Pile Groups Research Articles

Seismic Behavior and Failure Mechanism of Pile-Group in Mildly Sloping Liquefiable Soils with Crusts: Large-Scale Shaking Table Experiment

ABSTRACT A one-g shake table experiment was performed to reveal the failure mechanism of the pile group in sloping liquefiable soils with crusts. The results show that the shallow saturated sand exhibits the alternate behavior of dilatancy and shrinkage, which induces high-frequency peak acceleration. In addition, larger PGA tends to transfer vulnerable positions of the pile in the liquefiable layer from the shallow layer to the interface. Moreover, the pile group effect mainly manifested in piles at the bottom of saturated sand and pile-head during strong earthquakes.

Nonlinear optimization design of pile foundation based on settlement control principle

How to take certain measures to minimize the differential settlement of buildings is one of the urgent problems to be solved in the current pile-raft foundation design. In this paper, the nonlinear optimization design of pile foundation based on the principle of settlement control is developed. For the soil around the pile group, considering its nonlinear characteristics, when it yields, the ideal elastic-plastic model is adopted for calculation. Through numerical simulation, combined with the results of model test and field observation, some practical research results are obtained: the smaller the elastic modulus coefficient is, the flatter the load-settlement curve of CPF (Composite pile foundation) is, and the larger the fixed value is, the load-settlement curve is abrupt. Using settlement control to design rigid pile composite foundation has clear settlement. As a supplement to the insufficient bearing capacity of foundation soil, pile foundation makes full use of the bearing capacity of soil between piles. The design scheme is more economical, and it is a good nonlinear optimization method of pile foundation.

Practical macro‐element for vertical and batter pile groups

AbstractThis paper presents a novel macro‐element for vertical and batter pile groups. The numerical scheme is based on de‐coupled, single pile response. Each pile consists of two separate load‐displacement formulations (axial and transverse) that take a displacement increment as input and return a diagonal tangent stiffness value. The effect of rotation is implicitly incorporated in the transverse load‐displacement formulation. The presented macro‐element does not require pre‐defined failure surfaces or other parameters, and is therefore not restricted to a specific foundation configuration, soil profile or soil type. The macro‐element may be calibrated using any type of non‐linear pile‐soil model. The developed macro‐element is validated using rigorous numerical models for a variety of configurations.

An Analytical Method Evaluating the Evolution of Group Effect for Vertically Loaded Pile Groups Subjected to Tunnel Excavation

Tunnel excavations near existing vertically loaded pile groups are frequently encountered in urban areas, and most available studies have focused on the additional deformation and stress induced in the pile group, lacking in consideration of the variation in the pile-soil interaction (PSI) in the process, which plays an important role in pile group behavior with close pile spacing. In addition, for vertically loaded pile groups subjected to excavations in their proximity, the combined actions of the overlapping stress and shielding effect can lead to complicated variations in the group effect, which in turn results in difficulty in evaluating the PSI relationship and the pile group response. Thus, the modified Poulos method is extended in this paper to account for the effects of tunneling, and the variations in the group effect, load redistributions and pile settlements are also investigated. The validity of the proposed method is firstly verified by an available centrifuge model test with tunneling near a 2 × 2 fixed-head pile group. Further, the influences of the pile spacing and relative distance between the pile group and the tunnel are analyzed, and the most unfavorable working condition could be a tunnel excavated near the soil surface, close to a pile group with a small pile spacing.

Experimental and numerical study of group effect on the behavior of helical piles in soft clays under uplift and lateral loading

The applications of helical piles have grown significantly and they have become more popular for construction, especially as a potential offshore foundation system in recent years, owing to their distinct benefits over alternative systems. Helical piles may be installed in groups to support heavy loads; therefore, a reliable design requires an accurate assessment of their behavior. The present study used finite element modeling to extensively analyze the uplift and lateral behavior of group piles installed in soft clay soil. The problem was modeled using Plaxis 3D software, and the model was validated using laboratory scale model test data. The validated model is then utilized to investigate the group effect for three distinct configurations, namely rectangular, triangular, and square patterns, with helical piles placed at varied center-to-center spacing's. The term “group efficiency” is used to describe the group effect of each group on the ultimate capacity. The findings showed that the group efficiency is significantly influenced by the number of piles, center-to-center pile spacing, and the failure criteria assumed to interpret test data. The load-transfer mechanism was also investigated and reported for varying group configurations. Finally, for the assumed failure criteria, the provision of an optimum spacing ratio is suggested for both tensile and laterally loaded group helical piles.

Laboratory investigations on the thermo-mechanical behaviour of an energy pile group operated in heat release mode

Compared to the single energy pile, the thermo-mechanical behavior of pile group become more complicated due to mutual influences of different piles. A model test device of pile group with 2 × 2 layout was built to study the thermo-mechanical characteristics of pile group with different number of energy piles, inlet temperatures and connection forms of buried pipes. The results show that compared to single energy pile, the energy pile group mode will lead to the decrease of heat exchange performance and the increase of pile tip soil pressure and pile head displacement. But, the side friction and axial force of pile will decrease as a result of pile group effect. Meanwhile, increasing the inlet temperature can enhance heat exchange characteristics of pile group, but it will also result in the increase of the soil temperature, pile head displacement, pile tip soil pressure, pile shaft axial force and pile side friction. Additionally, reducing the number of energy piles in pile group can improve the heat exchange rate per unit pile depth, but the total heat transfer amount of energy pile group will decrease. With the increase of the number of energy pile in pile group, the temperature change and pile head displacement of the pile increase, but the pile side friction and pile body axial force decrease. Under current experimental conditions, the pile head displacement and pile body axial force in parallel connection mode are larger than those in series connection modes, and the pile body excess temperature is the smallest in parallel mode of four energy piles and the largest in series mode of four energy piles. For the series connection mode, the heat exchange performance, pile body excess temperature, pile head displacement and pile body axial force gradually decrease along the series direction due to the decrease of temperature change.

Random wave action on pile group foundations with complex geometry for sea-crossing bridges

To explore the mechanical properties of pile group foundations (PGFs) with complex geometry in sea-crossing bridges under ocean wave action, this study develops a numerical model for predicting wave loads on PGFs under multidirectional random wave action. Furthermore, an experimental model of the PGF composed of a quasi-elliptical pile cap and 13 tilted piles is designed and made based on the gravity similarity criterion. By performing model experiments and numerical analysis, the mechanical characteristics of the PGF model under random wave action, the effect of principal wave direction angle and random wave directionality, and the influence of the pile cap on wave loads of tilted piles are systematically investigated. The results show that the calculated results of the presented numerical model match well with the experimental data. The frequency characteristics of wave loads on the PGF model are mainly determined by the wave spectrum. The increase of the significant period improves the contribution of the pile group to the horizontal wave loads on the PGF. The effect of the principal wave direction on the vertical wave loads on the PGF is not obvious under the experimental wave conditions. Neglecting the wave directionality will overestimate the wave loads in the principal wave direction and vertical direction on the PGF. Under the influence of diffraction waves from the pile cap, the wave loads on the pile group and the piles where the wave finally acts are easily amplified when the wave number is small, but in the large wave number case, the wave loads on the pile group and the piles below the middle of the pile cap may be weakened.

Experimental Investigation of the Coupling Effect of Jackup Offshore Platforms, Towers, and Seabed Foundations under Waves of Large Wave Height

A large number of jackup offshore platforms with towers are widely applied in ocean engineering. The dynamic response of the platforms to waves of large wave height is critical, as such waves may cause platform accidents, property damage, and casualties. Therefore, it is important to investigate the coupling effect of jackup offshore platform, towers and seabed foundations under waves of large wave height. In this study, the coupling effect of offshore platforms, tower structures, and seabed foundations under the impact of waves of large wave height was studied via a physical flume model test. The experimental results show that the impact of waves of large wave height on the platforms is significant when the wave is blocked by the platform surface as the water body gathers under the platform surface, causing a pile group effect that results in the onshore piles being subjected to larger pressures than the front ones. The combined action of wave impact and pile leg squeezing force leads to an increase in the pore pressure of the foundation bed near the pile leg, and the soil near the pile leg becomes soft, revealing the mechanism of instability of the offshore platform’s pile foundation under waves of large wave height. The acceleration of the longitudinal movement of the platform increases under waves of large wave height, and the vortex-induced vibration of the platform includes the vibration along the direction of the wave and perpendicular to it. A coupled vibration effect between the tower structure and the platform occurs under waves of large wave height, reducing the vibration of the platform itself. Furthermore, damping members are installed on the tower structure, greatly reducing the natural vibration period and the motion response of the tower structure. This study provides significant enlightenment for the design of offshore platforms with towers to protect against waves of large wave height.

Uplift Load Carrying Capacity of Cylindrical and Belled Pile in Cohesive soil Bed

Foundation of some structures like transmission towers, mooring systems for ocean surface or submerged platforms, tall chimneys, jetty structures etc. are subjected to uplift loads. Literature reflects that scholars have conducted pull out field prototype and model test and failure pattern of soil is studied for belled piles in loess soil and cohesionless soil. In this research work, the authors have carried out 36 tests on single pile and pile groups and uplift load carrying capacity is obtained by experimental investigation of single pile, triangular pattern (2x1) and square pattern (2x2) using the model piles of cylindrical and belled shaped in cohesive soil of soft consistency. The piles are having 20 mm shaft diameter and varying L/d ratio of 6, 8,10,15,18 and 20 for both cylindrical pile and belled pile. Belled portion is cast in belled pile with an angle of 70° with horizontal and having base diameter of 60 mm and height 55 mm. Spacing between two piles in various pile group was kept three times the piles shaft diameter (3d) in all experiments. Based on the experimental results as the L/d ratio increases uplift load carrying capacity increases. Uplift load carrying capacity of single pile, triangular pile group and square pile group of belled pile is 410%, 280% and 240% more than cylindrical piles. Uplift load carrying capacity of triangular pile group and square pile group increases by 182% and 273% for cylindrical pile and 104% and 141% for belled pile in comparison with single pile. Failure pattern of soil is obtained from experiments performed on belled pile and by using this failure pattern, theoretical uplift load carrying of belled pile is obtained.Uplift load carrying capacity.

Testing pile foundations at the ETH Zurich drum centrifuge: recent developments

Motivated by the need to develop rational design methods for the retrofit of existing bridges on pile groups, this paper introduces recent experimental developments at the ETH Zurich drum centrifuge in Switzerland. Four set-ups are developed for vertical, pushover, combined and vibration testing. Their capabilities and limitations are demonstrated using as an example a 2 × 1 pile group on dense saturated sand. Single piles are subjected to vertical loading, exploring the role of installation effects and interface roughness. Pushover loading is employed to measure the moment capacity [Formula: see text] of a lightly and a heavily loaded group. In contrast to intuitive expectations, the heavily loaded system mobilises larger [Formula: see text]. The developed combined loading apparatus is proof-tested for a shallow foundation. Combined loading under constant vertical load is conducted to derive failure envelopes, revealing significant coupling between lateral and moment loading, and confirming the expansion of the failure envelope with increasing static vertical load. The vibration testing set-up is proof-tested, confirming the possibility of identifying the natural frequency of the system and the small-strain stiffness of the foundation through non-destructive testing. Although the study is fuelled by the ongoing work on pile groups, the developed experimental set-ups are of general applicability for the study of deep and shallow foundation systems.

Effect of Soil-Pile-Structure Interaction on Behaviour of Offshore Jacket Structure

Offshore jacket structures are generally supported on pile foundations. Studies have evaluated the effect of soil-pile interaction on design of foundation; however, effect of soil-pile-structure interaction on behaviour of jacket structure has received little attention. Hence, present study focuses on understanding the influence of soil conditions, soil-pile interaction and foundation modeling approach on deformation characteristics and member forces of jacket structure. Linear static analysis on a typical 4-legged battered jacket structure is performed using STAAD Pro., subjected to dead/live loads and environmental loads. The water depth of 120 m and wave heights of 5 m, 10 m and 15 m are considered for this study. Morison’s equation considering Stokes 5th order wave theory is used for calculation of wave forces on jacket structure. The supports are modelled as skirted pile groups. The piles are represented by springs, with stiffness calculated using soil-pile interaction analysis. The soil conditions used in the study are varied for different compaction states of sand and different consistency states of clay and various parameters such as lateral/vertical deflection, support reactions, forces in leg, beams and bracings have been compared. It is concluded that ignoring soil-pile-structure interaction during analysis of jacket structure would underestimate the lateral/vertical deflections, support reactions, shear force and bending moment for leg, and axial forces in beam and plan bracing of the structure. No substantial impact of the interaction on other member forces is observed. Jacket structure founded on clayey soil exhibits higher deformation and member forces as compared to sand in general. The study is expected to help structural engineers in adopting an appropriate modelling approach, considering soil-pile-structure interaction, to obtain more realistic response for jacket structures.

Numerical Modeling of a Pile Group Subjected to Seismic Loading Using the Hypoplasticity Model

Various simple and complicated models have been utilized to simulate the stress-strain behavior of the soil. These models are used in Finite Element Modeling (FEM) for geotechnical engineering applications and analysis of dynamic soil-structure interaction problems. These models either can't adequately describe some features, such as the strain-softening of dense sand, or they require several parameters that are difficult to gather by conventional laboratory testing. Furthermore, soils are not completely linearly elastic and perfectly plastic for the whole range of loads. Soil behavior is quite difficult to comprehend and exhibits a variety of behaviors under various circumstances. As a result, a more realistic constitutive model is needed, one that can represent the key aspects of soil behavior using simple parameters. In this regard, the powerful hypoplasticity model is suggested in this paper. It is classified as a non-linear model in which the stress increment is stated in a tonsorial form as a function of strain increment, actual stress, and void ratio. Eight material characteristics are needed for the hypoplastic model. The hypoplastic model has a unique way to keep the state variables and material parameters separated. Because of this property, the model can implement the behavior of soil under a variety of stresses and densities while using the same set of material properties.

A Review of Pile Foundations in Viscoelastic Medium: Dynamic Analysis and Wave Propagation Modeling

The dynamic viscoelastic theory of soil–pile interaction dominates the initial impedance calculation during the pile dynamic design and analysis. Further, it provides a firm theoretical ground for the wave propagation simulation, which could be the basis of seismic analysis and some geotechnical testing approaches. This review traces the development history and key findings of viscoelastic soil–pile interaction theory and expounds on the advantages and limitations of various theoretical advances in terms of dynamic design and wave propagation modeling. The review consists of three sub-divisions, which are the longitudinal, horizontal, and torsional viscoelastic soil-pile theories. The development and implement of multi-phase soil constitutive equations, multi-dimensional soil–pile interaction modeling methods, pile–soil–pile mutual interactions in pile groups, and the fluid–structure interaction problems in offshore piles are especially remarked and concluded. Finally, the shortcomings and deficiencies of the present development are pointed out with a view to addressing them in the future.

Optimized active learning Kriging reliability based assessment of laterally loaded pile groups modeled using random finite element analysis

This paper presents an optimization of the Active learning Kriging (AK) reliability assessment of laterally loaded pile groups modeled using random nonlinear finite element (FE) where the spatial variability in the soil response is discretized using three dimensional (3D) random fields. The input functions of the AK including the regression, correlation, and the learning functions (called AK configuration herein) are optimized for four AK based reliability estimation techniques: AK Monte Carlo simulation (MCS), AK first order reliability method (FORM), AK importance sampling (IS), and AK self-normalizing importance sampling (LS). The optimal AK configurations are obtained using an extensive parametric analysis (4320 reliability assessment analyses). Two rational-based methods are adopted to propose the optimal AK configurations: accuracy-based priority ranking and consistency-based priority ranking. Summary tables of the optimal AK configurations are included in the paper. The proposed optimal AK configurations can be used by engineers to assess the reliability of pile group-soil interaction problems using AK and random FE analysis.

Design of an Energy Pile Based on CPT Data Using Soft Computing Techniques

The present study focused on the design of geothermal energy piles based on cone penetration test (CPT) data, which was obtained from the Perniö test site in Finland. The geothermal piles are heat-capacity systems that provide both a supply of energy and structural support to civil engineering structures. In geotechnical engineering, it is necessary to provide an efficient, reliable, and precise method for calculating the group capacity of the energy piles. In this research, the first aim is to determine the most significant variables required to calculate the energy pile capacity, i.e., the pile length (L), pile diameter (D), average cone resistance (qc0), minimum cone resistance (qc1), average of minimum cone resistance (qc2), cone resistance (qc), Young’s modulus (E), coefficient of thermal expansion (αc), and temperature change (ΔT). The values of qc0, qc1, qc2, qc, and E are then employed as model inputs in soft computing algorithms, which includes random forest (RF), the support vector machine (SVM), the gradient boosting machine (GBM), and extreme gradient boosting (XGB) in order to predict the pile group capacity. The developed soft computing models were then evaluated by using several statistical criteria, and the lowest system error with the best performance was attained by the GBM technique. The performance parameters, such as the coefficient of determination (R2), root mean square error (RMSE), mean absolute error (MAE), mean biased error (MBE), median absolute deviation (MAD), weighted mean absolute percentage error (WMAPE), expanded uncertainty (U95), global performance indicator (GPI), Theil’s inequality index (TIC), and the index of agreement (IA) values of the testing data for the GBM models are 0.80, 0.10, 0.08, −0.01, 0.06, 0.21, 0.28, −0.00, 0.11, and 0.94, respectively, demonstrating the strength and capacity of this soft computing algorithm in evaluating the pile’s group capacity for the energy pile. Rank analysis, error matrix, Taylor’s diagram, and the reliability index have all been developed to compare the proposed model’s accuracy. The results of this research also show that the GBM model developed is better at estimating the group capacity of energy piles than the other soft computing models.

DESIGN OF MARTAPURA RIVER BRIDGE STRUCTURE, BANJAR REGENCY

The Martapura River Bridge is located on Jalan A. Yani KM 40 Martapura, Banjar Regency, South Kalimantan. Traffic processes that occur on Jalan A. Yani KM 40 Martapura often experience problems because congestion often occurs and the condition of the old IA bridge sometimes makes driving users feel restless when crossing the bridge located on the Martapura river. So that at the location of the Martapura river, it is deemed necessary to build a bridge next to the IA bridge so that the IB bridge to be built can be more sturdy and durable so that there is no anxiety for driving users and also to reduce congestion that occurs, where later the IB bridge will be used as a road with one way only towards Banjarmasin and the martapura IA bridge will be used as a one-way road towards the Hulu Sungai so that it will make it easier for traffic on Jalan A. Yani KM 40 Martapura.
 The methodology used in loading planning refers to SNI 1725-2016 concerning Loading Standards for Bridges. For the methodology in calculating the stress loss, refer to the NAASRA Bridge Design Specification on Chapter VI Bridge Design Specifications (Prestressed Concrete Design). For the methodology in calculating the moment of the vehicle floor using the Three Moment Equation method and for the method of subsidence of group pile foundations using the method of Schultze and Sheriff (1973), assuming that the pile group is the Equivalent Raft Foundation. The material used in the design of the upper structure is prestressed concrete, while the lower structure is planned to use reinforced concrete with a square pile.
 The results obtained are the T-Girder Prestressed type bridge with class A, 34 m span, 7 m traffic width, and 1 m wide sidewalk. Prestressed T-Girder is designed using fc' 40 MPa (K-482) Strands used are uncoated 7 wire super strands ASTM A-416 grade 270 with a diameter of 12.7 mm and an area of 100 mm2 with a tensile strength of 1860 MPa. As for the lower structure, the abutment uses concrete with a quality of fc' 25 MPa (K-300) with a height of 565 cm, a width of 480 cm and a length of 1050 cm.type piles Square Pile with a length of 15 m with a quality of 50 MPa (K-600) with a width of 60x60 cm with a configuration of 18 piles for each abutment. Estimated Budget Plan The cost of constructing the Martapura river bridge is IDR 8,129.511,475.00.-.

Pile group in clay subjected to cyclic lateral load: Numerical modelling and design recommendation

Major structures like offshore platforms, wind turbines, transport infrastructure, tall buildings, etc., resting on soft compressible clays, are often supported by pile foundations. Apart from usual vertical loading (dead load, live load, etc.), these piles are subjected to significant cyclic loads arising from actions of waves, ship impacts, winds or moving vehicles. Under such circumstances, the lateral mode of cyclic loading is predominant and affects the overall foundation stability. Such repetitive loading leads to stress reversal in adjacent soft clay initiating progressive degradation in soil strength and stiffness, deteriorating the pile capacity with unacceptable displacements. Although several past studies investigated the response of single pile under lateral cyclic loading, a detailed investigation on pile group in clay subjected to cyclic lateral loading, which is of immense practical interest to field engineers, is yet to be carried out. In this paper, in-depth study has been carried out by developing a three-dimensional dynamic finite element model. Comparison of the computed results with available test data validates the numerical model. Extensive parametric studies with field data indicate that both the axial and lateral pile capacities and displacements have been significantly influenced by the cyclic loading parameters. Relevant design curves are also constructed.

Pile Groups and Piled Footings Bearing in Weakly Cemented Residual Soil

Pile Groups and Piled Footings Bearing in Weakly Cemented Residual Soil

Evaluation of the Influence of De-sanding (Recycling System) Process on the Pile Bearing Capacity Using Full Scale Models

The present study investigates the effect of the de-sanding (recycling system) on the bearing capacity of the bored piles. Full-scale models were conducted on two groups of piles, the first group was implemented without using this system, and the second group was implemented using the recycling system. All piles were tested by static load test, considering the time factor for which the piles were implemented. The test results indicated a significant and clear difference in the bearing capacity of the piles when using this system. The use of the recycling system led to a significant increase in the bearing capacity of the piles by 50% or more. Thus it was possible to reduce the pile length by (15 % or more) thus, and implementation costs were significantly reduced. Furthermore, casting time for the pile group in which the system is used is less than for the pile group that did not use it (approximately half an hour per pile), and the amount of concrete was greater by an average of 2 cubic meters for each pile.

Analysis Stability of Abutment on the Railway Bridge

Railway bridge Bangunan Hikmah (BH 39) Pariaman (Padang– Pariaman Route) is a new bridge. This new bridge was built because the old one could not accommodate the load of the additional locomotive. The railway bridge consists of two parts: the upper structure and the substructure. The substructure consists of abutments and foundations. When the abutment accepts considerable lateral ground pressure, so the stability of the abutment will be disturbed. To resolve the problem, the need exists to study abutment reinforcement with geotextile or additional foundation pile to raise the stability abutments on the Railway bridge Bangunan Hikmah (BH 39) Pariaman. The result of the loading on the upper structure is obtained. The total vertical force acting on the abutment is 6111,624 kN, and the horizontal load is 2849,689 kN. Abutment stability analysis is carried out in 3 stages (without reinforcement, with reinforcement geotextiles, and with existence foundation pile (bored pile). The results of the analysis show value safety factor minimum without Reinforcement (SF) is 1,29; this shows that the abutment is unstable because the safety factor obtained is < 1.5,  with reinforcement geotextile, the value of the safety factor minimum  (SF) is 1,66,  this indicates that the abutment is stable but still critical and the value of the safety factor (SF) minimum with bored pile foundations is 2,10.  Installation of a bored pile foundation (pile group) at a depth of 10m shows a significant increase in the value of the safety factor. In the BH 39 Kurai Taji Pariaman railway bridge project, it is recommended to use a pile group foundation with a depth of 10 m.