scholarly journals Parametric Study on Behaviour of Retrofitted Piled Raft Foundation

2020 ◽  
pp. 308-315
Keyword(s):  
High Rise ◽  
Finite Element Software ◽  
Piled Raft ◽  
Spring Element ◽  
Piled Raft Foundation ◽  
Mat Foundation ◽  
Subgrade Modulus ◽  
Hybrid Foundation ◽  
Mat Thickness ◽  
Raft Foundations

Mat supported on piles is being increasingly used for high-rise buildings with basements in poor soils. Very little is known about the exact behaviour of piled raft foundations in service. However behaviour of retrofitted piled rafts, which are a hybrid foundation of mat provided as retrofitting solution and failed pile foundations, is non-identical. In order to model the mat for retrofitting, engineer needs to analyze the sensitivity of different parameters to their behaviour. In this paper, a numerical analysis has been carried out to investigate the influence of mat thickness and soil subgrade modulus of uniform and varying values to the behaviour of mat foundation rendered to retrofit a short felled pile foundation executed for a high-raised building in Kerala, by using finite element software SAFE v 16. The soil and the piles are modeled as spring element at discrete position below the mat and the mat foundation is modeled using elastic plate element. The results of the study show that mat thickness and soil subgrade modulus are found to be the governing parameters in designing a safe and economical retrofitting mat foundation. Furthermore, it is recommended to provide exact soil subgrade properties under the mat to perceive actual behaviour of foundation.

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.

scholarly journals INVESTIGATING THE BEHAVIOR OF PILED RAFT FOUNDATION IN CORE WALL FOUNDATION OF HIGH-RISE BUILDINGS

2021 ◽  
pp. 1-9
Author(s):  
Tuan Nguyen Anh
Keyword(s):  
Core Structure ◽  
High Rise ◽  
Geometry Model ◽  
The Core ◽  
Piled Raft ◽  
Piled Raft Foundation ◽  
Raft Foundation ◽  
Wall Foundation ◽  
The Moment ◽  
Plaxis 3D

Core structure is an indispensable part of high buildings. Normally, the foundation of the core structure has a raft of larger size than the other foundations in the same project; therefore, the foundation of the core structure can be viewed as a small piled raft foundation. Currently, when calculating the piled foundation of the core, it is mostly assumed that the piles system will bear all the project loads. But this calculation method is not suitable for the actual constructions as well as does not make full use of the bearing capacity of the structure and the ground, leading to using more materials and causing more waste. Core structure aims to increase both stiffness and horizontal load capacity in high-rise buildings, so the moment inside the core transmitted to the foundation is very large. One of the shortcomings of the Plaxis 3D Foundation software is its inability to declare the moment affecting on the foundation due to the loads in this program just includes distributed loads, line loads and point loads in the geometry model. Consequently, when using Plaxis 3D Foundation software to calculate the core wall foundation of high-rise buildings, this moment is converted into an equivalent pair of moments. The research shows that when the core foundation of a high-rise building is placed on soft soil, the pile carries 96%, most of the load transmitted to the foundation. However, when the foundation is placed on hard soil, the soil surrounding the raft will bear about 10% of the load transmitted to the foundation. If this matter is skipped, there will be a large error in calculation and design

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 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.

Sign in / Sign up

Export Citation Format

Share Document