The Calculation of Critical Pile Length for Super-Long Pile Based on Settlement Control

2011 ◽  
Vol 71-78 ◽  
pp. 4179-4183
Author(s):  
Li Nong Xia ◽  
Yun Dong Miao ◽  
Tie Qiang Tan ◽  
Xin Tong
Keyword(s):  
Shear Deformation ◽  
Field Measurement ◽  
Load Transfer ◽  
Working Condition ◽  
Transfer Model ◽  
Shaft Resistance ◽  
Pile Diameter ◽  
Pile Settlement ◽  
Deformation Transfer ◽  
Pile Length

Based on the analysis of character of load-transfer of super-long pile, for the purpose of pile settlement control, critical pile length for single friction super-long pile was calculated by Cooke’s shear deformation-transfer model, because the assumption of Cooke’s model is similar with working condition of super-long pile. In the analysis, compression of pile is taken into account. Then, the design chart of critical pile length for super-long pile is provided for normal design index. Lastly, the critical pile length of an engineering example is analysed by the method, the calculated results have agreed well with the field measurement. The analysis show that critical pile length is greatly concerned with ratio of Young’s module of pile and soil, the greater the ratio is, longer the critical pile length is. Pile diameter also affects the critical pile length, the larger the diameter is, longer the critical pile length is. In addition, the critical pile length of super-long pile is concerned with shaft resistance distribution along the pile.

scholarly journals Field Tests of Super-Long and Large-Diameter Drilled Shaft Pile Foundations

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Peisen Wang ◽  
Hongyan Ding ◽  
Jialin Zhou ◽  
Wenjun Hu ◽  
Xuechen Gu ◽  
...  
Keyword(s):  
Load Transfer ◽  
Large Diameter ◽  
Soil Layer ◽  
Field Tests ◽  
Load Test ◽  
Pile Foundations ◽  
Static Load Test ◽  
Mutual Compensation ◽  
Shaft Resistance ◽  
Pile Diameter

This study investigated the compressive behaviour of super-long pile foundations with large diameters. Three 52 m, 73 m, and 83 m long piles with a diameter of 1500 mm, 1500 mm, and 1800 mm were cast and tested, respectively. Given that large loading was required, an improved compressive static load test was introduced, and the load transfer mechanism, shaft resistance development, and distribution were analysed. This study found that the transferred load decreased along the pile during each applied load, but the gradients were different. For most layers, when increasing the load, the shaft resistance developed in the upper layers first, while the shaft resistance from the lower part did not always fully develop. Moreover, the “mutual compensation” phenomenon was discovered, which was when the shaft softening occurred from one soil layer, the shaft hardening of the other soil would occur simultaneously. Under consideration of the soil layer differences around these piles, it was recommended that shaft and base grouting should be applied on 52 m and 73 m piles, while only shaft grouting should be applied on the 83 m pile. For this longest pile design, whose toe resistance was discovered to be very small, increasing the pile length was not appropriate; thus, it was preferable to increase the pile diameter to increase the ultimate bearing capacity.

Experimental study of axial behaviour of tapered piles

1998 ◽  
Vol 35 (4) ◽  
pp. 641-654 ◽  
Author(s):  
Jinqi Wei ◽  
M Hesham El Naggar
Keyword(s):  
Cross Sections ◽  
Load Transfer ◽  
Confining Pressure ◽  
Transfer Model ◽  
Operating Characteristics ◽  
Unit Load ◽  
Shaft Resistance ◽  
Cylindrical Piles ◽  
Axial Response ◽  
The Difference

Tapered piles, which have greater top cross sections than bottom ones, have the potential for substantial cost advantages for static loading conditions. However, tapered piles have not often been considered a design option because of the lack of design tools and knowledge about the behaviour of these piles. The objectives of this study are to explore and better understand the operating characteristics of the axial response of tapered piles. A large laboratory facility for testing model piles was developed. In this facility, the soil was contained in a steel soil chamber and pressurized using an air bladder to model the confining pressure. Three instrumented steel piles with different degrees of taper were used in this study. As expected, it was found that as the taper angle increased, the shaft resistance increased. It was found that the shaft resistance of the tapered pile was up to 40% larger than that of the cylindrical pile. The difference in the shaft resistance of the two types decreased for higher values of confining pressure. It was also found that the load distribution along the pile shaft for both pile types had the same pattern. However, this pattern varied as the confining pressure increased. Furthermore, the unit load transfer was significantly affected by the initial sand density for both pile types at low confining pressure, but as the confining pressure increased, this effect diminished. It is concluded that the tapered piles offer a larger resistance than the cylindrical piles. However, for longer piles, it is suggested that the taper be limited to the top length corresponding to 20 diameters.Key words: tapered piles, shaft friction, axial response, load transfer, model testing.

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.

Numerical investigation of the monotonic drained lateral behaviour of large diameter rigid piles in medium dense uniform sand

Géotechnique ◽  
2021 ◽  
pp. 1-39
Author(s):  
Huan Wang ◽  
M. Fraser Bransby ◽  
Barry M. Lehane ◽  
Lizhong Wang ◽  
Yi Hong
Keyword(s):  
Numerical Investigation ◽  
Load Transfer ◽  
Large Diameter ◽  
Offshore Wind ◽  
Soil Pressure ◽  
Lateral Capacity ◽  
Pile Diameter ◽  
Centrifuge Tests ◽  
Lateral Response ◽  
Loading Eccentricity

This paper presents a numerical investigation of the monotonic lateral response of large diameter monopiles in drained sand with configurations typical of those employed to support offshore wind turbines. Results from new centrifuge tests using instrumented monopiles in uniform dry sand deposits are first presented and used to illustrate the suitability of an advanced hypoplastic constitutive model to represent the sand in finite element analyses of the experiments. These analyses are then extended to examine the influence of pile diameter and loading eccentricity on the lateral response of rigid monopiles. The results show no dependency of suitably normalized lateral load transfer curves on the pile diameter and loading eccentricity. It is also shown that, in a given uniform sand, the profile with depth of net soil pressure at ultimate lateral capacity is independent of the pile diameter because of the insensitivity of the depth to the rotation centre for a rigid pile. A normalization method is subsequently proposed which unifies the load-deflection responses of different diameter rigid piles at a given load eccentricity.

Piled Raft Structure Finite Element Analysis of Composite Foundation Settlement in Da XI Passenger Dedicated Line

2014 ◽  
Vol 937 ◽  
pp. 438-443
Author(s):  
Xiao Tong Ma ◽  
Guang Long Liu
Keyword(s):  
Finite Element ◽  
Composite Foundation ◽  
Foundation Settlement ◽  
Pile Spacing ◽  
Finite Element Software ◽  
Piled Raft ◽  
Pile Diameter ◽  
Foundation Treatment ◽  
Pile Length ◽  
Passenger Dedicated Line

Composite foundation settlement of piled raft structure in Da Xi passenger dedicated line is analyzed by the large finite element software MIDAS/GTS and established calculation model of foundation treatment. The problem of pile-soil contact is highlighted in the trail and analyzes the settlement nephogram and pile-soil stress nephogram. On this basis the foundation settlement factors was analyzed systematically that focus on the elastic modulus of pile, pile spacing, pile diameter and pile length in foundation treatment, especially for the characteristics parameters of contact element. Result shows that increasing the pile modulus, pile diameter, pile length and decreasing the pile spacing is all conducive to reducing settlement. The best advice is got that the pile diameter should be not more than 0.5m, pile length not more than 27m and the pile spacing be around 2m.

Field study of residual forces developed in pre-stressed high-strength concrete (PHC) pipe piles

2016 ◽  
Vol 53 (4) ◽  
pp. 696-707 ◽  
Author(s):  
Hai-lei Kou ◽  
Jian Chu ◽  
Wei Guo ◽  
Ming-yi Zhang
Keyword(s):  
Static Loading ◽  
High Strength Concrete ◽  
Large Scale ◽  
Load Transfer ◽  
High Strength ◽  
Neutral Plane ◽  
Shaft Resistance ◽  
Strength Concrete ◽  
Loading Tests ◽  
Residual Force

A large-scale field testing program for the study of residual forces in pre-stressed high-strength concrete (PHC) pipe piles is presented in this paper. Five open-ended PHC pipe piles with 13 or 18 m in embedded length were installed and used for static loading tests at a building site in Hangzhou, China. All the piles were instrumented with fiber Bragg grating (FBG) strain gauges. The residual forces in these piles were recorded during and after installation. The measured load transfer data along a pile during the static loading tests are reported. The effect of the residual force on the interpretation of the load transfer behavior is discussed. The field data show that residual force along the installed pile increases approximately exponentially to the neutral plane and then reduces towards the toe. The residual force decreases with time to a stable value after pile jacking due to the secondary interaction between the pile and the disturbed soil around the pile and other factors. The large residual forces along the PHC pipe piles significantly affect the evaluation of the pile load distributions, and thus the shaft and toe resistances. The conventional bearing capacity theory tends to overestimate the shaft resistance at positions above the neutral plane and underestimate the shaft resistance at positions below the neutral plane, and the toe resistance for an open-ended PHC pipe piles founded in stratified soils.

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