Lateral Soil Resistance Research Articles

Long-term effect of soil settlement on lateral dynamic responses of end-bearing friction pile

This paper presents a closed-form solution to evaluate the lateral dynamic responses of pile foundation adjacent to superficial surcharge. The equilibrium equation of soil is analyzed using continuum solutions, and the Euler-Bernoulli beam theory is employed to model the pile. The consolidation settlement of surrounding soil induced by the superficial surcharge is determined by Terzaghi's consolidation theory. The lateral soil resistance is formulated using potential functions, and the dynamic responses of the end-bearing friction pile are subsequently obtained by considering the vertical load and skin friction. Our results are compared with analytical approaches from previous literature to validate the effectiveness of the present solution. The evolutions of lateral dynamic responses of pile foundation are systematically analyzed. It is suggested that the superficial surcharge influences the distribution of skin friction of the pile foundation, thereby altering its lateral dynamic responses. This phenomenon does not manifest immediately but demonstrates significant long-term effects during the consolidation settlement of surrounding soil.

Effect of loose sand layers within dense sand on the lateral capacity of extra-extra-large monopiles

A series of 3D finite element analyses were performed to examine the influence of loose sand layers on the monotonic lateral capacity of an extra-extra-large semirigid monopile in dense sand. The SANISAND-04 advanced constitutive model, which was meticulously calibrated, validated and verified using triaxial compression tests, centrifuge tests and a numerical study based on field tests, was adopted for this study. The impact of loose sand layers on monopile response is discussed in terms of its mode of deformation, critical lateral capacity, bending moment, shear force and soil resistance. Results show that the magnitude of the reduction in the monopile lateral capacity is dependent on the thickness and depth of the loose sand layer. Presence of loose sand at the tip of the monopile is also shown to have a significant effect on its lateral capacity.

A developed soil reaction model for large- diameter monopiles in sand based on hyperbolic curves

Given the preference as the foundation for offshore wind turbines, this paper focuses on large-diameter monopiles and presents a series of finite element analyses to investigate the response to lateral loads. The contribution of four soil reactions, including distributed lateral load (p-y), distributed moment (m-θ), and base shear force and base moment, to the lateral resistance encountered by monopiles is quantified. It can be found that apart from the distributed lateral load, the contribution of distributed moment exceeds 14 %, while the proportion of base shear force and base moment is less than 5 % and is considered negligible. This research investigates how the diameter and embedded length of monopiles impact the load-bearing characteristics. A 'p-y + m-θ' model based on the two-parameter soil reaction curve is proposed. This model is not only straightforward and easy to use for engineering design but also considers the effect of rotational deformation on the soil reaction curves. Additionally, a relationship between ultimate lateral soil resistance and relative density is established, leading to an analysis model suitable for sands of various relative densities. Finally, the model effectively predicts the load–displacement relationship for large-diameter monopiles under lateral loads, providing valuable support for monopile design in the offshore wind industry.

Application of PISA method for monopile design in layered soil

The foundation design for offshore wind turbines (OWTs) is critical to ensuring their structural integrity and long-term stability. Large-diameter monopiles are widely used for OWTs owing to their proven effectiveness. The conventional design approach, derived from the oil and gas industry’s p-y model, has limitations when applied to monopiles for OWTs. Consequently, a novel design method based on the PISA joint industry research project was developed, which extends beyond the traditional lateral soil resistance (p-y curves) and incorporates additional soil reaction components from shaft friction, pile base shear, and base moment. Unlike the simplistic rule-based conventional approaches, the proposed method necessitates site-specific 3D finite element (FE) simulations for precise calibration of soil reaction curves. Although successfully applied in European offshore wind farms, the PISA method’s performance in regions with distinct seabed compositions, such as China, remains to be verified. Therefore, this paper presents a comprehensive case study conducted at the Xiangshan wind farm, a representative site characterized by layered soil. The study employed in-situ investigations (cone penetration test, borehole) and laboratory tests (direct simple shear, bender element) to delineate the seabed soil profile and derive essential soil parameters for accurate foundation design. To facilitate the design, an Abaqus-based design tool was developed, which automated the extraction of soil reaction curves from the 3D FE simulations, calibration of PISA springs, and execution of one-dimensional beam-spring analyses employing Timoshenko beam theory. Comparative analyses were performed on the computed responses of piles, encompassing load-deflection curves, pile deflections, and bending moment profiles. The outcomes from the 3D FE simulations, uncalibrated rule-based PISA model, and calibrated PISA model were compared to validate the PISA method for monopile design in layered soil conditions.

A Method for Predicting the Load Interaction between Reinforced Thermoplastic Pipe and Sandy Soil Based on Model Testing

This study aims to investigate the interaction between reinforced thermoplastic pipes (RTPs) and sandy soil. The mechanical properties of sandy soil in the South China Sea region were determined through shear tests to obtain fundamental data. Subsequently, a specialized experimental setup was designed and assembled to study the pipe–soil interaction, specifically measuring the lateral soil resistance of flexible pipes at varying burial depths. Data analysis revealed the relationship between soil resistance, lateral displacement, and initial burial depth. To simulate the mechanical behavior of the pipe–soil interaction, the coupled Eulerian–Lagrangian (CEL) method was employed for numerical simulations. The research findings indicate that the lateral soil resistance is influenced by the uplift height and accumulation width of the soil ahead of the pipe. Within a lateral displacement range of 0.5 times the pipe diameter (0.5D), the lateral soil resistance rapidly increases, resulting in a soil uplift along the circumferential direction of the pipe. This process not only enhances the load-bearing capacity of the pipe but also increases the accumulated soil resistance, consequently expanding the soil failure zone. Furthermore, the ultimate soil resistance exhibits an increasing trend with an increasing burial depth. Once the pipe reaches a certain burial depth, the uplift height of the soil reaches a critical state. To address the grid distortion caused by soil deformation, numerical simulations based on the CEL method effectively modeled the pipe–soil interaction forces under significant lateral displacements, exhibiting good agreement with the experimental results. This study provides a solution for investigating soil resistance in submarine pipelines, thereby contributing significantly to the design and performance prediction of underwater pipelines.

The influences of vertical load on lateral dynamic responses of end-bearing friction pile

This paper revisits the influences of vertical load on the lateral dynamic responses of a single pile with rigorous analytical methods. The vertical load of pile is supported by the combination of end-bearing and side friction that develops along the pile length. The equilibrium equations of surrounding soil are analyzed by making use of the continuum-based solution, whereas the pile is modeled by the conventional Euler-Bernoulli beam theory. According to the assumption of perfect contact between the pile and the soil, the axial force function is deduced, which yields the analytical forms of vertical load and mechanical parameters of the pile-soil system. Using the formulation of lateral soil resistance and taking into account the influences of vertical load, the dynamic responses along the end-bearing friction pile are subsequently achieved via the Adomian decomposition method. The results obtained in this scheme were compared with analytical techniques available in the previous literature, which are applicable to the dynamic responses in the absence of vertical load. The results of numerical analysis indicate that the influences of vertical load on both the lateral displacement and the bending moment of the pile could be significant and, in general, enable them to undergo remarkable redistribution.

Experimental study on vertical–lateral coupling pipe–soil interaction characteristics and speed amplification effect of marine pipelines

ABSTRACT Under actual marine environment, the steel catenary pipeline’s touchdown zone frequently interacts with the seabed. The existing understanding of vertical–lateral coupling effect and speed amplification effect is insufficient at present. In this paper, the mechanism tests for the vertical and lateral soil resistance of small-scale pipes are carried out in both dry soil and saturated soil environments. The pipe–soil interaction presents quite different characteristics in dry soil and saturated soil due to the soil liquefaction effect. The pipe movement speed affects the soil reaction force significantly, especially in the high-speed range. During the vertical penetration of the pipe, soil shear strength follows a tri-linear relation. The lateral pipe–soil interaction could be classified into three phases i.e. fast growth, fast descent and stable fluctuation. The vertical–lateral coupling has a significant influence on pipe–soil interaction, presenting that the penetration depth greatly affects the lateral soil resistance.

AN EXPERIMENTAL AND NUMERICAL STUDY OF LATERALLY LOADED SMALL GROUPS CFG PILE IN SOFT CLAY

The CFG pile comprises composite materials like cement, fly ash, and gravel with adequate water to achieve various grades. It is one of the best techniques to enhance ground bearing capacity in soft and problematic soil. CFG pile has a good amount of lateral resistance capacity. This research study’s main objective is to study a single and small group of casted CFG piles in the laboratory. Also, discussion on the Installation procedure of CFG pile in a confined area, temperature, and curing process. In order to improve the workability of the CFG pile, several laboratory experiments were conducted on various groups of CFG in this experimental analysis. They are made up of a variety of Cement, Fly ash, and gravel particle proportions. Moreover, the research looked at nine pile group combinations (2×1, 2×2, 3×2, 2×3 in square Paton, subjected to a lateral load in a longer direction when in three CFG piles triangular parallel and perpendicular to the base angle of triangular subjected to the lateral load) with a 1.5 D pile spacing values (where D is the pile diameter). In terms of load vs. lateral displacement, load vs. soil resistance, and associated double tangential curved method, the effects of load intensities, group configuration, and Pile are discussed. The improved plots can be used to plan laterally filled CFG piles and equations for group action design. As a result, architecture curves for assessing pile group activity using improvements were developed and implemented in experiments. Results show that the CFG pile was subjected to lateral load and lateral displacement within the permissible limit. The CFG Pile and Pile surrounding soil interaction comparative results were discussed. Suppose the suitable soil elastic modulus is selected. In that case, the numerical, analytical solution and the back load-settlement curve approach can reasonably estimate the lateral deformation concerning Depth and the group efficiency, respectively, according to the relation between numerical and experimental findings.

Deformation of trenched multilayer pipelines during large lateral displacement due to subsea geohazards

Large lateral displacement of trenched multilayer pipelines may be induced by ground movement, landslides, ice gouging, etc. The significant difference between the shear strength of the backfill material and the native soil may affect the pipeline-backfill-trench interaction, the failure mechanisms, and consequently the lateral soil resistance. However, this challenging and less-explored aspect has not been covered thoroughly in design codes, even for rigid pipes. This paper investigates the influences of multilayer pipeline-backfill-trench interaction on the deformation of pipe section, soil failure mechanism, resultant lateral soil resistance, and soil pressure on the pipe by large deformation finite element analyses. A decoupled model consisting a Coupled Eulerian-Lagrangian (CEL) approach with a rigid pipe in ABAQUS was created along with a finite element (FE) model of multilayer flexible pipe in ANSYS to assess their relative merits for this problem. A parametric study was conducted to investigate the influences of key factors, including the trench geometry, stiffness of backfill material, native seabed soil properties, burial depth, and intensity of pipeline-trench bed interaction. The study showed that the ignorance of the pipeline-backfill-trench interaction by using uniform soil might result in underestimation and overestimation of the lateral soil resistance at different displacement amplitudes.

Mechanical Response Analysis for an Active–Passive Pile Adjacent to Surcharge Load

Due to the complexity of pile–soil interaction, there is little research on active–passive piles that bear the pile-top load transmitted from the superstructure and the pile shaft load caused by the lateral soil movement around the pile simultaneously. The purpose of this study is to analyze the displacement and internal force of active–passive piles. Most of the pile design codes in China use the elastic resistance method to describe the relationship between the lateral soil resistance and the horizontal displacement of the pile, but this is not accurate enough to analyze the internal force and deformation of the pile when the pile displacement is large. For this case, the passive load on the pile shaft caused by the adjacent surcharge load can be described in stages, and the p–y curve method can be used to express the relationship between the lateral soil resistance and the horizontal displacement of the pile. Additionally, taking both the active load (vertical force, horizontal force, and bending moment on the pile top) and the passive load into account, the deflection differential equation of the pile shaft is herein established, and a corresponding finite difference method program is implemented to obtain the calculations pursuant to the equation. The correctness of the analysis method and program was verified by two test cases. The results show that our calculation method can effectively judge the flow state of the soil around piles and accurately reflect the nonlinear characteristics of pile-soil interaction. Moreover, the influence depth of the pile displacement under the passive pile condition caused by the adjacent load is significantly greater than that under active pile condition, and the maximum pile-bending moment appears near the interface of soft and hard soil layer.

Effect of eccentricity on ultimate lateral unit earth pressure of tetrapod piles in clay

This study investigates the ultimate lateral unit earth pressure of rigid tetrapod foundation imposed by eccentric loads, based on a couple of two-dimensional adaptive finite-element limit analyses with lower-bound, upper-bound and 15-node mixed Gauss element formulations. A parameter study is conducted to emphatically explore the influence of eccentricity as well as to assess the role of additional parameters such as soil–pile interface strength and pile spacing on the normalised lateral earth pressure factor Np. Results from the numerical analyses reflect that the presence of loading eccentricity may lead to significant reduction in lateral soil resistance, the maximum diminution is up to 45% for the case that eccentricity equals to 0·5 times spacing. Three representative failure mechanisms are identified associated with various eccentricities. Pile spacing and interface strength additionally affect the variation of failure mechanisms with eccentricity increases. Finally, the eccentricity reduction factor, defined as the ratio of the Np considering the effect of loading eccentricity to the Np omitting this effect, is proposed, and the variation of this factor with eccentricity is presented for different values of pile spacing and soil–pile adhesion factor.

Ultimate soil resistance of the laterally loaded pile in uniform sand

Piles have been widely used as foundations to resist lateral loads. For the design of a laterally loaded pile, one of the most important inputs is the ultimate soil resistance ( [Formula: see text] , where Kultis the ultimate lateral soil resistance coefficient, D is the pile diameter, and [Formula: see text] is the vertical effective stress). However, great discrepancy can be found in the existing design equations for piles in sand. To provide new insights and clarify the discrepancy in previous studies, in this study, a series of numerical simulations were performed on piles of different configurations using the finite element model validated by centrifuge pile tests. The computed results suggest that Kultis a function of depth ratios z/ D and z/ L for the flexible and rigid piles, respectively (where z is the absolute depth and L is the embedded pile length), and all existing design equations failed to reproduce the magnitude and distribution of Kult. Additionally, the Kultof horizontally translated fixed-head rigid piles exhibits the same pattern as that of free-head flexible piles, suggesting that the difference between free-head flexible piles and rigid piles is caused by the change of failure modes.

A lateral soil resistance model for XCC pile in soft clay considering the effect of the geometry of cross section

A lateral soil resistance model for XCC pile in soft clay considering the effect of the geometry of cross section

Effect of loading eccentricity on the ultimate lateral resistance of twin-piles in clay

This paper studies the effect of loading eccentricity and pile spacing on the ultimate lateral soil resistance of twin-piles using finite element limit analysis and analytical upper bound plasticity methods. Two kinematic mechanisms corresponding to the failure modes produced by the advanced finite element simulations are postulated with different eccentricity and pile spacing cases. Comparisons have shown excellent agreements between the two approaches. A series of parametric studies are then subsequently performed. Numerical results have shown that loading eccentricity considerably affects ultimate lateral soil resistance, leading to a maximum reduction of 50%. In addition, the curve of normalised pile resistance versus pile spacing ratio is dissimilar to that without considering the effect of loading eccentricity. The proposed solutions and failure mechanisms in this study will provide a deepened insight on the performance of twin-pile group under eccentric loads.

Experimental Study on Seismic Instability of Pile-Supported Structure Considering Different Ground Conditions

The stability of pile-supported structures under earthquake loads involves complex dynamic soil–structure interaction (SSI). A series of large-scale shaking table experiments was performed to investigate the seismic performance and SSI of pile-supported structures considering different ground conditions. Lateral soil resistance and dynamic displacements of superstructures located in nonliquefiable and liquefiable sites as well as a rigid foundation were measured during shaking tests. The measured responses were analyzed to investigate the P-Δ effect on structural stability. It was observed that the soil lateral resistance to the pile cap at the nonliquefiable site was large and represented the main component of the lateral bearing capacity resisting structure overturning. On the other hand, the lateral resistance of liquefied soil on piles was insignificant and the lateral bearing capacity was derived primarily from soil resistance to pile cap. The analysis of the measured dynamic displacements demonstrated that the seismic instability of the structure was mainly due to the P-Δ effect caused by the rotation of the foundation, especially in liquefied sites. In addition, comparison with the results of base shears and bending moments with the rigid base assumption allows for an in-depth discussion of the effect of SSI on structural seismic design.

Cyclically loaded risers and pipelines in cohesive soil

Lateral resistance and lateral displacement are important design factors of risers/pipelines. This work presents the behavior of the riser/pipeline-soil interaction due to the “zig-zag” cyclic movement (combined of vertical and lateral movements). This study has been based on a series of monotonic, lateral cyclic, and T-bar tests using a single gravity model test. This study aims to evaluate (1) the fundamental mechanism of riser/pipeline-soil interaction due to the zig-zag cyclic loading, (2) large monotonic deformation at different embedment depths of 0.5 and 1.0 D (where D = pipe diameter), (3) zig-zag cyclic loading for cyclic displacement amplitudes of 0.15–0.5 D, (3) lateral resistance degradation, and (4) trench formation. The findings from this paper are that (1) the pipe tends to rise due to the behavior of light pipes during the first few cycles. Continuing towards more cycles, the pipe tends to move downward, (2) the riser/pipeline lateral resistance drops after trench formation, continuing towards more cycles, the resistance starts to lightly increase, (3) lateral soil resistance on a shallowly embedded pipe (w/D = 0.3) drops significantly after forming the trench, and it is less pronounced at increased embedment depths, and (4) the depth and width of the trench depend on the zig-zag displacement amplitude.

Prediction of the nonlinear behavior of laterally loaded piles in unsaturated soils

This paper proposes an analytical method for estimating the load versus displacement curves for laterally loaded rigid piles in unsaturated soils taking account the influence of matric suction. The distribution of lateral soil resistance along the pile in this method considers three distinct states: (i) pre-tip yield state; (ii) post-tip yield state; and (iii) ultimate limiting state. The lateral earth pressure coefficient, Kc required in this method is derived by extending the three-dimensional (3D) effect factor for drained loading. A numerical technique is also proposed which incorporates a user-defined subroutine (USDFLD) into ABAQUS for simulating the behavior of laterally loaded piles extending 3D finite element analysis taking account of nonlinear behavior of shear strength and modulus of elasticity with respect to matric suction. The proposed analytical method and numerical techniques were validated, respectively using the results of seven field studies and two laboratory tests published from the literature. In addition, close agreement was observed between the predictions of the proposed analytical method and numerical technique for a single pile example problem placed in a soil with varying groundwater table conditions. The summarized studies are promising for use in practice for the rational design of laterally loaded piles in unsaturated soils.

The influence of pipeline-backfill-trench interaction on the lateral soil resistance: A numerical investigation

Large lateral displacement of trenched subsea pipelines may be induced by ground movement, landslides, ice gouging, etc. Pre-excavated seabed soil is usually used for backfilling as a cost-effective solution. The large difference between the shear strength of the highly remoulded backfill material and the native soil may significantly affect the pipeline-backfill-trench interaction, the failure mechanisms, and consequently the lateral soil resistance. However, this challenging and less-explored aspect has not been covered thoroughly in design codes. In this paper, the influences of pipeline-backfill-trench interaction on the failure mechanism and resultant lateral soil resistance were investigated by large deformation finite element analyses. Two different methods were considered and compared, including the remeshing and interpolation technique with small strain (RITSS) and coupled Eulerian-Lagrangian (CEL) methods, to assess their relative merits for this problem. A modified Tresca model considering strain-softening effects was incorporated and a parametric study was conducted to investigate the influences of key factors including the trench geometry, stiffness of backfill material, native seabed soil properties, burial depth, and intensity of pipeline-trench bed interaction. The study showed that the ignorance of the pipeline-backfill-trench interaction by using uniform soil may result in underestimation and overestimation of the lateral soil resistance against the pipeline moving inside the backfill and into the trench wall, respectively.

Lateral soil resistance of rigid pile in cohesionless soil on slope

A modified method is proposed in this paper to evaluate the ultimate lateral soil resistance of rigid piles in cohesionless soil on slopes, which is based on wedge-equilibrium analysis. The method assumes that the soil resistance in front of the pile is compressed under the lateral load and that a wedge is formed without damage. The frontal soil resistance and side shear resistance are mainly considered and the response of the lateral resistance rigid pile in the cohesionless soil slope is described by hyperbola p-y curves. To validate the modified theoretical solution, the model is compared with the test results of the field pile and numerical simulation results. Combined with numerical simulation, the effect of slope angles on the lateral resistance around the pile is discussed. The results show that the modified theoretical solution is feasible for rigid piles in cohesionless soil on slopes.

Pile groups under vertical and inclined eccentric loads: Elastoplastic modelling for performance based design

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.