Design and Load Testing of Large Diameter Open-Ended Driven Piles (2015) / Chapter Skim
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8 chapter two STATE OF PRACTICE AND LITERATURE REVIEW INTRODUCTION LDOEPs are prefabricated tubular steel or prestressed concrete cylinder piles that are 36 in. outside diameter or larger and are driven into the subsurface to provide axial and lateral foundation support for the structure.
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9 event loading such as a seismic event or vessel collision results in high foundation loadings. Several such examples are described in subsequent sections of this report.
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10 It is also worth noting that the ends of spiralweld pipe sections represent a cut in the pipe from the process of manufacturing a continuous pipe. When sections are to be subsequently spliced together in the field, it is advantageous to mark the cut ends so that these pieces can be re-joined at the same location and thus provide a better fit for field welding.
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11 piles to construct pile bents for a viaduct across coastal marshlands or a shallow bay, where the flexural strength and durability of the concrete cylinder section provides a simple and repetitive means of constructing the bridge without the need for cofferdam structures and footings in the water. A marine environment with water access to the site is conducive to delivery and installation of large cylinder piles.
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12 uncertainty in behavior associated with the soil plug within the pile during driving, testing, and subsequent static loading represent challenges that are unique to LDOEPs. Installation and performance of prestressed concrete LDOEPs present some unique conditions relative to steel, and an overview of these features is briefly described at the end of this section.
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13 This equation provides the simple results illustrated in Figure 5. Since measurements indicate that the acceleration of a large diameter steel pipe pile during driving is likely to be higher than 30 g [Stevens (1988)
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14 Base Resistance of Steel LDOEPs on Rock and Driving Shoes The base resistance of driven steel pipe piles has been observed to be relatively low until the pile is installed to bear on rock or a similar hard bearing stratum, suggesting that the base resistance is largely dependent on the bearing area of the pile wall itself. Dasenbrock (2006)
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15 tance at or near the pile base. However, it appears plausible that more extensive remolding of soil near the pile wall occurs in cohesive soils with vibratory installation.
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16 challenges compared with the use and interpretation of conventional dynamic measurements. The modeling of the behavior and inertial resistance of the soil plug within a large diameter pipe pile during driving presents a challenge unique to LDOEPs.
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17 void smaller. The potential for sandy soil arching within the void is greater (owing to the large area ratio and displaced soil volume)
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18 The depth of the concrete plug is controlled only by the need to achieve load transfer from the structure to the pile itself, although many agencies prefer to use concrete filling to a depth of a few feet below the scour elevation. This requirement is likely to necessitate the excavation of the soil plug within the pile to the appropriate depth.
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19 FIGURE 7 Pile to footing connection, Lafayette Bridge, Minnesota.
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20 The factor a can be computed by: α = ψ ψ ≤−0.5 for 1.0 (8)
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21 ple disturbance problems affecting side resistance using alpha methods. This method offers a potential way of addressing one of the most common problems with the use of undrained shear strength as a basis for design, namely the contamination of the design soil strength profile with data from "undisturbed" strength measurements that might be affected by sample disturbance.
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22 There exists some uncertainty about the distance from the ends of the pile required for the interior concrete to develop enough bond for full composite action, and it is understood that there are several research initiatives related to this issue for drilled shaft foundations that may have relevance to the structural behavior of concrete-filled LDOEPs. Design for Settlement/Uplift/Serviceability The design of groups of LDOEPs for settlement is fundamentally no different than that of any other deep foundation system, and general guidelines for estimating settlement of pile groups are provided by FHWA (Hannigan et al.
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23 Prestressed concrete LDOEPs have many similar issues related to the interpretation of driving resistance, soil plugging, setup, etc.; however, a distinctive feature of these piles relative to steel is the large area ratio of the pile cross section that certainly affects the behavior of the soil plug and the available cross-sectional area of the pile to engage base resistance during installation. Prestressed concrete LDOEPs also require consideration of potential tensile stress during driving, as with any prestressed concrete pile.
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