The Uplift Capacity of Foundations Under Oblique Loads

1973 ◽  
Vol 10 (1) ◽  
pp. 64-70 ◽  
Author(s):  
G. G. Meyerhof
Keyword(s):  
Ultimate Load ◽  
Field Tests ◽  
Uplift Capacity ◽  
Previous Theory ◽  
Uplift Resistance ◽  
Interaction Relationship

The previous theory of vertical uplift capacity of foundations has been extended to foundations under oblique loads. The analysis is compared with the results of model and some field tests on rigid anchors and piles in sand and clay. The influence of load inclination on the uplift resistance can be represented by an interaction relationship between the vertical and horizontal components of the ultimate load.

Tension tests on bored piles in cemented desert sands

1994 ◽  
Vol 31 (4) ◽  
pp. 597-603 ◽  
Author(s):  
Nabil F. Ismael ◽  
Hasan A. Al-Sanad ◽  
Fahad Al-Otaibi
Keyword(s):  
Load Transfer ◽  
Field Tests ◽  
Standard Penetration Test ◽  
Uplift Capacity ◽  
Calcareous Sand ◽  
Shaft Resistance ◽  
Bored Pile ◽  
Bored Piles ◽  
Cemented Sands ◽  
Strength Characterization

The load transfer of bored piles in medium dense cemented sands was examined by field tests at two sites. At the first site, two bored piles were tested in axial tension to failure. One pile was instrumented with strain guages to measure the axial load distribution at all load increments. The results indicate significant load transfer along the pile length. The average shaft resistance measured was 80 and 100 kN/m2 in medium-dense and very dense, weakly cemented calcareous sand, respectively. At the second site, a tension test was carried out on a bored pile in uncemented cohesionless sand. By comparing the results at the two sites the influence of cementation on the uplift capacity was assessed. The shaft resistance depends on many factors including the relative density, degree of cementation, soil fabric, and method of construction. It increases with the standard penetration test (SPT) N values; however, the SPT is not considered a reliable test for strength characterization of cemented sands. Analysis of the pile capacity can be made considering both components of soil strength, namely, cohesion intercept c and angle of shearing resistance [Formula: see text]. Key words : bored piles, cemented sands, uplift capacity, friction, shaft resistance.

scholarly journals Experimental investigation of reverse end bearing of offshore shallow foundations

2013 ◽  
Vol 50 (10) ◽  
pp. 1022-1033 ◽  
Author(s):  
Divya S.K. Mana ◽  
Susan Gourvenec ◽  
Mark F. Randolph
Keyword(s):  
Uplift Capacity ◽  
Medium Term ◽  
Centrifuge Model ◽  
End Bearing Capacity ◽  
Adjacent Soil ◽  
Uplift Resistance ◽  
External Face ◽  
Vertical Gap ◽  
Soil Interface ◽  
Centrifuge Model Tests

Shallow skirted foundations can mobilize uplift resistance from end bearing in the short to medium term. However, uncertainty exists over the magnitude of reverse end bearing resistance compared with resistance in compression, and how this might be affected by a gap between the external face of the foundation skirt and the adjacent soil. The study presented in this paper explores this problem through centrifuge model tests, investigating the effect of skirt embedment ratio on (i) the magnitude of reverse end bearing capacity compared with compression capacity, (ii) the uplift displacement associated with spontaneous loss of suction during uplift, and (iii) the existence of a vertical gap along the external skirt–soil interface. The results show that (i) peak uplift capacity equivalent to compression capacity can be mobilized for a fully sealed foundation with an intact skirt–soil interface, (ii) suction required for reverse end bearing can be maintained through considerable foundation displacement, even for a low skirt embedment ratio, and (iii) the presence of a vertical gap along the external skirt–soil interface causes abrupt loss of suction beneath the top plate after minimal foundation displacement, with subsequent uplift capacity being markedly reduced.

scholarly journals Analysis of Inclined Strip Anchors in Sand Based on the Block Set Mechanism

2014 ◽  
Vol 553 ◽  
pp. 422-427 ◽  
Author(s):  
S.B. Yu ◽  
J.P. Hambleton ◽  
Scott William Sloan
Keyword(s):  
Upper Bound ◽  
Limit Analysis ◽  
Experimental Studies ◽  
Collapse Mechanism ◽  
Uplift Capacity ◽  
Collapse Mechanisms ◽  
Kinematic Method ◽  
The Subject ◽  
Uplift Resistance ◽  
Modelling Assumptions

Anchors are widely used in foundation systems for structures requiring uplift resistance. As demonstrated by numerous theoretical and experimental studies on the subject, uncertainty remains as to both the theoretical uplift capacity of anchors in idealised soils and the suitability of the various modelling assumptions in capturing the responses observed during tests. This study, which deals exclusively with the theoretical uplift capacity, presents newly obtained predictions of uplift capacities and the corresponding collapse mechanisms for inclined strip anchors in sand. The analysis is based on the upper bound (kinematic) method of limit analysis and the so-called block set mechanism, in which a collapse mechanism consisting of sliding rigid blocks is optimised with respect to interior angles and edges of the blocks. It is demonstrated that the method provides lower (better) estimates of uplift capacity in some cases compared to previous upper bound calculations. Also, variations in the predicted collapse mechanism with changes in embedment and inclination are assessed in detail.

The Bearing Capacity Character of Enlarged Base Shallow Foundation under Uplift Load

2011 ◽  
Vol 243-249 ◽  
pp. 2151-2156 ◽  
Author(s):  
Xian Long Lu ◽  
Qiang Cui
Keyword(s):  
Shear Failure ◽  
Limit Equilibrium ◽  
Failure Process ◽  
Field Tests ◽  
Failure Surface ◽  
Theory Model ◽  
Shallow Foundation ◽  
Deformation And Failure ◽  
Uplift Load ◽  
Uplift Resistance

By theory analysis and field tests, failure model of soil around foundation and ultimate uplift resistance of enlarged bass shallow foundation were analyzed. The results showed that the deformation and failure process of soil around foundation under uplift load undergone three phases: 1) soil upon enlarged base compressed, 2) appearance and extension of plastic zone of soil around foundation, and 3) soil around foundation general shear failure. With the combination of the Limit Equilibrium Method, and Sliding Curve Theory, a simplified theory model to calculate net ultimate uplift resistance of shallow foundation assuming cir failure surface under uplift load was established. Then three examples were calculated by this method and the good agreement between theory calculation solution and experimental results validated the rationality of the model. The study in this paper provided an important theoretical support and brand-new idea on calculation method of uplift capacity of foundation with enlarged base and failure surface characteristics determination of soil around foundation.

Behavior of pressure-grouted anchors in gravel

2012 ◽  
Vol 49 (6) ◽  
pp. 719-728 ◽  
Author(s):  
Shih-Tsung Hsu
Keyword(s):  
Ultimate Load ◽  
Pressure Coefficient ◽  
Ground Surface ◽  
Field Tests ◽  
Earth Pressure ◽  
Free Length ◽  
Fixed Length ◽  
Normal Distribution Curve ◽  
Earth Pressure Coefficient ◽  
Deep Anchor

This study consisted of field tests conducted on nine vertical and three inclined low-pressure-grouted anchors to investigate their behavior in gravel. An anchor can be categorized as a deep anchor when the overburden depth (free length) Z exceeds 8D (D is the diameter of the anchor). The shape of the heave on the ground surface of a shallow anchor is similar to a normal distribution curve. The extended diameter of the heave was between 170 and 300 cm, which could be divided into two zones, primary and secondary, based on the failure mode of the ground. As the fixed length of a shallow anchor increased, the extended diameter also increased. The ultimate load on an anchor increased with the free length and, to a greater degree, with the fixed length of an anchor: a fixed length of only 3 m generated an ultimate load of over 1100 kN. However, the permissible load, determined from the creep coefficient, is inapplicable for short anchors in gravel. The earth pressure coefficient K of vertical anchors was approximately 29 and for an anchor shaft inclined at 25º it was approximately 17.7.

Vertical uplift capacity of a group of two coaxial anchors in a general c–ϕ soil

2012 ◽  
Vol 49 (3) ◽  
pp. 367-373 ◽  
Author(s):  
Jyant Kumar ◽  
Tarun Naskar
Keyword(s):  
Finite Element ◽  
Lower Bound ◽  
Friction Angle ◽  
The Other ◽  
Unit Weight ◽  
Uplift Capacity ◽  
Soil Cohesion ◽  
Uplift Resistance ◽  
Vertical Spacing ◽  
Unit Cohesion

The vertical uplift resistance of a group of two horizontal coaxial strip anchors, embedded in a general c–[Formula: see text] soil (where c is the unit cohesion and [Formula: see text] is the soil friction angle), has been determined by using the lower bound finite element limit analysis. The variation of uplift factors Fc and Fγ, due to the components of soil cohesion and unit weight, respectively, with changes in depth (H) / width (B) has been established for different values of vertical spacing (S) /B. As compared to a single isolated anchor, the group of two anchors provides a significantly greater magnitude of Fc for [Formula: see text] ≤ 20° and with H/B ≥ 3. The magnitude of Fc becomes almost maximum when S/B is kept closer to 0.5H/B. On the other hand, with the same H/B, as compared to a single anchor, hardly any increase in Fγ occurs for a group of two anchors.

Field Performance of Ground Anchors in Taichung Basin

2013 ◽  
Vol 718-720 ◽  
pp. 1882-1887
Author(s):  
Shih Tsung Hsu ◽  
Wen Chi Hu
Keyword(s):  
Ultimate Load ◽  
Distribution Curve ◽  
Ground Surface ◽  
Field Tests ◽  
Field Performance ◽  
Free Length ◽  
Fixed Length ◽  
Normal Distribution Curve ◽  
Ground Anchors ◽  
Deep Anchor

This research carried out field tests on nine vertical anchors to investigate their behavior in gravel of Taichung Basin. An anchor can be categorized as a deep anchor when the free length Z exceeds 8D (D is the diameter of the anchor). The shape of the heave on the ground surface of a shallow anchor is similar to a normal distribution curve. The extended diameter of the heave was between 170 and 300 cm, which could be divided into two zones, primary and secondary, based on the failure mode of the ground. As the fixed length of a shallow anchor increased, the extended diameter also increased. The ultimate load of an anchor increased with the free length and, to a greater degree, with the fixed length of an anchor: a fixed length of only 3 m (D = 0.12 m) generated an ultimate load of over 1100 kN.

Stability of circular vertical earth anchors

1987 ◽  
Vol 24 (3) ◽  
pp. 452-456 ◽  
Author(s):  
Hamed S. Saeedy
Keyword(s):  
Shear Strength ◽  
Functional Relationship ◽  
Load Capacity ◽  
Pressure Ratio ◽  
Relative Depth ◽  
Uplift Capacity ◽  
Angle Of Internal Friction ◽  
Uplift Resistance ◽  
Relationship Of ◽  
Range Of Values

This study aims to provide an extensive analytical approach for determining the uplift capacity of circular vertical earth anchors and to investigate the soil–anchor interaction. The solution is simplified by utilizing proper dimensionless parameters, in which controlling dimensionless factors [Formula: see text] are produced for a range of values of H/D and angle of internal friction. The factor [Formula: see text] is a pressure ratio representing gravitational and shear strength of the soil, and H/D signifies relative depth, which pertains to anchor geometry. The functional relationship of these parameters was previously studied for H/D ratios up to 6. The present work concludes that the greater the value of H/D the higher the uplift resistance, but with a decreasing rate until a constant value of uplift force is reached. The transitional value of depth, which defines the condition of failure, is a function of the shear strength of the burial soil. This transitional stage indicates the optimum possible value for uplift capacity for a given relative depth (H/D). Key words: tension foundation, uplift capacity, earth anchor load capacity, soil anchor interaction.

scholarly journals Experimental Investigation of Skirted Foundation in Sand Subjected to Rapid Uplift

2020 ◽  
Vol 67 (1-4) ◽  
pp. 17-34
Author(s):  
Marek Kulczykowski
Keyword(s):  
Experimental Investigation ◽  
Displacement Rate ◽  
Displacement Curve ◽  
Suction Pressure ◽  
Uplift Capacity ◽  
Test Results ◽  
Ultimate Capacity ◽  
Uplift Resistance ◽  
The Relationship ◽  
Rapid Uplift

Abstract This paper reports results from 1g model tests carried out under single gravity on a skirted foundation installed in sand and subjected to a rapid uplifting force. The effects of displacement rates ranging from 5 mm/s to 450 mm/s on the ultimate capacity, suction pressure inside the skirt compartment, and time of extraction were investigated. Test results indicate that the displacement rate significantly affected the magnitude of uplift resistance, as well as the magnitude of suction under the foundation lid, but had little effect on the relationship between stress and the displacement of the foundation. The shapes of the uplift capacity-displacement curve and the suction-displacement curve were similar for all experimental displacement rates.

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