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.

scholarly journals Scour Effects on the Lateral Behavior of a Large-Diameter Monopile in Soft Clay: Role of Stress History

2019 ◽  
Vol 7 (6) ◽  
pp. 170 ◽  
Author(s):  
Ben He ◽  
Yongqing Lai ◽  
Lizhong Wang ◽  
Yi Hong ◽  
Ronghua Zhu
Keyword(s):  
Large Diameter ◽  
Soft Clay ◽  
Small Diameter ◽  
Initial Stiffness ◽  
Stress History ◽  
Soil Stiffness ◽  
Hypoplastic Model ◽  
History Effects ◽  
Conservative Estimation ◽  
Lateral Behavior

Scouring of soil around large-diameter monopile will alter the stress history, and therefore the stiffness and strength of the soil at shallow depth, with important consequence to the lateral behavior of piles. The existing study is mainly focused on small-diameter piles under scouring, where the soil around a pile is analyzed with two simplified approaches: (I) simply removing the scour layers without changing the strength and stiffness of the remaining soils, or (II) solely considering the effects of stress history on the soil strength. This study aims to investigate and quantify the scour effect on the lateral behavior of monopile, based on an advanced hypoplastic model considering the influence of stress history on both soil stiffness and strength. It is revealed that ignorance about the stress history effect (due to scouring) underestimates the extent of the soil failure wedge around the monopile, while overestimates soil stiffness and strength. As a result, a large-diameter pile (diameter D = 5 m) in soft clay subjected to a souring depth of 0.5 D has experienced reductions in ultimate soil resistance and initial stiffness of the p-y curves by 40% and 26%, and thus an increase of pile head deflection by 49%. Due to the inadequacy to consider the stress history effects revealed above, the existing approach (I) has led to non-conservative estimation, while the approach (II) has resulted in an over-conservative prediction.

Design-Focused Stress Analysis of Cylindrical Pressure Vessels Intersected by Small-Diameter Nozzles

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Faisal M. Mukhtar ◽  
Husain J. Al-Gahtani
Keyword(s):  
Shell Theory ◽  
Large Diameter ◽  
Small Diameter ◽  
Vessel Diameter ◽  
Theory Of Elasticity ◽  
Pressure Vessels ◽  
Element Analysis ◽  
Overall Design ◽  
Design Charts ◽  
Thin Shell Theory

In a related work previously carried out by the authors, finite element analysis of cylindrical vessel–cylindrical nozzle juncture based on the use of thin shell theory, due to the fact that the intersecting nozzle sizes are moderate to large, have been presented. Such analysis becomes invalid in cases when the nozzles are small in sizes which may result in nozzles whose configuration violates the validity of shell assumption. As a result, use of solid elements (based on theory of elasticity) in modeling the cylindrical vessels with small-diameter nozzles is presented in the present paper. Discussions of the numerical experiments and the results achieved are, first, given. The results are then compared with the prediction by other models reported in the literature. In order to arrive at the overall design charts that cover all the possible ranges of nozzle-to-vessel diameter ratio, the charts for the vessels with moderate-to-large-diameter nozzles are augmented with those of cylindrical vessels intersected by small-diameter nozzles developed in this work.

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.

scholarly journals Ultimate Load Tests on Bearing Behavior of Large-Diameter Bored Piles in Weathered Rock Foundation

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Xiaoyu Bai ◽  
Xueying Liu ◽  
Mingyi Zhang ◽  
Yonghong Wang ◽  
Nan Yan
Keyword(s):  
Bearing Capacity ◽  
Limit State ◽  
Large Diameter ◽  
Diameter Ratio ◽  
Load Test ◽  
Single Pile ◽  
Rock Foundation ◽  
Deformation Characteristics ◽  
Lateral Resistance ◽  
Bored Piles

Based on the vertical compressive static load test and pile mechanics test of three large diameter bored piles (one of the test piles was treated with postgrouting) in granite gneisses foundation, the bearing capacity, deformation characteristics, and influencing factors of the single pile under the limit state are analyzed and compared with the recommended values of survey report and the recommended values of current codes. By comparing the measured and theoretical values of pile axial force, the bearing capacity of cast-in-place pile under normal and limit conditions is analyzed. The experimental results show that the Q-s curve of large-diameter rock-socketed mud wall retaining bored pile with a length-diameter ratio of 25–33 and rock-socketed depth of 5–8 d shows a rapid growth. After grouting treatment, the ultimate compressive bearing capacity of single pile is improved, the maximum settlement is reduced by 6.6%, the rebound rate is reduced by 11.1%, and the settlement effect of controlling pile top is not significant. The bearing capacity and deformation characteristics of the three test piles are less affected by length-diameter ratio and rock-socketed depth. For postgrouting piles, the ratio of frictional resistance of rock-socketed segment and the ratio of pile lateral resistance are less affected by length-diameter ratio and rock-socketed depth, while, for postgrouting piles, the ratio of pile lateral resistance is more affected by rock-socketed depth. The pile end resistance ratio of the three test piles is significantly affected by the rock-socketed depth, whether or not the pile side postgrouting treatment is carried out.

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.

Effects of Residual Stress on Fatigue Strength of Small-Diameter Welded Pipe Joint

1997 ◽  
Vol 119 (4) ◽  
pp. 428-434 ◽  
Author(s):  
T. Yamashita ◽  
T. Hattori ◽  
K. Iida ◽  
T. Nomoto ◽  
M. Sato
Keyword(s):  
Residual Stress ◽  
Fatigue Strength ◽  
Residual Stresses ◽  
Large Diameter ◽  
Small Diameter ◽  
Local Stress ◽  
Element Analysis ◽  
Fillet Weld ◽  
Pipe Joints ◽  
Welded Pipe

Bending fatigue tests were conducted to investigate the fatigue strength of small-diameter socket welded pipe joints. In most cases of large-diameter socket joints, a fatigue crack started from the root of the fillet weld, though the stress amplitude at the root was smaller than that at the toe of the fillet weld. Additionally, the fatigue strength was affected by the weld bead sequence. The residual stress was considered to be one of the important parameters governing fatigue strength; therefore, its effects were investigated. In several types of pipe joints, the local stress and residual stress distributions were calculated by finite element analysis. The residual stresses were compressive at the toe and tensile at the root of the socket welded joints. Based on these results, the effects of residual stresses on the fatigue strength are discussed for small-diameter welded pipe joints in the present work.

Bidirectional cell tests on non-grouted and grouted large-diameter bored piles

2015 ◽  
Vol 2 (3,4) ◽  
pp. 105-117 ◽  
Author(s):  
Minh Hai Nguyen ◽  
Bengt H. Fellenius
Keyword(s):  
Static Loading ◽  
Large Diameter ◽  
Soft Clay ◽  
Silty Sand ◽  
Foundation Design ◽  
Average Unit ◽  
Load Movement ◽  
Loading Tests ◽  
Bored Piles ◽  
Four Levels

Abstract The 37-storey apartment buildings of the Everrich II project in HoChiMinh City, Vietnam was designed to be supported on a piled foundation consisting of bored piles assigned a 22-MN working load per pile. The foundation design included performing bidirectional-cell, static loading tests on four test piles. The soil profile consisted of organic soft clay to about 28 m depth followed by a thick deposit of sandy silt and silty sand with a density that gradually increased with depth from compact to dense, becoming very dense at 65 m depth. In March 2010, the test piles, one 1.5-m diameter pile and three 2.0-m diameter piles, were installed to 80 m through 85 m depth and constructed using bucket drill technique with bentonite slurry and a casing advanced ahead of the hole. The bidirectional-cell assemblies were installed at 10 m through 20 m above the pile toes. The piles were instrumented with pairs of diametrically opposed vibrating wire strain-gages at three to four levels below and six to seven levels above the respective cell levels. After completed concreting, the shaft grouting was carried out throughout a 20 m length above the pile toe for the 1.5-m diameter pile and for one of the 2.0-m diameter piles. The static loading tests were performed about 34 through 44 days after the piles had been concreted. The analysis of strain-gage records indicated an average Young’s modulus value of about 25 GPa for the nominal crosssections of the piles. The average unit grouted shaft resistances on the nominal pile diameters were about two to three times larger than the resistance along the non-grouted lengths. The measured load distribution of maximum mobilized shaft resistances corresponded to effective stress proportionality coefficients, ß, of about 0.2 through 0.3. The ultimate shaft resistance for the pile lengths below the bidirectional cells reached an ultimate value after about 8 to 10 mm movement, whereafter the load-movement was plastic. The pile toe stress-movement responses to toe stiffness were soft with no tendency toward an ultimate value.

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