Uplift Behavior Research Articles

Uplift behaviour of screw anchors in sand. II: Hydrostatic and flow conditions : J Geotech Engng Div ASCE V117, N5, May 1991, P794–808

Uplift behaviour of screw anchors in sand. II: Hydrostatic and flow conditions : J Geotech Engng Div ASCE V117, N5, May 1991, P794–808

Uplift Behavior of Screw Anchors in Sand. II: Hydrostatic and Flow Conditions

The behavior of model single-pitch screw anchor installed in dense sand subjected to hydrostatic pressure or upward seepage flow is presented. The experimental setup described in a companion paper was modified to allow preparation of submerged sand and to provide upward seepage flow at a constant rate. The effect of the seepage flow velocity on the effective stress of the sand as well as on the ultimate uplift resistance of the anchor was examined. The theoretical model developed in the companion paper was used to predict the uplift capacity of this type of anchor installed in submerged sand or sand subjected to upward seepage flow velocity. An equation is proposed to account for the effect of the seepage flow velocity on the angle of inclination of the failure surface. Comparison of theoretical and experimental results showed good agreement. The present theory compared well with the available field results reported in the literature.

Uplift Behavior of Screw Anchors in Sand. I: Dry Sand

Experimental and theoretical investigations on the behavior of single‐screw helical anchors in sand are presented. A testing program included 56 tests conducted on five model anchors installed in dense, medium, and loose dry sands. A sand‐placing technique was developed and utilized over the testing program in order to achieve the predetermined unit weight. The experimental setup was instrumented to allow the measurement of the pullout load, the upward displacement of the anchor, and the deflection of the sand surface. It was observed that the failure mechanism as well as the pullout load varied with the installation depth of the anchor and the angle of shearing resistance of the sand. A mathematical model is developed using the limit‐equilibrium method of analysis and the observed failure mechanism of the anchor from the present experimental work. Based on experimental results, a simple equation is proposed to introduce the degree of shear mobilization on the coefficient of passive earth pressure. Compar...

Performance of piles with enlarged bases subject to uplift forces

The influence of embedment, base diameter, and backfill density on the uplift behaviour of piles with enlarged bases embedded in sand was investigated in a centrifuge. Comparitive tests on straight-shafted piles are also reported. For piles in dense sand, sensible agreement was found with earlier research on anchor plates and published field data. However, uplift capacities in loose sand were considerably lower than previously observed for anchor plates. A number of theories for anchors considerably overpredict the observed capacity for belled piers in both dense and loose sand, although in the case of dense sand, reasonable values are obtained using an empirical equation derived from centrifuge tests on anchor plates and a finite element based design approach. The normally conservative vertical slip-surface model is alone in providing reasonable agreement with the surprisingly low observations for piles in loose sand. Key words: piles, uplift capacity, centrifuge tests, sand.

Discussion of “ Uplift Behavior of Horizontal Anchor Plates in Sand ” by Edward A. Dickin (November, 1988, Vol. 114, No. 11)

Discussion of “ <i>Uplift Behavior of Horizontal Anchor Plates in Sand</i> ” by Edward A. Dickin (November, 1988, Vol. 114, No. 11)

Closure to “ Uplift Behavior of Horizontal Anchor Plates in Sand ” by Edward A. Dickin (November, 1988, Vol. 114, No. 11)

Closure to “ <i>Uplift Behavior of Horizontal Anchor Plates in Sand</i> ” by Edward A. Dickin (November, 1988, Vol. 114, No. 11)

Étude par éléments finis du comportement à l'arrachement des ancrages injectés dans le roc

The uplift behavior of grouted rock anchors is little known despite their increasing use within the last few years and during which their field of application has been greatly broadened. The behavior of anchors is usually controlled at great cost after installation through field tests. Generally, their design is based on experience and an engineer with lesser experience finds it extremely difficult to design one. Furthermore, present methods for dimensioning anchors generally result in oversizing the anchors' grouted length without a corresponding improvement in the safety factor. To provide a more fundamental approach to designing grouted rock anchors, a finite element analysis of the uplift behavior has been carried out. The results of the analysis using isoparametric quadrilateral elements with eight nodes are presented in this article. Results of failure loads and modes obtained from anchors installed in the field are well predicted by the model. Key words: rock mass, grouted anchor, cement grout, finite elements, uplift of an anchor.

Uplift behaviour of horizontal anchor plates in sand

Uplift behaviour of horizontal anchor plates in sand

Uplift Behavior of Horizontal Anchor Plates in Sand

The influence of anchor geometry, embedment, and soil density on the uplift capacity of one‐meter prototype anchors is investigated by subjecting 25‐mm models to an acceleration of 40 g in the Liverpool centrifuge. Uplift resistances expressed as dimensionless breakout facctors increase significantly with anchor embedment and soil density but reduce with increased aspect ratio. Failure displacements also increase with embedment but reduce with increased soil density and aspect ratio. The influence of anchor geometry is relatively insensitive to anchor size but increases with both embedment ratio and soil density. In general, the design approaches considered underestimate the observed capacity of one‐meter strip anchors in dense sand, although predictions using the Meyerhof and Adams and Rowe and Davis theories are acceptable. However, both these approaches appear overoptimistic for anchors in looser sand. In this case, Vesic's theory gives the closest agreement, while the formula of Majer yields overly co...

AN EXPERIMENTAL STUDY ON UPLIFT BEHAVIOR OF CAST-IN-PLACE CONCRETE PILES

AN EXPERIMENTAL STUDY ON UPLIFT BEHAVIOR OF CAST-IN-PLACE CONCRETE PILES

AN ANALYTICAL STUDY ON UPLIFT BEHAVIOR OF CAST-IN-PLACE CONCRETE PILES

AN ANALYTICAL STUDY ON UPLIFT BEHAVIOR OF CAST-IN-PLACE CONCRETE PILES

Uplift behaviour of short piles in uniform sand : Subba Rao, K S; Venkatesh, K H Soils FoundV25, N4, Dec 1985, P1–7

Uplift behaviour of short piles in uniform sand : Subba Rao, K S; Venkatesh, K H Soils FoundV25, N4, Dec 1985, P1–7

Uplift Behaviour of Short Piles In Uniform Sand

The results of laboratory studies on the uplift behaviour of short piles in uniform sands are presented. Smooth and rough mild steel piles (12.7 mm in diameter) in two uniform sands were used in the investigation. Tests were conducted for dry and submerged conditions of soil placed at either of the two densities (loose or dense). The uplift capacity was found to increase with L / D ratio, pile roughness, soil density and particle size. Pile movements of about 5% of pile diameter in loose sands and about 10% of pile diameter in dense sands were found to be necessary to mobilise the uplift capacity. These values are much more than 3 to 6% required for shaft loads during push-in tests. The unit skin frictions during pull-out tests are significantly less than during push-in tests, especially in case of rough piles for which it is as much as 80% less. Submergence resulted in reduction of uplift capacity in all cases, earth pressure coefficients, however, reduced only in case of piles in dense sand and remained almost unaffected for piles in loose sands.

Uplift of Rigid Vertical Piles in Frozen Sand

ABSTRACT Using a simple displacement field the vertical uplift behaviour of a single rigid pile (or pier) embedded in a frozen sandy soil is analyzed. Results of the analysis are represented by curves from which the magnitude of the butt movement can be estimated for given uplift forces. The procedure outlined in the paper is directly applicable to piles embedded in moderately to heavily overconsolidated clay deposits.

Foundation uplift resistance: The effects of foundation type and of seasonal changes in ground conditions

Various theories for estimating foundation uplift design are discussed. The shape of the foundation and the way it has been constructed, the type of applied loading and the strength of the soil surrounding the foundation, all affect its uplift behaviour. Tests on all these aspects are described. It is possible that any one of the above factors could be the cause of a foundation being under design strength, but the combination of more than one factor could be critical. Proposals are made for further studies, the conclusions from which should allow more accurate designs to be made in the future.

Experimental Seismic Study of Cylindrical Tanks

Earthquake response behavior of ground-supported, thin-shell, cylindrical liquid storage tanks was studied experimentally by means of the University of California at Berkeley shaking table. 12-ft x 6-ft and 7-¾-ft x 15-ft models, fabricated from sheet aluminum to represent steel tanks three times larger, were subjected to simulated earthquake accelerations with intensities up to 0.5 g. Principal test parameters included base fixity (fixed or free to uplift) and top condition (open, fixed, or floating roof). The most significant observation was that out-of-round distortions were induced in both fixed and free-base tanks in addition to the expected lateral deflection. Stresses and deflections associated with the out-of-round response were not negligible. Also, the uplift behavior of unanchored tanks differed greatly from design prediction, with observed stresses several times larger than expected. The models performed satisfactorily despite the unexpected behavior characteristics.