Research on Negative Skin Friction on Pile by a Simple Model Experiment

2014 ◽  
Vol 580-583 ◽  
pp. 693-696
Author(s):  
Ting Huang ◽  
Jin Hai Zheng ◽  
Wei Ming Gong
Keyword(s):  
Skin Friction ◽  
Model Test ◽  
Soil Surface ◽  
Test Methods ◽  
Negative Skin Friction ◽  
Experimental Scheme ◽  
Test Conditions ◽  
Surcharge Load ◽  
Conventional Test ◽  
Pile Model

Accompanied by the substantive construction of domestic ports, the negative skin friction on pile becomes a common problem. In order to provide references for the related experiment research in the future, the designs of model experiments reported in the literatures were emphatically analyzed and compared. Compared to conventional pile model test, the model test on negative skin friction on pile needs to apply load on soil surface and it is difficult to simulate large surcharge by conventional test methods. An experimental scheme which could produce large surcharge load by conventional test conditions is given in this paper. Pile stress, displacement of pile top and layered settlement of soil was tested under different surcharge level. The depth of neutral point and the group effect of NSF are discussed.

Analysis of Negative Skin-Friction on Single Piles by One-Dimensional Consolidation Model Test

2018 ◽  
Vol 16 (10) ◽  
pp. 1445-1461 ◽  
Author(s):  
Hyeong-Joo Kim ◽  
Jose Leo Mission ◽  
Tae-Woong Park ◽  
Peter Rey Dinoy
Keyword(s):  
Skin Friction ◽  
Model Test ◽  
Negative Skin Friction ◽  
One Dimensional ◽  
Consolidation Model ◽  
Single Piles

Scale model test study on negative skin friction of piles considering the collapsibility of loess

2021 ◽  
Author(s):  
Zhuangfu Zhao ◽  
Shuaihua Ye ◽  
Yanpeng Zhu ◽  
Hui Tao ◽  
Changliu Chen
Keyword(s):  
Skin Friction ◽  
Model Test ◽  
Scale Model ◽  
Negative Skin Friction ◽  
Test Study

scholarly journals Downdrag Measurements on a 160-Ft Floating Pipe Test Pile in Marine Clay

1972 ◽  
Vol 9 (2) ◽  
pp. 127-136 ◽  
Author(s):  
M. Bozozuk
Keyword(s):  
Skin Friction ◽  
Compressive Load ◽  
Marine Clay ◽  
Positive Skin ◽  
Negative Skin Friction ◽  
Pore Pressures ◽  
Excess Pore Pressures ◽  
Test Pile ◽  
Excess Pore

Large negative skin friction loads were observed on a 160 ft (49 m) steel pipe test pile floating in marine clay. The test pile was driven, open-ended, on the centerline of a 30 ft (9 m) high granular approach fill on the Quebec Autoroute near Berthierville. Since the installation was made in 1966 the fill has settled 21 in. (53 cm), dragging the pile down with it. Negative skin friction acting along the upper surface of the pile was resisted by positive skin friction acting along the lower end as it penetrated the underlying clay. Under these conditions the pile compressed about [Formula: see text] (2 cm). Analysis of the axial strains indicated that a peak compressive load of 140 t developed at the inflection point between negative and positive skin friction 73 ft (22 m) below the top of the pile. Negative and positive skin friction acting on the upper surface of the pile exceeded the in situ shear strength and approached the drained strength of the soil where excess pore water pressures had dissipated. At the lower end where the positive excess pore pressures were high and relative movement between the pile and the soil was large, the positive skin friction approached the remoulded strength as measured with the field vane. Skin friction was increasing, however, as positive escess pore pressures dissipated.This paper shows that skin friction loads are related to the combination of (a) in situ horizontal effective stresses, (b) horizontal stresses due to embankment loads, and (c) horizontal stresses due to differential settlement of the fill.

Centrifuge study of seismic response of soil-nailed walls supporting a footing on the ground surface

Géotechnique ◽  
2021 ◽  
pp. 1-41
Author(s):  
Mohammad Hassan Baziar ◽  
Alireza Ghadamgahi ◽  
Andrew John Brennan
Keyword(s):  
Ground Surface ◽  
Soil Surface ◽  
Seismic Stability ◽  
Soil Nails ◽  
Model Soil ◽  
Centrifuge Tests ◽  
Axial Tensile ◽  
Tensile Forces ◽  
Surcharge Load ◽  
Seismic Loadings

Seismic design of soil-nailed walls requires demonstrations of tolerable ranges of wall movements, especially when a surcharge load exists near the wall. In this study, the effect of surcharge location on seismically induced wall movements was investigated using four centrifuge tests. The axial tensile forces, developed along the soil nails during the seismic loadings, were also measured during the tests. At 50g centrifugal acceleration, model tests represented a 12-m-high prototype wall reinforced with five rows of soil nails. To apply a surcharge stress of 30 kPa at the specified location relative to the wall for each model test, a rigid footing was placed on the soil surface. The model soil-nailed walls were subjected to three successive earthquake motions. Surprisingly, it was found that the model wall with the footing located behind the soil-nailed region experienced the largest seismic movements, even more than when the footing was directly behind the wall. Further, the tests showed that the lower soil nails played a key role in the wall stability during earthquake shaking, acting as a pivot for the pre-collapse cases tested, whereas the upper soil nails needed to be sufficiently extended to properly contribute to the seismic stability of the wall.

The practical implementation of DIN EN ISO 16891 “Test methods for evaluating the degradation of characteristics of cleanable filter media“/Die praktische Umsetzung der Norm DIN EN ISO 16891 „Prüfmethode zur Ermittlung der Abnahme der Wirksamkeit von abreinigbaren Filtermedien“

Gefahrstoffe ◽  
2019 ◽  
Vol 79 (05) ◽  
pp. 176-180
Author(s):  
F. Schmidt ◽  
J. Weimann ◽  
C. König
Keyword(s):  
Test Methods ◽  
Practical Implementation ◽  
Filter Media ◽  
Uniform Loading ◽  
Normal Filter ◽  
Current Form ◽  
Safety Aspects ◽  
Test Conditions ◽  
Chemical Ageing ◽  
Praktische Umsetzung

Summary DIN EN ISO 16891:2016 “Test methods for evaluating the degradation of characteristics of cleanable filter media“ is the first standard in Germany that takes into account the thermal and chemical ageing of the filter media and stipulates how they are to be tested. These normative specifications were to be implemented as part of a research project. However, the boundary test conditions proved to be general conditions and many other details were not described in the standard. This is why, as well as there being many safety aspects, the filter testing has so far only been partially implemented. Uniform loading of several samples at the normal filter flow velocities used in practice could not be implemented. Doubt exists with regard to the comparability of the results of the tests that were based on the standard in its current form at different test institutes.

Addressing Paraffin Deposition Challenges Through New Technologies

2021 ◽  
Author(s):  
Saugata Gon ◽  
Christopher Russell ◽  
Kasper Koert Jan Baack ◽  
Heather Blackwood ◽  
Alfred Hase
Keyword(s):  
Temperature Gradient ◽  
Surface Temperature ◽  
New Technologies ◽  
Test Methods ◽  
Large Temperature ◽  
Mixing Condition ◽  
Cold Finger ◽  
Cold Surface ◽  
Bulk Oil ◽  
Conventional Test

Abstract Paraffin deposition is a common challenge for production facilities globally where production fluid/process surface temperature cools down and reach below the wax appearance temperature (WAT) of the oil. Although chemical treatment is used widely for suitable mitigation of wax deposition, conventional test methods like cold finger often fail to recommend the right product for the field. The current study will present development of two new technologies PARA-Window and Dynamic Paraffin Deposition Cell (DPDC)to address such limitations. Large temperature gradient between bulk oil and cold surface has been identified as a major limitation of cold finger. To address this, PARA-Window has been developed to capture the paraffin deposition at a more realistic temperature gradient (5°C) between the bulk oil and surface temperature using a NIR optical probe. Absence of brine and lack of shear has been identified as another limitation of cold finger technique. DPDC has been developed to study paraffin deposition and chemical effectiveness in presence of brine. Specially designed cells are placed horizontally inside a shaker bath to achieve good mixing between oil and water for DPDC application. A prior study by Russell et al., (2019) showed the effectiveness of PARA-Window in capturing deposition phenomena of higher molecular weight paraffin chains that resemble closely to field deposits under narrow temperature gradient around WAT. Conventional test methods fail to capture meaningful product differentiation in most oils under such conditions and hence can only recommend a crystal modifier type of paraffin chemistries. PARA-Window technique can expand product selection to other type of paraffin chemistries (paraffin crystal modifiers, dispersants and solvents) as shown earlier by Russell et al., (2021). The usage of DPDC allows us to create a dynamic mixing condition inside the test cells with both oil and water under a condition similar to production pipe systems. This allows DPDC to assess water effect on paraffin chemistries (crystal modifiers and dispersants). This study presents the usage of these two new technologies to screen performance of different types of paraffin chemistries on select oils and their advantages over cold finger. The results identify how mimicking field conditions using these new technologies can capture new insights into paraffin products.

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