scholarly journals Experimental investigation of reverse end bearing of offshore shallow foundations

2013 ◽  
Vol 50 (10) ◽  
pp. 1022-1033 ◽  
Author(s):  
Divya S.K. Mana ◽  
Susan Gourvenec ◽  
Mark F. Randolph
Keyword(s):  
Uplift Capacity ◽  
Medium Term ◽  
Centrifuge Model ◽  
End Bearing Capacity ◽  
Adjacent Soil ◽  
Uplift Resistance ◽  
External Face ◽  
Vertical Gap ◽  
Soil Interface ◽  
Centrifuge Model Tests

Shallow skirted foundations can mobilize uplift resistance from end bearing in the short to medium term. However, uncertainty exists over the magnitude of reverse end bearing resistance compared with resistance in compression, and how this might be affected by a gap between the external face of the foundation skirt and the adjacent soil. The study presented in this paper explores this problem through centrifuge model tests, investigating the effect of skirt embedment ratio on (i) the magnitude of reverse end bearing capacity compared with compression capacity, (ii) the uplift displacement associated with spontaneous loss of suction during uplift, and (iii) the existence of a vertical gap along the external skirt–soil interface. The results show that (i) peak uplift capacity equivalent to compression capacity can be mobilized for a fully sealed foundation with an intact skirt–soil interface, (ii) suction required for reverse end bearing can be maintained through considerable foundation displacement, even for a low skirt embedment ratio, and (iii) the presence of a vertical gap along the external skirt–soil interface causes abrupt loss of suction beneath the top plate after minimal foundation displacement, with subsequent uplift capacity being markedly reduced.

scholarly journals Effect of perforations on uplift capacity of skirted foundations on clay

2014 ◽  
Vol 51 (3) ◽  
pp. 322-331 ◽  
Author(s):  
Xiaojun Li ◽  
Christophe Gaudin ◽  
Yinghui Tian ◽  
Mark J. Cassidy
Keyword(s):  
Soft Soil ◽  
Failure Mechanisms ◽  
Operating Time ◽  
Shallow Foundations ◽  
Excess Pore Pressure ◽  
Uplift Capacity ◽  
Centrifuge Model ◽  
Uplift Resistance ◽  
Excess Pore ◽  
Centrifuge Model Tests

The retrieval of deep water subsea installations resting on soft soil, such as “mudmat” shallow foundations, can be a difficult and costly operation if significant resistance to uplift is experienced. At the mudmat invert, suctions may develop, increasing the uplift resistance to greater than the weight of the mat. In this paper, a series of centrifuge model tests are performed to determine the uplift resistance of rectangular mudmats resting on lightly overconsolidated kaolin clay. The study investigates the influence of perforation, in combination with skirt length and eccentric uplift, on the uplift resistance and suction generation at the foundation invert. The outcomes demonstrate that the central and eccentric uplift of mudmats have different failure mechanisms, resulting in a different distribution of excess pore pressure at the foundation invert. In contrast, perforations do not change the failure mechanism and only alter the magnitude of suction generated. The two different configurations of perforation investigated significantly reduce the suction at the mat invert and the uplift resistance, and may potentially shorten the operating time for centred uplift. The combination of perforation and eccentric uplift has the most beneficial effect on the reduction of the uplift resistance.

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.

Geotechnical Centrifuge Shaking Table Tests and Numerical Simulation of Soil-Structure

2012 ◽  
Vol 256-259 ◽  
pp. 372-376 ◽  
Author(s):  
Jing Bo Liu ◽  
Dong Dong Zhao ◽  
Wen Hui Wang ◽  
Xiang Qing Liu
Keyword(s):  
Numerical Simulation ◽  
Soil Structure ◽  
Shaking Table ◽  
Vertical Line ◽  
Shaking Table Tests ◽  
Geotechnical Centrifuge ◽  
Centrifuge Model ◽  
Soil Structures ◽  
Input Motion ◽  
Centrifuge Model Tests

Two geotechnical centrifuge model tests of a soil-structure system with different burial depths are performed to investigate the interaction between soil and structure. The tests are performed at 50 gravitational centrifuge accelerations and the input motion is Kobe wave. This paper focuses on the accelerations and displacements in the soil-structures system. The peak accelerations and displacements along the axis of the structure and along the vertical line 17cm away from the axis are presented. The acceleration and displacement response due to the interaction between soil and structure are studied.

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.

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