Undrained capacity of circular shallow foundations on two-layer clays under combined VHMT loading

2022 ◽  
Author(s):  
Pengpeng He ◽  
Tim Newson
Keyword(s):  
Bearing Capacity ◽  
Effective Area ◽  
Undrained Shear Strength ◽  
Chemical Processes ◽  
Shallow Foundations ◽  
Interface Condition ◽  
Failure Envelope ◽  
Limit States ◽  
Element Analysis ◽  
Clay Deposits

Wind turbines are typically designed based on fatigue and serviceability limit states, but still require an accurate assessment of bearing capacity. Overconsolidated clay deposits in Canada often have a thin layer of crust with a relatively high undrained shear strength developed from weathering, desiccation, and geo-chemical processes. However, existing design methods only assess the bearing capacity using effective area and inclination factor without consideration of surficial crusts. This paper studies the undrained VHMT (vertical, horizontal, moment and torsional) failure envelope of circular foundations founded on a surficial crust underlain by a uniform soil with a zero-tension interface condition using finite element analysis. An analytical expression for the VHMT failure envelope is derived.

The Effect of Shallow-Water Waves on the Stability and Bearing Capacity of Sea Beds

1974 ◽  
Vol 14 (04) ◽  
pp. 330-336
Author(s):  
R. Fernandez Luque ◽  
R. van Beek
Keyword(s):  
Bearing Capacity ◽  
Water Waves ◽  
Pressure Fluctuations ◽  
Wave Action ◽  
Shallow Foundations ◽  
Loose Sand ◽  
Dense Sand ◽  
Model Experiments ◽  
Sea Bottom ◽  
Clay Deposits

Abstract This paper reports a theoretical and experimental investigation of the influence of shallow water waves on the bearing capacity of foundations in sea beds. The propagation of pressure waves through a porous sea bed is calculated, assuming plane elastic-plastic soil deformation under undrained loading conditions, and including the effect of dilatancy. The effective stresses thus generated are compared with the soil-stability limits. The consequences for both sand and clay deposits are considered individually. Model experiments in a flume demonstrate how prolonged wave action increases the density of an initially very loose sand, whereas it expands an initially dense sand. Because small changes in void ratio have a significant effect on the bearing capacity of a sediment, the bearing capacity of a loose sand bed increases with prolonged wave action, but that of a dense sand decreases. It was found, however, that under all circumstances the ultimate bearing capacity of a sandy sea bottom is largely sufficient for pile-foundation purposes. In fact, stormy weather tends to stabilize the bearing capacity of a sandy sea bottom. In contrast, calculations for clay deposits show that the excess pore pressure caused by wave action on a normally consolidated clay cannot be dissipated within a practical time limit. Waves are thus unable to compact a clay deposit. The shearing forces generated by shallow waves in an underconsolidated clay may therefore cause soil instability during a severe storm. Our calculations and model experiments seem to indicate that shallow foundations subject to strong wave action will settle gradually within a plastic region of the sea bottom as a result of cyclic wave loading. This paper describes a practical method for calculating a safe depth of burial and bearing capacity for shallow foundations subject to wave action. INTRODUCTION Ocean waves are able to generate significant shearing forces in sea-floor sediments up to total (water + soil) depths of approximately half the length of the waves. Waves could thus affect the end bearing capacity of shallow foundations or the lateral resistance at shallow depths of deep foundation piles. We shall first calculate the pressure fluctuations at the sea bottom due to plane irregular waves using the small-amplitude wave theory. We shall then calculate the stresses and pore pressures generated in the sea bottom by such irregular pressure fluctuations at the bed surface, assuming plane elastic - plastic soil deformation and introducing a pore - pressure parameter for the saturated soil under undrained, biaxial loading condition s. We shall compare those stresses with the soil stability limits and consider soil consolidation due to wave action. Then we shall present the results of model experiments performed in a laboratory flume, showing that prolonged wave action increases the density of an initially very loose sand, whereas it expands an initially dense sand. We shall compare theory and experiment. Finally, we shall discuss a method for calculating a safe depth of burial and bearing capacity for shallow foundations subject to wave action.

Comparison of limits states design methods for bearing capacity of shallow foundations

1998 ◽  
Vol 35 (1) ◽  
pp. 175-182
Author(s):  
L D Baikie
Keyword(s):  
Bearing Capacity ◽  
Design Methods ◽  
Shallow Foundations ◽  
Limit States ◽  
The Difference

A comparison is made between several limit states design methods for the bearing capacity of shallow foundations. It is found that the main reason for the difference between the methods is the variation in the load factors.Key words: limit states design, shallow foundations, sand, clay.

scholarly journals Simplified 2D Finite Element Model for Calculation of the Bearing Capacity of Eccentrically Compressed Concrete-Filled Steel Tubular Columns

2021 ◽  
Vol 11 (24) ◽  
pp. 11645
Author(s):  
Anton Chepurnenko ◽  
Batyr Yazyev ◽  
Besarion Meskhi ◽  
Alexey Beskopylny ◽  
Kazbek Khashkhozhev ◽  
...  
Keyword(s):  
Finite Element ◽  
Bearing Capacity ◽  
Cross Sections ◽  
Three Dimensional ◽  
Element Model ◽  
Longitudinal Force ◽  
Effective Area ◽  
Element Analysis ◽  
Tubular Columns ◽  
Cfst Columns

Concrete-filled steel tubular (CFST) columns are widely used in construction due to effective resistance to compression and bending joint action. However, currently, there is no generally accepted effective calculation method considering both nonlinearities of the materials and lateral compression. The article proposes the finite element analysis method of concrete-filled steel tubular columns in a physically nonlinear formulation by reducing a three-dimensional problem to a two-dimensional one based on the hypothesis of plane sections. The equations of Geniev’s concrete theory of plasticity are used as relations establishing the relationship between stresses and strains. The technique was tested by comparing the solution with the calculation in a three-dimensional formulation in the LIRA-SAPR software package and with the experimental data of A.L. Krishan and A.I. Sagadatov. It has been established that the effective area of operation of circular-section columns are small eccentricities of the longitudinal force. The proposed approach can be applied to analyzing the stress–strain state and bearing capacity of pipe-concrete columns of arbitrary cross-sections. There are no restrictions on the composition of concrete, and the shell material can be steel and fiberglass.

Spatial Variability of Material Parameter and Bearing Capacity of Clay

2012 ◽  
Vol 629 ◽  
pp. 433-437 ◽  
Author(s):  
Md Mizanur Rahman ◽  
Hoang Bao Khoi Nguyen
Keyword(s):  
Spatial Variability ◽  
Bearing Capacity ◽  
Correlation Length ◽  
Material Parameter ◽  
Vertical Direction ◽  
Undrained Shear Strength ◽  
Element Analysis ◽  
Correlation Lengths ◽  
The Finite Element Analysis ◽  
Spatial Correlation Length

A stochastic analysis that incorporates spatial variability of material parameter of clay i.e. undrained shear strength, c within the finite element analysis was done. A smoother change of c between two neighbouring soil elements is expected than two elements at a distance apart, thus a spatial correlation length is used within the random field to describe the distance over which random values tend to be correlated. When the correlation lengths in horizontal and vertical directions are same, the soil elements can be described ‘isotropic’. Most of the previous studies investigated the effect of variation of c in terms of coefficient of variation, COV (standard deviation/mean) and the isotropic correlation length on bearing capacity. However, the correlation length of soil may not be isotropic as they may be deposited in layers i.e. correlation length in horizontal direction may be higher than that in vertical direction. Thus, this study investigated the effect of isotropic as well as anisotropic (in terms of correlation length) conditions and their lengths over a range of COV of c on the bearing capacity. The result of this study would help to understand the effect of soil anisotropy on bearing capacity.

scholarly journals Geotechnical ULS design issues of bridge shallow foundations

2021 ◽  
Author(s):  
Konstantina Papadopoulou ◽  
George Gazetas
Keyword(s):  
Bearing Capacity ◽  
Point Of View ◽  
Shallow Foundations ◽  
Cohesionless Soils ◽  
Limit States ◽  
Geotechnical Design ◽  
Layered Clay ◽  
2D And 3D ◽  
Ultimate Limit ◽  
Special Case

Some important issues referring to the Ultimate Limit States of geotechnical design of bridge shallow foundations are discussed using results of 2D and 3D FE analyses, as follows: (a) The effects of highly eccentric and inclined loadings on the bearing capacity of footings on cohesionless soils, (b) the effects of soil inhomogeneity in the special case of 2-layered clay, (c) the scour effects in case of abutment and piers in riverbed, from the geotechnical point of view.

scholarly journals Effect of perforations on the bearing capacity of shallow foundation on clay

2019 ◽  
Vol 56 (5) ◽  
pp. 746-752 ◽  
Author(s):  
Run Liu ◽  
Meng-meng Liu ◽  
Ying-hui Tian ◽  
Xinli Wu
Keyword(s):  
Shear Strength ◽  
Bearing Capacity ◽  
Three Dimensional ◽  
Shallow Foundations ◽  
Shallow Foundation ◽  
Two Dimensional ◽  
Element Analysis ◽  
Dimensionless Ratio ◽  
Undrained Strength ◽  
Strength Gradient

As a type of shallow foundation, a mudmat serves as the seabed support structure for subsea wells, pipeline manifolds, and pipeline terminations. The shallow foundations are usually designed with perforations to facilitate installation and removal, but the influence of these perforations has not been fully understood. This paper presents a method to analyze the bearing capacities of both two-dimensional (2D) and three-dimensional (3D) perforated shallow foundations using finite element analysis. The soil was idealized as a Tresca material, with the undrained strength increasing linearly with depth. The outcome indicates that perforations have nonnegligible effects on the bearing capacity of shallow foundations. The bearing capacity decreases with increasing perforation ratio, R, and the degree of reduction increases with the increase of the dimensionless ratio kB/Suo, where k is the shear strength gradient, B is the width of the foundation, and Suo is the shear strength at the mudline. For 2D shallow foundations, there exists a critical perforation ratio, Rc; when the perforation ratio is lower than the critical perforation ratio, the perforated foundation does not lose its bearing capacity. For 3D shallow foundations, the bearing capacity decreases directly with the increase of perforation ratio, R.

scholarly journals Geochemistry and Mineralogy of Ice-Dammed Lake Sediments of the Lębork Deposit

2021 ◽  
Author(s):  
Radosław Rogoziński ◽  
Alina Maciejewska
Keyword(s):  
Chemical Composition ◽  
Lake Sediments ◽  
Inductively Coupled Plasma ◽  
Mineralogical Composition ◽  
Raw Material ◽  
Element Analysis ◽  
X Ray ◽  
Dominant Component ◽  
Clay Deposits ◽  
Dammed Lake

AbstractVarved clay deposits from ice-dammed lakes are a particularly important and broadly applied raw material used for the production of high-quality ceramics (red bricks, roof tiles, etc.), but the mineralogy and geochemistry of these sediments are not fully understood. The aim of the present study was to determine the chemical and mineralogical composition of ice-dammed lake sediments of the Lębork deposit. Major-element analysis of the compositions of selected samples from the ice-dammed lake clays was performed by X-ray fluorescence (XRF) and trace elements were determined by inductively coupled plasma-mass spectrometry. The mineralogical composition of clay samples was determined by X-ray diffraction (XRD). Analyses of the chemical composition of the ice-dammed lake clays of the Lębork deposit showed that the dominant component was SiO2 with a mean content of 56.13 wt.%; the second most abundant component was Al2O3, with a mean content for the entire deposit of 11.61 wt.%. Analysis by ICP-MS indicated the presence of rare earth elements (REE), e.g. cerium, neodymium, lanthanum, and praseodymium; their mean contents are: 56.9, 27.0, 26.3, and 7.3 ppm, respectively. Mineralogical analysis of the varved clays identified quartz, muscovite, calcite, and clay minerals – illite, kaolinite, and montmorillonite. The material filling the Lębork basin is characterized by small lateral and vertical variability in chemical composition. The results of the present study may be of considerable importance in determining the parent igneous, metamorphic, and sedimentary rocks, the weathering products of which supplied material to the ice-dammed lake, as well as in determining the mechanisms and character of the sedimentation process itself.

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