Design of bored piles in residual soils based on field-performance data

1991 ◽  
Vol 28 (2) ◽  
pp. 200-209 ◽  
Author(s):  
M. F. Chang ◽  
B. B. Broms
Keyword(s):  
Load Transfer ◽  
Large Diameter ◽  
Design Procedure ◽  
Field Performance ◽  
Residual Soil ◽  
Residual Soils ◽  
Weak Rocks ◽  
Load Tests ◽  
Bored Piles ◽  
Load Displacement

The current practice for the design of large-diameter bored piles in residual soils in Singapore is based on the calculated static capacity of the piles. Insufficient consideration of the load-transfer mechanism and overreliance on pile load tests have led to conservative designs. A better alternative is to adopt a load–displacement analysis method that provides information on the load distribution along the pile and the complete load–displacement relationship. Results of full-scale load tests on instrumented piles indicate that bored piles in residual soils in Singapore behave in the same way as in stiff clay and weak rocks elsewhere in that the load transfer at the working load is dominated by shaft friction. Simple correlations exist between the standard penetration resistance and the load-transfer parameters. An example illustrates that the proposed design procedure that uses these simple correlations and the load-transfer method is an improvement over present design methods. Key words: bored piles, cast-in-place piles, design, drilled piers, field test, load transfer, residual soil, shaft resistance.

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.

scholarly journals In Situ Lateral Load Tests on Instrumented Bored Piles in Loessial Soils

2017 ◽  
Vol 13 (1) ◽  
pp. 1-11
Author(s):  
Sebastian Drăghici ◽  
Anatolie Marcu
Keyword(s):  
Large Diameter ◽  
In Situ Tests ◽  
Laterally Loaded Piles ◽  
Natural Moisture Content ◽  
Load Tests ◽  
Bored Piles ◽  
Strength And Stiffness ◽  
Laterally Loaded ◽  
Plaxis 3D

Abstract The aim of the paper is to provide some aspects regarding the behaviour of laterally loaded piles in loessial soils, by presenting and analysing the results of several in situ tests on large diameter bored piles in this type of soil. The major feature of loess is that it exhibits a massive decline of its strength and stiffness parameters when it comes into contact with water, leading to the collapse of its structure even under self-weight and creating difficult conditions for foundations. The load tests were performed both in natural moisture content loess and also in saturated loess. The results obtained by means of instrumentation are back-analysed using current analytical methods and also by finite element method using a numerical model in the geotechnical computation software Plaxis 3D.

scholarly journals Experimental and numerical analysis of foundation pilings partially embedded in rock

2013 ◽  
Vol 66 (4) ◽  
pp. 439-446
Author(s):  
Jean Rodrigo Garcia ◽  
Paulo José Rocha de Albuquerque ◽  
Rodrigo Álvares de Araújo Melo
Keyword(s):  
Load Transfer ◽  
Three Dimensional ◽  
Field Tests ◽  
Soil Surface ◽  
Residual Soil ◽  
Geotechnical Parameters ◽  
Weathered Rock ◽  
Load Tests ◽  
Geotechnical Design ◽  
Transfer Method

The behaviours of four foundation pilings (ϕ=0.41 m) constructed in Foz do Iguaçu, Paraná (PR), Brazil and subjected to slow loading tests were analysed. The results were compared with results from three-dimensional numerical modelling using the finite element method, which facilitates simulation of the elasto-plastic behaviour of soil. The local subsoil comprises varied stratigraphies; it is composed of a residual soil surface layer followed by weathered rock and bedrock, which are a few meters deep. The massif geotechnical parameters were determined through correlations obtained from field tests, whereby the values for cohesion, angle of friction, modulus of deformability and uniaxial compressive strength in the different subsoil layers were estimated. The load tests were interrupted at 3000 kN and displaced by less than 5 mm in the working load (1500 kN). The pilings were subjected to lateral friction work with an average stress of approximately 70 kPa for the surface portion (residual soil) and greater than 150 kPa for the weathered rock portions. The estimated geotechnical parameters provided values that were an exact match with the numerical analyses. Thus, given the analyses and load transfer method, the piling lengths can be reduced, which will facilitate the optimisation of the geotechnical design.

Back-Analysis for Design Parameters of Large Diameter Bored Piles

2013 ◽  
Vol 671-674 ◽  
pp. 186-189
Author(s):  
Werasak Raongjant ◽  
Meng Jing
Keyword(s):  
Test Data ◽  
Load Transfer ◽  
Static Load ◽  
Large Diameter ◽  
Back Analysis ◽  
Load Test ◽  
Design Parameters ◽  
Static Load Test ◽  
Friction Resistance ◽  
Bored Piles

Field test data from three instrumented large diameter bored piles in Pattaya city of Thailand were analyzed to study the behavior of load transfer mechanism from the pile to soil. The pile load test data were obtained from conventional static load test. These bored piles used for conventional static load test have the same diameter of 0.80 m and different length in the range of 25 m to 32 m. Results from back-analysis found that the skin friction resistance, β, has the value between 0.20 and 0.64 and the bearing capacity at end of piles, Nq, which is in the range of 10 to150, is much lower than the theoretical values proposed by other researchers before.

Methods of improving the performance of drilled piers in weak rock

1983 ◽  
Vol 20 (4) ◽  
pp. 758-772 ◽  
Author(s):  
R. G. Horvath ◽  
T. C. Kenney ◽  
P. Kozicki
Keyword(s):  
Load Transfer ◽  
Limit State ◽  
Elastic Behaviour ◽  
Weak Rock ◽  
Test Results ◽  
Shaft Resistance ◽  
Load Tests ◽  
Rock Interface ◽  
Load Displacement ◽  
State Analysis

Investigations were made of two methods to improve the load–displacement performance of concrete piers socketed into very weak rock. Results of load tests on six full-size piers are reported.One method involved cutting grooves into the socket wall to roughen the pier–rock interface and thus increase the shaft resistance component of load support. Two types of piers were tested: piers with a void at the base (shaft resistance only) and piers having both shaft resistance and end-bearing resistance. In the latter case, flatjack load cells were installed to measure base loads. The test results indicated that increasing the roughness of the socket wall can cause important increases in shaft resistance.The second method involved the application of preload to the socket base to increase the end-bearing component of load support at small displacements. The test results showed that preloading the socket base resulted in a stiffer load–displacement behaviour of the pier–socket system.The initial portions of the load–displacement curves from all the tests were linear, reflecting elastic behaviour of the pier–socket system. This elastic behaviour did not appear to rely on socket roughness. Beyond the limit of proportionality, the load–displacement behaviour of each pier departed from that of an elastic system, and this departure was more rapid for the piers with smooth sockets than for those with roughened socket walls. Preloading the socket base caused the elastic range of loading to be extended.Two design approaches, limit-state analysis and elastic-state analysis, are discussed. Keywords: drilled piers and caissons, large-bored piles, shaft resistance, grooved shaft, load transfer, preload, shale, weak rock.

Settlement Analysis of Single Large-Diameter and Super-Long Bored Piles in Cohesive Soils

2012 ◽  
Vol 594-597 ◽  
pp. 320-326 ◽  
Author(s):  
Rui Kun Zhang ◽  
Ming Lei Shi ◽  
Jin Wang
Keyword(s):  
Hybrid Method ◽  
Load Transfer ◽  
Large Diameter ◽  
Soft Clay ◽  
Small Diameter ◽  
Transfer Characteristic ◽  
Single Pile ◽  
Element Analysis ◽  
Bored Piles ◽  
Axially Loaded

The behavior of single axially loaded large-diameter and super-long bored piles have large difference to single small diameter short piles. The article analyzes the load transfer characteristic of single axially loaded large-diameter and super-long bored piles in deep soft clay in the Yangtze River Delta region. And the hybrid method of finite element analysis of rod structure coupling with the shear displacement method for single pile was utilized to simulating and predicting the single pile performance. It is verified that the settlement calculation hybrid method in this paper is reliable.

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