Figure - available via license: Creative Commons Attribution 3.0 Unported
Content may be subject to copyright.
(a) Pile load chamber and (b) cast-in-place pile set up and loading mechanism (figure not to scale).
Source publication
On the basis of evidence from model tests on increasing the end-bearing behavior of tapered piles at the load-settlement curve, this paper proposes an analytical spherical cavity expansion theory to evaluate the end-bearing capacity. The angle of tapering is inserted in the proposed model to evaluate the end-bearing capacity. The test results of th...
Similar publications
Finned pile is the foundation system that often resists larger lateral loads effectively than regular pile. In present study, a series of model tests were conducted to study the effect of the fin shape, its position along pile length, fin number, and effect of relative density on lateral resistance of finned piles embedded in sand. Two fin shapes,...
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 frictio...
![Figure 6. The relation between n h and D r [13].](publication/369680332/figure/fig2/AS:11431281133865136@1680324110397/The-relation-between-n-h-and-D-r-13_Q320.jpg)
A p-y curve method of pile near cohesionless soil slope under reversed lateral load is proposed. This method takes into account the failure mode of soil around the pile under reversed lateral load and the interaction mode between pile and soil, and derives the ultimate soil resistance of the pile. Considering the change of the original stress state...
In the present paper an attempt is made to evaluate the axial pullout and oblique pullout capacity of hollow aluminum belled piles embedded in sand. A series of model tests were conducted on a model piles with different length of piles of 240 mm, 360 mm and 480 mm respectively and length of the pile to diameter of pile (L/D) ratios employed are 5,...
An experimental model study is proposed to predict the load-displacement response and ultimate uplift resistance of pile in sand subjected to uplift load. Straight shafted solid vertical steel pipes are used as model piles to conduct the experimental tests with outer diameter of 12 mm. The embedment lengths to diameter (L/d) ratio of the piles are...
Citations
... The total bearing capacity of the pile is mostly met by the shaft capacity in friction piles and by the point capacity in the point bearing piles [9], [10]. However, the point capacity of piles installed in sandy soil constitutes a significant portion of the pile bearing capacity [11], [12], [13], [14]. Point and shaft capacities are not independent of one another because improving the load-bearing layer at the pile base is not only increases point capacity but at the same time improves the shaft capacity [15]. ...
In the present paper, an experimental study was conducted to determine the factors affecting the point bearing capacity of pile foundations constructed in dry and saturated sandy soils. Model piles were installed as reinforced concrete bored piles cast-in-situ. Model pile foundations of various geometries resting at different depths in homogeneous sand of different saturation degrees (%0-100) were loaded statically to failure. The test results showed that the bearing capacity of piles did not significantly affect by the loading rate. At most 10% difference was observed in pile bearing capacity when the loading rate was between 0.7 and 2.5 mm/min. Subsequently, the load bearing capacities of the piles were determined at a specified constant loading rate. The point and total capacities of the piles were measured separately in the experiments, then test results were compared with theoretical values. Pile point capacities provided from pile load tests are smaller than the theoretical values. The differences between experimental and theoretical results have been attributed to the Nq values. The Nq values not only dependent on the internal friction angle of the soil but also the saturation degree of the soil, the pile diameter, and the effective stress. Nq values decrease since the pile length/pile diameter ratio increases.
... Paik et al. [8] demonstrated that both side friction and tip resistance of tapered piles are greater than those for uniform piles. Manandhar and Yasufuku [9] investigated the tapering effect on the pile tip capacity by conducting experiments on three piles of same length and tip diameter but different taper angles. The interpretation of their tests data confirmed that tapering the pile creates a mechanism to restrain the failure mode and consequently increase the end bearing capacity. ...
The effect of tapered shaft on the performance of tapered pile groups under compression load has been investigated in this research. For this purpose, twelve axial compressive tests were conducted on groups of straight and tapered shaft piles installed in sand by using a geotechnical centrifuge. Three cross-section shapes of circular, square and X-shape cross sections for the pile groups were considered. The load–displacement behavior of X-shaped cross-section tapered and uniform (straight-side) single piles and also tapered and uniform pile groups is investigated for the first time. In each group, one pile was instrumented along its shaft to monitor the load transfer of the pile within the group. The results demonstrated that tapered pile group could tolerate at least 20% higher axial load than straight-sided shaft pile groups. Also, at least 35% higher initial stiffness was observed for a tapered pile group with 5D spacing compared to the uniform counterpart group. In addition, for a given group settlement, the straight shaft pile group transfers at least 9% greater load than the summation of loads carried by individual single piles within the same group, while in tapered pile groups, the load carried by the groups is almost equal to the summation of loads carried by individual piles within the same group. Tapered pile showed lower group efficiency compared to uniform piles. In addition, it is shown that tapering a pile enhances unit toe resistance as well as unit shaft resistance.
... The long-term compressive capacity of the tapered pile was about 80% greater than that of the straight-sided pile of the same length and volume. Manandhar and Yasufuku (2012) studied three piles with equal length and tip diameter but with various taper angles and volumes. They found that the end bearing capacity of the tapered pile with a corresponding taper angle of 1.4°increased by about 200% compared with the uniform pile. ...
... Despite these relatively small loads in non-uniform piles, Table 4 indicates that the unit toe resistance of non-uniform piles is at least 100% larger than that of uniform piles at the same level of pile head displacement. Thus, it is revealed that tapering the pile affects both side and tip behavior of piles, as also found by Manandhar and Yasufuku (2012). Figure 12 shows the axial load-head displacement variation for piles subjected to axial tensile loading. ...
The compressive behavior of tapered piles, particularly those with circular cross-sections, has been investigated during the last few decades. However, the tensile behavior of such piles has been rarely studied in the literature. In this paper, 12 static axial tests, including six compressive and also six tensile tests, were performed on instrumented piles with uniform and tapered cross-sections by using a geotechnical centrifuge. Three of the piles had correspondingly circular, square and X-shaped uniform cross-sections along their length, while the other three ones were non-uniform (tapered), all of which had the same length and volume. The results are presented in three main forms: the variation of load versus pile head displacement, the distribution of axial force along the pile length, and the distribution of the unit shaft resistance along the pile length. The behavior of tapered piles is compared with that of uniform cross-section piles. The results confirm the superiority of tapered piles over uniform cross-section piles in terms of load-bearing capacity and construction costs under both tensile and compressive loading.
... • Geometric alternatives to support structures-Foundation geometry is a defining factor for total loading capacity and pile displacement . Conical piles provide an increased bearing capacity compared to straight-sided cylindrical piles (Manandhar and Yasufuku, 2012). The lateral surface texture of foundation piles is another parameter to increase loading capacity by increasing shear strength of its interface with soil (Martinez and Frost, 2017). ...
The continuous increase in population and human migration to urban and coastal areas leads to the expansion of built environments over natural habitats. Current infrastructure suffers from environmental changes and their impact on ecosystem services. Foundations are static anchoring structures dependent on soil compaction, which reduces water infiltration and increases flooding. Coastal infrastructure reduces wave action and landward erosion but alters natural habitat and sediment transport. On the other hand, root systems are multifunctional, resilient, biological structures that offer promising strategies for the design of civil and coastal infrastructure, such as adaptivity, multifunctionality, self-healing, mechanical and chemical soil attachment. Therefore, the biomimetic methodology is employed to abstract root strategies of interest for the design of building foundations and coastal infrastructures that prevent soil erosion, anchor structures, penetrate soils, and provide natural habitat. The strategies are described in a literature review on root biology, then these principles are abstracted from their biological context to show their potential for engineering transfer. After a review of current and developing technologies in both application fields, the abstracted strategies are translated into conceptual designs for foundation and coastal engineering. In addition to presenting the potential of root-inspired designs for both fields, this paper also showcases the main steps of the biomimetic methodology from the study of a biological system to the development of conceptual technical designs. In this way the paper also contributes to the development of a more strategic intersection between biology and engineering and provides a framework for further research and development projects.
... Some of them have considered the plastic behaviour of the soil near the ground surface into account or used the finite-element method (Reddy and Ramasamy 1973, Kurian and Srinivas 1995, Gotman 2000. Some researchers used the cavity expansion theory to propose analytical models for predicting the end resistance or investigated the buckling and loadtransfer behaviour of a tapered rigid pile , Manandhar and Yasufuku 2012, Lee et al. 2018. A wellknown study carried out by Kodikara and Moore (1993) employing the axial behaviour of tapered piles in a cohesivefrictional ground. ...
The growing tendency to study the behaviour of tapered piles in the last two decades has made it necessary to gain a deeper insight into this specific kind of deep foundation. Tapered piles have been investigated through analytical, experimental, and numerical studies. These piles have revealed different behaviour under various loading conditions. Hence, reviewing and assessing these efforts to comprehend their response can be of great significance. In this paper firstly, it is attempted to go over experimental studies, conducted on tapered piles. Then, the proposed mathematical and numerical solutions, employed to calculate the bearing capacity of single tapered piles, are compared to have a better vision of how these piles behave. In the third section, the optimum tapering angles of tapered piles in loose, medium, and dense sand are discussed. All the efforts are investigated technically to find the advantages, disadvantages, and the research gaps for this specific kind of piles. In addition, another section entitled the directions and ideas for future research on tapered piles is provided comprising the most recent achievements in this area. Moreover, the implementation of tapered piles in a significant project as a case study is discussed.
... Paik et al. [44] reported an increase in the bearing capacity by 18% for the single tapered pile tested in the field. Model tests on instrumented tapered piles in sand, under static compressive loads were reported by Robinsky et al. [46], Wei and El Naggar [54], El Naggar and Wei [13], Ghazavi and Kalantari [14], Paik et al. [43] and Manandhar and Yasufuku [36,37]. The reported experimental test results confirmed the beneficial effect of tapered geometry of the pile, where the increase in the bearing capacity was reported as 1.1-1.6 [13] and 1.06-1.20 [14] times the bearing capacity of the equivalent cylindrical pile. ...
... Using these relations in a load transfer procedure proposed by Coyle and Resse [9], the average shear stress mobilized with the pile displacement was calculated. Manandhar and Yasufuku [36,37] further incorporated the stress-dilatancy relationship in the cavity expansion solution proposed by Yu and Houlsby [56], to evaluate the skin friction along the tapered piles, and to compute the end-bearing capacity of the tapered pile in sandy soils [36]. In the existing studies for the response of tapered piles under static axial compressive loads, the shear stress-displacement relationships do not account for the development of a nonlinear zone adjacent to the pile surface. ...
... Using these relations in a load transfer procedure proposed by Coyle and Resse [9], the average shear stress mobilized with the pile displacement was calculated. Manandhar and Yasufuku [36,37] further incorporated the stress-dilatancy relationship in the cavity expansion solution proposed by Yu and Houlsby [56], to evaluate the skin friction along the tapered piles, and to compute the end-bearing capacity of the tapered pile in sandy soils [36]. In the existing studies for the response of tapered piles under static axial compressive loads, the shear stress-displacement relationships do not account for the development of a nonlinear zone adjacent to the pile surface. ...
This paper presents a procedure for evaluating the load–displacement behavior of tapered piles under static axial compressive loads. The response of tapered piles under elastic phase is evaluated using nonlinear load transfer method, whereas the increase in stresses due to slippage at the soil–pile interface is obtained from a developed drained cylindrical cavity expansion solution based on a nonlinear stress–dilatancy relationship. The governing differential equation is solved using the differential quadrature element method. The methodology is validated using two reported experimental model testing of the tapered pile in cohesive–frictional soil and soft soil. A comparative analysis between the different nonlinear load transfer models is also carried out. Further, the effect of the heterogeneity of the soil properties along the length of the pile on the axial response of the tapered pile is studied.
... The end bearing capacity of drilled shafts can be estimated by static analysis, dynamic analysis, dynamic testing, in-situ testing and pile load test. Various investigations have been conducted for determination of the end bearing capacity of piles [7][8][9][10][11][12][13][14]. ...
Drilled shafts are a common type of pile foundations which are often used as foundations for buildings, bridges and other structures. The end bearing capacity of drilled shafts, which plays an important role in their design particularly in sandy soils, has traditionally been estimated using empirical or semi-empirical methods. With advances in computing power, it is now possible to conduct more realistic analyses. In this paper, at first, the end bearing capacity of drilled shafts in sandy soils is analyzed numerically and validated with the results of pile load test. Then, the numerical results are compared with the results of Standard Penetration Test (SPT)-based methods. The comparison indicated that there is a satisfactory agreement between the results of numerical method proposed in this paper and the results achieved by SPT-based methods.
... On the basis of evidence from model tests on increasing the end-bearing behavior of tapered piles at the load-settlement curve, Manandhar and Yasufuku (2012) proposed an analyti- cal spherical cavity expansion theory to evaluate the end-bearing capacity. The angle of tapering was inserted in the proposed model to evaluate the end-bearing capacity. ...
In this study, the dynamic response of pile foundation in dry sandy soil excited by two opposite rotary machines was considered experimentally. A small scale physical model was manufactured to accomplish the experimental work in the laboratory. The physical model consists of: two small motors supplied with eccentric mass (0.012 kg) and eccentric distance (20 mm) representing the two opposite rotary machines, an aluminum shaft as the pile, and a steel plate a pile cap. The experimental work was achieved taking the following parameters into considerations: pile embedment depth ratio (L/d, where L is the pile length and d is its diameter), and operating frequency of the rotary machines. All tests were conducted in medium dense fine sandy soil with 60% relative density. Twelve tests were performed to measure the change in load transferred through the pile's tip to the underlying soil. In order to predict precisely the dynamic load that will be induced from the rotary machines, a mini load cell with a capacity of 100 kg was mounted between the aluminum plate (the machine base) and the steel plate (pile cap).
The results revealed that, before machine operation, the pile tip load was approximately equal to the static load (machine and pile cap), whereas during machines operation, the pile tip load decreased for all embedment depth ratios and operating frequencies. This reduction was due to the action of skin friction that was mobilized along the pile during operation, and as a result the factor of safety against pile bearing failure increases. For all operating frequencies and pile lengths, the factor of safety against bearing failure increased during machines operation, where the pile tip load became less than its value before starting operation. During operation the skin friction resistance mobilized along pile length led to decrease the bearing load.
... The end bearing capacity of drilled shafts can be estimated by static analysis, dynamic analysis, dynamic testing, in situ testing and pile load test. Several investigations have been conducted for the determination of end bearing capacity of piles (Dung et al., 2007;Ishihara 2010;Dung et al., 2011;Veiskarami et al., 2011;Manandhar and Yasufuku, 2012;Yu and Yang, 2012). On the other hand, the acceptance of numerical analyses in geotechnical problems is growing and finite element calculations are more and more used in the design of foundations. ...
Determination of axial capacity of piles has been a challenging problem since the beginning of the geotechnical engineering profession. The axial capacity of a single pile can be estimated by summing the skin friction capacity and the bearing capacity of the pile toe. In this paper, an attempt is made to numerically analyze the end bearing capacity of drilled shafts in sand. The numerical results obtained were compared with the results of pile load test. The comparison between numerical and experimental base load-settlement curves showed that the proposed numerical analysis produces satisfactory predictions. Then, variations of the end bearing capacity of drilled shafts versus embedment depth and pile diameter were studied. Numerical results showed that with the increase in embedment depth and pile diameter, the end bearing capacity increases, but with a decreasing rate. Moreover, the range of failure zone surrounding the pile tip is discussed.
... (11) 1959 (440) The relatively low toe resistance calculated per Niazi's version of the UniCone method is especially noteworthy. Although the details are not shown here, the writer also calculated the toe resistance for this pile using several other methods found in the literature (Salgado et al. 2002, Manandhar and Yasufuku 2012, Togliani 2010 that are based on using cone penetrometer data for toe resistance, including a focus on pipe piles bearing in coarsegrain soil which are precisely the conditions applicable to Pipe Pile 2A. In all cases the calculated ultimate toe resistance from these other methods was not only much greater than Niazi's value but also greater than that of the writer as well. ...
