Piled Raft Foundation Research Articles

Parametric analysis and performance evaluation of piled raft foundations: comparing hollow and conventional systems

Parametric analysis and performance evaluation of piled raft foundations: comparing hollow and conventional systems

Simplified Calculation of Horizontal Dynamic Impedance of Piled Raft Foundation on Layered Soil

Simplified Calculation of Horizontal Dynamic Impedance of Piled Raft Foundation on Layered Soil

Numerical Analysis of Load-sharing Behavior of Combined Pile Raft Foundation System

This study investigates the application of combined pile raft foundations in the soft soil of Kathmandu Valley, taking into account varying pile spacing and length. Both embedded beams and volume piles were used in numerical analysis to assess the load-sharing behavior of the raft and pile under different conditions. The settlement results from the volume pile, and embedded beam element was comparable, with less than a 6.21% difference, indicating that both methods are equally suitable for evaluation. The embedded beam element was selected for further analysis. The analysis suggests that pile load sharing is primarily influenced by spacing, while an increase in pile stiffness due to increased pile length has a minor effect. The load-sharing factor follows a log-linear relationship when the spacing exceeds 3D. Regarding the normalized vertical settlement of the pile, the power rule governs the load-sharing factor. This power function related to normalized settlement is highly beneficial for designing the CPRF and choosing the appropriate pile spacing and length. Finally, the capacity utilization curve suggests that a spacing greater than three times the diameter results in higher pile capacity utilization. Conversely, a decrease in spacing significantly reduces the mobilized strength of the piles.

Understanding the Dynamic Behavior of Piled Raft Foundation through Previous Studies

Understanding the Dynamic Behavior of Piled Raft Foundation through Previous Studies

Experimental study on tunneling-induced soil arching evolution in pile-raft foundations

The evolution and progressive failure of the tunneling-induced soil arching effect in pile-raft foundations are still unclear. A series of tunnel-shaped trapdoor tests in a pile−raft foundation were conducted to study the effects of the tunnel−pile distance and the load on the subgrade surface on the progressive failure of the tunneling-induced soil arching effect. PIV technology was used to measure the evolution of the deformation pattern and shear bands of foundation soil with increasing tunnel volume loss. The ground reaction curve (GRC) for the tunnels and the pile settlement were measured by using a load cell and LVDTs. The results revealed that the minimum tunnel pressure in the pile-raft foundation was greater than that in the greenfield foundation because of the lower soil arching effect. The GRC curve in the pile−raft foundation can be divided into three stages: initial arching, maximum arching, and the ultimate stage. The minimum soil arching ratio decreased with increasing tunnel−pile distance and surface load. In the pile-raft foundation, a triangular disturbed zone was observed above the tunnel crown in the initial stage and gradually developed upward within a rectangular zone as the tunnel volume loss increased. The width of the tunneling-disturbed area was larger than the tunnel diameter in the ultimate stage. As the tunnel−pile distance increased, the evolution pattern of the tunnel-induced loosened area changed from “triangular expanding expansion” to “equal settlement expansion”. The effects of the tunnel−pile distance and surface loads on the tunneling-induced failure mechanism of pile−raft foundations are also discussed in this study, which provides valuable guidance for underground engineering construction.

Response of piled raft foundations using the disturbed state concept theory: Analysis and interpretation

In nearshore and marine environments, challenges arise from loading conditions, subsoil profiles, and dynamic soil states influenced by continuous wave action. Piles in such settings face complex interactions due to soil vulnerability to loading and over-consolidation. Accurate estimation of pile shaft and base resistances, as well as raft-soil interface stiffness, is crucial. The paper introduces the disturbed state concept for analysing piled raft foundations under vertical loading. This theory assumes interface strength between piles and soil follows an exponential distribution, expressed through the Weibull function. Interaction between piles is established using a modified displacement factor, which is a modified form of Mindlin's solution. Raft-soil interaction is modelled with springs connected to the pile head. The load transfer model exhibits both softening and hardening responses. Validation against numerical and field experimental studies demonstrates close agreement within a 5%–15% error range. Parametric investigation analyses load-settlement response, percentage of load on pile base with settlement increase, and axial load transfer along pile length under varying conditions. The impact of limiting pile-soil relative movement on piled raft response is also explored.

Effect of Rubber Scrap Tire Pads on the Behavior of Partially Connected Pile Raft Foundation System Subjected to Dynamic Loading

A partially tied piled foundation raft where both horizontal and vertical movements will be tamed. Interfacing RSTP changes are in structural dynamics and the way the forces are distributed. Nevertheless, the overall seismic behavior of this type of foundation in medium dry sand soil links to the pile raft foundation system with partial structural connection has not been studied adequately. To fill this gap we experimentally tested ten pile and group pile layouts in the laboratory in order to explore the interaction of the cushion layer with piles at different spacing. These tests concern the displacement mechanism of the raft foundation and the stressing change of the RSTP layers that occur during earthquakes. The results showed that using RSTP layers helps to minimize the variations in displacement between patterns with connected piles and those with disconnected piles when subjected to shaking loads. The pattern 1DR6cm showed a high settlement reduction ratio compared with 1DR2cm. Pattern 2C2D appeared less reduction in the vertical displacement. More significant displacements and rotating behavior anticipate lateral shaking due to reduce the number of connected piles for pattern 1C4D compare with pattern 4C1D. The pattern 3C6DHR2cm decreased the vertical displacement by 48.4% using one layer of RSTP. Using three layers of RSTP contributes to reducing the displacement by 36.4%. The number of the piles in a connection condition with the piled raft and the cushion thickness belongings on the strain deformation values.

The Influence of Raft Thickness on Settlement and Bending Moment of Pile Raft Foundation in Clay Soil

Geotechnical engineers often deal with shallow foundation designs to support relatively simple building structures. However, as the demand for construction grows over time, there is a need for larger and more complex building structures. This is closely related to the weight of the building that will be supported by the foundation as a substructure. Therefore, the development of knowledge about other types of foundations to support the structural loads above them is highly necessary. Pile foundations are a fairly good solution for supporting larger structural loads that cause significant settlement. In designing pile foundations as a structure, there will certainly be raft to combine each pile foundation into a unified group. Raft are often designed only for combining each pile, but in reality, It also provides additional influence on the foundation system besides just serving as pile heads and load distributors to the foundation system. The study will investigate the influence of raft thickness on settlement that occurs in piled raft foundations. The raft thickness varies, namely 0.25m; 0.40m; 0.80m; 1.50m; and 3.00m. The piled raft foundation will be modeled and analyzed using finite element program. This study shows that the raft thickness affects the differential settlement that occurs in the piled raft foundation system. The results indicate that the differential settlement can be addressed by designing the raft thickness.

A novel hybrid framework based on modified continued-fraction for pile-soil dynamic interaction of large-scale nuclear power structures

Accurate unbounded domain radiation damping and ground motion input in the near field are important for analyzing the dynamic safety of large-scale nuclear power structures (NPSs). The scaled boundary finite element method (SBFEM) can automatically satisfy the abovementioned radiation condition. However, owing to the coupling of time and space, conventional SBFEM is not competent to the analysis of large-scale structures. In this investigation, a novel coupled method is developed to improve the computational efficiency of unbounded domain dynamic stiffness using a modified continued-fraction technique. Furthermore, a set of systematic and efficient computational procedures for soil-structure interaction (SSI) are implemented based on parallel programming using a special preprocess. The proposed method is verified using three numerical examples, and another numerical application is analyzed for large-scale NPSs with a pile-raft foundation (PRF). The results show that the innovative method has wide engineering applicability with high numerical accuracy and stability, indicating that this method can be applied to the SSI dynamic seismic analysis of large-scale NPSs.

Straining Actions of Piles in Different Systems of Piled Raft Foundations for Tall Wind Turbines in Zafarana, Egypt

Straining Actions of Piles in Different Systems of Piled Raft Foundations for Tall Wind Turbines in Zafarana, Egypt

Seismic Behaviour of RC Framed Building Supported on Combined Piled Raft Foundation in Sandy Soil

Seismic Behaviour of RC Framed Building Supported on Combined Piled Raft Foundation in Sandy Soil

Influence of Separation Layer Properties on Seismic Response of Modified Piled Raft Foundations

Influence of Separation Layer Properties on Seismic Response of Modified Piled Raft Foundations

Comparison between the measured and the numerically predicted behaviour of an instrumented piled raft

This paper presents the results of numerical predictions for an instrumented piled raft foundation of a tall building in tropical soil. The analysis was performed using 3D finite element analysis and included a comparison of foundation settlements, pile loads, skin friction mobilisation, and raft-soil contact pressure. Initially, the geotechnical model was defined based on field and laboratory test data to conduct a Class A geotechnical prediction. Subsequently, the soil parameters used in the numerical model were re-evaluated to match the measured settlements, aiming for a Class C prediction. The study discusses the main factors that affect the accuracy of the computed settlements, providing valuable insights for foundation designers. Additionally, it highlights the significance of considering the pile-soil-pile and raft-soil-pile interactions in the design of the piles beneath the raft, as these interactions impact the mobilisation of the pile skin friction at different depths.

Soil Structure Interaction of R.C. Building with Basement Resting on Pile Raft Foundation

Abstract: Historically, Basements or underground stories were built in a castle to use as a dunged on oar store room. However, in modern construction, the restrain to go deeper below the grade level in term so basements which can be utilized for parking, shopping mall or combination of both. In such cases, dynamic soil properties have a significant effect of activating dynamic soil structure interaction phenomena on during earthquake. Here in present study an effort is made to study the behavior of a building by varying number so basements considering dynamic soil structure interaction. Issues like considering higher frequency modes, influence zone to be considered for dynamic soil structure interaction, behavior of building with basements under different water level conditions for two different types of layered soil and their comparison with fixed based structure is deal with. It is observed that dynamic soil structure interaction can significant change the behavior of the building and hence it is recommended to perform dynamic soil structure interaction for building with multiple basements. In addition, some important recommendations are provided at the end to serve as a guide for researchers and practicing engineers.

Geofoam integrated separation layer for enhancing seismic resilience in modified piled raft foundations

Geofoam integrated separation layer for enhancing seismic resilience in modified piled raft foundations

Seismic response of combined piled raft foundation using advanced liquefaction model

The design of earthquake resistant structures founded on combined piled raft foundation (CPRF) mainly depends on raft-pile-soil interaction (RPSI). This interaction become more complex for these heavy structures, if founded on the liquefiable soil. The CPRF is considered to be useful foundation in practice to support such heavy structure; in which both raft and pile increase the bearing capacity of the soil. Where raft reduces the liquefaction induced settlement and piles help to transfer the load of the structure to the non-liquefiable soil layer. The aim of this paper is to carry out the 3D nonlinear finite difference analysis of CPRF considering the RPSI. A recently developed constitutive model i.e. CycLiq for the liquefaction modelling of the soil is utilized to represent the behaviour of sand in inelastic range which consider the cyclic behaviour and large post-liquefaction shear deformation of sand. The validation of the model is carried out with the centrifuge data. The effect of CPRF over the raft and pile group is carried out for harmonic excitation with varying frequency and earthquake motion with varying PGA. The study provides important observations and insights that were not previously evident. The findings emphasize the need to consider frequency effects, geometrical nonlinearity, and material nonlinearity in the design of NPP structures. Additionally, the study introduces the application of the CycLiq liquefaction model and the development of a user-defined material for FLAC3D. Further, the outcome shows the useful conclusion on the importance of CPRF foundation over the conventional foundation i.e. raft and pile group in the liquefiable soil. It is found that excitation frequency, ground motion PGA, porosity of sand and pile spacing of CPRF have great effects on the response.

Bearing characteristics of a model piled raft foundation in unsaturated soil subjected to variations in the groundwater level

The bearing characteristics of a piled raft foundation (PRF) in saturated or dry soil ground have been investigated in previous studies. However, soils near the ground surface are generally in an unsaturated state. Matric suction occurs in unsaturated soils and influences the mechanical properties of soil. For more reasonable designs of PRFs, it is undoubtedly necessary to study the bearing characteristics of PRFs in unsaturated soil. In this study, model tests were conducted to investigate the bearing characteristics of a PRF in unsaturated soil subjected to variations in the groundwater level. The experimental results showed that, when the groundwater level was increased and the suction decreased, the load carried by the raft increased under dead load, leading to a significant settlement of the model PRF.

Dimensionless Reaction Coefficients for Embedded Piled Raft Foundations in Soft Clays under Vertical Loads

Dimensionless Reaction Coefficients for Embedded Piled Raft Foundations in Soft Clays under Vertical Loads

Numerical Analysis of Combined Helical Pile Raft Foundation (CHPRF) Under Compressive and Tensile Loadings

Numerical Analysis of Combined Helical Pile Raft Foundation (CHPRF) Under Compressive and Tensile Loadings

Effect of Seismic Loading on Porewater Pressure in Clayey Soil under Disconnected Piles-Raft Foundation

The disconnected piled raft foundation (DCPRF) is one of the newly introduced foundations for specialization in geotechnical engineering, which significantly reduces the moment and stress on the pile head. In addition, this type of foundation is an ideal choice in areas with seismic activity due to the presence of cushion material between the raft and the piles. This work aims to present a numerical model in PLAXIS 3D software for connected piled raft and disconnected piled raft foundations under the influence of seismic loads and investigate the effect of pore water pressure on the disconnected foundation compared to the connected foundation. The study will depend on the earthquake that struck Iraq in November 2017 in the Halabja region. Strength was 7.3 on the Richter scale with PGA (0.1g). The results of changing pore water pressure showed the variation of pore water pressure. In the case of a DCPRF, the porewater pressure and excess porewater pressure in the soil are much greater than in the case of a CPRF. The increase in the porewater pressure is due to the weight of the building and the weight of the additional cushion layer on the soil. The mechanism for transferring the load in the case of a DCPRF is carried out by raft, then to the cushion, and then to the soil and piles. The load transferred to the soil in the case of DCPRF is more than that transferred to the soil in the CPRF system.