Ultimate pullout resistance of groups of vertical anchors

1994 ◽  
Vol 31 (5) ◽  
pp. 673-682 ◽  
Author(s):  
Adel Hanna ◽  
Ashraf Ghaly
Keyword(s):  
Group Action ◽  
Theoretical Calculations ◽  
Limit Equilibrium ◽  
Companion Paper ◽  
Relative Depth ◽  
Uplift Capacity ◽  
Rupture Surface ◽  
Dense Sand ◽  
Pullout Resistance ◽  
Shearing Resistance

A theoretical investigation on the group action of vertical screw anchors installed in sands is presented. An experimentally observed rupture surface for single anchors was employed to establish the shape of the rupture surface for groups of anchors. A theory was developed to predict the uplift capacity of groups of anchors with different configurations utilizing the theoretical model described in a companion paper. To calculate the uplift capacity, weight and shear factors for shallow and deep groups of anchors are established. These factors are presented as functions of the angle of shearing resistance of the sand, relative depth ratio of an individual anchor within the group, and (or) the ratio between the height of embedded failure bulb and anchor diameter. The effect of overconsolidation due to the compaction technique used in placing the sand was incorporated in the theoretical calculations of uplift capacity. Comparison between theoretical and experimental results shows good agreement in the case of loose and medium sands and satisfactory agreement in the case of dense sand. An empirical equation, based on theory and experimental data, is proposed to mathematically quantify the effect of densification-on the angle of shearing resistance of the sand. Key words : anchors, group action, limit equilibrium, overconsolidation ratio, theoretical analysis, uplift capacity.

Ultimate pullout resistance of single vertical anchors

1994 ◽  
Vol 31 (5) ◽  
pp. 661-672 ◽  
Author(s):  
Ashraf Ghaly ◽  
Adel Hanna
Keyword(s):  
Theoretical Analysis ◽  
Limit Equilibrium ◽  
Shear Stresses ◽  
Relative Depth ◽  
Uplift Capacity ◽  
Pullout Resistance ◽  
Overconsolidation Ratio ◽  
Shearing Resistance ◽  
Shear Factors ◽  
Good Agreement

An investigation into the performance of single vertical screw anchors installed in sands is presented. Models were developed employing the limit equilibrium method of analysis to predict the uplift capacity of anchors installed into shallow, transition, and deep depths. An experimentally observed log-spiral rupture surface was used in the theoretical analysis. Shear stresses were calculated on the surface of rupture using Kötter's differential equation. Weight and shear factors for shallow and deep anchors are established to simplify the calculation of the uplift capacity from the theories developed. These factors are presented in simple graphs as functions of the angle of shearing resistance of the sand and the relative depth ratio of the anchor. The effect of sand overconsolidation resulting from the application of mechanical compaction was introduced by incorporating the overconsolidation ratio in the uplift capacity calculations. Comparisons between the theoretical values and the experimental results of the present investigation as well as field results reported in the literature showed good agreement. Key words : anchors, failure mechanism, limit equilibrium, overconsolidation ratio, theoretical analysis, uplift capacity.

Seismic uplift capacity of inclined strip anchors

2005 ◽  
Vol 42 (1) ◽  
pp. 263-271 ◽  
Author(s):  
Deepankar Choudhury ◽  
K S Subba Rao
Keyword(s):  
Limit Equilibrium ◽  
Ground Surface ◽  
Failure Surface ◽  
Friction Angle ◽  
Uplift Capacity ◽  
Principle Of Superposition ◽  
Seismic Acceleration ◽  
Acceleration Coefficient ◽  
Angle Of Internal Friction ◽  
Seismic Forces

Uplift capacities of inclined strip anchors in soil with a horizontal ground surface are obtained under seismic conditions. Limit equilibrium approaches with a logarithm-spiral failure surface and pseudostatic seismic forces are adopted in the analysis. The results are presented in the form of seismic uplift capacity factors as functions of anchor inclination, embedment ratio, angle of internal friction of the soil, and horizontal and vertical seismic acceleration coefficients. The uplift capacity factors are worked out separately for cohesion, surcharge, and density components. Use of the principle of superposition for calculating anchor uplift capacity is validated. The vertical seismic acceleration coefficient always reduces the uplift capacity, whereas the horizontal seismic acceleration coefficient reduces the uplift capacity in most cases. The roles of anchor embedment ratio, soil friction angle, and anchor inclination in determination of the seismic uplift capacity are also discussed. Comparisons of the proposed method with available theories in the seismic case are also presented. The present study gives the minimum seismic uplift capacity factors compared with the existing theory.Key words: seismic uplift capacity factors, inclined strip anchors, limit equilibrium, pseudostatic, c–ϕ soil.

Uplift Capacity of Suction Caissons in Sand for General Conditions Of Drainage

2021 ◽  
Author(s):  
Ragini Gogoi ◽  
Charles P. Aubeny ◽  
Phillip Watson ◽  
Fraser Bransby
Keyword(s):  
Constitutive Model ◽  
Load Capacity ◽  
System Capacity ◽  
Soil Conditions ◽  
Uplift Capacity ◽  
Soil Response ◽  
Dense Sand ◽  
Centrifuge Tests ◽  
Numerical Predictions ◽  
Suction Caissons

Abstract Suction caissons have emerged as a viable solution for the foundations of offshore wind turbines, which are gaining momentum worldwide as an alternate energy source. When used in a multi-bucket jacket system, the system capacity is often governed by the uplift capacity of the windward bucket foundation. Seabed conditions at offshore windfarm sites often comprise dense sand where the soil response may be drained, partially drained or undrained depending on the loading regime, the foundation dimensions and the soil conditions. Given the large difference in uplift capacity of caissons for these different drainage conditions, predicting the behavior of a suction caisson under a range of drainage conditions becomes a paramount concern. Consequently, this paper presents the findings of a coupled finite element investigation of the monotonic uplift response of the windward caisson of a multi-bucket jacket system in a typical dense silica sand for a range of drainage conditions. The study adopts a Hypoplastic soil constitutive model capable of simulating the stress-strain-strength behavior of dense sand. This choice is justified by conducting a comparative study with other soil models — namely the Mohr Coulomb and bounding surface sand models — to determine the most efficient soil failure model to capture the complex undrained behavior of dense sand. The numerical predictions made in this study are verified by recreating the test conditions adopted in centrifuge tests previously conducted at the University of Western Australia, and demonstrating that the capacity from numerical analysis is consistent with the test results. The Hypoplastic soil constitutive model also provides an efficient method to produce accurate load capacity transition curves from an undrained to a drained soil state.

Experimental investigation of the uplift behaviour of circular plate anchors embedded in sand

2002 ◽  
Vol 39 (3) ◽  
pp. 648-664 ◽  
Author(s):  
K Ilamparuthi ◽  
E A Dickin ◽  
K Muthukrisnaiah
Keyword(s):  
Experimental Investigation ◽  
Circular Plate ◽  
Large Scale ◽  
Alternative Methods ◽  
Scale Model ◽  
Uplift Capacity ◽  
Rupture Surface ◽  
Sand Surface ◽  
Plate Anchors ◽  
Loose Medium

An experimental investigation of the uplift behaviour of relatively large scale model circular plate anchors up to 400 mm in diameter embedded in loose, medium-dense, and dense dry sand is described. Uplift capacity is strongly influenced by anchor diameter, embedment ratio, and sand density. In tests on shallow half-cut models, a gently curved rupture surface emerged from the top edge of the anchor to the sand surface at approximately ϕ/2 to the vertical, where ϕ is the angle of shearing resistance. For a deep anchor, a balloon-shaped rupture surface emerged at 0.8ϕ to the vertical immediately above the anchor and was confined within the sand bed. The load-displacement behaviour of full-shaped models was three-phase and two-phase for shallow and deep anchors, respectively. Alternative methods of determining the critical embedment ratio are considered, and values of 4.8, 5.9, and 6.8 are proposed for loose, medium-dense, and dense sand, respectively. Empirical equations are presented which yield breakout factors similar to those from many published laboratory and field studies.Key words: circular anchor, uplift capacity, sand, critical embedment ratio, failure mechanism.

scholarly journals Towards a simple and reliable method for calculating the uplift capacity of plate anchors in sand

2020 ◽  
Author(s):  
Anamitra Roy ◽  
Shiao Huey Chow ◽  
Conleth D O'Loughlin ◽  
Mark F. Randolph
Keyword(s):  
Finite Element ◽  
Limit Equilibrium ◽  
Finite Element Simulations ◽  
Surface Model ◽  
Large Set ◽  
Uplift Capacity ◽  
Bounding Surface ◽  
Limit Equilibrium Methods ◽  
Current Limit ◽  
Plate Anchors

his paper investigates the uplift capacity of horizontal plate anchors in sand through finite element analyses and centrifuge experiments. Finite element simulations adopt a sophisticated bounding surface plasticity model that accounts for stress and density dependent behaviour, as well as loading and fabric related anisotropic effects in sands. Failure mechanisms at peak anchor capacity show that failure occurs progressively, with a marked decrease in mobilised friction angle within the shear bands close to the anchor edge. Numerical simulations of a large set of centrifuge experiments on rectangular, strip and circular plates at different relative densities and stress levels are in good agreement for dense conditions, but perform poorer for loose conditions due mainly to the open cone yield surface in the bounding surface model. Equivalent comparisons with current limit equilibrium methods highlight the challenges in direct application of element level strength equations. Finally, the paper proposes a modified limit equilibrium solution based on a ‘rigid-block’ failure mechanism extending to soil surface, but with anchor factors that encompass the results from the finite element simulations. The modified solution provides a higher level of agreement with results from a large database of plate and pipeline test data than existing limit equilibrium methods.

Studying The Settlement of Backfill Sandy Soil Behind Retaining Wall Under Dynamic Loads

2020 ◽  
Vol 38 (7A) ◽  
pp. 992-1000
Author(s):  
Reham E. Hamdi ◽  
Mohammed Y. Fattah ◽  
Mohammed F. Aswad
Keyword(s):  
Relative Density ◽  
Sandy Soil ◽  
Limit Equilibrium ◽  
Retaining Wall ◽  
Retaining Walls ◽  
Dynamic Loads ◽  
Dense Sand ◽  
Burden Test ◽  
Long Time ◽  
Cohesion Less Soil

For a long time, the seismic examination of retaining walls has been contemplated by a few strategies dependent on the basic augmentation of Coulomb's limit equilibrium investigation. These techniques cannot gauge the removal of the refill soil upheld by the wall. A trial examination is completed to contemplate the vertical settlement on sandy soil under dynamic loads with other burden amplitudes, vibration frequencies, relative density, and various separations between the establishment and holding divider. The model balance utilized in this investigation is square. Dynamic burden test is done on cohesion less soil with three burden amplitudes (0.25 ton, 0.5 ton and 1 ton), three vibration recurrence (0.5 Hz, 1 Hz and 2 Hz), two density of sandy soil (30% loose sand and 70% dense sand) and three unique separations between the establishment and retaining wall. It has been seen that the change is increment with the burden of abundance and decreased by increasing the separation between the establishment and retaining wall. There is an unimportant result of recurrence on the aggregate settlement. The settlement decrement by incrementing the relative density

Numerical study of natural convection in an enclosure with localized heating from below—creeping flow to the onset of laminar instability

1969 ◽  
Vol 36 (1) ◽  
pp. 33-54 ◽  
Author(s):  
K. E. Torrance ◽  
J. A. Rockett
Keyword(s):  
Natural Convection ◽  
Numerical Study ◽  
Theoretical Calculations ◽  
Hot Spot ◽  
Boussinesq Approximation ◽  
Companion Paper ◽  
Laminar Flows ◽  
Creeping Flow ◽  
Initial Flow ◽  
Transfer Rates

An analytical study was made of the natural convection induced in an enclosure by a small hot spot centrally located on the floor. The enclosure was a circular cylinder, vertically oriented, with height equal to radius. A Prandtl number of 0.7 (air) was assumed; the Grashof number (Gr) was based on cylinder height and hot spot temperature. The equations of fluid flow in axisymmetric cylindrical co-ordinates were simplified with the Boussinesq approximation. The equations were solved numerically with a computationally stable, explicit method. The computation, starting from quiescent conditions, proceeded through the initial transient to the fully developed flow. Solutions were obtained for Gr from 4 × 104 to 4 × 1010. The theoretical flows are in excellent agreement with experimentally observed laminar flows (Gr [lsim ] 1.2 × 109) which are discussed in a companion paper, Torrance, Orloff & Rockett (1969). Turbulence was observed experimentally for Gr [gsim ] 1.2 × 109. When the theoretical calculations were extended to Gr = 4 × 1010, a periodic vortex shedding developed, suggestive of the onset of laminar instability. The theoretical results reveal a √Gr scaling for the initial flow transients and, at large Gr, the velocities and heat transfer rates.

GENERALIZED SOLUTION FOR SEISMIC UPLIFT CAPACITY OF STRIP ANCHORS USING PSEUDO-STATIC APPROACH

2007 ◽  
Vol 01 (04) ◽  
pp. 311-328 ◽  
Author(s):  
DEEPANKAR CHOUDHURY ◽  
K. S. SUBBA RAO
Keyword(s):  
Limit Equilibrium ◽  
Failure Surface ◽  
Friction Angle ◽  
Present Theory ◽  
Generalized Solutions ◽  
Unit Weight ◽  
Uplift Capacity ◽  
Principle Of Superposition ◽  
Seismic Acceleration ◽  
Acceleration Coefficient

Generalized solutions for uplift capacity of inclined shallow strip anchors embedded in general c–ϕ soils with inclined slope carrying a uniform surcharge is developed in this paper for seismic condition. The individual effects of unit weight, surcharge and cohesion components on the computation of uplift capacity of anchors are considered. Limit equilibrium method with logspiral failure surface is adopted in the analysis and the effects of seismic forces are considered as pseudo-static forces. The results have been presented in the form of seismic uplift capacity factors as functions of anchor inclination, ground inclination, embedment ratio, soil friction angle and seismic acceleration coefficients both in the horizontal and vertical directions. Both the seismic accelerations change significantly the uplift capacity of anchors. Effect of the vertical seismic acceleration coefficient has been found to always reduce the uplift capacity whereas the effect of horizontal seismic acceleration coefficient has been found to reduce the uplift capacity in most of the cases. Results are presented in graphical and tabular forms. Estimation of error while using the principle of superposition to compute the seismic uplift capacity is also conducted. A comparative study between the present theory and available results in literature shows the merits and requirement of the present analysis.

scholarly journals Ultimate Capacity Analysis and Determination of the Position of Failure Surface for Uplift Piles

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Qian Su ◽  
Xiaoxi Zhang ◽  
Pingbao Yin ◽  
Wenhui Zhao
Keyword(s):  
Limit Equilibrium ◽  
Failure Surface ◽  
Equilibrium Analysis ◽  
Soil Parameters ◽  
Uplift Capacity ◽  
Ultimate Capacity ◽  
Potential Failure ◽  
Coulomb Failure Criterion ◽  
Slice Method

Ultimate capacity and failure surface position of uplift piles are dependent on soil parameters. In this paper, the horizontal slice method is used to discuss the relation among the ultimate uplift capacity, the failure surface position, and soil parameters with Mohr-Coulomb failure criterion. According to the limit equilibrium analysis, the ultimate uplift capacity is calculated by dividing soil around the pile into slices with considering the potential failure surface as a group of several sectional planes. Then the multivariate function used to calculate ultimate capacity is established and optimized by the sequential quadratic programming. Through the numerical calculation and comparison with the previous research, the results show that the method is reasonable and effective and can be used to determine the failure surface and the magnitude of the ultimate capacity of uplift piles.

A strain-based design method for the collapse limit state of reinforced soil walls or slopes

1992 ◽  
Vol 29 (5) ◽  
pp. 832-842 ◽  
Author(s):  
S-C. R. Lo ◽  
D-W. Xu
Keyword(s):  
Numerical Optimization ◽  
Limit Equilibrium ◽  
Limit State ◽  
Reinforced Soil ◽  
Equilibrium Equations ◽  
Rigid Plastic ◽  
Rupture Surface ◽  
Nonlinear Load ◽  
Soil Walls ◽  
Reinforced Soil Walls

A new design methodology was developed to predict the collapse of reinforced soil walls or slopes caused by failure of the reinforcing elements. The rupture surface was modelled by a generalized log spiral selected by numerical optimization, and the conventional assumption of rigid–plastic deformation at wall collapse was not made. The limit equilibrium equations were established by examining the equilibrium of slices of soil parallel to the reinforcing elements. A strain-based criterion was used to model the initiation of wall collapse by breakage of reinforcement. The tensile forces in the reinforcing elements were determined based on, approximately, strain compatibility along the rupture surface. The proposed method can model reinforcement with nonlinear load extension response that depends on embedment, non-uniform distribution of reinforcement, and dilatancy of soil. An expedient numerical scheme for performing the analysis is presented to enable the routine use of the analysis in a design office. The proposed method was validated by comparing the predictions with published observations and finite element simulation of a reinforced soil wall. Key words : collapse, kinematics, limit equilibrium, numerical optimization, reinforced soil, strain.

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