Evaluation of the efficiencies of helical anchor plates in sand by centrifuge model tests

2012 ◽  
Vol 49 (9) ◽  
pp. 1102-1114 ◽  
Author(s):  
C.H.C. Tsuha ◽  
N. Aoki ◽  
G. Rault ◽  
L. Thorel ◽  
J. Garnier
Keyword(s):  
Soil Mass ◽  
Model Tests ◽  
Uplift Capacity ◽  
Centrifuge Model ◽  
Different Types ◽  
Loading Tests ◽  
The Individual ◽  
Helical Plate ◽  
Anchor Plates ◽  
Centrifuge Model Tests

The uplift capacity of helical anchors normally increases with the number of helical plates. The rate of capacity gain is variable, considering that the disturbance caused by the anchor installation is generally more pronounced in the soil mass above the upper plates than above the lower plates, because the upper soil layers are penetrated more times. The present investigation examines the effect of the number of helices on the performance of helical anchors in sand, based on the results of centrifuge model tests. Uplift loading tests were performed on 12 different types of piles installed in two containers of dry sand prepared with different densities. The measured fractions of the uplift capacity related to each individual helical plate of multi-helix anchors were compared with the fractions predicted by the individual bearing method. The results of this investigation indicate that in double- and triple-helix anchors, the contributions of the second and third plate to the total anchor uplift capacity decreased with the increase of sand relative density and plate diameter. In addition, these experiments demonstrated that the variation of the anchor load–displacement behavior with the number of helices also depends on these parameters.

Correction: Evaluation of the efficiencies of helical anchor plates in sand by centrifuge model tests

2020 ◽  
Vol 57 (5) ◽  
pp. 783-783
Author(s):  
C.H.C. Tsuha ◽  
N. Aoki ◽  
G. Rault ◽  
L. Thorel ◽  
J. Garnier
Keyword(s):  
Model Tests ◽  
Centrifuge Model ◽  
Anchor Plates ◽  
Centrifuge Model Tests

scholarly journals Cyclic p-y Curves of Monopiles in Dense Dry Sand Using Centrifuge Model Tests

2019 ◽  
Vol 9 (8) ◽  
pp. 1641 ◽  
Author(s):  
Lee ◽  
Bae ◽  
Lee ◽  
Yoo
Keyword(s):  
Friction Angle ◽  
Model Tests ◽  
Soil Resistance ◽  
Backbone Curve ◽  
Centrifuge Model ◽  
Initial Modulus ◽  
Loading Tests ◽  
Dry Sand ◽  
Lateral Behavior ◽  
Centrifuge Model Tests

In this study, centrifuge model tests were used to examine the lateral behavior of amonopile embedded in dry sand through cyclic lateral loading tests. The soil specimens used in thetests were dry Jumunjin sand with a relative density of 80% and a friction angle of 38°. A staticloading test was performed once, and cyclic loading tests were performed four times using fourmagnitudes of cyclic load (30%, 50%, 80%, and 120% of static lateral capacity). The experimentalcyclic p‐y curve was obtained through the tests, and the maximum soil resistance points that werefound for each load were used to find the cyclic p‐y backbone curve for each depth. The twovariables which are needed to define the cyclic p‐y backbone curve, i.e., the initial modulus ofsubgrade reaction (kini) and ultimate soil resistance (pu), were suggested as functions of the soil’sphysical properties and the pile. The cyclic p‐y curve of the first cycle and the 100th cycle wereformulated to present the upper limit and lower limit. The suggested cyclic p‐y curve had anoverestimated soil resistance compared with the existing API (1987) method, but the initial modulusof subgrade reaction was underestimated.

Evaluation of the seismic response of stone pagodas using centrifuge model tests

2014 ◽  
Vol 12 (6) ◽  
pp. 2583-2606 ◽  
Author(s):  
Heon-Joon Park ◽  
Dong-Soo Kim ◽  
Yun Wook Choo
Keyword(s):  
Seismic Response ◽  
Model Tests ◽  
Centrifuge Model ◽  
Centrifuge Model Tests

scholarly journals Evaluation of seismic behavior of box culvert buried in the ground through centrifuge model tests and numerical analysis

2019 ◽  
Vol 4 (2) ◽  
pp. 147-167 ◽  
Author(s):  
Hitoshi Yatsumoto ◽  
Yasuo Mitsuyoshi ◽  
Yasuo Sawamura ◽  
Makoto Kimura
Keyword(s):  
Numerical Analysis ◽  
Seismic Behavior ◽  
Model Tests ◽  
Centrifuge Model ◽  
Box Culvert ◽  
Centrifuge Model Tests

scholarly journals Modelling the embedment process during offshore pipe-laying on fine-grained soils

2013 ◽  
Vol 50 (1) ◽  
pp. 15-27 ◽  
Author(s):  
Z.J. Westgate ◽  
D.J. White ◽  
M.F. Randolph
Keyword(s):  
Deep Water ◽  
Small Amplitude ◽  
Model Tests ◽  
Soil Parameters ◽  
Sea State ◽  
Field Surveys ◽  
Centrifuge Model ◽  
Fine Grained ◽  
Displacement Patterns ◽  
Centrifuge Model Tests

Subsea pipelines are becoming an increasingly significant element of offshore hydrocarbon developments as exploration moves into deep-water environments further from shore. During the lay process, pipelines are subject to small amplitude vertical and horizontal oscillations, driven by the sea state and lay vessel motions. Centrifuge model tests have been used to simulate these small-amplitude lay effects, with varying degrees of idealization relative to the real lay process. In the soft soils found in deep water, pipe embedment can exceed a diameter or more, thus significantly affecting the lateral pipe–soil interaction, axial resistance, and thermal insulation. In this paper, results from centrifuge model tests are used to calibrate a model for calculating the dynamic embedment of a subsea pipeline. The model uses elements of plasticity theory to capture the effects of combined vertical and horizontal loading, and incorporates the softening of the surrounding soil as it is remoulded due to the pipeline motions. Influences from the lay rate, lay geometry, and sea state are included in the calculation process. The model is compared with observed as-laid pipeline embedment data from field surveys at three different offshore sites. Using site-specific soil parameters obtained from in situ testing and idealized pipe loads and motions to represent the load and displacement patterns during offshore pipe-laying, respectively, the model is shown to capture well the final as-laid embedment measured in the field surveys.

RESPONSE OF SOFT CLAY STRATA AND CLAY-PILE-RAFT SYSTEMS TO SEISMIC SHAKING

2007 ◽  
Vol 01 (03) ◽  
pp. 233-255 ◽  
Author(s):  
SUBHADEEP BANERJEE ◽  
SIANG HUAT GOH ◽  
FOOK HOU LEE
Keyword(s):  
Soft Clay ◽  
Ground Surface ◽  
Model Tests ◽  
Pile Foundations ◽  
Kaolin Clay ◽  
Natural Period ◽  
Soil System ◽  
Centrifuge Model ◽  
Inertial Loading ◽  
Centrifuge Model Tests

The behavior of pile foundations under earthquake loading is an important factor affecting the performance of structures. Observations from past earthquakes have shown that piles in firm soils generally perform well, while the performance of piles in soft or liquefied ground can raise some questions. Centrifuge model tests were carried out at the National University of Singapore to investigate the response of pile-soil system under three different earthquake excitations. Some initial tests were done on kaolin clay beds to understand the pure clay behavior under repetitive earthquake shaking. Pile foundations comprising of solid steel, hollow steel and hollow steel pile filled with cement in-fill were then embedded in the kaolin clay beds to study the response of clay-pile system. Superstructural inertial loading on the foundation was modeled by fastening steel weight on top of the model raft. The model test results show that strain softening and stiffness degradation feature strongly in the behaviour of the clay. In uniform clay beds without piles, this is manifested as an increase in resonance periods of the surface response with level of shaking and with successive earthquakes. For the pile systems tested, the effect of the surrounding soft clay was primarily to impose an inertial loading onto the piles, thereby increasing the natural period of the piles over and above that of the pile foundation alone. There is also some evidence that the relative motion between piles and soil leads to aggravated softening of the soil around the pile, thereby lengthening its resonance period of the soil further. The centrifuge model tests were back-analyzed using the finite element code ABAQUS. The analysis shows that the simple non-linear hypoelastic soil model gave reasonably good agreement with the experimental observations. The engineering implication arising from this study so far is that, for the case of relatively short piles in soft clays, the ground surface motions may not be representative of the raft motion. Other than the very small earthquakes, the raft motion has a shorter resonance period than the surrounding soil.

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