buried in a landslide dam bears a bending effect under lateral loadings in the absence of overlying fill. The lower part of the wall may have a potential to form cracks induced by large bending moments. The wall is in a tension-shear failure mode with an inclined crack. A parametric study demonstrates that properties of the wall and the soil have a significant effect on the damage behavior of the wall. Also, creep deformation of the dam body does not elongate the crack significantly, but it expands the width of the crack. The crack tends to stabilize over a period of time. [ABSTRACT FROM AUTHOR]