Capacity Of Piles In Sand Research Articles

Analysis of the End-Bearing Capacity of Piles in Sand Under Limited Region Failure by a Mixed Zero-Extension Line Method

Analysis of the End-Bearing Capacity of Piles in Sand Under Limited Region Failure by a Mixed Zero-Extension Line Method

Effect of cyclic loading at a large number of cycles on the bearing capacity of piles in sand

Effect of cyclic loading at a large number of cycles on the bearing capacity of piles in sand

Dynamic response of open pipe pile under vertical cyclic loading in sand and clay

The bearing capacity of a pile under vertical cyclic loading is one of key factor in the design of pile foundation. In this study, an innovative large-scale model test of double-wall open-ended pipe pile was conducted to investigate the cyclic bearing characteristics of open-ended pipe pile under various soil conditions and load frequencies. The experimental results show that the ultimate bearing capacity of piles in sand is much larger than that in clay. Under cyclic loading, the cumulative settlement in clay was found to be larger than that in sand, which was clearly indicated by clear increasing and stabilizing trends. Furthermore, the external friction of pipe pile in sand changes in an oblique “V” shape with depth, whereas that of the pipe pile in clay is inclined “W”. With increase in number of cycles, the external friction of upper part of the pipe pile and the internal friction of lower part of the pipe pile in sand decrease first and then tend to be stabilize. On the other hand, the external friction of upper and middle parts of pipe pile and internal friction of lower part of pipe pile in clay observed to have the same trend. Contrarily, the external friction in the middle of pipe pile in sand is an opposite trend. Moreover, the load frequency of dynamic cycle loading tends to have a great influence on the friction resistance, and this influence is more significant in clay than that in sand.

A field investigation into the mechanisms of pile ageing in sand

The design of axially loaded piles has been an area of focus for the offshore industry in recent years. A number of studies report substantial increases in the shaft capacity of piles driven in sand, known as pile ageing. The offshore industry has been slow to implement ageing into practice because of uncertainty over the mechanisms controlling ageing and variability on the impact of ageing. This paper presents the results of tests using an instrumented pile with two separate installations considered, one where the pile was load tested 4 days after installation and the second where the load test was performed after an ageing period of 116 days. Data from the installation, ageing period, load testing and pile extraction provide further insights into the mechanisms governing the effect of time on the axial capacity of piles in sand.

Design equations of uplift capacity of circular piles in sands

Uplift capacity of circular piles in sands is one important design parameter for many pile foundations supporting important structures subjected to tensile forces. Even though a number of formulas based on the limit equilibrium or semi-empirical methods are proposed to predict the uplift capacity of piles in sands, there is a major limitation of the methods in obtaining the accurate predictions. In this paper, the computational limit analysis is employed to investigate the uplift capacity of circular piles in sands. The effects of the important variables including pile length and diameter, soil friction angle and unit weight, and roughness factor at soil-pile interface are examined extensively using the dimensionless parameters while the predicted failure mechanisms associated with the parameters are discussed and compared. Approximate statistical design equations of the uplift capacity of circular piles in sands are developed based on the numerically derived solutions and the existing experimental data. It is found that the proposed design equations provide the most accurate prediction of the uplift capacity of circular piles in sands as compared to the existing formulas.

Neural networks and principle component analysis approaches to predict pile capacity in sand

Determination of pile bearing capacity from the in-situ tests has developed considerably due to the significant development of their technology. The project presented in this paper is a combination of two approaches, artificial neural networks and main component analyses that allow the development of a neural network model that provides a more accurate prediction of axial load bearing capacity based on the SPT test data. The retropropagation multi-layer perceptron with Bayesian regularization (RB) was used in this model. This was established by the incorporation of about 260 data, obtained from the published literature, of experimental programs for large displacement driven piles. The PCA method is proposed for compression and suppression of the correlation between these data. This will improve the performance of generalization of the model.

Neural networks and principle component analysis approaches to predict pile capacity in sand

Determination of pile bearing capacity from the in-situ tests has developed considerably due to the significant development of their technology. The project presented in this paper is a combination of two approaches, artificial neural networks and main component analyses that allow the development of a neural network model that provides a more accurate prediction of axial load bearing capacity based on the SPT test data. The retropropagation multi-layer perceptron with Bayesian regularization (RB) was used in this model. This was established by the incorporation of about 260 data, obtained from the published literature, of experimental programs for large displacement driven piles. The PCA method is proposed for compression and suppression of the correlation between these data. This will improve the performance of generalization of the model.

Bearing Capacity of T-Cross Section Piles in Sand

Abstract This paper describes a series of pile tests in sand. T-cross and square cross section piles were jacking by static vertical load with a vibration. Special tests were carried out to examine the influence of T-cross section pile form on it bearing capacity, and the results of comparison bearing capacity on one cub meter of T-cross and square cross section jacking piles in the same ground conditions are described. The jacking vertical static load, sizes of displacements and compaction zones of a ground around a shaft of the experienced piles were investigated.

Predicting the axial capacity of piles in sand

Currently, although several tools have been proposed for the numerical modelling of the pile–soil interface, there is not a well-established framework concerning the quantitative impact that different estimations of the mechanical properties of this setting have on the prediction of the bearing capacity of piles. With reference to the results of a finite element prediction of a centrifuge test on a pile in saturated sand, this paper presents a sensitivity analysis based on a design of experiment approach in an effort to solve this problem. The work proves the contribution of specific material parameters to the variation of the analyses results. Furthermore, the work highlights fundamental aspects to consider when modelling pile-related problems through the finite element method, looking at a comparable adherence to physical reality of the results.

A numerical approach to estimate shaft friction of bored piles in sands

A new approach to estimate shaft capacity of bored piles in sandy soils, based on numerical analysis, is presented. The topic is relevant as current design methods often largely underestimate the shaft capacity of piles in sands, thus resulting in an over-conservative design. The proposed approach is based on explicitly modelling the thin cylinder of soil surrounding the pile, where strain localization concentrates (shear band), and on the fundamental mechanic behaviour of sandy soils (e.g. dilatancy, softening). This approach is both simple and easy to apply. Results of a broad parametric study involving axially loaded single piles embedded in different sandy soils are presented, highlighting that relative density and grain size distribution mainly affect the shaft capacity. The capability of the procedure to predict shaft friction is checked against data from a well-documented full-scale axial load test on instrumented pile. Some suggestions for calibration and application of the method are also reported.

Theoretical breakage mechanics and experimental assessment of stresses surrounding piles penetrating into dense silica sand

This letter extends an earlier theoretical and numerical analysis that aimed to improve predictions for the large-displacement end-bearing capacity of piles in sand by considering the boundary conditions applying to steady penetration and the effects of grain crushing via breakage mechanics. The earlier work led to good agreement with the end-bearing capacities, soil displacements and evolution of grain size distributions observed in experiments of penetrating model piles. The purpose of the current paper is to complement the previous evaluation through comparisons with more recently published calibration chamber measurements of the stresses surrounding instrumented model piles penetrating into dense silica sand. Encouraging agreement is demonstrated for the radial, circumferential and vertical stress components. Scope for further improvements is also identified.

Effect of Stress Level of Surrounding Soil on Bored Pile Capacity in Sand

Effect of Stress Level of Surrounding Soil on Bored Pile Capacity in Sand

Erratum for “Estimation of Lateral Load Capacity of Rigid Short Piles in Sands Using CPT Results” by Junhwan Lee, Minki Kim, and Doohyun Kyung

Erratum for “Estimation of Lateral Load Capacity of Rigid Short Piles in Sands Using CPT Results” by Junhwan Lee, Minki Kim, and Doohyun Kyung

The effect of ageing on the axial capacity of piles in sand

Open-ended steel pipe piles are used to support jacket structures in the offshore wind sector. These piles experience significant tensile axial loading in-service and the tensile shaft resistance thus governs their design. Although pile ageing (increased shaft resistance with time) has been noted by a number of workers and incorporation in design could lead to significant efficiencies, there is a dearth of high-quality field test data that measure its effects. This paper presents the results from an experimental investigation designed to examine the effect of ageing on the tension shaft resistance developed by open-ended piles in sand. As part of this investigation, four 340 mm diameter open-ended steel piles are driven 7 m into a dense sand deposit in Blessington, Ireland. Each pile is subjected to a series of static axial tension load tests at different time intervals after driving and the effects of ageing are assessed. The tension capacity of the piles is seen to increase by as much as 185% over a period of 7 months after driving.

Estimation of Ultimate Lateral Load Capacity of Piles in Sands Using Calibration Chamber Tests

Abstract Current practice for the estimation of the ultimate lateral load capacity of piles is typically based on the vertical effective stress σ′v, while the effect of the lateral effective stress σ′h is not specifically considered. In the present study, calibration chamber lateral pile load tests are conducted to investigate the load response and ultimate lateral load capacity Hu of laterally loaded piles under various soil and stress conditions. In order to determine Hu from load-deflection curves, different criteria are explored and analyzed. From the test results, it is shown that Hu increases significantly with increasing σ′h for a given σ′v. It is also found that lateral deflection of pile at ultimate state tends to increase as the relative density and lateral stress increase. On the basis of the test results, the lateral stress correction factor reflecting the effect of the lateral effective stress σ′h on Hu is proposed. From the test results, it is seen that the proposed procedure using the lateral stress correction factor produces more realistic estimation of Hu. Case examples are selected from the literature and used to compare results measured and predicted using the proposed approach.

Effect of spatial correlation of standard penetration test (SPT) data on bearing capacity of driven piles in sand

In this paper, the effect of spatial correlation of standard penetration test (SPT) data on the bearing capacity of driven piles in sand is analyzed. First, the direct approach for using SPT data to determine the bearing capacity of piles in sand is used to derive the expressions for probabilistic prediction of pile bearing capacity by considering the spatial correlation of the SPT data. To analyze the relationship between the probability of failure and the factor of safety, a procedure based on the advanced first-order, second-moment (FOSM) method is used. Then parametric studies are conducted on the spatial correlation between the spatial average of SPT numbers over the pile length, NLV, and the spatial average of SPT numbers over an interval near the pile base, NbV, and its effect on the bearing capacity of piles. The results indicate that it is important to consider the spatial correlation between NLVand NbVin the probabilistic prediction of pile bearing capacity. Ignoring this spatial correlation will underestimate the probability of failure and lead to unsafe design. Finally, three tested piles are analyzed to demonstrate the probabilistic analysis of piles by considering the spatial correlation of SPT data and the procedure for probabilistic analysis of pile bearing capacity is summarized.

Experimental study on the effect of compressive loads on uplift capacity of model piles in sand

In this study, a total of twenty one model tests were performed on single piles embedded in dense sand to investigate the influence of compressive loads on uplift capacity of piles. The tests were carried out using smooth steel pile with a 25-mm outside diameter and a 55-mm length. The piles were embedded in uniform deposit of dense sand for depth-to-diameter ratios of 10, 14 and 20. Static compressive loads of 0%, 25%, 50%, 75%, and 100% of the ultimate compressive pile capacity were applied to the model piles and the piles were subjected to pull out loads. The experimental results showed that the percentage of compressive loads is a significant parameter influencing the net uplift capacity of the pile. The net uplift capacity decreases with the increase in the percentage of compressive loads. There is almost a gradual decrease in net uplift capacity with increase in compressive loads. Maximum decrease in net uplift capacity is observed at the 100% of compressive loading.

Database Assessment of CPT-Based Design Methods for Axial Capacity of Driven Piles in Siliceous Sands

Numerous cone penetration test (CPT)-based methods exist for calculation of the axial pile capacity in sands, but no clear guidance is presently available to assist designers in the selection of the most appropriate method. To assist in this regard, this paper examines the predictive performance of a range of pile design methods against a newly compiled database of static load tests on driven piles in siliceous sands with adjacent CPT profiles. Seven driven pile design methods are considered, including the conventional American Petroleum Institute (API) approach, simplified CPT alpha methods, and four new CPT-based methods, which are now presented in the commentary of the 22nd edition of the API recommendations. Mean and standard deviation database statistics for the design methods are presented for the entire 77 pile database, as well as for smaller subset databases separated by pile material (steel and concrete), end condition (open versus closed), and direction of loading (tension versus compression). Certain methods are seen to exhibit bias toward length, relative density, cone tip resistance, and pile end condition. Other methods do not exhibit any apparent bias (even though their formulations differ significantly) due to the limited size of the database subsets and the large number of factors known to influence pile capacity in sand. The database statistics for the best performing methods are substantially better than those for the API approach and the simplified alpha methods. Improved predictive reliability will emerge with an extension of the database and the inclusion of additional important controlling factors affecting capacity.

Use of State-Dependent Strength in Estimating End Bearing Capacity of Piles in Sand

The pressure and density dependence of the shear strength of sand poses a tricky problem in pile foundation design. In this study, a correlation is suggested to link the effective friction angle of sand with its initial confining pressure and relative density, and a simple approach incorporating this correlation is presented for predicting pile end bearing capacity. Assessment of the approach against pile load tests shows reasonably good agreement between predictions and measurements. It is also shown that the effect of the state-dependent strength is particularly important in cases where long piles are installed in dense sand deposits and the use of critical state friction angle will produce a conservative prediction in such cases.

Discussion of “Determination of Bearing Capacity of Open-Ended Piles in Sand” by Kyuho Paik and Rodrigo Salgado

Discussion of “Determination of Bearing Capacity of Open-Ended Piles in Sand” by Kyuho Paik and Rodrigo Salgado