Lateral bearing behaviour of vibro‐ and impact‐driven large‐diameter piles in dense sand

geotechnik ◽  
2020 ◽  
Vol 43 (3) ◽  
pp. 147-159 ◽  
Author(s):  
Martin Achmus ◽  
Kirill Alexander Schmoor ◽  
Volker Herwig ◽  
Benjamin Matlock
Keyword(s):  
Large Diameter ◽  
Dense Sand

Axial performance of micropile groups in cohesionless soil from full-scale tests

2020 ◽  
Vol 57 (7) ◽  
pp. 1006-1024
Author(s):  
Maged A. Abdlrahem ◽  
M. Hesham El Naggar
Keyword(s):  
Group Performance ◽  
Large Diameter ◽  
Small Diameter ◽  
Element Model ◽  
Cohesionless Soil ◽  
Drill Bit ◽  
Load Testing ◽  
Dense Sand ◽  
Full Scale Tests ◽  
Square Configuration

Hollow bar micropile (HBMP) groups are used for supporting large loads as an alternative foundation option to large diameter drilled shafts. In such cases, it may be necessary to increase the micropile’s diameter by increasing the drill bit diameter (Db). This paper investigates experimentally and numerically the effect of increasing Db and micropile spacing on the group performance. A field load testing program was conducted on four groups of HBMPs installed in sand; each group comprised four micropiles arranged in a square configuration. All micropiles were constructed with the same size hollow bar, Dh = 51 mm; two groups comprised micropiles constructed with drill bit, Db = 115 mm, and two groups comprised micropiles constructed with drill bit, Db = 152 mm. One group of each set was installed with spacing to micropile diameter ratio, S/Db = 3 and the other group with S/Db = 5. In addition, full 3D finite element model (FEM) was developed and calibrated to simulate the behaviour of micropile groups and to evaluate the failure load for groups that were not loaded to failure. The results demonstrated that micropile groups constructed with the large diameter drill bits displayed higher stiffness and load carrying capacity than the groups constructed with small diameter bits, which confirms the effectiveness of using a larger drill bit. In addition, the group efficiency ratio values at both working load and ultimate capacity were found to be close to unity for all groups. The ultimate skin friction values of grouted micropiles obtained from this study were higher than the values suggested by the US Federal Highway Administration for medium to very dense sand. It was also found that the settlement of the 4-HBMP group increased by 25% to 33% over that of a single HBMP due to group effect.

Liquefaction Analysis of Large Diameter Long Pile Foundation in Medium Dense Sand under Earthquake Based on Finite Difference Method

2012 ◽  
Vol 602-604 ◽  
pp. 1532-1535
Author(s):  
Min Min Jiang ◽  
Zhao Ran Xiao ◽  
Shang Yu Han
Keyword(s):  
Finite Difference ◽  
Finite Difference Method ◽  
Pore Pressure ◽  
Difference Method ◽  
Large Diameter ◽  
Peak Acceleration ◽  
Dense Sand ◽  
Large Pore ◽  
Pressure Zone ◽  
Pile Length

Liquefaction properties of large diameter long pile in medium dense sand under earthquake was investigated based on finite difference method. Dynamic property of foundation soil was modeled with equivalent linear model, three peak acceleration of 0.2g, 0.15g and 0.1g was studied. Numerical calculation results show that: peak acceleration affects large pore pressure zone and maximum pore pressure, when peak acceleration increase from 0.1g to 0.2g, large pore pressure zone moved from middle to bottom of pile, maximum pore pressure raised from 45 kPa to 350 kPa; liquefaction zone of foundation has a heart shape, and expanded with increase of peak acceleration, peak acceleration increase from 0.1g to 0.2g, depth of liquefaction zone bottom increase from 27% to 41% pile length, width of liquefaction zone increase from 34% to 41% pile length, peak acceleration reached to 0.2g, liquefaction zone extended to ground surface.

Determining the Embedded Pile Length for Large-Diameter Monopiles

2010 ◽  
Vol 44 (1) ◽  
pp. 24-31 ◽  
Author(s):  
Victor D. Krolis ◽  
Gerrit L. van der Zwaag ◽  
Wybren de Vries
Keyword(s):  
Large Diameter ◽  
Design Approach ◽  
Soil Conditions ◽  
Preliminary Design ◽  
Foundation Design ◽  
Support Structure ◽  
Dense Sand ◽  
The North ◽  
Vertical Tangent ◽  
Pile Length

AbstractThe use of the monopile support structure farther offshore requires a large amount of construction steel. Designing an efficient foundation can significantly reduce the amount of steel needed and thus the total costs. This paper evaluates the applicability of current foundation design criteria for large-diameter monopiles. Emphasis will be on the vertical tangent criterion as suggested by Germanischer Lloyd and the “zero-toe-kick” criterion for determining the required embedded pile length under static loading conditions. The lateral behavior of a total of 40 different design cases of monopile support structures in water depths ranging from 15 to 35 m has been studied. The soil conditions ranged from loose to very dense sand, which is typical for the North Sea. It has been concluded that the vertical tangent and the “zero-toe-kick” criteria leads to overly conservative embedded pile lengths. A preliminary design approach is presented, which is based on the knowledge that shortening the embedded pile length will decrease the natural frequency of the support structure. The results from this preliminary design approach study have been compared with the current monopile design practice, and it was concluded that the embedded monopile length can be reduced while achieving both lateral stability and maintaining small values of deflection at mudline and the pile toe.

Finite Element Modeling of Large Diameter Monopiles in Dense Sand for Offshore Wind Turbine Foundations

2015 ◽  
Author(s):  
Sheikh Sharif Ahmed ◽  
Bipul Hawlader ◽  
Kshama Roy
Keyword(s):  
Finite Element ◽  
Wind Turbine ◽  
Large Diameter ◽  
Three Dimensional ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Physical Model Test ◽  
Arbitrary Lagrangian Eulerian ◽  
Dense Sand ◽  
Strain Behavior

With increasing demand of energy, attention to the alternative sources of sustainable energy is getting priority over the last decades. Offshore wind turbine is one of them. The most widely used foundation system for the wind turbine is the monopile, which is a large diameter single pile. In the present study, three-dimensional finite element (FE) analyses are performed to evaluate the capacity of large diameter monopiles in dense sand using the Arbitrary Lagrangian-Eulerian (ALE) approach available in Abaqus/Explicit FE software. The behavior of sand is modeled using the Mohr-Coulomb (MC) and a modified Mohr-Coulomb (MMC) model where the pre-peak hardening, post-peak softening and the effects of mean effective stress and relative density on stress-strain behavior of dense sand are considered. Comparison with physical model test results shows that the MMC model can simulate better the load-displacement response than that with the MC model. The mechanisms involved in soil deformation are also explained using FE results.

scholarly journals Analysis of Above-Ground Steel Storage Tanks Resting Over Piles or Stone Columns

2021 ◽  
Vol 15 (57) ◽  
pp. 40-49
Author(s):  
Tarek Salem ◽  
Hassan Maaly ◽  
Ahmed Abdelbaset
Keyword(s):  
Numerical Models ◽  
Large Diameter ◽  
Soft Clay ◽  
Soil Layer ◽  
Three Dimensional ◽  
Stone Columns ◽  
Storage Tanks ◽  
Dense Sand ◽  
Concrete Piles ◽  
Steel Tanks

Static and dynamic behavior of above-ground steel storage oil tanks resting on end bearing piles or stone columns are studied and analyzed using ADINA (2019) program. The studied soil profile is an upper soft clay soil layer, followed by an extended dense sand layer. The main purpose of this research is to explore to what extent stone columns can be used as an effective alternative to concrete piles under steel storage tanks. Therefore, many three-dimensional numerical models are conducted to analyze and study the performance of such tanks in both static and dynamic cases. Ten of the studied cases are steel tanks resting over stone columns with different numbers and properties. On other hand, one model studied the behavior of steel tank resting on large diameter concrete piles. Results indicate that stone columns can be used instead of end bearing piles as long as the computed settlements are safe. In addition, stone columns are behaving better than concrete piles in decreasing of hoop stress in tank shell. It is also noticed that stone columns with high elastic modulus are effective in reducing the sloshing height of the oil surface during earthquakes.

Development of a digital SEM

1991 ◽  
Vol 49 ◽  
pp. 358-359
Author(s):  
A. Yamada ◽  
A. Shibano ◽  
K. Harasawa ◽  
T. Kobayashi ◽  
H. Fukuda ◽  
...  
Keyword(s):  
Large Diameter ◽  
Objective Lens ◽  
Large Specimen ◽  
Backscattered Electrons ◽  
Digital Scanning ◽  
Junction Type ◽  
High Resolution Images ◽  
Working Distance ◽  
Type Detector ◽  
Short Working

A newly developed digital scanning electron microscope, the JSM-6300, has the following features: Equipped with a narrower conical objective lens (OL), it allows high resolution images to be obtained easily at a short working distance (WD) and a large specimen tilt angle. In addition, it is provided with automatic functions and digital image processing functions for ease of operation.Conical C-F lens: The newly developed conical C-F objective lens, having low aberration characteristics over a wide WD range, allows a large-diameter (3-inch) specimen to be tilted up to 60° at short WD, and provides images with low magnifications starting at 10*. On the bottom of the lens, a p n junction type detector is provided to detect backscattered electrons (BE) from the specimen. As the narrower conical 0L increases the secondary electron (SE) detector's field intensity on the specimen surface, high SE image quality is obtained.

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