Instrumented Foundations for two 43-storey Buildings on Till, Metropolitan Toronto

1972 ◽  
Vol 9 (3) ◽  
pp. 290-303 ◽  
Author(s):  
W. Trow ◽  
J. Bradstock
Keyword(s):  
Differential Settlement ◽  
The Other ◽  
Load Redistribution ◽  
Raft Foundation ◽  
Total Settlement ◽  
Flexible Foundation

Settlement records have been obtained for a two-year period during and following construction of two 43-storey buildings in mid-town Metro Toronto, Ontario. One structure is supported on caissons varying in length from 45 to 70 ft (13.7 to 21.3 m) long, belled to a maximum of 12 ft (3.7 m) diameter and supported on dense silt till. The other is supported upon a raft foundation above the till. Protected rods have been inserted in four heavily loaded caissons to determine total settlement as well as differential settlement along the concrete shaft. Settlement devices have been installed at two levels in the till below the raft foundation and a pattern of differential settlement under the building has been established. It appears that all load has reached the base of the caissons and therefore that no load of consequence is being taken by the massive caisson caps or by the shafts. The settlement under the raft follows the flexible foundation pattern only approximately. In both buildings there appears to be load redistribution due to rigidity.

scholarly journals Analysis and Geotechnical Design of Hybrid Foundation for Tall Wind Turbine

2021 ◽  
Vol 9 (9) ◽  
pp. 346-350
Author(s):  
Shruti Birhare
Keyword(s):  
Bearing Capacity ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Energy Demand ◽  
Differential Settlement ◽  
Raft Foundation ◽  
Total Settlement ◽  
Geotechnical Design ◽  
Hybrid Foundation

Abstract: The significance of wind turbines in meeting the expanding energy demand is critical. Taller towers should be employed to boost the power producing capability. The foundation must be efficient in order to securely carry the heavier loads of taller towers. When sustaining loads from superstructure are considered then bearing capacity of raft is taken into account for pile raft foundation. Piles help to strengthen the raft's bearing capacity while also regulating settlement in this arrangement, particularly differential settlement. A hybrid foundation, i.e. a pile raft foundation, is investigated and geotechnically designed here. The effectiveness of this system is demonstrated using the measures total settlement, differential settlement, and rotation. Keywords: Pile raft foundation, differential settlement, total settlement, wind turbin, bearing capacity

Numerical Analysis on Interaction of Superstructure-Piled Raft Foundation-Foundation Soil

2011 ◽  
Vol 261-263 ◽  
pp. 1578-1583
Author(s):  
Yong Le Li ◽  
Jiang Feng Wang ◽  
Qian Wang ◽  
Kun Yang
Keyword(s):  
Design Method ◽  
Bending Moment ◽  
Load Sharing ◽  
Differential Settlement ◽  
Pile Head ◽  
Secondary Stress ◽  
Foundation Soil ◽  
Piled Raft Foundation ◽  
Raft Foundation ◽  
Soil Load

based on the finite element method of superstructure-the pile raft foundation-the foundation soil action and interaction are studied. Research shows that the common function is considered, fundamental overall settlement and differential settlement with the increase of floor of a nonlinear trend. The influence of superstructure form is bigger for raft stress, the upper structure existing in secondary stress, and the bending moment and axial force than conventional design method slants big; With the increase of the floors, pile load sharing ratio is reduced gradually,but soil load sharing ratio is increased. Along with the increase of the upper structure stiffness, the load focused on corner and side pile; Increasing thickness of raft, can reduce the certain differential settlement and foundation average settlement, thus reducing the upper structure of secondary stress and improving of foundation soil load sharing ratio, at the same time the distribution of counterforce on the pile head is more uneven under raft, thus requiring more uneven from raft stress, considering the piles under raft and the stress of soils to comprehensive determines a reasonable raft thickness, which makes the design safety economy. As the foundation soil modulus of deformation of foundation soil improvement, sharing the upper loads increases, counterforce on the pile head incline to average, raft maximum bending moment decrease gradually.

Consolidation Settlement Analyses on a Composite Foundation System Combined with Walled and Columniform Soil Improvement

2010 ◽  
Vol 163-167 ◽  
pp. 2318-2327
Author(s):  
Wei Li ◽  
Fei Gao ◽  
He Huang ◽  
Haruyuki Yamamoto ◽  
Kinji Takeuchi
Keyword(s):  
Environmental Influence ◽  
Soil Layer ◽  
Soil Improvement ◽  
Differential Settlement ◽  
Composite Foundation ◽  
Shallow Foundation ◽  
Hydraulic Pressure ◽  
Raft Foundation ◽  
Consolidation Settlement ◽  
Geological Situation

To satisfy the geotechnical strength requirements and the serviceability requirements, types of foundation systems (such as shallow foundation, pile foundation and composite foundation) have been developed. Of course, the type of foundation system is determined by many factors such as ground condition, economy and environmental influence of construction. To cope with weak or compressible soils, the authors present a raft foundation system with walled and columniform soil improvement for multistory buildings, which is economical and environment-friendly. In this raft foundation system, different columniform soil improvements in size and depth are used, and the subgrade under the edge of the foundation is walled by soil improvement. It can effectively control differential settlement and prevent relative rising of the structure by adjusting the size and depth of columniform soil improvements according to the soil layer difference of geological situation under the building. We have performed series numerical analyses under two-dimensional plane strain condition to study the settlement behaviors of the composite foundation system, and its effects on controlling differential settlement and improving bearing capacity were verified for immediate condition. As a continuous research, consolidation settlement analyses are performed, the process of excess hydraulic pressure dispersion with time and the consolidation settlement development are studied in this paper.

scholarly journals Numerical Simulation of Combined Pile-Raft Foundation under Horizontal Loading

2020 ◽  
Vol 9 (3) ◽  
pp. 448-452
Keyword(s):  
Numerical Simulation ◽  
Diameter Ratio ◽  
Differential Settlement ◽  
Thickness Effect ◽  
Horizontal Load ◽  
Static Response ◽  
Pile Diameter ◽  
Raft Foundation ◽  
Horizontal Loading ◽  
Raft Foundations

Raft foundations generally have the ability to reduce differential settlement, contrarily causing excessive settlement. In order to overcome this, piles are used along with the raft termed as combined pile-raft foundation system. Due to the lack of availability of simplified tools and intricacy of work, the combined pile raft foundation remains as an untouched area in research. This paper explores the performance of 2x2 numerically simulated combined pile-raft foundation embedded in sand exposed to pure horizontal load using ABAQUS 3D. The effect of horizontal loading in terms of displacement is studied by varying the raft thickness, length and spacing to diameter ratios respectively for the combined pile-raft foundation having a pile diameter of 500mm. The model is validated using the existing findings. Based on this study, it is inferred that the raft thickness effect remains inconsequential whereas the length to diameter ratio and spacing to diameter ratio has an impact on the static response of the combined pile-raft foundation system.

scholarly journals Probabilistic considerations for the design of deep foundations against excessive differential settlement

2016 ◽  
Vol 53 (7) ◽  
pp. 1167-1175 ◽  
Author(s):  
Farzaneh Naghibi ◽  
Gordon A. Fenton ◽  
D.V. Griffiths
Keyword(s):  
Differential Settlement ◽  
Deep Foundations ◽  
Foundation Settlement ◽  
Design Practice ◽  
Probabilistic Theory ◽  
Small Probability ◽  
Limit States ◽  
Foundation Design ◽  
Total Settlement ◽  
Acceptable Probability

Current foundation design practice for serviceability limit states involves proportioning the foundation to achieve an acceptably small probability that the foundation settlement exceeds some target maximum total settlement. However, it is usually differential settlement that leads to problems in the supported structure. The design question, then, is how should the target maximum total settlement of an individual foundation be selected so that differential settlement is not excessive? Evidently, if the target maximum total settlement is increased, the differential settlement between foundations will also tend to increase, so that there is a relationship between the two, although not necessarily a simple one. This paper investigates how the target maximum total settlement specified in the design of an individual foundation relates to the distribution of the differential settlement between two identical foundation elements, as a function of the ground statistics and the distance between the two foundations. A probabilistic theory is developed, and validated by simulation, which is used to prescribe target maximum settlements employed in the design process to avoid excessive differential settlements to some acceptable probability.

How distribution characteristics of a soil property affect probabilistic foundation settlement — from the aspect of the first four statistical moments

2020 ◽  
Vol 57 (4) ◽  
pp. 595-607 ◽  
Author(s):  
Yongxin Wu ◽  
Yufeng Gao ◽  
Limin Zhang ◽  
Jun Yang
Keyword(s):  
Elastic Modulus ◽  
Probability Model ◽  
Differential Settlement ◽  
Shallow Foundation ◽  
Statistical Moments ◽  
Foundation Settlement ◽  
Spectral Representation Method ◽  
Total Differential ◽  
Total Settlement ◽  
Representation Method

The effects of the first four statistical moments defining the statistical characteristic of elastic modulus on the probabilistic foundation settlement are investigated in this study. By combining the Hermite probability model and spectral representation method, a method to simulate nonGaussian homogenous fields based on the first four statistical moments is proposed. Linear elastic finite element models are employed to study the total settlement and the differential settlement of a shallow foundation. Probabilistic measurements of total–differential settlement obtained by the Monte Carlo simulations are presented. For the cases considered, the effects of skewness and kurtosis defining the probabilistic characteristic of elastic modulus on the total–differential settlement of a probabilistic foundation are illustrated. The computed results show that the value of skewness has a more significant effect on the probabilistic foundation settlement than kurtosis, and the case with the smallest skewness is observed as the most critical one.

scholarly journals Design of Foundations Against Differential Settlement

2021 ◽  
Author(s):  
Farzaneh Naghibi ◽  
Gordon A. Fenton
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Limit State ◽  
Differential Settlement ◽  
Angular Distortion ◽  
Equivalent Stiffness ◽  
Distribution Of The Maximum ◽  
Bias Factor ◽  
Total Settlement ◽  
Design Requirements

The serviceability limit state (SLS) design of foundations typically proceeds by limiting the total settlement of individual foundations and thereby attempting to restrict the differential settlement between pairs of foundations. Due to the uncertain nature of the supporting ground, the magnitude of settlement and differential settlement are random. As it is often the differential settlement which governs serviceability, it is desirable to provide design requirements which suitably restrict differential settlements. This paper investigates, by Monte Carlo simulation, the distribution of the maximum differential settlement between pairs of foundations as a function of the spacing between foundations and the number of foundations – groups of 4, 9, or 16 foundations, arranged on a grid, are considered. The effects of the correlations between the equivalent stiffness of the ground under each foundation, as well as between the loads applied to the foundations, on the distribution of the maximum differential settlements and angular distortions are investigated. Ratios of resistance factor to resistance bias factor are presented that can be used to calibrate design requirements on the total settlement of individual foundations which also simultaneously achieve acceptable performance with respect to angular distortion.

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.

Optimization Design Study on Variable Stiffness of the Pile Raft Foundation in High-Rise Building

2011 ◽  
Vol 243-249 ◽  
pp. 2498-2502 ◽  
Author(s):  
Yong Le Li ◽  
Jiang Feng Wang ◽  
Qian Wang ◽  
Kun Yang
Keyword(s):  
Optimization Design ◽  
Variable Stiffness ◽  
Internal Force ◽  
Differential Settlement ◽  
Foundation Soil ◽  
High Rise ◽  
High Rise Building ◽  
Raft Foundation ◽  
Calculation Results ◽  
Pile Arrangement

The finite element calculation results indicated: interaction of the superstructure-the pile raft foundation-foundation, the stress of the pile raft foundation appeared "disc type" distribution, namely, was big in the middle, and was small in the edge. Generation of differential settlement was due to the upper structure secondary stress and raft internal force. Through adjusting the foundation soil stiffness and pile length, pile diameter and pile distance, the influence of variable stiffness on differential settlement was analyzed. The results showed that changing the pile arrangement and adjusting the stiffness of foundation soil was optimal scheme of the pile raft foundation in high-rise building.

Application Study of Long-Short-Piled Raft Foundation

2012 ◽  
Vol 170-173 ◽  
pp. 242-245
Author(s):  
Xin Yu Xie ◽  
Ming Xin Shou ◽  
Jie Qing Huang ◽  
Kai Fu Liu
Keyword(s):  
Bearing Capacity ◽  
Pile Foundation ◽  
National Standard ◽  
Application Study ◽  
Existing Building ◽  
Piled Raft ◽  
Piled Raft Foundation ◽  
Raft Foundation ◽  
Total Settlement ◽  
Reinforcement Design

The long-short-piled raft foundation is an unusual type of building base. This kind of foundation is usually applied for pile foundation reinforcement of existing buildings when shortage of bearing capacity of piles occurs. The bearing capacity of pile foundation is improved and less settlement is expected. Since this method has so many obvious advantages, it is recommended in the reinforcement design of piled raft foundation of an existing building in Tianjin. Longer reinforced concrete bored piles are adopted as the supplementary ones. The bearing capacity of this kind of piled raft foundation was studied. The settlement was also analyzed with the National standard method together with the finite element numerical method. According to the study, the bearing capacity of piled raft foundation is enhanced effectively after adding piles. Also, the results show that the total settlement and differential settlement during the construction is in control respectively.

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