scholarly journals Optimization Method of Reducing the Differential Settlements of Piled Raft Foundations Based on Pile-to-Pile Interaction Theory

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Yunfei Xie ◽  
Shichun Chi
Keyword(s):  
Optimization Design ◽  
Optimization Method ◽  
Differential Settlement ◽  
Interaction Theory ◽  
Pile Groups ◽  
Piled Raft ◽  
Piled Raft Foundation ◽  
Pile Interaction ◽  
Single Piles ◽  
Raft Foundations

In order to reduce the differential settlement of piled raft foundations, an optimization method based on pile-to-pile interaction theory is proposed in this paper, which translates the problem of pile-to-pile interaction (PPI) in pile groups into that in single piles using the interaction factor method. The pile lengths were adjusted via the relationship between load, settlement, and the length of single piles during the optimization design. ANSYS software, in conjunction with nonlinear elastic soil model, is used to analyze piled raft foundation models. Two cases with different safety factors that suffer different kinds of surface loads (uniform load and nonuniform load) are used to verify this method. The differential settlements of the raft in different cases are all reduced by nearly or more than 80% after optimization design. The results show that the optimization method proposed in this paper has high efficiency and stability. This study can help practicing engineers optimize the pile lengths in pile groups to satisfy higher differential settlement requirements.

scholarly journals Optimization Method for Irregular Piled Raft Foundation on Layered Soil Media

2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Yunfei Xie ◽  
Shichun Chi
Keyword(s):  
Stress Distribution ◽  
Power Plants ◽  
Large Scale ◽  
Optimization Method ◽  
Differential Settlement ◽  
Optimized Design ◽  
Pile Spacing ◽  
Piled Raft ◽  
Piled Raft Foundation ◽  
Raft Foundations

Important buildings such as nuclear power plants always require stricter control of differential settlement than ordinary buildings. Therefore, it is necessary to provide an optimized design for the piled raft foundations of important buildings. In this paper, a new optimization method (using different pile diameters and different pile spacing) was proposed for the design of piled raft foundations. This method adjusts the pile diameters and pile spacing according to the stress distribution at the pile top of the initial design to achieve a more uniform settlement of the raft and stress distribution on top of piles, which can solve the differential settlement problems caused by uneven loads of the superstructure. After optimized design, the differential settlement and integral bending moment of the raft decreased more than 64% and 52%, respectively, and the differential stress on top of piles decreased by at least 63%. The new method proposed in this paper could be applied to large-scale piled raft foundations with complex superstructure loads.

AN ESTIMATING METHOD FOR LATERAL BEHAVIOR OF PILED-RAFT FOUNDATION

2017 ◽  
Vol 4 (1) ◽  
Author(s):  
Haruyuki Yamamoto ◽  
He Huang
Keyword(s):  
Ground Surface ◽  
Surface Displacement ◽  
Lateral Loading ◽  
Location Factors ◽  
Location Factor ◽  
Piled Raft ◽  
Piled Raft Foundation ◽  
Raft Foundation ◽  
Cone Model ◽  
Raft Foundations

Some simplified design methods were proposed to predict behavior of lateral loaded piled-raft foundations on homogenous soil. One of them is the cone model method. However, only one average solution of pile behavior can be given by this method. It can’t evaluate the location factors of piles. Therefore, this paper describes a new simplified method to predict behavior of lateral loaded piled raft foundations covering the location factor of piles. At first, ground surface displacement is derived theoretically by Cerutti’s solution, then assuming that the raft foundation has rigid stiffness, these displacements are the same to calculation lateral loading distribution. Second, the ground displacement where pile placed could be estimated under calculated lateral loading. Third, the piles behavior are evaluated based on these lateral ground displacements. In addition, 3-D FEM numerical analysis were performed to compared with these solutions.

scholarly journals Behaviour of Load-Bearing Components of a Cushioned Composite Piled Raft Foundation Under Axial Loading

2014 ◽  
Vol 22 (4) ◽  
pp. 25-34 ◽  
Author(s):  
V. J. Sharma ◽  
S. A. Vasanvala ◽  
C. H. Solanki
Keyword(s):  
Soil Profile ◽  
Axial Loading ◽  
Load Bearing ◽  
Piled Raft ◽  
Piled Raft Foundation ◽  
Raft Foundation ◽  
The World ◽  
Raft Foundations ◽  
Flexible Pile

Abstract In the last decade piled raft foundations have been widely used around the world as intermediate foundation systems between piles and rafts to control the settlement of foundations. However, when those piles are structurally connected to rafts, relatively high axial stresses develop in relatively small numbers of piles, which are often designed to fully mobilize their geotechnical capacities. To avoid a concentration of stress at the head of piles in a traditional piled raft foundation, the raft is disconnected from the piles, and a cushion is introduced between them. Also, to tackle an unfavourable soil profile for a piled raft foundation, the conventional piled raft has been modified into a cushioned composite piled raft foundation, where piles of different materials are used. In the current study the behavior of cushioned foundation components, which transfer the load from the structure to the subsoil, are analyzed in detail, i.e., the thickness of the raft, the length of a long pile and the modulus of a flexible pile.

Compensated piled rafts in clayey soils: behaviour, measurements, and predictions

2010 ◽  
Vol 47 (3) ◽  
pp. 327-345 ◽  
Author(s):  
Maurício M. Sales ◽  
John C. Small ◽  
Harry G. Poulos
Keyword(s):  
Clayey Soils ◽  
Deep Excavation ◽  
Piled Raft ◽  
Simplified Method ◽  
Measured Time ◽  
Pile Interaction ◽  
Numerical Tools ◽  
Raft Foundations

This paper presents a method of analysis of the behaviour of piled rafts in clayey soils, in which a deep excavation was necessary for buildings with two or more basements. In these cases, the piled raft foundations are called a “compensated piled raft.” The soil stresses reduce due to excavation, and the reloading of the soil should be taken into account for this kind of foundation. Many important factors that are required to achieve a satisfactory comparison of “measurement versus prediction” are pointed out, and they are grouped in a proposed simplified method of analysing compensated piled rafts using numerical tools that can consider the raft–soil–pile interaction. Finally, two well-known cases of compensated piled rafts (Hyde Park Barracks in London and the Messeturm building in Frankfurt) and a newer building (the Skyper Tower, Frankfurt) are analyzed using the presented approach and the computed and measured time–settlement behaviours are compared.

scholarly journals Experimental Investigation for Effects of Mini-piles on the Structural Response of Raft Foundations

2019 ◽  
Vol 5 (5) ◽  
pp. 1084-1098
Author(s):  
Huda Hussein Ahmed ◽  
Salah Rohaima Al-Zaidee
Keyword(s):  
Structural Response ◽  
Cost Effective ◽  
Bending Moments ◽  
Historical Structures ◽  
Piled Raft ◽  
Piled Raft Foundation ◽  
Raft Foundation ◽  
Significant Difference ◽  
Scale Down ◽  
Raft Foundations

Mini-piles made their debut as a cost-effective way to stabilize the historical structures. Recently, mini-piles have increased in popularity all over the world and are being used for bridges, buildings, slope stability, antenna towers, and residential construction. This paper presents the preparing, executing, data acquisition, and result presentation for an experimental work concerns with five scale-down mini-piled raft foundation models. All models were prepared to study the effectiveness of the mini-piled raft foundation in reducing the settlement and the bending moments. Five tests have been achieved. The reference first test includes a raft foundation with 15mm thickness. Second, third, and fourth tests are mini-piled raft foundations with five mini-piles and with thicknesses of 15 mm, 10 mm, and 8mm respectively. Finally, the fifth test dealt with a single mini-pile 178mm in length and 6mm in diameter. It has been adopted to investigate the reference behavior of the single mini-pile. When they were used, the piles have 42 mm center to center distances. A scale-down factor of , a sandy soil with with  of , and relative density of 60% have been considered in all tests. Test results indicated a 45% decrease in settlement for 15mm mini-piled raft foundation comparing with the reference 15mm raft foundation. Moreover, there is no significant difference in settlement between 15mm mini-piled raft foundation comparing with the 10mm and 8mm thick mini-piled raft foundations. Regarding to the bending moments, they decrease at the mid and edge of the 15mm mini-piled raft foundation comparing to those of the reference raft foundation. It has also been noted that the moments are inversely proportional to the thickness of the piled raft foundations. With respect to the mini-piles, it has been found that most of the pile axial loads are transferred to the underneath soil through friction and this friction increases as the raft thickness decreases.

scholarly journals ESTIMATING THE INTERNAL FORCES OF RAFT IN PILED RAFT FOUNDATION FOR NORMAL AND GROUNDWATER PUMPING CONDITIONS: A CASE STUDY SOC TRANG PROVINCE, VIETNAM

2021 ◽  
Vol 1 (42) ◽  
pp. 86-93
Author(s):  
Hiep Van Huynh ◽  
Tri Huu Huynh ◽  
Truyen Gia Ngo ◽  
Tuan Van Tran
Keyword(s):  
Shear Force ◽  
Soft Soil ◽  
Groundwater Pumping ◽  
Piled Raft ◽  
Piled Raft Foundation ◽  
Raft Foundation ◽  
Length Width ◽  
Internal Forces ◽  
Raft Foundations

Piled raft foundations are widely used in infrastructure built on soft soil to reduce the settlement and enhance bearing capacity. The raft can be used for basements and to share the load. In this paper, Poulos method, in which the raft was cut into many piled strips, was used as an analytical method. The study also used Plaxis2D and SAP 2000 to calculate internal forces for the raft in a piled raft foundation. A case of Vietcombank building with 10 floors and 1 basement, constructed on a soil profile in Soc Trang province, was studied. The piled raft with a 35m×19m×1m (length×width×thickness) raft and 28 piles were used for the analysis. Normaland groundwater pumping conditions were applied for the soil. The results showed that the maximum moment and shear force that occurred in the raft were affected when the groundwater pumping condition was applied to the model. The internal forces of the raft in the piled raft foundation for different conditions were captured,discussed, and presented in this paper.

scholarly journals Influence of Variable Rigidity Design of Piled Raft Foundation on Seismic Performance of Buildings

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Yunfei Xie ◽  
Shichun Chi ◽  
Maohua Wang
Keyword(s):  
Seismic Performance ◽  
Nuclear Power ◽  
Soft Soil ◽  
Optimized Design ◽  
Variable Rigidity ◽  
Structure Interaction ◽  
Piled Raft ◽  
Piled Raft Foundation ◽  
Pile Arrangement ◽  
Raft Foundations

In order to reduce the costs and improve the overall performance of building systems, the static optimized design with variable rigidity of piled raft foundations has been widely used in recent years. Variable rigidity design of piled raft foundations that support midrise buildings in high-risk seismic zones can alter the dynamic characteristics of the soil-pile-structure system during an earthquake due to soil-pile-structure interaction. To investigate these aspects, a nuclear power plant sitting on multilayered soil is simulated numerically. The paper describes a numerical modeling technique for the simulation of complex seismic soil-pile-structure interaction phenomena. It was observed that the total shear force on top of the piles and the rocking of the raft are reduced after optimization, whereas the displacement of the superstructure is nearly unaffected. The findings of this study can help engineers select a correct pile arrangement when considering the seismic performance of a building sitting on soft soil.

ANALYTICAL STUDY OF PILED-RAFT FOUNDATIONS CONSIDERING PLAN GEOMETRY AND NONLINEAR BEHAVIOR OF GROUND

2015 ◽  
Vol 2 (1) ◽  
Author(s):  
Haruyuki Yamamoto ◽  
He Huang
Keyword(s):  
Pile Foundation ◽  
Analytical Study ◽  
Nonlinear Behavior ◽  
Theory Of Elasticity ◽  
Piled Raft ◽  
Piled Raft Foundation ◽  
Raft Foundation ◽  
Raft Foundations

The piled-raft foundation transfers loading to the ground by the raft and the piles together. It was proposed in the 1970s and is widely used for controlling settlement. Simplified estimate equations are used for the primary design. Equations by Randolph can presume the settlement stiffness of the piled-raft foundation and the loading share ratio from the settlement stiffness of raft and pile foundation. Raft foundations not only have regular shapes as squares, they also have some particular shape like triangular or L-plan. Therefore, different shape plans are discussed in this paper to verify the applicability of these equations. Also, these equations are proposed based on a theory of elasticity. However, the ground has nonlinear behavior even under small loading levels, so estimating the applicability of these equations when the ground behaves nonlinearly is necessary.

A Parametric Study of Piled Raft Foundation in Clay Subjected to Concentrated Loading

2021 ◽  
Vol 13 (4) ◽  
Author(s):  
Chong Yi Hong ◽  
◽  
Lee Min Lee ◽  
Kok Sien Ti ◽  
Wong Soon Yee ◽  
...  
Keyword(s):  
Parametric Study ◽  
Load Distribution ◽  
Differential Settlement ◽  
Concentrated Load ◽  
Piled Raft ◽  
Piled Raft Foundation ◽  
Raft Foundation ◽  
Controlling Parameter ◽  
Sandy Material ◽  
Concentrated Loading

The use of piled raft foundation in building and infrastructure constructions is increasingly popular because of its effectiveness in reducing overall and differential settlements. Parameters influencing the performance of the piled raft foundation need to be comprehended in order to optimize the design of the piled raft system. Most of the current available literature focused on the piled raft foundation subjected to a uniform distributed load in sandy material. This parametric study aims to provide insights into the performance of the piled raft foundations subjected to concentrated loading in clay. A series of 2D finite element analyses were performed to investigate the influencing parameters affecting the load distribution and settlement behaviour of the piled raft. The results suggested that increases in both pile length and raft thickness, as well as a decrease in pile spacing would reduce the differential settlement of the piled raft. Comparatively, raft thickness was the most significant controlling parameter affecting the differential settlement. The study also revealed the importance of placing the pile nearer to the location of concentrated load as it would yield a more uniform load distribution, and hence a lower differential settlement.

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