Driven Steel Piles Research Articles

The Effect of Setup Time in Geotechnical Resistance Factor of Driven Steel Piles in Alberta: a Case Study

Determining the bearing capacity of driven steel piles is a critical concern in geotechnical engineering particularly when constructing major structures in oil and gas and infrastructure projects in Alberta. To verify pile capacity, the pile driving analyzer (PDA) and static load tests (SLTs) are widely used. In recent years, PDA testing has become a regular part of pile quality assurance programs on projects and increasingly used as full-scale load tests. Several studies have shown that geotechnical resistance factor (GRF) values can be calibrated with the aim of PDA testing results which can help designers to potentially reduce the number and length of piles. Nevertheless, uncertainty remains regarding the extent to which the GRF value can be optimized following the implementation of the PDA. In this paper, a database of PDA tests and SLTs are compiled from several projects in Alberta, Canada. The primary objective of this study is to assess the impact of time on the recommended GRFs by several codes. To achieve this, the study employs a well-established probabilistic technique known as Monte Carlo Simulation (MCS) to quantify the influence of time, referred to as “setup time”. To enhance the assessment of setup time’s effect, the recorded bearing capacities are collected during two distinct time points: after the completion of pile installation or the end of drive (EOD) condition, and after a specific setup time at the Beginning-of-Restrike (BOR) condition. The results suggest that by taking into account the time impact, GRF values can be optimized, leading to an increase in factored pile resistance and ultimately resulting in a more cost-effective design process for steel-driven piles.

The role of physicochemical processes in aging of shaft friction of driven steel piles in sand

Several studies have reported substantial increases in the shaft capacity of driven steel piles in the months following installation. This study investigates factors influencing this time dependence of shaft capacity by conducting a series of field tests on piles and a parallel series of interface shear tests using a newly developed apparatus. The piles and interfaces used in the experiments employ mild steel, stainless steel, and galvanized steel, while the aging periods allowed in the laboratory and field were 1 and 3 years, respectively. Chemical analyses of the crusts that developed at the sand–steel interfaces are reported. It is shown that the aging characteristic of sand-steel friction depends on the relative contributions of interlocking and dilation but is controlled by dilation at the crust–sand interface adjacent to the shaft of a driven pile. There is no gain in shaft friction with time in dry sand or for piles with non-reactive steel. The operational friction angle for mild steel piles in moist or saturated sand is the soil–soil friction angle.

Calibration of resistance factors for reliability-based design of driven steel piles considering separate factors for toe and shaft resistances

ABSTRACT The LRFD method employs the geotechnical resistance factor (GRF) to design pile foundations. Different resistance mechanisms at the end and side of the pile lead to the requirement of separate GRF values for the shaft and toe capacities. The main aim of this study is to establish regionally separate GRFs for the toe and shaft resistances of pile foundations using different reliability analysis methods. A comprehensive database was gathered from field tests conducted in Alberta, Canada, involved 623 Pile Driving Analyzer (PDA) tests and 28 static load tests. Two criteria called ‘70% rule’ and ‘R ratio’ were used to evaluate the results. Due to certain limitations in the definition of the ‘70% rule’, the ‘R ratio’ method yielded more realistic results. The results indicated that employing separate GRFs for shaft and toe resistances can lead to a significant increase in the factored pile resistance when compared to the values suggested by the Canadian Foundation Engineering Manual (CEFM) in the case of redundant piles.

Pelješac bridge, Croatia – Part 1: Concept and Design/Pelješac-Brücke, Kroatien – Teil 1: Konzept und Planung

The 2 404 m long Pelješac Bridge, Croatia, ranks among the most demanding bridges in the Europe in terms of both the technological complexity of construction and the complexity of the design. The bridge is located in an area of very high seismic activity, exposed to strong and gusty north and south winds. The compact bedrock is located at a depth of up to 100 m below the seabed so very demanding foundation on up to 128 m long driven steel piles was required. The bridge is designed as a multi-span cable-stayed bridge with a semi-integral hybrid structure with five 285 m long central spans. Part 2 deals with execution and assembly.

Investigation of Cyclic Loading of Aged Piles in Sand

In recent years, there has been a significant push to develop optimized pile designs in the offshore industry, driven by the growth of offshore wind. One of the largest remaining uncertainties governing axial pile design in sands is the influence of ageing effects and how an aged pile responds under axial cyclic loading. This paper presents results from a long-term campaign of field tests on pile ageing and axial cyclic loading in sands, undertaken at the Blessington geotechnical test site in Ireland. Five open-ended driven steel piles were subjected to a total of 33 static and cyclic tension pile load tests undertaken over a 3-year period. The tests were planned and coordinated in order to accurately quantify the effects of ageing and cyclic loading on the pile shaft capacity over time. The tests showed that significant gains in pile shaft capacity occurred over time as a result of pile ageing, in line with results presented by other researchers. Piles subjected to cyclic tension loading remained stable under cyclic loading at load levels much larger than their 1-day capacity. The 1-day capacity appears to offer a lower bound for the degraded pile capacity following tension cyclic loading to failure. The reduction in capacity caused by cyclic loading to failure was related to the pretest increase in capacity caused by ageing. The findings from these field tests in addition to reinterpretation of previous testing indicated that previously published cyclic interaction boundaries may be overly conservative.

Capacity degradation method for piles under cyclic axial loads

Piles used for jacket type foundation of offshore wind turbine are subjected to highly cyclic tension and compressive loading. The pile capacity under cyclic tension loading decreases with increased number of loading cycles due to reduction of the pile shaft resistance. A numerical simulation scheme is presented, which allows the calculation of the pile capacity degradation (CDM) due to cyclic loading for driven steel piles. The volume compaction of soil near the pile surface during the cyclic loading is determined from the cyclic simple shear test results and then applied to the pile-soil system.From the limited number of tests available, interaction diagrams have been developed, which give the number of load cycles leading to failure dependent on the mean load and the amplitude of the cyclic load portion, which are both related to the static pile capacity. However, such diagrams cannot account for different soil conditions or pile geometry and pile stiffness. The calculation results for different piles in sandy soil under cyclic axial loading are presented and compared with existing interaction diagrams. Finally, recommendations regarding further investigations and improvements of the method are given.

Effects of steel pile corrosion on permeability of hydraulic barriers

An increasing economic interest leads to construction on old landfills and waste deposits, raising questions about potential contamination of groundwater due to installation of piles through clay barriers. The current consensus in the geotechnical practice, that penetration of clayey hydraulic barriers by driven steel piles with closed conical tips should not cause pollution of the underlying aquifers, is challenged in this paper. Consolidometer and flow-column tests on clays with iron-rich pore fluid were performed for the assessment of pile corrosion effects on hydraulic barriers. Based on the results of these tests, a constitutive model for the coupled chemomechanical behaviour was modified to account for different pore-fluid chemistry and incorporated into a finite-element code to solve the problem of iron diffusion originating from a corroding source in a case study on groundwater pollution. The combined action of diffusion, corrosion and increased convection resulted in an overall increased transport rate and therefore a significantly earlier arrival of critical concentrations of the pollutant in the aquifer that was initially protected by a hydraulic barrier. Once this barrier is perforated by foundation piles subjected to corrosion, small concentrations can arrive in the aquifer up to four times earlier than implied by the initially low hydraulic conductivity.

Laboratory investigations to assess the feasibility of employing a novel mixed-in-place offshore pile in calcareous deposits

ABSTRACTCalcareous sands are typical of warmer seas and are encountered in several high growth locations around the world. Despite having high frictional resistance with friction angles exceeding those of siliceous sands, the in situ behaviour is characterised by particle damage and extreme contraction at high confining stresses. This behaviour results in very low values of skin friction for driven piles in calcareous deposits, where the contraction dominates the pile response. The MIxed Drilled Offshore Steel (MIDOS) pile is a novel mixed-in-place technology which has many advantages over driven steel piles and conventional drilled-and-grouted (D&G) piles. The MIDOS is based on the deep-mixing technology normally used as an onshore ground improvement technique. The mechanical technology and in situ pile performance were successfully demonstrated during an in situ test in silica sand. A laboratory based study was undertaken to assess the MIDOS performance in calcareous sand. Geotechnical tests, grout tests and steel–grout pull out tests were performed to assess the sands and to model the behaviour at the interface of the steel reinforcement and the grout body. These preliminary results demonstrate that the frictional shaft resistance at the pile–soil interface is comparable for both silica and calcareous sands, and as there is no stress relief or contraction during the installation process, the geotechnical performance of the MIDOS pile is deemed comparable for both soil types tested.

Axial compressive response of large-capacity helical and driven steel piles in cohesive soil

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.

Field validation of fibre Bragg grating sensors for measuring strain on driven steel piles

In recent years, fibre Bragg grating (FBG) sensors have emerged as a relatively new strain sensing technology for civil engineering applications. This paper presents a field trial to assess the feasibility of using FBG sensor arrays to measure strain in driven steel piles. Two FBG arrays were installed in grooves within the wall of an open-ended steel pile such that the finished profile was completely flush with the pile shaft. The pile was then driven into a dense sand deposit using an impact hammer to provide the required installation energy. The FBG gauges were monitored throughout driving in conjunction with accelerometers to quantify the scale of the hammer impacts. The FBG sensors were subjected to hammer blows that yielded pile accelerations between 500 g and 1400 g during installation. The fibre optic sensors were measured throughout driving, where they were observed to respond to the hammer impacts, showing a rapid increase in strain and a return to their initial values between hammer strikes. After installation, a lateral load test was performed with independent load measuring devices. Excellent agreement was observed between the measured moments and those inferred from the FBG strain output. The output of this trial demonstrates that FBG strain sensors are a viable means of measuring load transfer in foundation systems and are suitably robust to withstand high pile driving accelerations.

Instrumentation and axial load testing of displacement piles

Despite the fact that results of many instrumented pile load tests have been reported in the literature, it is difficult to find well-documented instrumentation procedures that can be used when planning a load testing programme. A load test programme designed to investigate various aspects of the design and behaviour of driven steel piles is discussed in the present paper. Although the literature contains information on load testing of instrumented piles driven in either sand or clay, limited information is available regarding their axial load response in transitional soils (soils composed of various amounts of clay, silt and sand). Results are presented for fully instrumented axial load tests performed on an H pile and a closed-ended pipe pile driven into a multilayered soil profile consisting of transitional soils. In addition, the load testing planning, the instrumentation of the piles, the testing methods and the interpretation of the pile testing data are discussed in detail in the context of this and other load testing programmes described in the literature, in order to illustrate the various steps.

Dynamic response of vertically loaded helical and driven steel piles

The dynamic performance of helical piles is of significant interest because such piles can offer an efficient alternative to conventional piling systems in many applications where the foundation is subjected to dynamic loads. This paper presents the results of full-scale dynamic vertical load tests on a 9.0 m double-helix, large-capacity helical pile and a driven steel pile of the same length and shaft geometry. Comparing the results is considered necessary to evaluate, qualitatively and quantitatively, the dynamic performance characteristics of large-capacity helical piles. The test piles were closed-ended steel shafts with an outer diameter of 324 mm. The piles were subjected to harmonic (quadratic) loading of different force intensities acting within a frequency range that covered the resonant frequencies of the tested pile–soil–cap systems. The dynamic and static properties of the subsurface soil adjacent to the test piles were determined using the seismic cone penetration technique and the conventional soil boring and testing methods. In addition, field observations are compared with calculated responses using the program DYNA 6 to better understand the pile–soil interaction for the case of helical piles. The effects of soil nonlinearity and pile–soil separation were accounted for in the analysis by employing a weak boundary zone around the piles in the analytical model. The experimental results show that the dynamic behaviour of helical piles is essentially the same as that of driven steel piles with the same geometric properties (without the helix plates). In addition, it was demonstrated that the program DYNA 6 can accurately simulate the behaviour of both helical and driven piles.

A Method for Predicting Pile Bearing Capacity From Dynamic Penetration Tests

This paper presents a new method for predicting the axial capacity of piles from dynamic penetration tests which is based on the concepts of soil dynamics and principles of energy conservation. The energy delivered to the hammerrod-sampler system and transferred to the soil is computed from the numbers of blow counts Nspt and is analytically converted in a penetration dynamic force. The dynamic force allows the unit resistance mobilized in the SPT sampler (model) to be determined, which is then used to predict the unit resistance mobilized in a prototype pile. The strong direct relationship between the ultimate resistance of driven steel piles and the SPT dynamic force, without any bias of soil type, validates the method. Extension of the method to other pile types requires empirical parameters to account for installation effects. Predictions of 89 instrumented static pile load test database demonstrate that the proposed methodology can be efficiently used in the assessment of axial pile capacity, providing a practical way of increasing reliability in pile design by accounting for effects controlling dynamic penetration.

Results from long-term measurement in piles of drag load and downdrag

Several full-scale, long-term tests on instrumented piles performed since the 1960s and through the 1990s are presented. The results of the tests show that a large drag load will develop in piles installed in soft and loose soils. The test cases are from Norway, Sweden, Japan, Canada, Australia, United States, and Singapore and involve driven steel piles and precast concrete piles. The test results show that the transfer of load from the soil to the pile through negative skin friction, and from the pile back to the soil through positive shaft resistance, is governed by effective stress and that already a very small movement will result in mobilization of ultimate values of shaft shear. The pile toe resistance, on the other hand, is determined by downdrag of the pile and the resulting pile toe penetration. Reconsolidation after the pile installation with associated dissipation of pore pressures will result in significant drag load. An equilibrium of force in the pile will develop, where the sustained loads on the pile head and the drag load are equal to the positive shaft resistance plus the pile toe resistance. The location of the force equilibrium, the neutral plane, is also where the pile and the soil move equally. The drag load is of importance mostly for very long piles (longer than 100 pile diameters) for which the pile structural strength could be exceeded. Downdrag, i.e., settlement of the piled foundation, is a very important issue, however, particularly for low-capacity short piles. Soil settlement at the neutral plane will result in a downdrag of the pile. The magnitude of the downdrag will determine the magnitude of the pile toe penetration into the soil, which will determine the pile toe resistance and affect the location of the neutral plane. Nature's iteration of force and soil settlement will decide the final location of the neutral plane.Key words: piles, negative skin friction, drag load, downdrag, neutral plane, pile settlement.

Pile foundation problems in Kuala Lumpur Limestone, Malaysia

Abstract The geology and karstic nature of the Kuala Lumpur (Malaysia) limestone are described in relation to pile foundation problems of heavily loaded structures. The presence of cavities, pinnacles, cantilever slabs, floating slabs and pockets of soft silty clay and loose sand in the underlying limestone bedrock presents formidable challenges to foundation engineers. Other problems include insufficient seating and damage to pile tips due to irregular and sloping bedrock surfaces. There is also the added difficulty of detecting the location and extent of cavities. Empirical design methods and local construction techniques have been successfully used such as: (i) bridging limestone cavities and slabs by filling with concrete, (ii) utilizing numerous small diameter high yield stress piles to distribute the loads and to withstand high driving stresses, (iii) filling cavities with concrete, and (iv) using micropiles to redistribute the loads. Two case histories are presented, consisting of an access ramp and a tall building. In each of these case histories, the soil investigation methods, the pile bearing capacity calculations, the selection of pile types, the pile load tests, the pile driving criteria, and construction problems are outlined and discussed. The pile foundation used consisted of H-section, high yield stress, 355 × 368 mm, driven steel piles with capacities of 750 kN to 1280 kN for the access ramp structures and the same H-section steel piles with pile capacities of 965 kN to 1070 kN for the tall building.

Geotechnically allowable stress for driven piles : Fellenius, B H Civ Engng, N YV54, N11, Nov 1984, P72–75

There are opposing opinions on what value to use for allowable stress in driven steel piles. The key is that two types of stress must be considered: the structurally allowable stress, and the geotechnically allowable stress. Consequently, the structural engineer will always need input from the geotechnical engineer to determine the pile capacity. Three case histories illustrate the difference between the structural and geotechnical capacities of driven piles, and a relation for determining the geotechnically allowable stress is proposed.