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Pile Tests, Low-Sill Structure, Old River, Louisiana

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Abstract

A comprehensive pile testing program was undertaken at the site for the low-sill structure for control of the Old River, Louisiana. The object of the program was to determine the required type, size, and length of piles necessary to carry the design compression and tension loading without any significant movement of the structure. Information regarding the driving of displacement and nondisplacement types of piles was also desired. Fourteen-inch H-piles and pipe piles ranging from 16 in. to 20 in. in diameter were driven and tested. The details of the loading arrangement and test procedures are described. Because from 50 ft to 60 ft of alternating strata of silty sands, sandy silts, and clay overlie the sand beneath the structure, both the total bearing capacity and the bearing capacity of only the section of the piles penetrating into the sand were measured. The lo ad carried by that section was computed from strain measurements that were made on rods attached at different points along the pile. After the compression tests were completed, the piles were allowed to rest and tension tests were performed on all piles but one. From the pile-load tests, either 20-in. steel-pipe piles, 20-in. precast-concrete piles, or 14-in., 73-lb-per-ft, steel H-beam piles, with respective penetrations of 15 ft, 12 ft, and 27 ft into sand, were considered satisfactory for carrying the design load of 100 tons in compression and 40 tons in tension, with an ample factor of safety against both detrimental settlement and sudden plunging. The estimated average unit skin friction in the silts was 0.64 ton per sq ft for the piles tested in compression and 0.26 ton per sq ft for the piles tested in tension. The average angle of internal friction of the sand, which was computed from bearing-capacity formulas and the maximum load carried in the pile tip, was 33°. The strain-rod installation proved to be satisfactory and reliable in determining the distribution of applied load in the silt and sand strata.

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... There are several interpretation methods to evaluate the ultimate loads given by Vesic 1977[2];Mansur and Kaufman 1956[9]; Davison 1972[10]; Weltman 1980[11]; Hirany and Kulhaway 1989[12]. For the present study the ultimate load was determined by the tangent intersection method (Mansur and Kaufman 1956[9]) at the point of intersection of initial and final tangent to the load displacement curve. ...
... There are several interpretation methods to evaluate the ultimate loads given by Vesic 1977[2];Mansur and Kaufman 1956[9]; Davison 1972[10]; Weltman 1980[11]; Hirany and Kulhaway 1989[12]. For the present study the ultimate load was determined by the tangent intersection method (Mansur and Kaufman 1956[9]) at the point of intersection of initial and final tangent to the load displacement curve. The discussions of the results obtained from the experiments carried out to examine i) Settlement of pile for applied load. ...
... A review of the load-displacement curves for all tests indicates that the load-displacement curves do not show a peak behavior, with the axial compressive load increasing with the increase of pile displacement. There are several interpretation methods to evaluate the failure loads (Mansur and Kaufman, 1956;Davisson, 1972;Vesic, 1977;Weltman, 1980;Hirany and Kulhawy, 1989). ...
... In this study, the failure load was determined by the tangent intersection method (Mansur and Kaufman, 1956) at the point of intersection of the initial and final tangents to the load displacement curve. The failure loads (axial pile capacity) obtained for all tests were plotted against loading rate. ...
Article
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A total of sixty tests on model steel piles embedded in a sand of medium density were carried out in the laboratory to investigate the behavior of pile groups under different loading rates. Model piles having an outside diameter of 25 mm and embedment length of 500 mm were tested under four different loading rates : 1.0 mm/min., 0.5 mm/min., 0.1 mm/min. and 0.05 mm/min. The piles were subjected to axial compressive loads using different configurations (2x1, 3x1, 2x2, 2x3, 3x3). The center to center spacing of piles in the groups was 3d, 6d and 9d (d is the pile diameter). The experimental results indicated that the axial compressive capacity of pile group increases as the loading rate increases. The relationship between the pile capacity and the loading rate can be represented by straight line on semi-log plot. The slope of the linear relationship between the pile capacity and the loading rate increases as the number of piles in a group increases. However, the slope decreases as the spacing between piles in a group increases.
... Additionally, failure was evaluated according to two other approaches. The tangent intersection method, proposed by Mansur and Kaufman (1956), was applied to the results to define the failure loads. The intersection of the tangents of the initial and final portions of the load-displacement curve defines the failure point. ...
... The field failure loads [at a relative displacement (δ=D) of 3% (Consoli et al. 2009)] were 50, 86, and 111 kN for the 450-, 600-, and 900-mm cemented layers, respectively. The failure loads determined through the tangent intersection method (Mansur and Kaufman 1956) were 46, 85, and 109 kN for the 450-, 600-, and 900-mm cemented layers, respectively. Analogous analysis using the Laboratoire Central des Ponts et Chaussées method (Cudmani 1994) yielded failure loads of 49, 87, and 104 kN for the 450-, 600-, and 900-mm cemented layers, respectively. ...
Article
The usage of soil-cement reinforced layers to bear shallow foundations is a viable option in low-bearing-capacity soils. Existing methodologies that can determine the bearing capacity in such cases tend to consider the cemented layer's bounds to be infinite, depending solely on the ratio between the footing width and the layer's thickness. The present study intends to assess the influence of the reinforcement width on the load-settlement behavior of a circular steel footing resting on square-edge soil-cement layers bearing on a weak highly porous residual soil. Static load tests were carried out on footings (diameter of 300 mm) resting on sand-cement reinforced layers with distinct areas (edges of 450, 600, and 900 mm) and constant thickness of 300 mm. The results have shown two distinct failure modes that rely on the cemented layer's width. A punching mechanism was observed for the two smaller reinforcement's layers and they did not fail. The 900-mm square cemented layer, on the other hand, had a failure that was initiated by the formation of tensile cracks and fissures in the center of its bottommost segment. This study highlights the importance of considering the soil-cement layer's width in the bearing capacity estimation of footings resting on treated layers above weak cohesive-frictional soils.
... Mansur & Kaufman (1956) Old River (Low-Sill) * Values of S refer to equation (9). tensile and compressive capacity, and these have been discussed by De Nicola & Randolph (1993). ...
Article
Estimation of the axial capacity of piles driven into sand involves considerable uncertainty, and design rules are generally not consistent with the physical processes involved. This paper reviews current understanding of the factors that determine the axial capacity of piles driven into sand, and outlines a new framework for design which takes account of the physical processes, is consistent with the existing database of load test results, and is sufficiently flexible to permit refinement as new data becomes available. It allows for the effects of confining stress on the frictional and compressibility characteristics of sand, and hence on endbearing capacity. -from Authors
... The bearing capacity of a footing can be determined from load-displacement curves in many ways. The "tangent intersection method" was applied in this study [9]. In this procedure, as illustrated in Fig. 5, the corresponding load in the intersection point of the tangents of the start and the end parts of the load-displacement curve is assumed to represent the ultimate bearing capacity. ...
Article
This paper presents the results of a series of small-scale model tests and numerical analyses conducted on circular and ring model footings located near geogrid reinforced sand slopes. Layers of geogrid were used as reinforcement. For numerical analyses Finite Element Method (FEM) was used. The effects of reinforcement depth, size, number of layers, and the horizontal distance between reinforcement and the slope surface were experimentally investigated. Additionally, the effects of other parameters such as slope angle, the distance of the footing from the slope crest (for circular footings) and the ratio of inner to outer diameters (for ring fittings) were also investigated, numerically. The results of numerical analyses were compared with the laboratory test results and found to be in fair agreement. Optimum bearing capacity values were found for some studied parameters. The results indicate that if the reinforcement layers are implemented correctly, the bearing capacity of circular and ring footings over slopes would significantly increase.
... These ratios are almost constant and independent of the batter angle. Mansur and Kaufman [9] were reported that the critical depth value of 16 for dense sand, however, Mohab [10] reported this value as 30, 26 and 18 for dense, medium density and loose sand respectively. It is concluded that the sand density has a significant effect on the critical depth for the pile installed either vertical or inclined subject to axial pullout. ...
Article
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Many offshore structures are subjected to overturning moments due to wind load, wave pressure, and ship impacts. Also most of retaining walls are subjected to horizontal forces and bending moments, these forces are due to earth pressure. For foundations in such structures, usually a combination of vertical and batter piles is used. Little information is available in the literature about estimating the capacity of piles under uplift. In cases where these supporting piles are not vertical, the behavior under axial pullout is not well established. In order to delineate the significant variables affecting the ultimate uplift shaft resistance of batter pile in dry sand, a testing program comprising 62 pullout tests was conducted. The tests are conducted on model steel pile installed in loose, medium, and dense sand to an embedded depth ratio, L/d, vary from 7.5 to 30 and with various batter angles of 0°, 10°, 20°, and 30°. Results indicate that the pullout capacity of a batter pile constructed in dense and/or medium density sand increases with the increase of batter angle attains maximum value and then decreases, the maximum value of Pα occurs at batter angle approximately equal to 20°, and it is about 21–31% more than the vertical pile capacity, while the pullout capacity for batter pile that constructed in loose sand decreases with the increase of pile inclination. The results also indicated that the circular pile is more resistant to pullout forces than the square and rectangular pile shape. The rough model piles tested is experienced 18–75% increase in capacity compared with the smooth model piles. The suggested relations for the pullout capacity of batter pile regarding the vertical pile capacity are well predicted.
... The vertical (Vo), horizontal (Ho) and moment (Mo) bearing capacities were determined using the tangent intersection method (Mansur and Kaufman, 1956), as shown in Fig. 3. The method plots two tangential lines along the initial and latter portions of the load-displacement curve. ...
... The bearing behavior of the bucket foundation was investigated in terms of normalized bearing capacities V 0 /(A Á S u ) and H 0 /(A Á S u ), where V 0 and H 0 are the vertical and horizontal bearing capacities respectively, and A is the cross-sectional area of the bucket. The bearing capacities V 0 and H 0 were determined using the tangent intersection method (Mansur and Kaufman, 1956), as shown in Fig. 4. The method plots two tangential lines along the initial and later portions of the load-displacement curve, and the load corresponding to the intersection point of these two lines is taken as the bearing capacity. ...
... by applying the probe method with a small displacement ratio of h=v ¼ 1=1000 (Taiebat and Carter, 2000). The Ho and Mo were determined using the tangent intersection method (Mansur and Kaufman, 1956), as shown in Figure 4. The method plots two tangential lines along the initial and later portions of the load-displacement curve, and the load corresponding to the intersection point of these two lines is taken as the bearing capacity. ...
Article
A series of three-dimensional finite element analyses was conducted to investigate the effects of the embedment depth, the non-homogeneity of clay, and combined loads on the undrained bearing capacities of bucket foundations. The undrained shear strength and Young's modulus of clay were assumed to vary linearly with depth. Meanwhile, the stress-strain response of clay was simulated using the Tresca criterion. The numerical modeling adopted in this study was verified by comparing the calculated capacities with those from previous studies. Based on the results of the finite element analyses over 1400 cases, new equations were proposed to calculate the vertical, horizontal, and moment bearing capacities as well as to define the capacity envelopes under general combined loads. Comparisons with the capacity envelopes of previous studies showed that the proposed equations properly predicted the bearing capacities of the bucket foundation by considering the effects of the non-homogeneity of clay and embedment depth.
... A review of the load-displacement curves for all tests indicates that the load-displacement curves do not show a peak behavior, with the axial compressive load increasing with the increase of pile displacement. Therefore failure loads were evaluated using three interpretation methods: the tangent intersection method (Mansur and Kaufman, 1956), the slope tangent method (Davisson. 1972), and the 10% diameter method (Vesic, 1977;Weltman. ...
Article
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In this study, forty-five compressive bearing capacity tots were conducted on a model pile embedded la sand to la vest! (ate iki influence of loading rate on the bearing capacity of the puc. The tests were carried out using a model steel pile with a 30-nan diameter and depth-to-dlameter ratios of 7,10, and 15 in uniform deposits of loose, medium, and dense sand. Loads were applied to the model pde at five different rates: 1 mnVmiBU, OS ramfosW, 0.1 ma'niln, 0.05 mnVmln., and 0.01 mm/nan. Experimental results showed that bearing capacity of the model pile Increases with Increasing the rate of loading. The relationship between the compressive bearing capacity and the loading rate can be represented by a straight Una on a log-log pic*.
... J. Downloaded from www.nrcresearchpress.com by University of Western Ontario on 02/17/15 diameter piles and some pile types. In this study, the ultimate load capacities of the test piles were established using four commonly used interpretation methods: Davisson's method(Davisson 1972); tangent intersection method(Mansur and Kaufman 1956); O'Neill and Reese (1999) method; and Livneh and El Naggar ...
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The axial compression performance of large-capacity helical piles is of significant interest because they can offer an efficient alternative to conventional piling systems in many applications such as in oil processing facilities, transmission towers, and industrial buildings. This paper presents the results of seven full-scale axial compression load tests conducted on 6.0 and 9.0 m large-capacity helical piles and a 6.0 m driven steel pile. The results are considered essential to qualify and quantify the performance characteristics of large-capacity helical piles in cohesive soils. The test piles were close-ended steel shafts with an outer diameter of 324 mm. The test helical piles were either single or double helix, with a helix diameter of 610 mm and interhelix spacing that varied between 1.5 and 4.5 times the helix diameter. The subsurface soil properties at the test site were determined using field and laboratory testing methods. The 6.0 m piles were tested 2 weeks after installation, while the 9.0 m piles were tested 9 months after installation. The load-settlement curves were presented to better understand the behaviour of test piles. An ultimate capacity criterion was proposed to estimate the ultimate load of large-capacity helical piles. The test helical piles developed ultimate resistances up to 1.2-1.8 times that of the driven pile. The load-transfer mechanisms of large-capacity helical piles were studied, and it was found that soil disturbance during pile installation had a significant effect on the pile failure mechanism regardless the value of the interhelix spacing to helix diameter ratio. The mobilized soil strength parameters were back-calculated and compared with the estimated intact soil strength parameters.
... Interestingly, there is a clue in this respect in the case studies reported by Randolph et al. (1994): quite large measured-to-predicted values (2. 02 and 1. 99) were also obtained for two piles driven in a sand deposit containing a significant amount of silt (Mansur & Kaufman, 1956). ...
Article
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An approximate analytic relationship is developed between the maximum radial stress on the shaft of a displacement pile in sand and the base resistance of the pile. Using the cavity expansion analogy, together with a confined failure mechanism, the ratio between the two quantities, defined as a factor S t , is established as a function of the friction angle, shear stiffness, compressi-bility and mean effective stress of the sand near the pile tip. It is shown that, given otherwise identical input parameters, the value of S t will decrease with increasing friction angle, and with decreasing mean stress level. It also tends to decrease with an increase in relative density. It is predicted that S t has typical values between 0. 03 and 0. 05, in broad agreement with the range of empirically derived values in the literature. The relationship also predicts that S t may take much higher values (,0. 1) for piles installed in dense sand or in highly compressible sand. Because of the analytical nature, the established relationship provides useful insights into the mechanisms involved and important implications for design practice. La présente communication développe des rapports d'analyse approximatifs entre les contraintes radiales maximales appliquées sur le fû t d'un pieu a ` déplacement dans le sable et la résistance de base de ce pieu. En utilisant l'analogie de l'expansion de cavité, ainsi qu'un mécanisme de rupture renfermé, on e ´tablit le rapport entre les deux quantités , défini comme un facteur S t , en fonction de l'angle de frottement, de la rigidité au cisail-lement, de la compressibilité et de la tension efficace moyenne du sable a ` proximité de la pointe du pieu. On démontre qu'en présence de paramètres d' entrée a ` tous autres e ´gards identiques, la valeur de S t diminue au fur et a ` mesure de l'augmentation de l'angle de frottement et de la diminution de la contrainte moyenne. En outre, elle a e ´galement tendance a ` diminuer sous l'effet d'une augmentation de la masse volumique. On est en mesure de prédire que les valeurs de S t sont généralement comprises entre 0,03 et 0,05, et correspondent dans l'ensemble a ` la plage de valeurs dérivées de façon empirique, dans des ouvrages pertinents. Ce rapport permet e ´galement de prédire que les valeurs de S t peuvent e ˆtre beaucoup plus e ´levées (,0. 1) lorsque les pieux sont installés dans du sable dense ou du sable extrêmement compressible. Compte tenu de la nature analytique, le rapport e ´tabli fournit un aperçu utile sur les mécanismes en présence et des implications importantes pour la pratique du design. INTRODUCTION The shaft resistance of displacement piles in sand has been an area of great uncertainty, and thus of considerable interest , in foundation design. Recent experiments with instru-mented model piles in the field (Lehane et al., 1993; Chow, 1997), through measurement of radial effective stresses acting on the pile shaft, have significantly improved understanding of shaft friction characteristics. This has allowed the development of new design approaches with increased rationality (Randolph et al., 1994; Jardine et al., 2005). These new approaches, while presented in different forms, share two important considerations (Fig. 1): (a) a maximum shaft friction, associated with a maximum radial effective stress, exists in the vicinity of the pile tip; and (b) a degradation of the maximum shaft friction or the maximum radial effective stress will occur as the pile tip advances further. The physical basis for friction degradation has been revealed by the aforementioned model tests in the field, and later by model tests on the centrifuge (Klotz & Coop, 2001;
... 02 and 1 . 99) were also obtained for two piles driven in a sand deposit containing a significant amount of silt (Mansur & Kaufman, 1956). Lastly, it should be noted that in the cavity expansion analysis, the shear stiffness affects the rigidity index – an indicator for the average volumetric strain of the sand near the pile tip. ...
Article
Full-text available
An approximate analytic relationship is developed between the maximum radial stress on the shaft of a displacement pile in sand and the base resistance of the pile. Using the cavity expansion analogy, together with a confined failure mechanism, the ratio between the two quantities, defined as a factor St, is established as a function of the friction angle, shear stiffness, compressibility and mean effective stress of the sand near the pile tip. It is shown that, given otherwise identical input parameters, the value of St will decrease with increasing friction angle, and with decreasing mean stress level. It also tends to decrease with an increase in relative density. It is predicted that St has typical values between 0.03 and 0.05, in broad agreement with the range of empirically derived values in the literature. The relationship also predicts that St may take much higher values (~0.1) for piles installed in dense sand or in highly compressible sand. Because of the analytical nature, the established relationship provides useful insights into the mechanisms involved and important implications for design practice.
... The tangent intersection method was used to determine the limit states (Mansur and Kaufman 1956). Fig. 16 outlines the variation of predicted vertical bearing capacity factors [V ðd=DÞ ¼ d cV V ðd=D¼0Þ ]. ...
Article
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This paper presents the results from a series of physical modeling and three-dimensional finite-element (FE) analyses in which the authors examined the uniaxial vertical capacity of suction caissons for offshore wind turbines. The experiments were carried out in quartz sand and involved monotonic application of vertical load. It was found that the drained capacity of suction caissons is dependent on embedment ratio. In contrast, predictions from conventional semiempirical depth factors were found to somewhat underestimate when applied to rough foundations. On the basis of the tests and FE analyses, new expressions for the depth factor of shallow foundations were validated for embedment ratios (aspect ratios) up to unity, calibrating the fitting parameters by using data from a range of soil profiles.
... Displacement-control method was used to determine the load- The bearing capacities were determined from full load-displacement curves by using tangential intersection method (Mansur and Kaufman, 1956;Villalobos, 2006), as shown in Fig. 5. However, several load-displacement curves were not fully obtained because FE simulations were terminated caused by instability. ...
Article
Bearing capacities of tripod bucket foundations differ from those of single bucket foundations because of the interaction among individual buckets of the tripod. This study analyzed the bearing capacities of tripod bucket foundations in medium and dense sands by performing a series of 3D finite element analyses. The sandy soil was modeled by using an elasto-plastic model following the Mohr-Coulomb failure criterion. The Young's modulus of the sands increased with depth because of the stress-dependency of the modulus. Parametric studies were performed, in which the spacing between each bucket, the embedded depth of the bucket, the bucket diameter, and the magnitude of vertical loading were varied. Results showed that the horizontal bearing capacities of tripod bucket foundations reached the maximum values at a spacing ratio of S/D=1.5 to 3.5 for the foundation with an embedment ratio of L/D=0.5 to 1 (where S is the bucket spacing, D is the bucket diameter, and L is the skirt length of the tripod bucket). However, the moment bearing capacities increased linearly as the S/D ratios increased. Finally, bearing capacity equations were proposed in consideration of bucket spacing, embedment depth, effect of foundation diameter and vertical load, and soil density.
... The bearing behavior of the bucket foundation was investigated in terms of normalized bearing capacities V 0 /(A Á S u ) and H 0 /(A Á S u ), where V 0 and H 0 are the vertical and horizontal bearing capacities respectively, and A is the cross-sectional area of the bucket. The bearing capacities V 0 and H 0 were determined using the tangent intersection method (Mansur and Kaufman, 1956), as shown in Fig. 4. The method plots two tangential lines along the initial and later portions of the load-displacement curve, and the load corresponding to the intersection point of these two lines is taken as the bearing capacity. ...
... In addition, the displacement ratio was changed in order to obtain the subsequent points along the capacity envelope (Fig. 18). The tangent-intersection method [45] was used to determine the horizontal and moment bearing capacities. The tripod configuration with a spacing ratio of S/D = 3.0 and a bucket diameter of D = 6.5 m was used (S is the spacing between the center of the individual buckets and the center of the structure; denoted as the reference point RP). ...
Article
Bucket foundations have been increasingly used to support offshore wind turbines as alternatives to monopiles and can be classified into two types: monopod and tripod/jacket supported on multiple shallow foundations. Despite the recent research on the bearing capacity and stiffness of skirted foundations, knowledge regarding the monotonic and cyclic responses of multiple bucket foundation systems in saturated sand is scarce. In this study, the angular rotation of mono-bucket and tripod foundation systems in dense sand due to drained monotonic and cyclic loading was analyzed by performing a series of three-dimensional finite element (FE) analyses. The Hardening Soil Model with Small Strain Stiffness (HS small) and the UBC3D-PLM soil model were employed to analyze the moment response of offshore foundations subjected to wind and wave loading. The procedures were validated against a database of well-documented centrifuge tests. Calibration was carried out based on the monotonic and cyclic model tests, in-situ shear wave velocity measurements, and empirical relationships for shear moduli. Long-term deformations and the resulting decreasing trend in accumulated rotation, which is a unique feature of tripod suction caisson foundations (the so-called “self-healing’’ mechanism), uncertainties, and nonlinearities in centrifuge tests and numerical predictions involving different alternative calibration scenarios of the models are discussed. Based on the numerical results, a closed-form expression is proposed that enables the prediction of drained bearing capacity of multiple caissons under combined loading. This expression was validated for a range of embedment ratios.
... The bearing capacities of the braid-reinforced soil bed derived from plate load tests are analyzed in this section. According to Mansur and Kaufman (1956), when the failure type of soil bed is not a well-defined type (local or punching shear failure), and the pressure-settlement curve of plate load test has no peak point, the approximate value of the ultimate bearing capacity can be obtained by tangent intersection method (TIM). Furthermore, Bowles (1996) suggested the foundation settlement approach for determination of ultimate bearing capacity in PLT tests. ...
Article
In this study, the Taguchi design of experiments (TDOE) is employed to enhance the bearing capacity of geotechnical structures. To this end, two different case studies, including tapered helical piles as a novel kind of deep foundation (Case 1) and a shallow foundation resting on braid-reinforced soil as a new type of soil reinforcing technique for shallow foundation beds (Case 2), are studied. A series of large-scale tests, including pile loading tests in frustum confining vessel (Case 1) and standard plate load tests in test pit (Case 2), have been conducted in conjunction with numerical analyses. To the best of the authors’ knowledge, this study is the first of this kind that uses the capability of the TDOE method to evaluate and improve the bearing capacity using large-scale tests. After conducting the tests, analysis of signal-to-noise, analysis of means, and analysis of variance were used to interpret the experimental results, to obtain the optimum condition, and to determine the percentage of each factor’s participation in bearing capacity. Moreover, the Taguchi method output predictions are compared with the test observations and numerical modeling results. The comparison between test results and TDOE method predictions confirms that the Taguchi method can predict the bearing capacity well (R2 > 0.95). Additionally, verification tests on optimum models show a low level of relative error (RE < 5%) between the TDOE predictions and test results for both the case studies. Therefore, the results prove the ability of the TDOE method to predict and determine the optimum condition in geotechnical bearing capacity problems.
... The pullout capacity of the bucket V 0 was determined by applying the tangent intersection method (Fig. 11). This method determines the capacity as the load at the intersection point of two tangent lines fitted at the beginning and the latter parts of the curve (Graham et al., 1982;Mansur and Kaufman, 1956;Samtani and Nowatzki, 2006;Hung et al., 2018). Compared with other conventional methods, this approach is most suitable to estimate yield loads (Villalobos, 2006). ...
Article
A series of 1 g model tests was performed to investigate the effect of loading rate on the vertical pullout capacity of offshore bucket foundations in sand. The bucket model had a length-to-diameter ratio of 1.0. Loading rates varied from 0.004 N/s to 2.05 N/s. The pullout load increased with bucket displacement and loading rate. The loading rate of 0.004 N/s induced drained conditions with negligible suction pressure and high skin resistance. Increasing the loading rate induced high suction pressures inside the bucket. The bucket pullout capacity increased with bucket displacement and loading rate. Suction pressure increased with bucket displacement and loading rate and contributed considerably to the pullout capacity. The bucket resistance to pullout load increased with the increase in loading rate. Equations were proposed to evaluate the drained and undrained pullout capacities of the bucket.
... There are different methods to estimate the approximate value of the ultimate bearing capacity of footing. In this study, two methods including the tangent intersection method or TIM [53] and foundation settlement approach or FSA [48] (the pressure corresponding to the settlement ratio reaching a value of 10% of the footing diameter) were used. The values of BCR u , based on the two methods and the average values of BCR u obtained from two methods as the strength improvement ratio (BCR avg ), are presented in Table 5. ...
Article
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This study introduces the tubular braided structure as a new geosynthetic material for sand reinforcement. The performance of a tubular braid under the influence of similar soil–reinforcement interaction mechanisms has been investigated to emphasize the effect of the reinforcement form on the performance of the reinforced soil composite. For this purpose, three series of interaction element tests including direct shear tests, pull-out tests, and soil stress control tests were conducted on the unreinforced and reinforced sand. Finally, the overall performance of the reinforced foundation bed with the planar and tubular reinforcing textile (with similar materials, properties, texture, and areal density) was evaluated through a series of standard plate load tests. The results indicated that the performance of the sand-braid composite was better compared to the similar typical planar reinforcement, except for the case of pull-out test. Tubular braid resulted in the enhanced shear strength of the reinforced soil composites, mobilization of the excess compressive stress in the enclosed soil inside the tubular braids, reduction in the vertical stress level of the footing model transferred down through the soil bed, the increase of the average bearing capacity of the footing model, and a significant reduction in the footing settlement.
... Because the curves of the bearing plate tests were not maximised in any tests, it can be said that there was local shear failure in all cases. Thus, the tangent intersection method was used to measure the ultimate bearing capacity (Mansur and Kaufman, 1958). According to Figure 6, in the reinforced foundation bed, the bearing pressure at a specific settlement level increased and the settlement values at a specific pressure level decreased significantly compared with the unreinforced soil. ...
Article
Estimation of the shaft resistance component of the axial capacity of a driven pile into sand involves considerable uncertainty, and most of the current design methods are not consistent with the observed pile behavior during installation and axial loading. In this paper, a method for the estimation of the ultimate uplift shaft resistance of a single pile driven into sand was developed based on a database of 34 pullout pile load tests collected exclusively from the current geotechnical literature. The collected database comprises steel and concrete piles (open- and closed-ended) driven into loose to very dense sand with varying normalized penetration depth with respect to pile diameter. The developed method accounts for the degradation of shaft friction during pile installation. At any given location, the earth pressure coefficient is assumed to degrade from a maximum value (near the pile tip) to a minimum value as an exponential or as a power function of the length of pile driven past that location. The maximum earth pressure coefficient value has been linked to sand relative density, level of effective vertical stress, and pile diameter. The method is extended for the estimation of the compressive shaft resistance of a driven pile into sand by applying De Nicola and Randolph (1) correction for the direction of loading. Comparisons of measured and predicted shaft friction profiles of some field cases showed reasonable agreement and indicated that the method is useful in estimating shaft resistance of driven piles in sand and has sound physical meaning.
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This paper proposes a new design method for the axial capacity of driven piles in glacial deposits with the standard penetration test (SPT) based on a database of 53 full-scale pile load tests. These static load tests were conducted on driven steel H and pipe piles in glacial deposits across the province of Ontario, Canada. The piles were tested in either compression and/or tension to plunging failures and had sufficient soil measurements, in particular SPT measurements, along their length for further analyses. The SPT is the most popular, and in many cases the only, field exploration technique applied in Ontario for gravel or cobble rich glacial deposits. First, the performance of existing SPT-based design methods was evaluated with the results from these pile load tests. On average, the existing design methods overestimated the measured capacity by a factor of 1.62 with a coefficient of variation (COV) of 58%. Second, a new design method was proposed according to the effective stress method to better correlate side and tip resistances with the SPT blow count (N-value). The new design method considers both the pile type and soil gradation. A set of pile load tests collected from literature were applied to validate the newly proposed method. It was found that the newly proposed design method can provide an unbiased prediction with a significantly reduced variation.
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The application of a new criterion to compute the axial capacity of pipe piles driven into sands is described for offshore conditions. The new criterion is tested, independently, against measured capacities from 64 pile load tests and is compared with current recommended practice of API RP2A. These comparisons show that the new criterion is more reliable than the current API criterion and that the new criterion can provide greater capacities for long, large‐diameter pipe piles used in the marine environment. Topics also discussed include (1) the use of limiting values for unit shaft resistance and unit end bearing, (2) computing the capacity of piles in layered soil profiles, (3) the soil plug resistance in overcoming end bearing resistance, and (4) the influence of rate of loading and cyclic loading on pile capacity. A few examples are included to demonstrate the applications.
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In recent years field methods of soil exploration have found ever wider use in our country. Therefore, the use of these methods in the USA is of definite interest. At the request of the editorial board an article on this subject was prepared by the prominent American specialist G. P. Tschebotarioff. For the most part the methods described in this article are known to us. Of interest are how these methods are regarded and their evaluation by a specialist who is both a theoretician and practician in the area of foundation engineering in the USA.
Thesis
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ABSTRACT CAMPELO, N. Behavior of piles submitted to axial tensile forces in collapsible soil, São Carlos, 1994, 139 p. Dissertação (Mestrado) - Escola de Engenharia de São Carlos, Universidade de São Paulo. This dissertation deals with an analysis by comparison of results obtained with piles submitted to axial uplilt foreces using several prediction methods of ultimate loads. The pile tests were performed in the Experimental Site of the Departament of Geotechnical Engineering of USP/São Carlos, on bored, hammed and Strauss pile types, with diameters varying from 0,20 to 0,32 m and 6 to 9 m long. It was observed that the methods that took into account the pile-soil interface failure yelded better results. Moreover, the pile-soil interface colapsibility was analyzed, once the shaft of the studied piles were embedded in soil whose structure are truly collapsible. For this, pile testings were performed both in the natural soil conditions and soaked during 48 h for workmg load. Collapse was observed in the pile-soil interface in tive piles. For threc of them (two of which were bored and one hammed) the failure took place with working loads under 48 h soaking time; in two others, the failure, occured after 48 h soaking time with loads equivalents to 60% and 78% of natural soifs ultimate loads, respectively. Keywords: Pile; pile test; tensile; colapsible soil.
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Conference Paper
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Article
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This paper is dedicated to estimate the capacity of tension piles installed by dynamic driving in cohesionless soil. Using a database comprising 23 closed-ended piles, a new design approach for closed-ended piles in sand under tensile loading was developed. The new approach was extended to open-ended piles using three methods and a database comprising 14 open-ended piles. The first method (method 1) is based on a plug indicator which accounts for the effect of incremental filling ratio and vertical effective stress at the pile tip. In the second method (method 2), open-ended pile is transformed to equivalent solid pile (considered as closed-ended pile with equivalent diameter equal to D*). The third method (method 3) is a combination of methods (1) and (2) with the required adjustments. Six independent well-documented full-scale pile load tests collected from literature were used as independent database to examine the validity of the proposed methods. Comparison of predicted capacities using the three proposed methods for open-ended piles with measured values for the collected six field cases showed good agreement when using the first method and suggested that this method had sound theoretical physical meaning.
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Although the load applied on a pile is usually a combination of a vertical and a lateral load, there have been few studies done on the response of piles subjected to combined loading; these studies; in addition, produce results that are inconsistent with respect to the effects of axial loads on the lateral load response of piles. In this paper, we present the results of model pile load tests performed to assess the influence of axial loads on the lateral response of piles driven in sand. Using a drop hammer, an instrumented circular model pile was driven into large-scale sand samples prepared in a cylindrical steel tank with various densities using a pluviation method. Lateral load tests were performed on the model pile subjected to different axial loads. The combined load test results showed that the presence of an axial load on a driven pile is detrimental to its lateral capacity, for the lateral deflection of the model pile head increased with increasing axial load. The bending moments at the pile head increased substantially (by 10%, 36 % and 39 % for loose, medium dense and dense sand, respectively) in the presence of axial loads.
Article
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Article
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Article
Suction piles fabricated with glass fiber-reinforced plastic (GFRP) have been regarded as alternatives to conventional steel or reinforced-concrete suction piles to reduce the transportation cost and corrosion risk. However, difficulty may arise in suction installation due to the small weight of the GFRP pile. In this study, a concrete pile cap was attached to the top of the GFRP pile to add weight, provide additional resistance against lateral loading by increasing the contact area with soil, and thus solve the problem. The field applicability of the GFRP suction pile was verified by performing field tests on suction installation and numerical simulations to analyze structural integrity against design loads. Results obtained from numerical analyses showed that the GFRP suction pile was stable during penetration and under various loading conditions. Suggestions for the design of GFRP suction piles were proposed based on the field test results and in consideration of the suction pressure inside the pile.
Article
A genetic algorithm (GA) was used in this study to develop a standard penetration test (SPT)-based design method for the axial capacity of driven piles. A total of 72 pile load tests was collected from literature and divided into two groups based on their measurements. The first group had the load-transfer distribution measurements for extracting both the unit side and tip resistances. These unit resistances were correlated by the GA with soil measurements and pile properties to develop the design method. The second group, where only the total capacity measurements were available, were used to validate the new design method and compare its performance with three existing SPT-based design methods. The new GA-derived design method considers nonlinear relationships with the effective stress and pile length and provides an unbiased prediction with a low coefficient of variation (COV) of 40.0 %, while the three existing methods overestimate the capacity by a factor of 1.62 to 1.65 with a high COV of 40.3 % to 52.8 %, which could result in an under design of pile foundations. This study shows that the GA was able to obtain complex relationships with great accuracy and the new design method can be applied to new cases reasonably well.
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