Analysis Of Pile Groups Research Articles

ALEM-FEM-BEM coupling for response analysis of pile group in laminated fluid-saturated geomaterials induced by tunnel excavation

This paper proposes a two-stage analytical methodology for predicting the response of pile groups in layered fluid-saturated soils induced by tunnel excavation. The Loganathan analytical approach is adopted for estimating the free-field response induced by tunneling. At the second phase, the solution to the surrounding soil of pile groups is employed as the kernel function based on the analytical layer-element method (ALEM). Subsequently, the analysis of soil-structure interaction is presented using the boundary element method (BEM). The Timoshenko-beam model is utilized to simulate each monopile combined with finite element method (FEM). Finally, the responses of adjacent pile groups are derived by the coordination conditions and coupling of BEM and FEM. Comparisons are made between the presented analytical solutions and existing experimental and numerical results. Parametric analyses are performed to evaluate the influence of soil permeability, material stratification, tunnel-pile distance, tunnel buried depth, and pile slenderness ratio on the mechanical behavior of grouped piles. The results show that the pile group in hard top and soft bottom saturated soils demonstrates better load-bearing capacity than that in soft upper and hard lower soils. Then, with the increment of tunnel-pile distance, the displacement and bending moment are reduced by 22.2 %-50 % and 41.2 %-66.7 %, respectively, and the increased rate of mechanical response over time slows down. Moreover, increasing the burial depth reduces the displacement by 8.6 %-33.3 % and the bending moment by 33.4 %-50 %, respectively, and the locations of peak responses increase from 0.6 times the pile length to 0.8 times the pile length.

Analysis of Pile Group under Vertical Loading in Clay and Sand using FEM

Abstract: Pile foundations are the preferred choice for supporting heavy structures when hard bedrock is situated at considerable depths beneath weak soil conditions. The ultimate load-carrying capacity of these piles hinges on several factors, including material composition, soil properties, geometric attributes, and the mechanism of load transfer (end bearing or friction). This research focuses on investigating the load-bearing capacity and settlement characteristics of end-bearing piles in both soft clay and medium sand. The study explores these parameters by varying pile diameter, length, and spacing within a pile group. Utilizing ANSYS for analysis, the study draws comparisons between clay and sand. The study's findings reveal that clay exhibits a higher load-carrying capacity compared to sand. Additionally, it highlights that sand experiences significantly greater settlement compared to clay when an optimal pile diameter of 0.4 meters and a length of 4 meters are employed.

Numerical analysis of pile group, piled raft, and footing using finite element software PLAXIS 2D and GEO5

Foundation plays a vital role in weight transfer from the superstructure to substructure. However, foundation characteristics such as pile group, piled raft, and footing remain unfolded due to their highly non-linear behaviour in different soil types. Bibliography analysis using VOSvierwer algorithm supported the significance of the research. Hence, this study investigates the load-bearing capacity of different types of foundations, including footings, pile groups, and piled rafts, by analyzing experimental data using finite element tools such as PLAXIS 2D and GEO5. The analysis involves examining the impact of various factors such as the influence of surcharge and the effect of different soil types on the load-bearing capabilities of the different types of foundation. For footing, parametric investigations using PLAXIS 2D are conducted to explore deformational changes. Pile groups are analyzed using GEO5 to assess their factor of safety (FOS.) and settling under various criteria, such as pile length and soil type. The study also provides insight into selecting the right type of foundation for civil engineering practice. Findings showed that different soil types have varying deformational behaviours under high loads with sandy soil having less horizontal deformation than clayey soil. Also, it was observed that increasing the pile thickness by 50% resulted in a reduction of 13.88% in settlement and an improvement of 16.66% in the FOS. In conclusion, this study highlights the importance of professionalism, exceptional talent, and outstanding decision-making when assessing the load-bearing capabilities of various foundation types for building structures.

Dynamic Interaction Factor of Pipe Group Piles Considering the Scattering Effect of Passive Piles

Based on the plane–strain assumption, a calculation model of pile–soil–pile vertical coupling vibration response considering the scattering effect of passive piles is established in this paper. Using this model, the vertical displacement expressions of pile core soil and pile surrounding soil, soil displacement attenuation function, and longitudinal complex impedance are obtained. Then, based on the strict pile–soil coupling effect, the displacement of the active pile under vertical load and scattering effect, as well as the displacement of the passive pile under incident waves, are solved separately. A new type of dynamic interaction factor for pipe group piles is derived by introducing scattering effect factors. A numerical example shows that the degenerate solution in this paper is in good agreement with the existing solution, which verifies the rationality of the solution. Considering the scattering effect is helpful in improving the accuracy of vibration response analysis of pile groups. The variation in parameters such as slenderness ratio, pile spacing, and outer diameter has significant effects on the interaction factor, and compared with the solid pile, the influence of parameter change on the pipe pile is smaller.

Thermo-visco-elastic analysis of thermomechanical behavior of energy pile groups considering time-dependent deformation characteristics of soils

Energy piles are increasingly being exploited worldwide for their dual functions of bearing structural loads and utilizing geothermal energy. However, scarce knowledge is available on the time-dependent thermomechanical behavior of energy pile groups constructed in soft soils. In this paper, an analytical approach was proposed for the thermomechanical analysis of energy pile groups considering the time-dependent deformation of viscoelastic soils and validated against field test data. The impact of the soil creep behavior on the axial load–displacement response and pile-soil-pile interaction of the energy piles was further investigated. Finally, a simplified method and design charts were provided for displacement estimation and design of energy pile groups in soft soils. The results indicated that the displacement of energy piles would change with time until stabilization because of the viscous properties of the soil. The interaction between energy piles was directly related to the pile-soil stiffness ratio, the soil viscosity coefficient, the pile slenderness ratio, the pile spacing, and the number of piles. The soil creep behavior would result in a decrease in the displacement ratio of energy pile groups under thermal loading and an increase under mechanical loading.

Optimal intensity measure selection and probabilistic seismic demand model of pile group supported bridges in sandy soil considering variable scour effects

Scour of pile group foundations is a common hazard for cross-river bridges and can produce considerable damage to piles in earthquake-prone regions. The fragility-based performance assessment for pile group supported bridges subjected to earthquake and scour hazards has drawn increasing attention from engineering practice and academic communities. Such assessment requires numerical models that are computationally efficient and accurate in describing the mechanical behavior associated with the complex soil-pile interaction of these soil-bridge systems. Additionally, selecting an optimal ground motion intensity measure (IM) is generally required for such assessments. However, modeling the pile group effect for seismically excited pile groups and the optimal IM for the scoured bridges have not been well addressed in previous related studies. To this end, a practical pile group effect modeling approach is adopted in this study and validated by a set of shake table tests on scoured pile group bridge available in the literature. Based on the validated numerical modeling approach for the soil pile interaction, a series of coupled soil-bridge models are generated considering the structural and soil parameter uncertainty and analyzed in the OpenSees platform. The optimal IM for various engineering demand parameters (EDPs) is identified from thirty-nine scalar IM candidates through the criteria of efficiency, practicality, sufficiency, and hazard computability. Finally, a straightforward form of probabilistic seismic demand model (PSDM), incorporating the effect of scour depth changes, is developed for pile group supported bridges. Results show that the increase of scour depth significantly increases the curvature demand of a pile group and statistically reduces the embedded depth of the belowground plastic hinge of the pile shaft. The rank of optimal IM candidates directly depends on the selection criteria of an optimal IM and the selection of EDP. In addition, the scour depth slightly affects the rank of optimal IMs. Generally, VSI, PGV, and Sv,1.0 are recommended for the probabilistic seismic demand analysis of pile group supported bridges in sandy soils with scour potentials.

Reliability analysis of pile group in spatially variable unsaturated expansive soil based on load transfer method

ABSTRACT Accurate assessment of pile group's performance in spatially variable unsaturated expansive soil has long been a challenge in geotechnical engineering. This paper presents a methodology to perform reliability analysis for vertically loaded pile group, where the modified load transfer method (LTM) is utilised to investigate the load–displacement response considering the pile–pile interaction and the non-linear relationship of the pile–soil interface under the influence of matric suction reduction and the swelling of expansive soil; the Karhunen–Loève (KL) expansion method is adopted to simulate the spatial variability of soil parameters; the first–order reliability method (FORM) is utilised to perform reliability analysis of each pile in the pile group; and the reliability analysis of pile group is then performed using the sequential compounding method (SCM) by considering the pile group as a parallel system. By applying the proposed methodology to a 3 × 3 pile group under different vertical loads and infiltration times, the relative magnitudes of reliability indices for different piles in the pile group and the pile group system under two failure modes of uplifting and sinking are identified. The effects of soil's spatial variability and pile spacing on the reliability of pile group are also analysed.

A simple load transfer method for energy pile groups

Various analysis methods have been developed to simulate the performance of energy pile groups subjected to thermal and mechanical loads. Although they considered the interactions between piles in the group, the ‘sheltering-reinforcing’ effect was usually ignored during the analysis, or the methods were not experimentally validated. Therefore, to address this gap, we propose an experimentally validated load transfer model that considers the ‘sheltering-reinforcing’ effect for the thermomechanical analysis of energy pile groups. The proposed method modeled two well-documented full-scale field tests and two finite-element simulation cases. The comparison results showed that the proposed method could capture several essential aspects of the energy pile group, including thermally induced strain, stress, displacement, and group effects. Furthermore, a parametric analysis was performed to evaluate the effects of relevant parameters on the thermomechanical behavior of the energy pile group.

Evaluation of Liquefaction-induced Lateral Force on Pile in Slope by Centrifuge Tests

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.

Analysis of energy pile groups subjected to non-uniform thermal loadings

Sequentially coupled thermal-stress finite element analyses were performed to investigate the mechanical behaviors of an energy pile group subjected to non-uniform thermal loadings. The group effect was highlighted by comparing the thermo-mechanical responses with those of the single pile case. Due to the thermal interactions between piles, the group piles’ temperatures were higher than that of the isolated single pile. If only part of the piles served as heat exchangers, i.e., the pile group was thermal loaded unevenly, there were differential deformations between the heated and the non-heated piles. Due to the pile-raft-pile interaction, the axial forces of the piles changed significantly. The location of the heated pile had an important influence on the thermally induced axial force, while the effect of the soil’s coefficient of thermal expansion was not significant. Inspired by the numerical result, a simplified method was proposed to capture the main characteristics of energy pile groups and to facilitate the design. The proposed method was developed in the framework of the traditional load transfer approach, and the pile-raft-pile interaction was included. By applying different temperature increments to different piles, the non-uniform thermal loading was modeled. The proposed method was verified by comparing with the finite element analysis results and the data collected from the literature.

Dynamic stability analysis of pile groups under wave load

As marine resources have been exploited in recent years, the number of offshore buildings has greatly increased. Foundations of these buildings are mainly pile and pile group foundations. Compared with the single pile, the interaction between piles in the pile group is more complicated. The dynamic stability analysis of pile groups under wave load has not been reported thus far. On this basis, based on the theory of diffraction, the modified Vlasov foundation model and the principle of dynamics, the high-order vibration differential equation is obtained. The interaction factor method and transfer matrix method are combined to establish dynamic stability equations of the active pile and passive pile. The dynamic interaction factor between piles and the group pile impedance are obtained. Parametric analysis is carried out. The ratio of the pile spacing to the pile diameter S/Dis found to be the major factor in pile group dynamic interaction. As for the pile group, the displacement of the pile u increases with increasing wave height Hlinearly and increases with increasing wavelength Lnonlinearly, both increments are much lesser than that of the single pile. the topsoil is of vital importance to the pile group impedance. In engineering practice, the pile group stability can be improved by increasing Young's modulus of the topsoil.

Strategies for Modeling Partial Pile Head Fixity in Laterally Loaded Pier Foundations

When designing pile groups subjected to lateral loading, modeling and analysis of the connections between piles and the overlying pile caps require careful consideration. For a given pier foundation, characterization of the pile-to-cap connections typically corresponds to one of: pinned (no moment transfer); fixed (moment transfer up to pile rotational capacity); or, partially fixed pile head conditions. The present study aims to provide bridge engineers with practical resources for modeling laterally loaded pile group behaviors, in association with partially fixed pile head conditions. Modeling strategies are presented for both relatively simple (i.e., highly idealized) configurations, as well as for an array of conceivable pier foundations. In particular, an analytical approach is presented, which is suitable for preliminary design of configurations analyzed in a linear elastic manner, and on a representative-pile basis. For nonlinear analysis of pile groups (including soil–structure interaction), a search algorithm is developed that converges on a given target level of partial pile head fixity and associated pile group response (e.g., group lateral displacements, pile head moments). The search algorithm is utilized to investigate 20 unique pier foundation configurations under various lateral load intensities and across target levels of partial fixity. Pairing of the computed foundation responses with the levels of partial fixity, in the ensemble, is intended to serve as a resource to bridge engineers when making initial estimates to model partially fixed pile head conditions.

Failure envelopes of pile groups under inclined and eccentric load

A novel numerical procedure for defining failure envelopes of pile groups under inclined and eccentric load is proposed. The starting point is a closed-form exact solution for interaction diagram of pile groups under combined axial-moment loading recently published in the literature. Failure envelopes in the generalised force space are then derived as an extension of this solution by means of an incremental algorithm. It is shown that the axial load at foundation level has always a beneficial effect on the lateral capacity of the pile group, even if this favourable effect is often neglected in practice. On the contrary, the amount of interaction between the horizontal and moment components of the resultant action at failure is usually very small, with the exception of piles groups with end-bearing piles. Some example applications of the proposed method are provided and a simple, yet reliable procedure for ultimate limit-state analysis of pile groups subjected to inclined and eccentric loads is suggested.

Effect of spudcan penetration on laterally loaded pile groups

Engineering cases, where jack-up rigs with large-diameter spudcan foundations operate near a jacket platform supported by pile groups, are increasing. Therefore, the group interaction of lateral-loaded pile groups should be re-evaluated. A pile group analysis method that is able to evaluate the effect of spudcan penetration on the pile group interaction is proposed in this study. This method is based on the modified Poulos method and is universally used in current ocean engineering practices. The pile group interaction-induced additional pile head deflection of a pile group, when subjected to both spudcan penetration and the influence of another pile group, is initially determined by elastic analysis. Next, the nonlinear foundation beam (NFB) method is adopted to calculate the head deflection of an isolated pile, which we utilise to calculate the head deflection of the pile group after considering the effects of spudcan penetration. Finally, the Y multiplier is obtained by several pilot modifications of p-y curves of the isolated pile in the NFB model, whose variation during spudcan penetration indicates the effect that such penetration has on the pile group interaction. Predicted results were compared with those of the centrifuge model test, and further with numerical simulation results, in order to prove the validity of the method in analysing a free-head and a fixed-head pile group.

A simplified method for geotechnical analysis of energy pile groups

A simplified method for geotechnical analysis of energy pile groups

Reliability Analysis of Settlement of Pile Group in Clay Using LSSVM, GMDH, GPR

Robust and reliable design at certain levels of safety has earned lot of attention in recent. To build over the limitations of FOSM based reliability analysis, the paper proposes least square support vector machine (LSSVM), The Group Method of Data Handling (GMDH) and Gaussian process regression (GPR) based reliability analysis of pile group resting on cohesive soil. LSSVM is an improvement over support-vector machines (SVM) which uses linear systems instead of complex quadratic equations. GMDH is a self-organized neural network capable of solving complex non-linear problems. GPR is an effective Bayesian tool of machine learning the performance of the developed models is ascertained using various statistical parameters and Taylor curves. The reliability indices of the simulated values are compared to that of the actual values obtained from FOSM. The results show that all the models are applicable for reliability analysis of settlement of pile group.

Seismic Analysis of Pile Group with Different Variations in Dimensions and Parameters

As per demand of current construction many project are running such as metro construction, bridges, tall building, industries, etc. In such type of construction where the soil bearing capacity (SBC) is very low it is necessary to provide pile foundation. Dynamic analysis is also necessary to be carried out for different pile group for earthquake. The stress resting action increases with the group action of piles. In the present study, describe about pile group, modeling of four piles and eight pile groups were done taking space between them as 2.5D and 3D, where D is the dia. of the pile. Diameter of four pile group is 0.6 and diameter of eight pile group is 0.4, shape chosen to arrange the pile group are Rectangle, Square, Diamond and Staggered. The analysis of different shape pile groups has done using the response spectrum method based using STAAD Pro. Parameters such as displacement, shear force (SF) and bending moment (BM) were taken in consideration for pile group analysis. Pile cap is analyzed for bending moment in ‘y’ and ‘z’ direction.

P-y Curves of 2x2 pile group in liquefiable soil under dynamic loadings

The seismic analysis of pile groups subjected to lateral and axial loads is often implemented separately. As a result, the calculated bending moment and deflection are found to be nonrealistic in nature, as compared with conditions where a combined analysis is carried out. In reality combined loadings are encountered in almost all situations and the occurrence of pure loadings (either lateral or vertical) is either nonexistent or scarce. In the present study, the numerical analysis of a 2 × 2 pile group under the action of combined loadings (lateral load, vertical load, and seismic ground motions) and embedded in a layered soil is carried out using the FLAC3D computer program. The liquefiable soil layer is modeled using the Mohr-Coulomb with Byrne constitutive model, while the non-liquefiable soil layers are modeled with the conventional Mohr-Coulomb constitutive model. The pile group is considered an elastic model. The proposed numerical model is validated with the existing dynamic centrifuge test results and good agreement between the results is observed. Finally the dynamic P-y (P denotes the lateral load applied at the pile cap and y is the lateral pile group deflection at the pile head) curves are generated for different combinations of vertical load, lateral load, and input seismic ground motions in liquefiable and non-liquefiable soil. It is observed that for a constant vertical load (V) having a magnitude equal to 0.50 times the ultimate pile load capacity (0.50Vult), the pile group deflection increases by 36% when the lateral load increases from 300 to 900 kN, while the increase is by 48.5% for V = Vult and for the same increase in the lateral load. Similarly 2001 Bhuj and 2011 Sikkim motions caused an amplification of deflection by 8.4 and 9 times, respectively. The influence of vertical loads increases the pile head displacement and should be considered for determining the dynamic P-y curves. The proposed dynamic P-y curves will be beneficial to geotechnical engineers for understanding the qualitative response of pile groups under combined loading conditions.

A new dynamic interaction factor for the analysis of pile groups subjected to vertical dynamic loads

Τhis paper presents an analytical method for calculating the steady-state impedance factors of pile groups of arbitrary configuration subjected to harmonic vertical loads. The derived solution allows considering the effect of the actual pile geometry on the contribution of pile-soil-pile interaction to the response of the group, via the introduction of a new dynamic interaction factor, defined on the basis of soil resistance instead of pile displacements. The solution is first validated against a published solution for single piles that accounts for the effect of pile geometry on the generated ground vibrations. Accordingly, we show that the derived soil attenuation factor agrees well with existing solutions for pile groups in the high frequency range, but considerable differences are observed in both the stiffness and damping components of the computed impedance when the relative spacing between piles decreases. Numerical results obtained for typical problem parameters suggest that ignoring pile geometry effects while estimating the contribution of pile-soil-pile interaction in the response may lead to inaccurate results, even for relative large pile group spacings.

A Review: Earthquake Analysis of Pile Group with Different Variations in Dimensions & Parameters

A Review: Earthquake Analysis of Pile Group with Different Variations in Dimensions & Parameters