scholarly journals Static loading tests on small-scale pile groups

2021 ◽  
Vol 72 (1) ◽  
pp. 84-94
Author(s):  
Lan Bach Vu Hoang
Keyword(s):  
Soft Clay ◽  
Pile Group ◽  
Scale Model ◽  
Small Scale ◽  
Outer Diameter ◽  
Pile Groups ◽  
Pile Spacing ◽  
Circular Model ◽  
Group Piles ◽  
Pile Length

36 small-scale model tests in soft clay were conducted to research the performances of pile groups under rigid caps. The parameters studied were the effect of pile length, pile spacing, and the number of piles in a group. The group piles consisted of 4, 6, and 9 circular model piles of 16mm in outer diameter (D), while four kinds of the pile spacing between pile centers 3; 4; 5; and 6 times of the diameter and three types of the embedded pile lengths: 20D; 25D; and 30D were used. For comparison, three single piles with the same diameter and length were also tested under the same condition. The experimental results were discussed based on the following 3 points of view: the pile group efficiency, the settlement ratio, load distribution per pile location in the group pile. All discussion suggested that the pile number and pile spacing in a pile group caused a remarkable interactional effect between piles, whereas the settlement ratios are significantly affected by the pile length. Besides, each pile in the group of 6D pile spacing behaved more individually.

Small scale model test on lateral behaviors of pile group in loose silica sand

2021 ◽  
Vol 18 (1) ◽  
pp. 41-54
Author(s):  
Amir Vakili ◽  
Seyed Mohammad Ali Zomorodian ◽  
Arash Totonchi
Keyword(s):  
Model Test ◽  
Pile Group ◽  
Lateral Load ◽  
Reduction Factor ◽  
Silica Sand ◽  
Scale Model ◽  
Small Scale ◽  
Pile Groups ◽  
Pile Spacing ◽  
Group Reduction

The accurate predictions of load- deflection response of the pile group are necessary for a safe and economical design. The behavior of piles under the lateral load embedded in soil, is typically analyzed using the Winkler nonlinear springs method. In this method, the soil-pile interaction is modeled by nonlinear p-y curves in a way that the single pile p-y curve is modified using a p-multiplier (Pm) for each row of piles in the group. The average Pm is called the group reduction factor. The Pm factor depends upon the configuration of pile group and the pile spacing (S). The present study was conducted to investigate the effects of various parameters, such as the pile spacing in the group, different layouts and the lateral load angle (Ѳ) change as a new parameter on the Pm factor and group efficiency based on the 1-g model test. The Pm factor is well comparable with the results of the full-scale test on pile group. However, based on the results, the calculated values of the Pm factor for 3×3 pile groups under 2.5-diameter spacing was estimated about 0.38 and under 3.5-diameter spacing was estimated about 0.52, so the calculated values at S/D=3, obtained from interpolation the values of group reduction factor at S/D=2.5 and S/D=3.5, are close to the AASHTO recommendation.

scholarly journals Numerical Study of Laterally Loaded Piles in Soft Clay Overlying Dense Sand

2021 ◽  
Vol 7 (4) ◽  
pp. 730-746
Author(s):  
Amanpreet Kaur ◽  
Harvinder Singh ◽  
J. N. Jha
Keyword(s):  
Layer Thickness ◽  
Soft Clay ◽  
Bending Moment ◽  
Layered Soil ◽  
Clay Layer ◽  
Pile Groups ◽  
Dense Sand ◽  
Lateral Capacity ◽  
Laterally Loaded ◽  
Pile Length

This paper presents the results of three dimensional finite element analysis of laterally loaded pile groups of configuration 1×1, 2×1 and 3×1, embedded in two-layered soil consisting of soft clay at liquid limit overlying dense sand using Plaxis 3D. Effects of variation in pile length (L) and clay layer thickness (h) on lateral capacity and bending moment profile of pile foundations were evaluated by employing different values of pile length to diameter ratio (L/D) and ratio of clay layer thickness to pile length (h/L) in the analysis. Obtained results indicated that the lateral capacity reduces non-linearly with increase in clay layer thickness. Larger decrease was observed in group piles. A non-dimensional parameter Fx ratio was defined to compare lateral capacity in layered soil to that in dense sand, for which a generalized expression was derived in terms of h/L ratio and number of piles in a group. Group effect on lateral resistance and maximum bending moment was observed to become insignificant for clay layer thickness exceeding 40% of pile length. For a fixed value of clay layer thickness, lateral capacity and bending moment in a single pile increased significantly with increase in pile length only up to an optimum embedment depth in sand layer which was found to be equal to three times pile diameter and 0.21 times pile length for pile with L/D 15. Scale effect on lateral capacity has also been studied and discussed. Doi: 10.28991/cej-2021-03091686 Full Text: PDF

scholarly journals Working Mechanism of Pile Group with Different Pile Spacing in Dense Sand

2019 ◽  
Vol 2019 ◽  
pp. 1-16 ◽  
Author(s):  
Yadong Chen ◽  
Fan Lu ◽  
Abdoullah Namdar ◽  
Jiangdong Cai
Keyword(s):  
Three Dimensional ◽  
Interaction Mechanism ◽  
Pile Group ◽  
Resistance Pattern ◽  
Pile Groups ◽  
Pile Spacing ◽  
Dense Sand ◽  
Energy Mechanism ◽  
Tip Resistance ◽  
Displacement Zone

Complex interaction mechanism exists between the pile group and soil. To realize the pile-soil load transmission mechanism in detail, the failure pattern of pile groups installed in dense sand considering different pile spacing was investigated by means of laboratory experimental model test and three-dimensional discrete element method. The results suggested that the narrow pile spacing was beneficial to the development of the pile tip resistance, and it enhanced the bearing performance of the pile group at the initial stage of settlement. The pile spacing changed the shaft resistance pattern with modification of the strain energy mechanism released within the subsoil. The pile group with 6b pile spacing had higher composite group efficiency. A joint fan-shaped displacement zone was formed beneath the pile tip for the pile group with 3b pile spacing; this pile foundation presented the block failure mechanism. The sand displacement beneath the cap for the pile group with 6b pile spacing mainly located on the upper part of the piles, the sand displacement around both sides of the piles presented asymmetric, and a relatively independent fan-shaped displacement zone was formed beneath the pile tip.

scholarly journals PILE SETTLEMENT INDUCED FROM SOIL MOVEMENT DUE TO BREAKDOWN OF RETAINING WALL

2020 ◽  
Vol 60 (4) ◽  
pp. 338-348
Author(s):  
Rajesh Prasad Shukla
Keyword(s):  
Experimental Model ◽  
Retaining Wall ◽  
Pile Group ◽  
Small Scale ◽  
Embedment Depth ◽  
Pile Groups ◽  
Soil Movement ◽  
Pile Settlement

Very few studies measured the settlement of retaining wall supported piles foundation under a soil movement. This study explores the pile settlement induced from the sudden breakdown of a closely located retaining wall using a small-scale experimental model. Various factors affect the pile settlement, but the influence of the embedment ratio of the pile and collapsed height of the retaining wall is relatively more visible. The induced settlement decreases with pile embedment depth and increases with the collapsed height of the retaining wall. The pile settlement initially increases at a higher rate with an increase in the collapsed height to a certain extent, beyond which, becomes relatively less observable. Pile group settlement reduces with the increase in spacing and the number of piles in longer piles. However, opposite trends have been observed in piles with a smaller embedment ratio. The settlement reduces logarithmically with the increase in the distance between piles and the retaining wall. Pile groups with small embedment ratio are severely more affected by the breakdown of the retaining wall than the piles of a large embedment ratio. Pile groups placed parallel to the retaining wall are more affected than those placed orthogonally.

Negative skin friction from surface settlement measurements in model group tests

1995 ◽  
Vol 32 (6) ◽  
pp. 1075-1079 ◽  
Author(s):  
Mehmet Ufuk Ergun ◽  
Devrim Sönmez
Keyword(s):  
Soft Clay ◽  
Soil Surface ◽  
Pile Group ◽  
Friction Model ◽  
Model Group ◽  
Pile Groups ◽  
Negative Skin Friction ◽  
Dense Sand ◽  
Model Study ◽  
Negative Friction

Groups of model wood piles driven to end bearing through dense sand over soft clay were used to determine the relative settlement of the soil surface inside and outside the groups as the soil was compressed by air pressure. Square 30 mm piles at spacings of 2 to 6 times the pile width were used in groups of 3 × 3, 4 × 4, and 5 × 5. The results indicate that pile group effects were negligible at pile spacings at 5 to 6 pile widths. Key words : negative friction, model study, pile groups, sand.

scholarly journals Large-scale model tests of a single pile and two-pile groups for an offshore platform in sand

2021 ◽  
Author(s):  
Aligi Foglia ◽  
Khalid Abdel-Rahman ◽  
Elmar Wisotzki ◽  
Tulio Quiroz ◽  
Martin Achmus
Keyword(s):  
Large Scale ◽  
Load Transfer ◽  
Pile Group ◽  
Scale Model ◽  
Single Pile ◽  
Pile Groups ◽  
Group Efficiency ◽  
Large Scale Model ◽  
Load Tests ◽  
The Given

Estimating pile group efficiency for open-ended steel piles in small group arrangements is a challenging task for designers. This paper reports on the large-scale experimental campaign performed for the BorWin gamma offshore converter platform, which involved single piles and two-pile group systems on a scale of 1:10. The experimental works included installation, dynamic end-of-driving tests, dynamic restrike tests, and static load tests of a single pile and a pair of two-pile groups in densely compacted, artificially prepared homogeneous sand. The CPT profiles and the blow counts confirmed that the foundation systems are comparable to each other. The experimental results of the single pile system were compared with conventional design methods. Such comparison indicated that CPT-based methods and load-transfer methods are applicable at the considered model scale. The bearing capacity prediction obtained via the CAPWAP method is conservative with respect to the static capacity. A consistent setup effect can be detected by analyzing the complete dynamic loading session. The pile group efficiency for the given foundation system was found to be less than 1.0 at both very small and very large soil strains, while it equaled 1.0 at failure.

Numerical investigation on pile group efficiency embedded in soft clay

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Abdelkrim Ferchat ◽  
Mohamed Nabil Houhou ◽  
Sadok Benmebarek
Keyword(s):  
Goodness Of Fit ◽  
Mechanical Response ◽  
Soft Clay ◽  
Pile Group ◽  
Numerical Results ◽  
Efficiency Coefficient ◽  
Content Type ◽  
Pile Spacing ◽  
Group Efficiency ◽  
Geological Conditions

Purpose This paper aims to investigate the pile group efficiency based on the load-settlement response in soft clay conditions, considering several pile configurations using a variable number of piles and pile spacing. The overall objective of the present paper is to provide further insight into the mechanical response of the pile group and aim at helping the engineers in taking a logical path in an iterative design process for pile group efficiency. Design/methodology/approach To investigate the pile group efficiency, three-dimensional (3D) numerical simulations were performed using the finite-difference code FLAC3D. Findings The obtained numerical results are validated by comparing them to those of similar subgrade structure and in comparable geological conditions provided within the literature. The results indicated that although the bearing capacity of the pile group increases with increasing number of piles, the efficiency of the pile group is very important for a small number of piles. However, increasing of pile spacing has a positive effect on pile group efficiency depending on piles number and settlement level. The pertinence of the 3D numerical results of efficiency coefficient is judged by comparison with those obtained from the most popular formulas available in the literature. Originality/value A predicted model is also proposed which is validated with the obtained numerical results to a better goodness of fit.

scholarly journals Influences of different factors on the three-dimensional heat transfer of spiral-coil energy pile group with seepage

2020 ◽  
Vol 15 (3) ◽  
pp. 458-470
Author(s):  
Tian You ◽  
Hongxing Yang
Keyword(s):  
Three Dimensional ◽  
Pile Group ◽  
Heat Pumps ◽  
Pile Groups ◽  
Groundwater Velocity ◽  
Ground Source Heat Pumps ◽  
Spiral Coil ◽  
Energy Pile ◽  
Pile Spacing ◽  
Ground Source

Abstract Energy pile group is an important component of ground source heat pumps with foundation piles as ground heat exchangers. Among different energy piles, those with spiral pipes have a large heat exchange area between the pipe and the concrete, achieving good heat exchanging performance and wide applications. To analyze the influence of geometrical parameters (pile layout, pile spacing and pile depth) and external parameter (groundwater velocity) on the heat transfer of spiral-coil energy pile groups, a three-dimensional analytical model of spiral-coil energy pile groups with seepage is used, considering the thermal interaction among different piles, the geometry of spiral pipe and the velocity of groundwater. The soil temperature distribution in the energy pile group is studied under conditions with different factors (pile layouts: 3 × 2, L shape and line shape; pile spacing distances: 3, 5 and 7 m; pile depths: 10, 30 and 50 m; and groundwater velocities: 0, 1.2 × 10−6 and 2.0 × 10−6 m/s). The 3-year outlet fluid temperature of energy pile group affected by the above different factors under different inlet fluid temperatures and velocities or soil thermal exchange ratios is investigated. Results show that for the low fluid velocity inside the piles, the influence of above factors on the thermal performance of energy piles is more obvious. Large groundwater velocity, line shape pile layout, large pile spacing distance and short pile depth can alleviate the long-term temperature variation caused by unbalanced soil heat exchange. This work will facilitate the research, design and application of the energy pile group in ground source heat pumps.

Influencing Factors of Bearing Behavior of Settlement Reducing Pile Foundation for Immersed Tunnel

2013 ◽  
Vol 353-356 ◽  
pp. 779-784
Author(s):  
Xiao Hui Huang ◽  
Wei Ming Gong ◽  
Ting Huang ◽  
Ri Cheng Xie ◽  
Guo Ping Xu
Keyword(s):  
Influencing Factors ◽  
Pile Foundation ◽  
Earth Pressure ◽  
Load Sharing ◽  
Pile Groups ◽  
Pile Spacing ◽  
Immersed Tunnel ◽  
Pile Cap ◽  
Bearing Behavior ◽  
Pile Length

Settlement reducing pile foundation has recently been proposed as an important progress in the design theory of pile foundation, which is one type of deformation-based foundations. Compared with the common design method, settlement reducing pile foundation can greatly reduce the number of required piles. Aimed to the influence of pile cap, cushion, pile spacing, pile length on bearing behavior of settlement reducing pile foundation, the indoor tests on steel pipe settlement reducing pile foundation for immersed tunnel were carried out in sand. Based on uniform design, the six groups of tests with 3×4 pile groups were conducted, furthermore, earth pressure, axial force of pile shaft, and foundation settlement were measured. When the load applied increased, the plastic failure of the soil occurred under the corner of immersed tunnel. The result shows that the earth pressure distribution against immersed tunnel is similar to the normal base reaction in sand which is big in the center and small in the border. The correlation analysis result indicates that apply pile cap, reduce cushion thickness, increase pile spacing and increase pile length can increase the pile load sharing ratio. Compared with the average value of correlation coefficient of each influencing factor, pile length has the most remarkable effect on the pile load sharing ratio, then cushion and pile cap, and pile spacing has the minimal effect among these influencing factors. The research can provide a reference for design of relevant projects.

A practical approach for the consideration of single pile and pile group installation effects in clay: Numerical modelling

2015 ◽  
Vol 2 (3,4) ◽  
pp. 119-142
Author(s):  
Brian B. Sheil ◽  
Bryan A. McCabe ◽  
Christopher E. Hunt ◽  
Juan M. Pestana
Keyword(s):  
San Francisco ◽  
Soft Clay ◽  
Pile Group ◽  
Practical Approach ◽  
Soil Parameters ◽  
Single Pile ◽  
Installation Effects ◽  
Additional Group ◽  
2D Data ◽  
Group Piles

Abstract In this paper, a practical approach for the consideration of single pile and pile group installation effects in clay is presented using some novel procedures implemented in the finite element (FE) software package PLAXIS 2D. Data reported at a soft clay site at Islais Creek, San Francisco are used to provide calibration for the constitutive model and to validate initial predictions of single pile installation effects. A short parametric study was then undertaken to examine the influence of a number of pile/soil parameters on the soil stresses generated around a single pile after installation and subsequent consolidation. In addition, a new simplified method is proposed to consider group installation effects over-and-above those associated with an equivalent single pile involving the volumetric expansion of tunnels within a plane-strain framework. Remarkably, results show that the installation of additional group piles has a negligible influence after consolidation.

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