Piled raft with hollow auger piles founded in a Brazilian granular deposit

2015 ◽  
Vol 52 (8) ◽  
pp. 1005-1022
Author(s):  
Wilson Cartaxo Soares ◽  
Roberto Quental Coutinho ◽  
Renato Pinto da Cunha
Keyword(s):  
Load Transfer ◽  
Load Capacity ◽  
Northeastern Brazil ◽  
Deep Foundations ◽  
Piled Raft ◽  
Piled Raft Foundation ◽  
Conventional Design ◽  
Detailed Assessment ◽  
Load Tests ◽  
The City

Geotechnical projects typically achieve load transfer to the ground using shallow or deep foundations. The conventional design approach does not provide for the combination of these two types of foundation. The piled raft philosophy allows the association of the soil elements, raft, and piles to obtain technical and economic advantages over conventional design. The city of João Pessoa, in northeastern Brazil, has developed foundation practices with hollow auger piles in piled raft design. The coastal area of the city has topsoil layers with favorable conditions for using such a technique. This paper addresses the results of a research project with instrumented load tests on foundation systems of hollow auger piles and a piled raft. The analysis is based on the load–settlement curve through extrapolation criteria. The Poulos–Davis–Randolph (PDR) method is applied according to a trilinear and hyperbolic approach to simulate the load–settlement curve of piled rafts. The results indicate that the raft absorbs most of the load, and the raft–soil contact significantly increases the load capacity of the foundation. The PDR hyperbolic method could apply to practical use in the foundations of the region, as it allows a more detailed assessment of the behavior of the foundation and can forecast the behavior of the (locally nontraditional) piled raft foundation system.

scholarly journals RECALQUES EM FUNDAÇÕES PROFUNDAS – ANÁLISE EM ESTACAS HÉLICE CONTÍNUA

2017 ◽  
Vol 14 (1) ◽  
Author(s):  
Pedro Lucas Prununciati ◽  
Jean Rodrigo Garcia ◽  
Tiago Garcia Rodriguez
Keyword(s):  
Sampling Error ◽  
Load Capacity ◽  
Limit State ◽  
Load Test ◽  
Limiting Factor ◽  
Deep Foundations ◽  
Slow Type ◽  
Load Tests ◽  
Penetration Tests ◽  
The City

RESUMO:  O recalque em fundações profundas e sua influência numa edificação tem se mostrado um parâmetro crítico, já que em diversos projetos a capacidade de carga não é o fator limitante, mas sim o recalque que a estrutura pode suportar em seu estado limite de serviço (ELS). Neste trabalho, são analisados resultados de deslocamento para uma estaca, estimados a partir dos métodos de Poulos e Davis (1980), Vésic (1969, 1975a) e Cintra e Aoki (2010), comparando-os com o valor recalque obtido por ensaios de prova de carga. Para tal, se apresentam três ensaios com carregamento do tipo lento, seguindo instruções da NBR12131 (ABNT, 2006), executados em estacas hélice contínua instrumentadas, com comprimentos de 14,75 m, 12,85 m e 21,80 m e diâmetros de 70 cm, 60 cm e 70 cm, respectivamente. Essas estacas foram ensaiadas no munícipio de Itatiba, em uma região onde sondagens à percussão demonstram a predominância de areia e silte. Para as estacas analisadas, o método proposto por Cintra e Aoki (2010) mostrou melhor resultado para a estimativa do recalque, quando comparado aos resultados de recalque obtidos em prova de carga. O método Poulos e Davis (1980) obteve desempenho menos satisfatório, resultando uma margem de erro de 16%, para mais ou para menos. O método de Vésic (1969, 1975a) se mostrou conservador e, nos casos analisados, resultou uma superestimativa de 138%, quando comparados aos valores de prova de carga.ABSTRACT: The settlement in deep foundations and its influence appears to be a critical parameter, as in many projects, the load capacity of a pile is not the limiting factor, but the settlement which the structure can suffer on its serviceability limit state (SLS) is. In this research, the settlement results of a pile, estimated by the methods of Poulos e Davis (1980), Vésic (1969, 1975a) and Cintra e Aoki (2010) will be analyzed, to be compared with the value of settlement obtained from load tests. Three slow type load tests, following the instructions of NBR12131 (ABNT, 2006) are presented, carried out in instrumented continuous flight augers, with lengths of 14,75 m, 12,85 m and 21,80 m and diameters of 70 cm, 60 cm and 70 cm, respectively. Those piles were tested in the city of Itatiba, in a region where standard penetration tests evidenced the predominance of sand and silt. In the analyzed piles, the Cintra e Aoki (2010) method has shown the best result for a settlement estimate, when compared with the value obtained by a load test. The Poulos e Davis method (1980) obtained a less satisfactory performance, resulting a margin of sampling error of plus or minus 16%. The Vésic method (1969, 1975a) has shown to be conservative, resulting, in the analyzed cases, an overestimate of 138%, when compared with the load tests values.

scholarly journals Limitations of the Danish driving formula for short piles

2021 ◽  
Vol 44 (2) ◽  
pp. 1-6
Author(s):  
Silvio Heleno de Abreu Vieira ◽  
Francisco R. Lopes
Keyword(s):  
Load Capacity ◽  
Precast Concrete ◽  
Free Fall ◽  
Technical Note ◽  
Driven Piles ◽  
Concrete Piles ◽  
Load Tests ◽  
Semi Empirical ◽  
The City ◽  
Pile Length

Dynamic formulae are a widely used expedient for the control of driven piles to ensure load capacity. These formulae have considerable limitations when used in the prediction of the load capacity on their own, but are very useful in the control of a piling when combined with other tests. This technical note presents an evaluation of the Danish Formula for 54 precast concrete piles, comparing its results with High Strain Dynamic Tests (HSDTs), Static Load Tests (SLTs) and predictions by a semi-empirical static method (Aoki & Velloso, 1975). The data used in the comparison come from three works in the city of Rio de Janeiro, Brazil. All piles were driven with free-fall hammers and in one particular work the piles were relatively short. The predictions of the Danish Formula were evaluated in relation to the pile length/diameter ratio. It was concluded that for short piles - with lengths less than 30 times the diameter - this formula indicates bearing capacities higher than the actual ones. A correction for a safe use of the Danish Formula for short piles is suggested.

Instrumented load tests in mudstone: pile capacity and settlement prediction

2002 ◽  
Vol 39 (6) ◽  
pp. 1254-1272 ◽  
Author(s):  
J R Omer ◽  
R Delpak ◽  
R B Robinson
Keyword(s):  
Load Transfer ◽  
Load Capacity ◽  
Large Diameter ◽  
Soft Rock ◽  
Site Investigation ◽  
Alternative Methods ◽  
Vertical Loading ◽  
South Wales ◽  
Pile Design ◽  
Load Tests

The present work stems from the design of a viaduct in South Wales, U.K., where full-scale pile testing was carried out to assess whether the proposed design methods would meet the required load capacity and settlement criteria for the working piles. Five fully instrumented large diameter bored cast in situ piles, up to 30 m deep, were installed in weathered mudstone and tested under vertical loading. A sixth pile, which had no shaft instrumentation, was formed with a voided toe. In conjunction with vast soil data from 218 site investigation boreholes, the extensive data produced from the load tests were analyzed to quantify the key parameters considered to influence load transfer and settlement behaviour. Each pile was first calibrated using four methods to establish the as-built stiffness, taking into account the nonlinearity of concrete and the effect of partial steel encasement. It is demonstrated that the current national norms for bored pile design in cohesive soil – soft rock are overconservative for South Wales ground conditions. To ameliorate this, alternative methods are proposed, which lead to improved reliability and accuracy in shaft and base capacity assessment. In addition, a numerical model is developed that can be used to predict the complete load-settlement variation up to the ultimate state. The model is sufficiently expounded to allow its immediate application in pile design by geotechnical engineers.Key words: piled foundations, load tests, bearing capacity and settlement, Mercia mudstone.

Behaviour of Vertically Loaded Piled Raft System

2020 ◽  
Vol 17 (5) ◽  
pp. 2383-2387
Author(s):  
K. Merin Jose ◽  
Divya Krishnan ◽  
P. T. Ravichandran
Keyword(s):  
Bearing Capacity ◽  
Load Capacity ◽  
Load Test ◽  
Ultimate Load Capacity ◽  
Foundation Soil ◽  
Total Load ◽  
Piled Raft ◽  
Piled Raft Foundation ◽  
Raft Foundation ◽  
Dense State

A foundation gives the overall strength to a building by providing a level surface for the building to stand and distributing the total load uniformly to the underlying soil. The type of foundation to be chosen varies with the foundation soil and site conditions. Piled raft system are a type of foundation preferred when the bearing strata has less soil bearing capacity and a huge load has to be transferred. Thus Piled raft foundation is a foundation system which uses the combined effects of both rafts and piles such that it is expected to transfer huge loads without large settlement. An ample evaluation of factors like number of piles, length of piles, and degree of compaction of soil that affects the performance of the foundation is required, to understand the concept of piled raft foundation. This study was based on the behaviour of vertically loaded piled raft system by varying the length of pile as 100 mm, 150 mm and 200 mm with 4 and 9 numbers of pile conducted on loose and dense state in cohesion less soil. A vertical load test was conducted on unpiled raft both in loose and dense state of soil also and the results obtained from both piled and unpiled rafts were compared together. The compared results indicated an improvement in ultimate load capacity and settlement reduction. A settlement reduction of 32.71% and increased bearing capacity of 63.67% were observed when compared to unpiled raft under dense condition. About 84% of increase in bearing capacity of the piled raft system was observed with varying the degree of compaction of soil from loose to dense state of soil. An optimum design of this piled raft foundation can provide an alternative foundation for high rise buildings, transmission towers, bridges etc. and it can provide an aid to the threat of differential settlement for heavy loaded buildings in poor bearing strata.

scholarly journals Proposal for considering the group effect in the prediction of settlements in pile groups through load transfer methods

2021 ◽  
Vol 44 (2) ◽  
pp. 1-8
Author(s):  
Francisco Vladson Cardins Gomes Filho ◽  
Alfran Sampaio Moura
Keyword(s):  
Load Transfer ◽  
Load Capacity ◽  
Experimental Results ◽  
Interactive Effects ◽  
Group Effect ◽  
Pile Groups ◽  
Limit States ◽  
Load Tests ◽  
Settlement Ratio

When designing a foundation project, it is necessary to ensure that all the elements meet both ultimate and serviceability limit states, which call for predictions of settlement and load capacity. The load transfer methods are a widely used alternative to estimate the load-settlement ratio of piles in the design of foundation projects. However, traditional load transfer methods do not consider the interactive effects between the elements in pile groups. This study proposes changes to the load transfer curves developed by Bohn et al. (2016), aiming to incorporate the group effect in the analysis of load-settlement relationships in pile groups. Comparisons between the predicted settlements obtained using the proposed method and the results of load tests performed by Dai et al. (2012) in Jiangsu, China, showed that the modifications proposed in this study agreed well with the experimental results for most of the analyzed groups.

scholarly journals Use of the dynamic load test to obtain the pile capacity – the Brazilian experience

DYNA ◽  
2021 ◽  
Vol 88 (217) ◽  
pp. 169-177
Author(s):  
Tiago de Jesus Souza ◽  
André Querelli ◽  
Felipe Vianna Amaral de Souza Cruz ◽  
Pablo Cesar Trejo Noreña
Keyword(s):  
Dynamic Load ◽  
Load Capacity ◽  
Test Procedure ◽  
Field Tests ◽  
Load Test ◽  
Deep Foundations ◽  
Pile Capacity ◽  
Dynamic Load Test ◽  
Load Tests ◽  
Semi Empirical

The dynamic load test is currently an important and usual tool for design, control, and quality assurance of deep foundations. The objective of this paper is to compare the expected geotechnical load capacity through empirical and semi-empirical Brazilian methods with the ultimate pile load obtained from the interpretation of Dynamic Load Tests (DLT; PDA). The stress-settlement curve was constructed from CAPWAP analysis with blows of different drop heights of increasing energy – test procedure proposed by Aoki (1989). Continuous flight augering (CFA) Franki and Root piles were evaluated in this study. These piles were tested in different cities in Brazil. Additionally, DLT results were compared with static load tests, and a good correlation was found with these field tests. The article aims to provide comparative background to guide foundation designers, as well as those who routinely develop these projects in Brazil.

Issues on Design of Piled Raft Foundation

2018 ◽  
Vol 14 (1) ◽  
pp. 6057-6061 ◽  
Author(s):  
Padmanaban M S ◽  
J Sreerambabu
Keyword(s):  
Contact Area ◽  
Concrete Slab ◽  
Design Procedure ◽  
Bending Moment ◽  
Foundation Design ◽  
Detailed Review ◽  
Piled Raft ◽  
Piled Raft Foundation ◽  
Raft Foundation ◽  
Influencing Parameters

A piled raft foundation consists of a thick concrete slab reinforced with steel which covers the entire contact area of the structure, in which the raft is supported by a group of piles or a number of individual piles. Bending moment on raft, differential and average settlement, pile and raft geometries are the influencing parameters of the piled raft foundation system. In this paper, a detailed review has been carried out on the issues on the raft foundation design. Also, the existing design procedure was explained.

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