Resistance Of Piles Research Articles

Uncertainty in pile resistance from static load tests database

This paper tabulates the results of 175 static load tests carried out in Ireland, and includes bored, continuous flight auger and driven piles in fine- and coarse-grained material, and also piles terminating in rock. These data are used to show that the ultimate pile resistance (defined at 0·1 times the effective pile diameter, D) predicted using Chin's extrapolation method was within the range 85–100% of the measured resistance when the pile head settlement was greater than 0·05D. The coefficient of variation of the compressive resistance of the ground against a pile, Rc, for a varying number of load tests carried out on a site reduced from 40% where a single test was carried out to 20% where eight tests occurred. This is considered to be a reasonable lower bound to the within-site variation in Rc, and it is recommended that this level of variation be considered for pile design.

Field and Theoretical Analysis on the Response of Destructive Pile Subjected to Tension Load

Most field tests are carried out using working piles for verification purposes in China, and loading tests are terminated before achieving true pile capacity. In this work, two full-scale destructive loading tests on tension piles instrumented with strain gauges were conducted to capture true pile capacity. The load-displacement response, load transfer, and threshold of the pile-soil relative displacement for fully mobilizing skin resistance in the uplift case were discussed. It was found that the shaft resistance degradation is observed to be along the pile depth with a reduction factor of 0.905 to 0.931, and the thresholds of pile-soil relative displacement for fully mobilizing skin resistance of the tension pile in different soils are found to be in the range 0.67% to 1.34% of the pile diameter. Based on the field test results, a simple softening model was proposed to describe the degradation behavior of skin friction along the pile-soil interface. Further study was conducted to assess the influence of the threshold of pile-soil relative displacement for fully mobilizing skin friction and the reduction factor on the skin friction. As to the analysis of the response of single pile subjected to tension load, a highly effective iterative computer program was developed using the proposed skin friction softening model. Comparisons of the load-settlement response for the well-instrumented tests were given to demonstrate the effectiveness and accuracy of the proposed simple method.

Model Test Research on Mechanism of Close-Ended Variable Section Pipe Pile

Base on indoor model experiments of two constant section pipe piles and three variable section pipe piles performed in foundation pit,the load transfer mechanism of two kinds of close-ended pipe piles are studied by comparing load-settlement curves,shaft load distribution behaviors,skin resistance and resistance on pile end.Results show bearing capacity of variable section pipe piles is bigger than constant section pipe piles when settlements on pile top are equal.The bearing vertical capacity, unit volume bearing vertical capacity and availability of material of pipe pile will increase with improvement of average diameter and variable section ratio of variable section pipe piles.To variable section pipe pile, shaft load distribution suffered a sudden drop on position of variable section and shaft load distribution of small diameter pipe piles decrease quickly than constant section pipe piles.Resistance on pile end of variable section pipe piles are bigger than constant section pipe piles and resistance, ratio of resistance on pile end to bearing capacity of variable section pipe piles will increase with improvement of average diameter of variable section pipe pile. Action point of max skin resistance of variable section pipe piles are closer to pile top than constant section pipe piles .Max skin resistance will increase with decline with ratio of variable section pipe pile.If settlements on pile top are equal,force of skin resistance of variable section pipe piles are bigger than constant section pipe piles when the average diameters are same.

Effect of load eccentricity and stress level on monopile support for offshore wind turbines

Currently monopiles are the most common foundation solution for offshore wind turbines. The design of monopiles relies on empirical data from tests performed on long, slender, small-diameter piles loaded predominantly in shear. In contrast, a monopile is a large-diameter, relatively short pile on which load is applied with a large eccentricity. With centrifuge tests as the basis, this paper investigates the behaviour of a rigid pile loaded with a high eccentricity. A test series was carried out to simulate idealized monotonic load cases for monopiles supporting an offshore wind turbine. Centrifuge tests were performed on model monopiles subjected to stress distributions equal to prototype monopiles with pile diameters ranging from 1–5 m and eccentricities ranging from 8.25–17.75 pile diameters. It was possible to identify a unified response of all of these tests by using dimensional analysis and Rankine’s passive earth pressure coefficient as a normalization parameter. The normalized ultimate soil resistance was unaffected by acceleration level and load eccentricity, indicating that the failure mechanism was the same for all tests. Based on the centrifuge tests, a reformulation of soil–pile interaction curves is presented. The normalized initial stiffness of the soil–pile resistance curves was seen to increase linearly with depth in the centrifuge tests. The reformulation differs from current guidelines in terms of the shape of the interaction curve and magnitude of ultimate resistance.

Variation of limiting lateral soil pressure with depth for pile rows in clay

Pile group interaction effects on the lateral pile resistance are investigated for the case of a laterally loaded row of piles in clay. Both uniform undrained shear strength and linearly increasing with depth shear strength profiles are considered. Three-dimensional finite element analyses are presented, which are used to identify the predominant failure modes and to calculate the reduction in lateral resistance due to group effects. A limited number of two-dimensional analyses are also presented in order to examine the behaviour of very closely spaced piles. It is shown that, contrary to current practice, group effects vary with depth; they are insignificant close to the ground surface, increase to a maximum value at intermediate depths and finally reduce to a constant value at great depth. The effect of pile spacing and pile–soil adhesion are investigated and equations are developed for the calculation of a depth dependent reduction factor, which when multiplied by the limiting lateral pressure along a single pile, provides the corresponding variation of soil pressure along a pile in a pile row. This reduction factor is used to perform p–y analyses, which show that, due to this variation of group effects on the lateral soil pressures with depth, the overall group interaction effects depend on the pile length. Comparisons are also made with approaches used in practice that assume constant with depth reduction factors.

Influences of Cross Section Parameters on Bending Resistance of TSC Pile

Precast thin-wall steel and spun concrete composite pile (TSC pile) is a kind of new type of steel-concrete composite pile whose bearing performance is between steel pile and concrete pile. This article adopted FEM software to set up 3D TSC pile model to analyze its performance. Through the comparison with actual pure bending bearing experiment results, the model’s reliability was verified and the results showed that the model was reliable. Then lots of bending bearing capacity contrast calculations were conducted by using different cross section parameters (outside diameter, concrete pipe’s wall thickness and steel pipe’s wall thickness), and the influences of these parameters on bending resistance of TSC pile were discussed. The results showed that: with the increase of outside diameter, concrete pipe’s wall thickness and steel pipe’s wall thickness, TSC pile’s ultimate flexural bearing capacity increased. The influences of different parameters were not the same, outside diameter was the most important parameter, then concrete pipe’s wall thickness, and the last one was steel pipe’s wall thickness.

Experimental Study on Bearing Mechanism of Jacked Pipe Pile in Sand

Study on bearing mechanism of jacked pipe pile in sand is useful of optimizing the pile foundation design, and the research of the regularity of side resistance and tip resistance of pile has a very important theoretical significance. In this paper, a new effective method is used to test the tip resistance of the jacked pipe pile during the press-in process, and then the side resistance can be deduced [1]. Based on the field tests, the inherent laws of interaction between pile and soil in sand is explored, which provides some theoretical basis for the pile foundation design and engineering application.

Decomposition of Dynamic p-y Curves Considering Liquefaction during Earthquakes

There is an established fact known that, there is a relation between the p-y resistance of piles and liquefaction formation. To investigate this fact, a single pile foundation in liquefiable soils composed of liquefiable sand and overlying soft clay was subjected to sinusoidal shaking motions will be tested. That is the basic purpose of this study was to analyze and construct a p-y curve of liquefied soil under different shaking loading conditions companied with the effects of several key design parameters were undertaken to understand the effect of pile characteristic and pore water pressure response in the zones of responding area.

An interaction chart design method for Eurocode compliant railway electrification mast foundations

The UK Department for Transport plans to install 25kV overhead electrification on existing major routes in Great Britain as part of route modernisation and operational carbon reduction strategies. The design of foundations for railway electrification masts is a particular challenge for geotechnical engineers. Foundations may be required for hundreds or thousands of structures, each with different load and ground conditions. The large number of structures and tight programme timescales mean that site-specific ground investigation and design is not feasible or economic and a set of generic designs must be developed to encompass as much of the inherent variation as possible. This paper proposes a new method for designing laterally loaded piles – which avoids the large number of calculations for specific load cases and focuses instead on underlying system dynamics of vertical and lateral pile resistances and deflections to derive interaction relationships.The methods proposed in this paper can be adapted for use with various formulae and codes of practice to suit the designer’s preference, although the focus of this paper is on the use of Eurocode 7. This paper does not propose modification to design formulae but provides a more effective use of these formulae to develop designs. The results are ultimately presented in a series of design charts upon which the allocation engineer can plot applied structural loads to determine a pile’s design length for given design criteria. This method yields many benefits: the end product is simple to use, it is able to cope with the large variations in applied loads inherent in electrification schemes, it provides a Eurocode compliant design and the time required to produce these designs is significantly reduced when compared to calculation based on site-specific loads. A particular benefit is that the method can cope more easily with iterations and variations in the assumed loads and system layout that arise during the design process.

Numerical investigation of the ultimate lateral resistance of piles in soft clay

The paper presents a numerical study on the undrained lateral response of a single, free-head, reinforced concrete pile in soft clays. Soil conditions simulating normally consolidated clays are examined—undrained shear strength increasing with depth—and the pile-soil interaction under static lateral loading is analyzed. The nonlinear p-y curves proposed in literature for soft clays are imported into a beam-on-nonlinear-Winkler-foundation simulation in order to predict the pile head lateral load—displacement curve and the distribution of the horizontal displacement and bending moment along the pile. The striking differences among these methods require further investigation via 3D finite element analyses. The determination of the ultimate soil resistance p ult from the results of the finite element analyses aims at providing the estimation of a range of values for the ultimate soil resistance coefficient N p with depth and the comparison of the derived values to the corresponding ones proposed by existing methodologies.

Design of spiral coil PHC energy pile considering effective borehole thermal resistance and groundwater advection effects

This study presents experimental and numerical research results in determining an effective borehole thermal resistance of a spiral coil energy pile. A precast high-strength concrete (PHC) energy pile with a spiral coil GHE was installed and thermal response test was carried out to evaluate the thermal behavior of the energy pile and to validate the effective borehole thermal resistance. Besides, parametric studies using a numerical analysis were carried out to suggest a multiple regression equation for the effective borehole thermal resistance of spiral coil energy piles. The adjusted coefficient of determination (adjR2) of the regression equation was 92.4%, which was also verified by comparison with experimental results. Furthermore, using current analytical models, this paper examined the effect of groundwater advection on the long-term ground temperatures. In the long-term period operation, groundwater advection attenuates the average temperature rise in the ground compared to the case with the absence of groundwater advection, and this phenomenon ultimately causes a decrease of the temperature penalty value. The temperature penalty value, considering the effect of groundwater advection, was calculated and compared for various groundwater advection velocity values in different pile arrays.

Centrifuge model tests on piled raft foundation in sand subjected to lateral and moment loads

Piled raft foundation has been widely recognized as a rational and economical foundation system with the combined effects of raft and piles. However, the behavior of laterally loaded piled raft foundation has not been well understood due to the complicated interaction of raft–ground–piles. A series of static horizontal loading tests were carried out on three types of foundation models, i.e., piled raft, pile group and raft alone models, on sand using a geotechnical centrifuge. In this paper, the influences of relatively large moment load and rotation on the overall performance of laterally loaded piled raft foundation were examined. From the centrifuge model tests, it is found that the vertical displacement due to horizontal loads is different between piled raft and pile group foundation, and this vertical displacement has significant influences on the performance of laterally loaded piled raft foundation. The horizontal resistance of the pile part in the piled raft foundation is higher than those observed in the pile group foundation due to raft base contact pressure. The vertical displacement of the foundation due to the horizontal loads affects the vertical resistances of piles, which results in the different mobilization of moment resistances between the piled raft and pile group foundations.

Effect of Pile and Load Inclination on the Pile Resistance In both Compression and Tension

According to this theoretical study which was about loading of piles under different condition of loading (compression and up-lift forces ) and for deferent pile installation (vertical and inclined pile ) by which it called (positive batter pile ) when the inclination of the load and pile is in the same direction and called (negative batter pile) when the inclination of load is opposite to the pile inclination, and from studying these cases the results of analysis can be summarize in the flowing points:
 1-Variation of load inclination on piles effects on the bearing capacity and uplift resistance. It was found that bearing capacity of the piles increase with increasing of load inclination up to the inclination angle (37.5ͦ) which represents the maximum bearing capacity and then the bearing capacity decrease with increasing of load inclination.
 2- Variation of batter pile affects the bearing capacity of the pile and up-lift resistance. by which equivalent angle will be used as result between the load and piles inclination and this angle will be used in calculation of piles resistance .
 3- It was noticed the shape of soil failure is highly affected by the inclination of pile.
 The shape of failure for the soil which is in contact with pile and this include (vertical and batter piles) is highly affected by the angle of inclination.

An experimental study on the resistance and movement of short pile installed in sands under horizontal pullout load

In this study, the model tests were conducted on the short piles installed in sands under a horizontal pullout load to investigate their behavior characteristics. From the horizontal loading tests where dimensions of the pile diameter and length, and loading point were varied, the horizontal pullout resistance and the rotational and translational movement pattern of the pile were investigated. As a result, the horizontal pullout resistance of the pile embedded in sands was dependent on the pile length, diameter, loading point, etc. The ultimate horizontal pullout load tended to increase as the loading point (h/L) moved to the bottom from the top of the pile, regardless of the ratio between the pile length and diameter (L/D), reached the maximum value at the point of h/L = 0.75, and decreased afterwards. When the horizontal pullout load acted on the upper part above the middle of the pile, the pile rotated clockwise and moved to the pullout direction, and the pivot point of the pile was located at 150–360mm depth below the ground surface. On the other hand, when the horizontal pullout load acted on the lower part of the pile, the pile rotated counterclockwise and travelled horizontally, and the rotational angle was very small.

Uplift Resistance of Wooden Pile using Soil box According to Soil type

Uplift Resistance of Wooden Pile using Soil box According to Soil type

Response of 1 × 2 pile group under eccentric lateral loading

A large scale model test of a 1×2 pile group was conducted in silts to investigate its behavior under eccentric lateral loading. The model pile group consisted of two well instrumented steel piles and was installed in a large soil tank with a close spacing of three-pile diameters on centers. The test results revealed that the eccentricity of lateral loads had limited effect on the overall performances of the 1×2 pile group, but significantly contributed to the unevenness of internal forces of the individual piles. The coupling effect between the lateral deflection and torque gave rise to the substantial increase in the torsional resistance of individual piles within the group, comparing to that of a torsionally loaded single pile. The contribution provided by the torsional resistances of individual piles in resisting the external torque continually decreased when the applied lateral load increased. In addition, a three-dimensional finite-element analysis for the pile group was performed and the simulated response was found to be in good agreement with the measured test results. Based on the same model, more cases with different loading conditions were further analyzed. It could be concluded from the analyses that the layout of individual piles within the group obviously affected the behavior of the 1×2 pile group under eccentric lateral loads.

Field Investigation of Pile Setup in Mixed Soil

An instrumented test pile was installed at the Bayou Zourie bridge reconstruction site as part of a Louisiana Department of Transportation and Development (LADOTD) research initiative to study the setup phenomenon of piles driven in Louisiana soils. Pile instrumentation included pressure cells to measure the total pressure at the pile face, piezometers to monitor the excess pore water pressure at the pile face, and “sister bar” strain gauges to measure the strain distribution along the pile. Additional instrumentation consisted of multilevel piezometers installed within soils at different locations/depths from the pile and accelerometers attached to the piles during dynamic load testing. A total of two static load tests and four dynamic load tests were conducted on the test pile. During the static load tests, the strains within the pile were measured by the strain gauges, which were used to calculate the distribution of load transfer along the pile. Both static and dynamic load tests demonstrated the increase in pile resistance with time (setup). Results of dynamic load tests confirmed that pile setup occurs at a logarithmic rate after the end of driving (EOD) and is mainly attributed to the increase in side resistance. Good correlation was observed in this study between the pile setup and the percentage of dissipated excess pore water pressure with time. The measured excess pore water pressure suggested that the surrounding soil, along the pile (within distance 2B), is significantly influenced during pile driving. Results indicated that the changes in side resistance are directly related to the changes in the horizontal effective stress acting on the pile face.

EFFECT OF STIFFNESS OF THIN BEARING LAYER ON TOE BEARING MECHANISM OF STEEL PIPE PILE WITH A CONCRETE BULB

It has been known that the sufficiently stiff layer can be considered as a load-bearing layer of piles, even if its thickness is thin. The authors have studied the toe bearing resistance of pile on a thin load- bearing layer, in order to establish the design method about pile on a thin load-bearing layer. In this paper, the effect of stiffness of load-bearing layer on characteristics of toe resistance of steel pipe pile on a thin load-bearing layer is discussed through a series of numerical analyses. First, a field loading test of steel pipe piles with a concrete bulb on a thin load-bearing layer is reproduced through the numerical analysis, in which a soil-water coupled with an elast-plastic finite element method is applied, to confirm the availability of the numerical analysis proposed. Second, a series of numerical analyses are carried out in which the deformation modulus of the load-bearing layer and the thickness of load-bearing layer are chosen as a variable parameter. The results of the numerical analyses show that the stiffness of load-bearing layer affects the resistance when the yielding of load-bearing layer occurs.

Case Study on Instrumenting and Testing Full-Scale Test Piles for Evaluating Setup Phenomenon

Over time, piles driven in cohesive soils usually experience a large increase in resistance, known as setup or freeze. Dynamic load tests (DLT) and static load tests (SLT) are usually performed to verify the axial resistances of piles at specific times after end of driving (EOD) and to quantify these resistances. An extensive field testing program was performed on full-scale instrumented precast prestressed concrete piles driven in cohesive soils at the Bayou Lacassine Bridge in Louisiana, to evaluate the pile setup phenomenon. The testing program included instrumenting two full-scale test piles with a network of vibrating wire strain gauges, pressure cells, and piezometers and instrumenting the surrounding soils with multilevel piezometers. Five SLTs and three DLTs were conducted on each test pile at different times after EOD to quantify the magnitude of setup. Measurements from the load tests on both piles confirmed that the pile setup after EOD followed a logarithmic rate with time. An increase in piles’ total resistances (or setup) of 1.60 to 1.77 times the EOD resistances was observed after the final restrikes. Piezometer data demonstrated a close relationship between the dissipation of excess pore water pressures that were generated during pile driving, following EOD, and pile setup. The load transfer curves derived from the strain gauge measurements were used to separate the side and tip resistance profiles from the total resistance. Piezometers installed in the ground showed that the influence zone, caused by pile driving, extends beyond the 3B distance (B = pile width).

Experimental Research on Statnamic Load Test of Long Rock Socket Bored Pile

Through the Statnamic load test on working bored pile, the displacement of pile top and the distributing of axis force along the bored pile were brought forward and two methods were used for interpretation the test result. The bearing capacity, axial force, shaft friction and pile toe resistance of pile were all illustrated. The result show that the Statnamic load test method can check the pile capacity quite easily, it is quite difficult to test the ultimate pile capacity.