scholarly journals Laboratory Model Study on the Pile-Forming Mechanisms and Bearing Deformation Characteristics of CFA Piles

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Deliang Zhu ◽  
Yue Li ◽  
Lingwei Zheng ◽  
Pengfei Fang ◽  
Xinyu Xie
Keyword(s):  
Model Test ◽  
Load Transfer ◽  
Soil Improvement ◽  
Model Tests ◽  
Laboratory Model ◽  
Drilling Process ◽  
Deformation Characteristics ◽  
Friction Resistance ◽  
Total Settlement ◽  
Lateral Friction

To study the pile-forming mechanism and bearing deformation characteristics of continuous flight auger (CFA) piles, a series of procedures, including helical drilling, pulling up/grouting, and inserting cage/pile forming, were simulated in clay-sand double-layer foundations by a homemade model drilling machine system in laboratory model tests. The effects of two different pile-forming methods on the load transfer and bearing characteristics of the piles were investigated by performing a model test comparison of CFA piles and bored piles. The experimental results show that there exist a soil improvement effect around the pile and a diameter expansion effect during the drilling process and grouting process for the CFA pile, which can effectively improve the lateral friction resistance of the pile. Compared with the bored pile, the pile diameter in the middle of the CFA pile increased by 19%, and the total lateral friction resistance of the CFA pile increased by 9.1% at a high load (1500 N). The comparative results of the model tests show that the bearing capacity of a single CFA pile increased by 50.0% and that the total settlement decreased by 40.5%. The results of the in situ test piles show that the load-settlement curves of the two pile types are similar under low-medium loads and that the lateral friction resistance of the CFA pile under high loads is better developed, which is relatively consistent with the model test results.

scholarly journals Limiting Force Profile and Laterally Loaded Rigid Piles in Sand

2014 ◽  
Vol 553 ◽  
pp. 452-457
Author(s):  
Hong Yu Qin ◽  
Wei Dong Guo
Keyword(s):  
Load Transfer ◽  
Unit Length ◽  
Confining Pressure ◽  
Model Tests ◽  
Laboratory Model ◽  
Resistance Force ◽  
Subgrade Reaction ◽  
Modulus Of Subgrade Reaction ◽  
Closed Form Solutions ◽  
Laterally Loaded

In this paper, closed-form solutions were used to analyze the response of eight laterally loaded rigid piles obtained from field test, centrifuge test, and 1g laboratory model tests, allowing the modulus of subgrade reaction and the profile of limiting lateral resistance force per unit length (LFP,puprofile) to be back calculated. The study shows that (1) with a constant modulus of subgrade reaction, a linear increasing LFP and elasto-plasticp~ycurves, the response of laterally loaded rigid piles can be well predicted in the framework of load transfer approach; (2) the gradient of the LFP is 0.64 ~ 3.0 times that of the Barton LFP; and (3) the gradient of the LFP and modulus of subgrade reaction increases approximately linear with the confining pressure in the model tests.

scholarly journals Fiber Bragg Grating-Based Performance Monitoring of Piles Fiber in a Geotechnical Centrifugal Model Test

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Xiaolin Weng ◽  
Jianxun Chen ◽  
Jun Wang
Keyword(s):  
Fiber Bragg Grating ◽  
Model Test ◽  
Performance Monitoring ◽  
Fiber Optic ◽  
Small Scale ◽  
Bragg Grating ◽  
Centrifugal Model Test ◽  
Friction Resistance ◽  
Centrifugal Model ◽  
Lateral Friction

In centrifugal tests, conventional sensors can hardly capture the performance of reinforcement in small-scale models. However, recent advances in fiber optic sensing technologies enable the accurate and reliable monitoring of strain and temperature in laboratory geotechnical tests. This paper outlines a centrifugal model test, performed using a 60 g ton geocentrifuge, to investigate the performance of pipe piles used to reinforce the loess foundation below a widened embankment. Prior to the test, quasidistributed fiber Bragg grating (FBG) strain sensors were attached to the surface of the pipe piles to measure the lateral friction resistance in real time. Via the centrifuge actuator, the driving of pipe piles was simulated. During testing, the variations of skin friction distribution along the pipe piles were measured automatically using an optical fiber interrogator. This paper represents the presentation and detailed analysis of monitoring results. Herein, we verify the reliability of the fiber optic sensors in monitoring the model piles without affecting the integrity of the centrifugal model. This paper, furthermore, shows that lateral friction resistance developed in stages with the pipe piles being pressed in and that this sometimes may become negative.

Research on Load Transfer Model of Super-Long Single Pile

2011 ◽  
Vol 243-249 ◽  
pp. 1028-1032
Author(s):  
Hua Cong Zhou ◽  
Wen Juan Yao ◽  
Ze Rong Zhang
Keyword(s):  
Load Transfer ◽  
Transfer Model ◽  
Single Pile ◽  
Friction Resistance ◽  
Transfer Function Method ◽  
Proposed Model ◽  
Tip Resistance ◽  
Load Transfer Model ◽  
Load Transfer Function ◽  
Lateral Friction

Currently, super-long piles are designed based on the theory of normal long piles. There is no recognized reasonable mechanical model for qualitative analysis. In this paper, based on load transfer function method, an improved load transfer model is proposed, which gives consideration to both the degradation of skin friction and the asynchronous work between lateral friction resistance and pile-tip resistance caused by pile-soil slip. By applying it in various working conditions, the corresponding pile-soil displacement and axial force of super-long piles are derived. Finally, the proposed model is validated by comparing its analytical solutions to the results of FEM and practical survey of super-long piles, and it provides a new efficient approach for the study of the mechanical behavior of super-long single pile.

Guidelines for CFD Simulations of Spar VIM

2013 ◽  
Author(s):  
Charles Lefevre ◽  
Yiannis Constantinides ◽  
Jang Whan Kim ◽  
Mike Henneke ◽  
Robert Gordon ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Test Data ◽  
Model Test ◽  
Model Tests ◽  
Full Scale ◽  
Mooring System ◽  
Time Step ◽  
Cfd Simulations ◽  
Scaled Model ◽  
Sway Motion

Vortex-Induced Motion (VIM), which occurs as a consequence of exposure to strong current such as Loop Current eddies in the Gulf of Mexico, is one of the critical factors in the design of the mooring and riser systems for deepwater offshore structures such as Spars and multi-column Deep Draft Floaters (DDFs). The VIM response can have a significant impact on the fatigue life of mooring and riser components. In particular, Steel Catenary Risers (SCRs) suspended from the floater can be sensitive to VIM-induced fatigue at their mudline touchdown points. Industry currently relies on scaled model testing to determine VIM for design. However, scaled model tests are limited in their ability to represent VIM for the full scale structure since they are generally not able to represent the full scale Reynolds number and also cannot fully represent waves effects, nonlinear mooring system behavior or sheared and unsteady currents. The use of Computational Fluid Dynamics (CFD) to simulate VIM can more realistically represent the full scale Reynolds number, waves effects, mooring system, and ocean currents than scaled physical model tests. This paper describes a set of VIM CFD simulations for a Spar hard tank with appurtenances and their comparison against a high quality scaled model test. The test data showed considerable sensitivity to heading angle relative to the incident flow as well as to reduced velocity. The simulated VIM-induced sway motion was compared against the model test data for different reduced velocities (Vm) and Spar headings. Agreement between CFD and model test VIM-induced sway motion was within 9% over the full range of Vm and headings. Use of the Improved Delayed Detached Eddy Simulation (IDDES, Shur et al 2008) turbulence model gives the best agreement with the model test measurements. Guidelines are provided for meshing and time step/solver setting selection.

scholarly journals Deformation Characteristics of Raising, Widening of Old Roadway on Soft Soil Foundation

Symmetry ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 2117
Author(s):  
Keke Li ◽  
Wenyuan Xu ◽  
Liang Yang
Keyword(s):  
Lateral Displacement ◽  
Soft Soil ◽  
Ground Surface ◽  
Surface Settlement ◽  
Deformation Characteristics ◽  
Construction Methods ◽  
Ground Surface Settlement ◽  
Total Settlement ◽  
Soil Foundation ◽  
Soft Soil Foundation

The deformation characteristics of a raised and widened old Chinese roadway on a soft soil foundation are investigated in this study via finite element numerical simulation. The rules of ground surface settlement, slope foot lateral displacement, and ground surface settlement evolution of the roadbed under three modes (one-time construction of an eight-lane expressway, widened four-lane expressway, and raised/widened four-lane expressway) are compared. The ground surface settlement process of the eight-lane road foundation, which is formed by first widening and then raising the road, is highly complex. The ground surface settlement curve under the old road foundation increases and then decreases. The lateral displacement of the slope foot also interacts with the widening and raising of the eight-lane roadbed foundation. The range of lateral displacement is 70.05, 42.58, 124.81, 104.54 mm. Fifteen years after construction, the total settlement of the raised and widened roadbed is much larger than that of the one built directly. The total settlement values at the center of the two roadbeds are 297.05 and 234.85 mm, respectively. This manuscript provides data support for the reconstruction and expansion of roads on soft soil foundations, for choosing appropriate construction methods to build roads, and for avoiding major road damage, which is of great significance to the construction of road infrastructure in the future.

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