Effect of loading history on the compression and uplift capacity of driven model piles in sand

1992 ◽  
Vol 29 (2) ◽  
pp. 334-341 ◽  
Author(s):  
R. C. Joshi ◽  
Gopal Achari ◽  
Shenbaga R. Kaniraj
Keyword(s):  
Key Words ◽  
Load Transfer ◽  
Uplift Capacity ◽  
Loading History ◽  
Pile Capacity ◽  
Rate Of Penetration ◽  
Constant Rate ◽  
Tip Resistance ◽  
Tension And Compression ◽  
Load Tests

Model piles were tested in dry uniform sand to study the effect of loading history on the behaviour of piles in compression and tension. A sand bed was prepared by the raining technique, and a smooth cylindrical instrumented pile was driven into the sand. Load tests on piles were conducted at a constant rate of penetration of 0.5 mm/min. The effects of length to diameter (L/D) ratio and sand density were also investigated. The load transfer along the pile surface was studied for an L/D ratio of 33. The pile tip resistance was measured for model piles with L/D ratios of 20–33 and was generally found to be constant. A significant decrease in the pile capacity both in tension and compression was noted for piles having a loading history. When a pile was loaded in compression after being loaded in tension, the tip load could be mobilized only after a certain movement of the pile. The mobilization of the shaft load, however, started immediately. Key words : load tests, model piles, dry sand, loading history, tip capacity, shaft capacity, compression, tension, load transfer.

Uplift behaviour of tapered piles established from model tests

2000 ◽  
Vol 37 (1) ◽  
pp. 56-74 ◽  
Author(s):  
M Hesham El Naggar ◽  
Jin Qi Wei
Keyword(s):  
Load Transfer ◽  
Compressive Loading ◽  
Compressive Load ◽  
Tensile Load ◽  
Confining Pressure ◽  
Cohesionless Soil ◽  
Uplift Capacity ◽  
Experimental Modelling ◽  
Confining Pressures ◽  
Load Tests

Tapered piles have a substantial advantage with regard to their load-carrying capacity in the downward frictional mode. The uplift performance of tapered piles, however, has not been fully understood. This paper describes the results of an experimental investigation into the characteristics of the uplift performance of tapered piles. Three instrumented steel piles with different degrees of taper were installed in cohesionless soil and subjected to compressive and tensile load tests. The soil was contained in a steel soil chamber and pressurized using an air bladder to facilitate modelling the confining pressures pertinent to larger embedment depths. The results of this study indicated that the pile axial uplift capacity increased with an increase in the confining pressure for all piles examined in this study. The ratios of uplift to compressive load for tapered piles were less than those for straight piles of the same length and average embedded diameter. The uplift capacity of tapered piles was found to be comparable to that of straight-sided wall piles at higher confining pressure values, suggesting that the performance of actual tapered piles (with greater length) would be comparable to that of straight-sided wall piles. Also, the results indicated that residual stresses developed during the compressive loading phase and their effect were more significant on the initial uplift capacity of piles, and this effect was more pronounced for tapered piles in medium-dense sand.Key words: tapered piles, uplift, axial response, load transfer, experimental modelling.

Comportement, en chambre triaxiale, d'un pieu à frottement dans l’argile

1991 ◽  
Vol 28 (3) ◽  
pp. 434-445
Author(s):  
Marius Roy ◽  
Sylvain Roy ◽  
Jean Dubé
Keyword(s):  
Key Words ◽  
Rate Of Penetration ◽  
Pore Pressures ◽  
Model Pile ◽  
Constant Rate ◽  
Order Of Magnitude ◽  
Loading Tests ◽  
Full Scale Tests ◽  
Friction Pile ◽  
Lateral Friction

This study deals with the behaviour of a friction pile in a clay, in a triaxial chamber, and in particular with the generation of pore pressures during driving, and with the mobilization of lateral friction during loading tests at constant rate of penetration and static. The results show that the setting compares with that of a piezocone, and that the pore pressures generated at the point during driving, in the laboratory, are of the same order of magnitude as those obtained on the field. The conditions of reconsolidation used in the laboratory, which define the effective stresses around the pile, allow the calculation of the lateral friction on the model pile. The same conditions of reconsolidation were applied to the full-scale tests, on the Maskinongé site, and yielded values of angles of friction δ of 16° for steel and 20° for concrete. Key words: pile, clay, triaxial chamber, friction, pore pressure. [Journal translation]

Use of the piezocone test to predict the axial capacity of driven and jacked piles in clay

1996 ◽  
Vol 33 (1) ◽  
pp. 23-41 ◽  
Author(s):  
Marcio SS Almeida ◽  
Fernando AB Danziger ◽  
Tom Lunne
Keyword(s):  
Key Words ◽  
Skin Friction ◽  
Penetration Test ◽  
Cone Penetration ◽  
Pile Capacity ◽  
Axial Capacity ◽  
Tension Tests ◽  
Load Tests ◽  
Pile Load Tests ◽  
Correlation Factors

Results of 43 load tests on driven and jacked piles performed at eight calyey sites have been back-analysed using piezocone test data. A method to evaluate the axial capacity of piles has been proposed in which the pile unit skin friction and the unit end bearing resistance are computed from the net corrected cone resistance, qnet. Correlation factors between piezocone and pile load tests were back-calculated using this approach. As most of the pile tests performed were tension tests, special emphasis was given to the evaluation of the pile unit skin friction. Key words: clay, pile, piezocone, cone penetration test, axial pile capacity, skin friction.

Axial testing and numerical modeling of square shaft helical piles under compressive and tensile loading

2008 ◽  
Vol 45 (8) ◽  
pp. 1142-1155 ◽  
Author(s):  
Ben Livneh ◽  
M. Hesham El Naggar
Keyword(s):  
Numerical Modeling ◽  
Shear Failure ◽  
Load Transfer ◽  
Failure Surface ◽  
Correlation Factor ◽  
Axial Loads ◽  
Element Analysis ◽  
Pile Capacity ◽  
Helical Piles ◽  
Load Tests

Helical piles are increasingly used to support and rehabilitate structures subjected to both tensile and compressive axial loads. This paper presents a detailed investigation into the axial performance of helical piles. The study encompasses 19 full-scale load tests in different soils and numerical modeling using finite element analysis. The ultimate load criteria and load transfer mechanisms for helical piles were examined. In addition, the relationship between the installation effort (torque) and pile capacity was explored to determine its suitability for predicting pile capacity. The piles tested were made of three circular pitched bearing plates welded at a spacing of three helical diameters to a solid-square, slender steel shaft. It is proposed to determine the ultimate pile capacity as the load corresponding to pile head movement equal to 8% of the largest helix diameter plus the pile elastic deflection. A torque correlation factor, KT = 33 m–1 for compression and KT = 24 m–1 for uplift, was established to relate the ultimate pile capacity to the installation torque. It was found that load transfer to the soil is predominantly through a cylindrical shear failure surface that follows the tapered profile of the interhelices soils and the bearing capacity of the lead helix in the direction of loading.

Evaluation of 18 Direct CPT Methods for Estimating the Ultimate Pile Capacity of Driven Piles

2019 ◽  
Vol 2673 (9) ◽  
pp. 127-141 ◽  
Author(s):  
Mohsen Amirmojahedi ◽  
Murad Abu-Farsakh
Keyword(s):  
Prestressed Concrete ◽  
Dimensional Space ◽  
Soil Classification ◽  
Cumulative Probability ◽  
In Situ Tests ◽  
Pile Capacity ◽  
Concrete Piles ◽  
Pile Penetration ◽  
Tip Resistance ◽  
Load Tests

Cone and piezocone penetration tests (CPT, PCPT) are widely acknowledged to be useful and powerful in-situ tests for soil classification and characterization, and for evaluating different soil properties, such as strength and consolidation parameters. Due to similarity, between the cone and the pile penetration, CPT data have been used effectively for estimating ultimate pile capacity. Researchers have developed various direct CPT methods to estimate the ultimate capacity of piles ( Qp) from CPT/PCPT data (tip resistance and sleeve friction) with depth. In this study, the measured ultimate pile capacities ( Qp) obtained from static load tests on 80 square precast prestressed concrete piles in Louisiana were used to evaluate 18 direct pile-CPT methods for estimating ultimate pile capacity. Two approaches were used. In the first approach, three criteria (best fit line, arithmetic mean and standard deviation, and cumulative probability of Qp/Qm) were adopted, and the sum of ranking of all criteria was used to determine the final ranking of each method. A second approach, multidimensional unfolding, was used to display the ranking data in a two-dimensional space. This approach helps to reveal the typical ranking of the pile-CPT methods, the extent of agreement between the piles, the existence of outliers among the piles, and the similarity between the CPT methods. Based on the results of this study, Bustamante and Gianeselli (LCPC), probabilistic, UF, Philipponnat, CPT2000, UWA, De Ruiter and Beringen, and Schmertmann were found to be the best CPT methods (in order) for estimating the ultimate pile capacity of driven PPC piles.

Experimental Study of the Rotary Filling Piles with Large-Diameter under the Axial Load

2012 ◽  
Vol 594-597 ◽  
pp. 527-531
Author(s):  
Wan Qing Zhou ◽  
Shun Pei Ouyang
Keyword(s):  
Experimental Study ◽  
Axial Load ◽  
Load Transfer ◽  
Soft Soil ◽  
Large Diameter ◽  
Shaft Resistance ◽  
Tip Resistance ◽  
Soil Foundation ◽  
Soft Soil Foundation ◽  
Deep Soft Soil

Based on the experimental study of rotary filling piles with large diameter subjected to axial load in deep soft soil, the bearing capacity behavior and load transfer mechanism were discussed. Results show that in deep soft soil foundation, the super–long piles behave as end-bearing frictional piles. The exertion of the shaft resistance is not synchronized. The upper layer of soil is exerted prior to the lower part of soil. Meanwhile, the exertion of shaft resistance is prior to the tip resistance. For the different soil and the different depth of the same layer of soil, shaft resistance is different.

Driven cast-in-situ pile capacity: insights from dynamic and static load testing

2021 ◽  
Author(s):  
Kevin N. Flynn ◽  
Bryan A. McCabe
Keyword(s):  
Dynamic Load ◽  
Shear Stresses ◽  
Load Testing ◽  
Pile Capacity ◽  
Compression Load ◽  
Shaft Resistance ◽  
Pile Installation ◽  
Cast Concrete ◽  
Load Tests

Driven cast-in-situ (DCIS) piles are classified as large displacement piles. However, the use of an oversized driving shoe introduces additional complexities influencing shaft resistance mobilisation, over and above those applicable to preformed displacement piles. Therefore, several design codes restrict the magnitude of shaft resistance in DCIS pile design. In this paper, a series of dynamic load tests was performed on the temporary steel driving tubes during DCIS pile installation at three UK sites. The instrumented piles were subsequently subjected to maintained compression load tests to failure. The mobilised shear stresses inferred from the dynamic tests during driving were two to five times smaller than those on the as-constructed piles during maintained load testing. This was attributed to soil loosening along the tube shaft arising from the oversized base shoe. Nevertheless, the radial stress reductions appear to be reversible by the freshly-cast concrete fluid pressures which provide lower-bound estimates of radial total stress inferred from the measured shear stresses during static loading. This recovery in shaft resistance is not recognised in some European design practices, resulting in conservative design lengths. Whilst the shaft resistance of DCIS piles was underpredicted by the dynamic load tests, reasonable estimates of base resistance were obtained.

scholarly journals Pengaruh Waktu Terhadap Daya Dukung Fondasi Tiang Pada Tanah Lunak Dengan Variasi Kekasaran

2020 ◽  
Vol 16 (1) ◽  
pp. 12
Author(s):  
Zoni Satria ◽  
Ferry Fatnanta ◽  
Soewignjo Agus Nugroho
Keyword(s):  
Rate Of Penetration ◽  
Constant Rate

Kapasitas daya dukung tanah lunak sangat kecil, untuk peningkatan daya dukung digunakan fondasi tiang friksi yang menggunakan kekasaran permukaan tiang dengan waktu pemancangan yang telah ditentukan yaitu 0, 4, 8, 16, 32, dan 64 hari. Tujuan penelitian ini adalah Menentukan seberapa besar peningkatan kapasitas daya dukung fondasi tiang dengan variasi kekasaran permukaan tiang dan waktu pengujian pembebanan. Pengujian pembebanan menggunkan metode CRP (Constant Rate of Penetration Method) sedangkan untuk interpretasi kapasitas aksial tiang pancang menggunakan metode Terzaghi dan Peck. Semua variasi waktu akan dianalisis dan dibandingkan hasil daya dukung aksial dari fondasi tiang polos, kekasaran spasi dan kekasaran penuh. Hasil penelitian menunjukan peningkatan daya dukung selalu meningakat dari umur 0 sampai 64 hari. Kapasitas daya dukung fondasi tiang terbesar terdapat pada tiang kekasaran spasi yaitu 55,9 N. tiang kekasaran penuh sebesar 54,5 N dan tiang polos sebesar 22,8 N. Faktor peningkatan daya dukung (∆10) tiang polos sebesar 0,04,  tiang spasi 0,07 dan tiang penuh 0,09 dengan waktu referensi (t0) = 1 hari. Faktor peningkatan (∆10 ) menunjukan faktor peningkatan kapasitas daya dukung tiang seiringnya dengan pertambahan waktu. 

Predicting the Ultimate Bearing Capacity of Single Piles Based on CPTU

2011 ◽  
Vol 243-249 ◽  
pp. 4402-4407
Author(s):  
Yong Hong Miao ◽  
Guo Jun Cai ◽  
Song Yu Liu
Keyword(s):  
Load Test ◽  
Load Testing ◽  
Pile Capacity ◽  
Piezocone Penetration Test ◽  
Load Carrying ◽  
Load Tests ◽  
Pile Load Test ◽  
Single Piles ◽  
Pile Load Tests ◽  
Best Fit

Six methods to determine axial pile capacity directly based on piezocone penetration test (CPTU) data are presented and evaluated. Analyses and evaluation were conducted on three types piles that were failed during pile load testing. The CPT methods, as well as the CPTU methods, were used to estimate the load carrying capacities of the investigated piles (Qp ). Pile load test were used to determine the measured load carrying capacities (Qm). The pile capacities determined using the different methods were compared with the measured pile capacities obtained from the pile load tests. Two criteria were selected as bases of evaluation: the best fit line for Qp versus Qm and the arithmetic mean and standard deviation for the ratio Qp /Qm. Results of the analyses showed that the best methods for determining pile capacity are the CPTU methods.

Helical Pile Capacity-to-Torque Correlation: A More Reliable Capacity-to-Torque Factor Based on Full Scale Load Tests

2020 ◽  
Vol 14 (2) ◽  
Author(s):  
Moncef Souissi
Keyword(s):  
Axial Load ◽  
Static Load ◽  
Full Scale ◽  
Load Direction ◽  
Pile Capacity ◽  
Helical Piles ◽  
Load Tests ◽  
High Torque ◽  
Low Torque ◽  
The One

The capacity-to-torque ratio, Kt, has been used in the design of helical piles and anchors for over half a century. Numerous research efforts have been conducted to accurately predict this capaci-ty-to-torque ratio. However, almost of all these Kt factors are based on shaft geometry alone. The ca-pacity-to-torque ratio described herein was found to depend on the shaft diameter, shaft geometry, helix configuration, axial load direction, and installation torque. In this study, 799 full scale static load tests in compression and tension were conducted on helical piles of varying shaft diameters, shaft geometry, and helix configurations in different soil types (sand, clay, and weathered bedrock). The collected data were used to study the effect of these variables on the capacity-to-torque ratio and resulted in developing a more reliable capacity-to-torque ratio, Km, that considers the effect of the variables mentioned above. The study shows that the published Kt values in AC358 (ICC-ES Acceptance Criteria for Helical Piles Systems and Devices) underestimate the pile capacity at low torque and overestimate it at high torque. In addition, and based on probability analysis, the predicted capacity using the modified Km results in a higher degree of accuracy than the one based on the published Kt values in AC358.

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