Behavior Of Piles Research Articles

Time dependent thermal behavior of geothermal energy pile (GEP) for summer and winter periods using CFD analysis

This study investigates the thermomechanical behavior of geothermal energy piles, which serve the dual function of providing structural support and facilitating heat exchange with the surrounding ground. The thermal energy transfer is achieved by circulating a working fluid through U-shaped heat exchanger pipes embedded in the pile, enabling cooling during summer and heating in winter. Unlike conventional piles, the thermomechanical coupling in energy piles alters their load transfer mechanisms, with distinct responses during summer (cooling) and winter (heating) periods that require separate evaluation. While energy pile modeling is relatively new compared to borehole systems, both share operational similarities. To explore this, a numerical simulation was conducted using ANSYS Fluent, incorporating a polyethylene tube, concrete, and surrounding soil. The analysis was performed under various Reynolds numbers (500, 1000, 1500, and 2000) and time intervals (60 min, 360 min, and 720 min) to capture the time-dependent thermal behavior for both cooling and heating periods. The simulations demonstrated satisfactory outcomes, suggesting promising potential for geothermal energy applications in Algerian residential buildings.

Bearing behaviors of rock-socketed piles in layered dynamically compacted soil-rock mixtures: A case study

After layered dynamic compaction (DC) treatment in a mountainous area with deep backfill in Chongqing, China, a series of pile tests and analyses were conducted to evaluate the vertical bearing capacity of rock-socketed piles and to investigate their mechanical characteristic and load-bearing behavior. Static pile load tests (SPLT) were carried out on three types of rock-socketed piles with different diameters (800 mm, 1000 mm, and 1200 mm). Based on the test data of pile reinforcement stress, the pile axial force, frictional resistance, and load-sharing ratio were calculated and analyzed. The results indicate that load-settlement curves of static load tests for all piles change progressively, and the S-lgt curves are relatively straight lines without obvious downward bending. The pile axial force exhibits the characteristics of “large at the top and small at the bottom”, resulting in stress concentration at the pile top, especially prominent in longer piles (lengths of 33.2–37.1 m). Additionally, the overall frictional resistance increases with the increase of pile top load. In shorter piles (lengths of 16.5–22.6 m), the frictional resistance presents a C-type curve with depth, while in longer piles, it presents an S-type curve distribution. Comparatively, the test pile bears the upper load mainly by the side friction resistance, which is more prominent in the longer pile. With the increase of pile top load, the load-sharing ratio of side friction decreases and the load-sharing ratio of pile tip resistance increases.

Vertical bearing behavior and pile group effect for cemented-soil composite pile groups based on on-site experiments

Bearing characteristics and interactions of a pile group are complex. and there is almost no on-site full-scale test data for cemented-soil composite pile group. In this research, vertical static load tests were conducted on two isolated pile, two-pile group and six-pile group for long-core SDCM pile. The bearing behavior of long-core SDCM pile and the interaction between pile groups have been studied. The results indicate that the long-core SDCM single pile is a typical friction type pile, and cemented soil provides most of the lateral friction resistance for the bearing capacity. In pile groups, pile spacing is the main factor affecting the pile group effect. The model calculation results based on the equivalent pier method are verified using on-site test data and the key parameters in the pile group for long-core SDCM pile including pile spacing Sij, cemented soil Elastic modulus Ec and PHC pipe pile Elastic modulus Ep are analyzed using a mathematical model. Parameter analysis results indicate that the pile group interaction for long-core SDCM pile is mainly reflected in settlement. Group effect is inapparent at pile spacing greater than 4 D. The appropriate value of Ec and Ep are taken in the range of 1.2–1.6 GPa and 30–40 GPa.

Bearing capacity of eco-friendly RC short piles exposed to groundwater salts

AbstractTwenty-eight piles were divided into four groups. Two groups were made of natural aggregate, while the other two were made of full replacement of recycled aggregate. In each group, the cement was replaced with 0, 5, 10, 15, 20, 25 and 30% of silica fume. Two groups were stored for 270 days under normal water conditions, while the other two were stored underground water conditions. Tests results have shown that it’s possible to improve the strength and the structural behavior of piles under sulfate attack considerably by using 20% of silica fume, while 15% is sufficient when the piles are under normal conditions. However, high levels of silica fume 25–30% in recycled aggregate concretes piles and 20–30% in normal aggregate concretes piles gave a clear decrease in ultimate load capacity.

Analysis of the screw pile group subjected to combined V–H loading for energy application

ABSTRACT The present study investigates the behaviour of screw piles in very stiff clay under the combined vertical and horizontal loads using a three-dimensional finite element analysis. The soil is modelled using the Mohr–Coulomb elastic, perfectly plastic material, whereas the pile shaft and helices are modelled as a linear elastic material. This study examines the effect of the number of helices, helix diameter, inter-helix spacing, and pile spacing on the performance of screw piles under both vertical compression and lateral loads. The study shows that the effect of the number of helices is negligible under the combined load. The increase in the helix diameter (D h) improves the pile performance. The results also reveal that the optimum interhelix spacing is 3D h, and the optimum pile spacing is 2D h. Thus, the present study demonstrates that optimizing the geometry of the screw pile enhances its performance, making it suitable for offshore wind turbines.

Model scale tests on the behaviour of single piles in cohesive soils under combined loads

ABSTRACT Model scale tests were conducted to study the influence of combined loads (uplift + compressive, uplift + lateral, lateral + compressive and lateral + uplift) on stress distribution, ultimate capacities and deformations of single piles in Indian black cotton soils, in comparison to pure uplift and lateral loads. Numerical analysis was performed in Plaxis 3D to examine the effect of pile slenderness ratio (L p /d = 15, 20 and 25) on ultimate capacity and pile head displacements. The test results showed that uplift capacity and pile head displacements increased by 35–49% and 30–50% with an increase in staged compressive loads, respectively. Therefore, piles subjected to combined uplift and compressive loads should be designed for pile head displacements rather than uplift capacity. The compressive loads did not affect the stress distribution along the pile–soil interface. However, lateral loads altered stress distribution, resulting in a curved failure plane and a substantial increase of 80–150% in the uplift capacity of piles under combined uplift + lateral loads. The lateral load–deflection curve for 60% and 80% of staged uplift loads showed an elastic response, indicating that the pile and surrounding soil did not yield under the applied lateral loads.

Experimental study on the effect of surface-projected conditions on the mechanical behavior of pile embedded in sand

Surface-projected piles, such as helical and under-reamed piles, are widely utilized in geotechnical engineering to enhance the load-carrying capacities of pile structures with surface projection part. Despite the use of a wide variety of surface-projected conditions, detailed investigations considering various dimensions and angles of surface-projected piles remain limited in the current literature. This study aims to assess the effects of surface-projected widths wp (10 mm, 20 mm, 40 mm) and angles θ (18°, 27°, 45°, 90°) on pile penetration resistance using a two-dimensional model and PIV analysis. Wider projections increased resistance, with a maximum of 1.84 kN—57% higher than conventional piles in the model ground. Penetration resistance was proportional to width at 90°; for wp = 20 mm, penetration resistance decreased with increasing θ, while for wp = 40 mm, it increased. Theoretical ultimate bearing capacity calculations emphasize differences from experimental results due to neglected shaft friction. Residual penetration resistance and particle displacement were observed for wp of 20 mm and 40 mm after failure. This study provides insights into optimizing surface-projected pile design and understanding ground failure mechanisms.

Extended Winkler Model for design of offshore wind turbine large diameter monopiles

We propose a new model for the design of large diameter monopiles in this paper. These foundations are increasingly used for offshore wind turbines in water depths of up to 35 m. Our model extends the Winkler Model by incorporating rigid rotation effects relevant to large diameter piles, using conventional p-y and t-z curves to account for additional soil reactions. The current model primarily focuses on lateral loading; however, it is designed to accommodate axial loading as well, allowing for flexibility in future analyses should axial effects be incorporated. We demonstrate that our model adequately accounts for soil reaction due to rigid rotation by comparing its results with those of the PISA model. Furthermore, we validate our numerical results against available experimental data, showing that the proposed model can accurately predict pile behavior under lateral loading.

Experimental and numerical evaluation of sustainable application of steel slag as an alternative to gravel in compaction piles

The study investigates the application of steel slag as an innovative material for compaction piles in the stabilization of soft soils, offering an eco-friendly alternative to conventional gravel compaction piles (GCPs). Through a comprehensive series of laboratory tests, field experiments, and numerical simulations, this study evaluated the performance, environmental impact, and long-term behavior of steel slag compaction piles (SSCPs). The key findings revealed that steel slag not only provides immediate soil improvement comparable to gravel but also exhibits significant time-dependent increases in strength and stiffness. Standard Penetration Test (SPT) N-ratios (N1/N0, where N1 = N value after improvement and N0 = N value before improvement) were similar for soils reinforced with SSCPs and GCPs after 0 months, but were about 30 % higher in SSCP-reinforced soils after 3 months. This increase was attributed to the cementation of steel slags, suggesting that the compaction pile with increased stiffness due to cementation acts as a compaction pile with an increased area replacement ratio (α). Environmental assessments confirmed that steel slag meets regulatory standards for soil contamination, positioning it as a sustainable option. Settlement analysis after embankment construction showed reduced and more uniform settlements with SSCPs, suggesting superior load distribution capabilities. Finite element analysis compared the behavior of SSCP-reinforced soils at varying α and stiffness of compaction piles, confirming that the cementation of steel slag produces an effect equivalent to increasing α in uncemented piles, thus enhancing the reinforcement effect.

Field investigations on the thermo-mechanical behavior of a partially activated energy pile in Miocene sediments

The City of Vienna, as one of the largest public clients in Austria, initiated a research project to determine the load-bearing behavior of various foundation elements in typical Viennese soils. Numerous large-scale tests were carried out on bored piles, micro piles, anchors, and jet grouted columns. In addition, two energy piles were installed in different soil layers to investigate their behavior under mechanical and thermal loading in each soil layer separately. This paper discusses the energy pile in the Miocene sediments, which consist mainly of silty fine sand and some sandy silt. The energy pile – fully instrumented with strain gauges, extensometers, heat gauges and optical fiber sensors – was loaded for two and a half months. The mechanical load was kept constant throughout the thermal cycles to determine the response of the pile to thermal loads. The measured temperature data were used in numerical back-calculations to determine the thermal parameters of the soil layers and the concrete. Based on the measured strain and deformation data, the deformation behavior of the energy pile due to the thermal load was investigated. Finally, a static pile load test was carried out on the energy pile and the results are compared with those of the conventional reference piles installed in the vicinity, which have not been subjected to thermal loading. The test demonstrated that, after several weeks of cyclic thermal loading, the energy pile exhibited more favorable load-deformation behavior compared to conventional reference piles.

Fatigue Behavior of H-Section Piles under Lateral Loads in Cohesive Soil

Most structures supporting solar panels are found on thin-walled metal piles partially driven into the ground, optimizing costs and construction time. These pile foundations are subjected to repetitive lateral loads from various external forces, such as wind, which can compromise the integrity of the pile-soil system. Given that the expected operational lifespan of photovoltaic solar plants is generally 20–30 years, predicting their service life under fatigue loads is crucial. This research analyzes the response of H-section piles to lateral fatigue loads in cohesive rigid soils through four field tests, subjected to load cycles of 55%, 72%, and 77% of the static failure load, corresponding to maximum loads of 25 kN, 32 kN, and 35 kN, respectively. Additionally, the effect of load cycles on the degradation of pile-soil adhesion is studied through two pull-out tests following cyclic tests. This study reveals that soil fatigue does not occur under repetitive loads and that soil stiffness remains constant once the cycles causing soil compaction have been overcome. Nevertheless, the accumulated plastic deflection of the soil increases steadily once soil compaction occurs due to cyclic loading. The implications of these results on the fatigue life of photovoltaic solar panel foundations are discussed.

Influence of Loading Angle on Pullout Behavior of Helical Pile

Influence of Loading Angle on Pullout Behavior of Helical Pile

Damage features and mechanism of prestressed hollow square piles subjected to non-contact underwater explosion

Critical hydraulic structures are increasingly vulnerable to underwater explosion attacks, with the supporting piles being prime targets for terrorist activities. This study investigates the damage effects and mechanisms of prestressed concrete hollow square (PCHS) piles under non-contact underwater explosions. A series of underwater explosion experiments was conducted on four PCHS piles. The dynamic response of PCHS piles throughout the underwater explosion process was simulated using a coupled fluid-solid numerical model. The mechanisms of dynamic damage to the PCHS piles were elucidated through an integrated analysis of both experimental and numerical results. The research indicates that the damage characteristics of PCHS piles include longitudinal and oblique cracks on the lateral surfaces, transverse cracks on the rear side, and localized fragmentation of concrete. Three primary damage modes have been identified: bending failure(L¯c= 0.59 m/kg1/3), combined bending-shear failure(L¯c= 0.36 m/kg1/3), and punching failure(L¯c= 0.24 m/kg1/3). The local and global responses induced by shock waves are the primary causes of structural damage. Furthermore, as the stand-off distance decreases, the impact of explosive bubbles increases the magnitude of the overall response. A comparative analysis also examined the impact of prestress and axial load on the damage behavior of hollow square piles.

Bond–Slip Behavior of Concrete Pile–Cemented Soil Interface Considering Thermal–Temporal Effect: Experimental Study and Constitutive Modeling Based on Disturbed State Concept

Bond–Slip Behavior of Concrete Pile–Cemented Soil Interface Considering Thermal–Temporal Effect: Experimental Study and Constitutive Modeling Based on Disturbed State Concept

Seismic Performance of Pile Groups under Liquefaction-Induced Lateral Spreading: Insights from Advanced Numerical Modeling

Post-earthquake investigations have shown that piles in liquefiable soils are highly susceptible to damage, especially in sloping sites. This study examines the seismic performance of pile groups with lateral spreading through advanced numerical modeling. A three-dimensional finite element model, validated against large-scale shaking table test results, is implemented to capture the key mechanisms driving the dynamic response of pile groups under both inertial and kinematic loading conditions. Parametric seismic response analyses are conducted to compare the behavior of batter and vertical piles under varying ground motion intensities. The results indicate that batter piles experience increased axial compressive and tensile forces compared to vertical piles, up to 70% and 20%, respectively. However, batter piles provide enhanced lateral stiffness and shear resistance compared to vertical piles, reducing horizontal displacements by up to 20% and tilting the cap by 85% under strong ground motion. The results demonstrate that batter piles not only enhance the overall seismic stability of the structure but also mitigate the risk of liquefaction-induced lateral spreading in the near-field through pile-pinning effects. While vertical piles are more commonly used in practice, the distinct advantages of batter piles for seismic stability highlighted in this study may encourage using more advanced numerical modeling in engineering projects.

WITHDRAWN: Pullout Capacity of Piles in Unsaturated High Plasticity Clayey Soil: An Experimental Model Study

Unsaturated soils exhibit distinct physical and mechanical characteristics compared to dry or saturated soils. Ignoring the influence of unsaturation (matric suction) and assuming either dry or saturated conditions can lead to unreliable predictions of pile behavior in unsaturated soils. In this study, the pullout capacity of different physical model piles driven in an unsaturated Kaolinite-Bentonite matrix is investigated. A series of lab-scale pullout tests were carried out to examine the influence of matric suction, pile type, pile L/D ratio, and undrained cohesion (cu) of soil on the ultimate pullout capacity of model piles. Soil samples were prepared and compacted in a tank, and holes were created using a pile. Four model piles (solid and hollow stainless steel) were driven into the holes, ensuring proper spacing. Incremental loading was applied until the piles slipped out, with displacement measured by an LVDT. The pile pullout capacity increased with increased matric suction and undrained cohesion. The uplift capacity increased by 50 % to 136% as matric suction increased by 157.97% as the compaction state was changed from 0.95 γd(max) on the wet side of optimum moisture content (OMC) to 0.95 γd(max) on the dry side of OMC of the compaction curve. However, for the compaction state of 0.90 γd(max), the matric suction increased by 398.80%, leading to a 275% to 800 % increase in the uplift capacity. As the cohesion of the five samples increased from 17.84 kPa to 137.84 kPa, the uplift capacity of all the model piles increased. In Kaolinite-Bentonite mixes compacted on the dry side of OMC, hollow model piles resisted higher pull-out loads than solid model piles. The increase in uplift capacity was found to be in the range of 11.11% to 75% for different combinations of pile type and compaction density (matric suction). The results from the study imply a strong influence of matric suction, undrained cohesion, L/D ratio, and pile type on pullout capacity for piles driven in unsaturated Kaolinite-Bentonite mix.

Experimental Study on the Behavior of Single Piles Under Combined Torsional and Vertical Loads in Contaminated Sand

Experimental Study on the Behavior of Single Piles Under Combined Torsional and Vertical Loads in Contaminated Sand

Effect of Lateral Load to the Behavior of Single Piles Subjected to Earthquake Load in Sand

In fact, pile usually carry static and dynamic load in same time, the case of simulations lateral and dynamic load is possible occurred. This case is not cover enough by previous researches especially by laboratory model. Therefore, the purpose of this study is to determine the extent to which altering the horizontal lateral loads impacts the behavior of individual piles during seismic events. An experimental test was devised using a physical model with an advanced shaking table that using El Centro earthquake. Sandy soil with 65% relative density used raining technique. Lateral loads were applied at levels of 0%, 50% and 100% from allowable lateral load capacity. It was observed that when lateral load increased from 0% to 50% and 100%, the lateral displacement response decreased by 32.10% and 49.59% respectively. While the vertical displacement increased by 49.96% and 76.95%. Finally, the acceleration decreased by 34.39% and 41.03%. This is possibly due to the load acts at an angle opposite to the earthquake as a restraining factor for the pile. led to a decrease in lateral displacement, vertical displacement, and peak ground acceleration.

Analytical approach for vertical dynamic responses of stiffened deep cement mixing pile in unsaturated ground

Stiffened deep cement mixing (SDCM) piles present excellent engineering performance compared with conventional pipe piles and thus are often applied to the structure foundation in coastal soft-soil area. This study intends to explore the vertical dynamic behavior of a SDCM pile in unsaturated soil by developing an analytical approach. In the proposed approach, the SDCM pile divides into two parts. The first part is considered as a composite pile formed by a prestressed high-strength concrete (PHC) pipe pile and a cement mixing pile through high-strength bonding, and the second part formed by the PHC pipe pile and an unsaturated soil column. The closed-form solution for the dynamic impedance of the SDCM pile has been determined and then verified by contrasting with the existing solutions, where the dynamic impedance is mainly characterized by dynamic stiffness and dynamic damping at SDCM pile head in the vertical direction. Numerical discussions are finally implemented to analysis the dependence of physical parameters of cement mixing pile, PHC pipe pile, and unsaturated soil on the vertical dynamic impedance of SDCM pile. It can be concluded that increasing the depth, radius and elastic modulus of the cement mixing pile at relatively low load excitation frequencies is beneficial for enhancing the vertical vibration resistance of the SDCM pile, while the reverse is true at higher load excitation frequencies. Quantitatively, under relatively low load excitation frequencies, the reinforcement depth of the cement mixing pile should not exceed 2/3 of the length of the PHC pipe pile, while its elastic modulus should be 5 ‰ to 2 % of the elastic modulus of the PHC pipe pile.

Development of improved finite element formulations for pile group behavior analysis under cyclic loading

AbstractThe effect of cyclic loading is an essential factor leading to progressive soil strength degradation. Therefore, a comprehensive analysis of the pile‐soil system behavior under cyclic loading is required to ensure the stability of pile group. There is room for improvement in the inherent constraint of the conventional numerical model in terms of approximating the soil resistance distribution along the pile by point loads at element nodes, necessitating a specific element that integrates considerations of pile group effect and cyclic loading within a unified framework. This study aims to develop a newly specific type of element for efficiently predicting nonlinear behavior within the pile‐soil system, addressing simulations involving nonlinear pile‐soil interaction, pile group effect, and cyclic loading. Modified element formulations based on soil stiffness matrices and soil resistance vectors specifically address pile group effect and consider parameters that influence pile behavior under cyclic lateral loading. The numerical solution procedure with Newton‐Raphson iteration allows the calculation of pile responses in geometric and material nonlinear analyses. The validation of the proposed method includes several examples, comparing it with existing numerical solutions and experimental tests of single piles and pile groups under cyclic loading. These comparisons further support the consistency of the proposed method with measured data and validate its accuracy in considering group effect and cyclic loading. The parametric study illustrates the ability of the proposed method to capture cyclic loading parameters while considering the influence of the number and magnitude of load cycles, the cyclic load direction, and the installation methods.