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.

Effect of Second Loading on the Instrumented Continuous Flight Auger Concrete Pile on Porous Soil

2017 ◽  
Vol 753 ◽  
pp. 285-289
Author(s):  
Paulo Jose Rocha Albuquerque ◽  
David de Carvalho
Keyword(s):  
Load Capacity ◽  
Load Test ◽  
Silty Clay ◽  
Residual Soil ◽  
Concrete Pile ◽  
Clayey Silt ◽  
Slow Type ◽  
Load Tests ◽  
Site Test ◽  
The University

This paper presents the results of two load tests carried out in a continuous flight auger pile of 0.4 m in diameter and 12 m in length. The pile was instrumented in depth with strain gages in order to obtain the load capacity along the shaft and the tip. The load tests were carried out at the University of Campinas Experimental Site Test. The subsoil where the pile was installed is constituted by a first stratum of Silty Clay, which is porous and collapsible, of 6.5 m in thickness, followed by a stratum of residual soil of Clayey Silt up to 14 m depth. The first load test was the slow type, and a quick load test in the same pile after five days. From the results obtained with the use of instrumentation, the values for both lateral and tip load were determined in each one of test carried out in the pile studied. With these results and applying the Cambefort’s Law, it was could evaluate the evolution of the shaft friction and tip load in relation to the associated settlements, as well as the occurrence of residual load. The ultimate load obtained in the test was 960 kN and 810 kN for the first and second tests, respectively. The stress for the tip was 853 kPa and 655 kPa for the first and second tests, respectively.

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 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.

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.

scholarly journals Feedback of the behaviour of a silo founded on a compressible soil improved by floating stone columns

2018 ◽  
Vol 149 ◽  
pp. 02008
Author(s):  
Ramdane Bahar ◽  
Omar Sadaoui ◽  
Fatma Zohra Yagoub
Keyword(s):  
Soft Soil ◽  
Limit State ◽  
Soil Improvement ◽  
Stone Columns ◽  
Soil Conditions ◽  
Deep Foundations ◽  
The Stability ◽  
Compressible Soil ◽  
The City ◽  
Ongoing Monitoring

The coastal city of Bejaia, located 250 kilometers east of the capital Algiers, Algeria, is characterized by soft soils. The residual grounds encountered on the first 40 meters usually have a low bearing capacity, high compressibility, insufficient strength, and subject to the risk of liquefaction. These unfavorable soil conditions require deep foundations or soil improvement. Since late 1990s, stone columns technique is used to improve the weak soils of the harbor area of the city. A shallow raft foundation on soft soil improved by stone columns was designed for a heavy storage steel silo and two towers. The improvement of 18m depth have not reached the substratum located at 39m depth. The stresses transmitted to the service limit state are variable 73 to 376 kPa. A rigorous and ongoing monitoring of the evolution of loads in the silo and settlements of the soil was carried out during 1400 days that is from the construction of foundations in 2008 to 2012. After the loading of the silo in 2010, settlement occurred affecting the stability of the towers due to excessive differential settlements. Consequently, the towers were inclined and damaged the transporter. This paper presents and discusses the experience feedback of the behavior of these structures. Numerical calculations by finite elements have been carried and the results are compared with the measurements.

Evaluation of peak side resistance for rock socketed shafts in weak sedimentary rock from an extensive database of published field load tests: a limit state approach

2019 ◽  
Vol 56 (12) ◽  
pp. 1816-1831 ◽  
Author(s):  
Pouyan Asem ◽  
Paolo Gardoni
Keyword(s):  
Test Data ◽  
Limit State ◽  
Deformation Modulus ◽  
Load Test ◽  
Resistance Factors ◽  
Strength Limit ◽  
Side Resistance ◽  
Load Tests ◽  
Load And Resistance Factor

This paper presents analyses of the measured peak side resistance of rock sockets constructed in weak claystone, shale, limestone, siltstone, and sandstone. The peak side resistance is obtained from in situ axial load tests on drilled shafts, anchors, and plugs. The parameters that affect the development of peak side resistance are determined using in situ load test data. It is found that peak side resistance increases with the unconfined compressive strength and deformation modulus of the weak rock, and decreases with the increase in length of the shear surface along the rock socket sidewalls. The increase in socket diameter also slightly decreases the peak side resistance. Additionally, it is found that the initial normal stresses do not significantly affect the measured peak side resistance in the in situ load tests. The in situ load test data are used to develop an empirical design equation for determination of the peak side resistance. The proposed model for peak side resistance and the reliability analysis are used to determine the corresponding resistance factors for use in the load and resistance factor design framework for assessment of the strength limit state.

Resistance Factors at Serviceability Limit State Using the Texas Cone Penetrometer as the Predictive Model

2021 ◽  
Vol 15 (1) ◽  
Author(s):  
Rozbeh Moghaddam
Keyword(s):  
Limit State ◽  
Drilled Shafts ◽  
Load Test ◽  
Deep Foundations ◽  
Driven Piles ◽  
Resistance Factors ◽  
Serviceability Limit State ◽  
First Order Second Moment ◽  
Texas Cone Penetrometer ◽  
Load And Resistance Factor

This study presents the development and calibration of resistance factors for the serviceability limit state (SLS) condition (φSLS) used in the load and resistance factor design (LRFD) of deep foundations. The performance function was established based on load corresponding to tolerable displacement (Qδtol) and design load (Qd). A dataset of published full-scale load tests including projects from Texas, Missouri, Arkansas, Louisiana, and New Mexico was compiled and consisted of 60 load test cases comprising 33 driven piles and 27 drilled shafts. Resistance factors for SLS conditions were calibrated for tolerable displacements using both the Monte Carlo simulation (MCS) and the First Order Second Moment (FOSM) approaches. From the calibration study, resistance factors at SLS conditions were obtained ranging from 0.33 to 0.62 using FOSM method and 0.37 to 0.67 using the MCS for driven piles. In the case of drilled shafts, SLS resistance factors ranged from 0.37 to 0.77 following the FOSM method and 0.41 to 0.86 based on MCS.

Reliability-based design of deep foundations based on differential settlement criterion

2009 ◽  
Vol 46 (2) ◽  
pp. 168-176 ◽  
Author(s):  
Lance A. Roberts ◽  
Anil Misra
Keyword(s):  
Soil Structure ◽  
Load Capacity ◽  
Limit State ◽  
Interaction Model ◽  
Differential Settlement ◽  
Model Parameters ◽  
Deep Foundations ◽  
Deep Foundation ◽  
Reliability Based Design ◽  
Service Limit State

Load–displacement analysis of a single deep foundation element can be accomplished by utilizing a soil–structure interaction model, such as the “t–z” model. By combining the soil–structure interaction model with a probabilistic analysis technique, such as Monte Carlo simulation, methods to rationally incorporate variability in the model parameters can be developed. As a result, the service limit state load capacity of a single deep foundation element can be computed for an allowable total head displacement. However, in design, differential settlement between individual foundation elements is often the event of interest. This paper develops a reliability-based design methodology for deep foundations based on a differential settlement design criterion. The design methodology is developed for various levels of uncertainty in the model parameters. The results are presented in the form of cumulative distribution functions that, combined with the calculated service limit state load capacity, form the basis for serviceability design of deep foundations based on a differential settlement criterion.

scholarly journals Static load test curve (Q–s) conversion in to pile of different size

2018 ◽  
Vol 50 (2) ◽  
pp. 171-182
Author(s):  
Zygmunt Meyer ◽  
Kamil Stachecki
Keyword(s):  
Mathematical Description ◽  
Static Load ◽  
Load Capacity ◽  
Limit Load ◽  
Load Test ◽  
Static Load Test ◽  
Load Curve ◽  
Load Tests ◽  
Different Diameters ◽  
Calculation Analysis

Abstract In the work authors analysed possibility of obtaining static load tests curve for a pile in case of changed diameter, using load curve based on results of static load tests for given diameter. In calculation analysis authors used Meyer–Kowalów (M-K) method. A mathematical description was shown of determining new M-K curve for a pile with changed diameter, taking as a basis original M-K curve obtained from static load tests. Then an example of calculations is presented in which parameters of M-K model for a new curve were determined. Simulation calculations were carried out in the original computer program, the results of which includes load curves for piles with different diameters and relations between diameter changes, limit load capacity and settlement of a pile.

Evaluation of model uncertainties in reliability-based design of steel H-piles in axial compression

2018 ◽  
Vol 55 (11) ◽  
pp. 1513-1532 ◽  
Author(s):  
Chong Tang ◽  
Kok-Kwang Phoon
Keyword(s):  
Axial Compression ◽  
Limit State ◽  
Load Test ◽  
Hyperbolic Model ◽  
Ultimate Limit State ◽  
Model Uncertainties ◽  
Deep Foundation ◽  
Mean Values ◽  
Reliability Based Design ◽  
Load Tests

To account for uncertainties of load and resistance in a more rational way, reliability-based design (RBD) concepts have been increasingly applied to design bridge foundations. One of critical elements in the geotechnical RBD process is the characterization of model uncertainties. This paper compiles 126 and 23 reliable static load tests for steel H-piles in axial compression from two databases: Pile-Load Tests (PILOT) and Deep Foundation Load Test Database (DFLTD), respectively. The Davisson offset limit is adopted to define the measured resistance in clay, sand, and layered soil, which is verified with the L1–L2 method developed for drilled shafts. A hyperbolic model with two parameters is chosen to fit the measured load–settlement curves. The uncertainties in resistance calculations and the load–settlement curves are captured by a ratio (or model factor) of measured to calculated resistance and the hyperbolic parameters. The mean values, coefficients of variation, and the probability distributions of the model factors are established from 149 load tests. The statistics of the resistance model factor are applied to calibrate the resistance factors (for the ultimate limit state) in load and resistance factor design of steel H-piles in axial compression. In future, the statistics of the hyperbolic parameters can be incorporated into the development of RBD of steel H-piles at the serviceability limit state.

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