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This paper presents some possible interpretations of the physical meaning of the lumped, toe, and skin Case damping factors, j(cL), j(ct), and j(cs), respectively, which are extensively utilized in the dynamic analysis of pile driveability and capacity. A single degree of freedom model is employed to relate the Case damping to the hysteretic damping ratios of soil and pile materials. This relation and the damping ratios of soils and piles show that the Case damping factors for piles in sandy and clayey soils may overlap at all strain magnitudes. Coupling of pile toe and skin resistance is analyzed, and the j(cL) factor is found to be a function of the skin and toe resistance ratio of the pile. Consequently, the j(cL) factor is an important indicator with which the skin friction and toe resistance of piles can be separated. A database of 133 cases of dynamic pile tests in Florida has been used to substantiate the analyses and interpretations. The effects of the assumptions made in this paper are also discussed.

A series of lateral load tests were performed on 3 x 3 and 4 x 4 pile groups in loose and medium-dense sands in the centrifuge with their caps located at variable heights to the ground surface. Four cases were considered: Case 1, pile caps located above the ground surface; Case 2, bottom of pile cap in contact with the ground surface; Case 3, top of pile cap at the ground surface elevation; and Case 4, top of pile cap buried one cap thickness below ground surface. All tests with the exception of Case 1 of the 4 x 4 group had their pile tips located at the same elevation. A special device, which was capable of both driving the piles and raining sand on the group in flight, had to be constructed to perform the tests without stopping the centrifuge (spinning at 45 g). The tests revealed that lowering the pile cap elevation increased the lateral resistance of the pile group anywhere from 50 to 250 percent. The experimental results were subsequently modeled with the bridge foundation-superstructure finite element program FLPIER, which did a good job of predicting all the cases for different load levels without the need for soil-pile cap interaction springs (i.e., p-y springs attached to the cap). The analyses suggest that the increase in lateral resistance with lower cap elevations may be due to the lower center of rotation of the pile group. However, it should be noted that this study was for pile caps embedded in loose sand and not dense sands or at significant depths. The experiments also revealed a slight effect for the case of the pile cap embedded in sand with a footprint wider than the pile row. In that case the size of the passive soil wedge in front of the pile group, and consequently the group's lateral resistance, increased.

The coupled bridge foundation-superstructure finite-element code FLPIER was employed to predict the lateral response of the single piles and 3 × 3 to 7 × 3 pile groups founded in both loose and medium dense sands. The p-multiplier factors suggested by McVay et al. for laterally loaded pile groups with multiple pile rows were implemented for the predictions. The soil parameters were obtained through a back-analysis procedure based on single pile test results. The latter, as well as the numerical predictions of both the single and group tests, are presented. It was found that the numerical code FLPIER did an excellent job of predicting the response of both the single piles and the 3 × 3 to 7 × 3 pile groups. The latter involved the predictions of lateral load versus lateral deflection of the group, the shears and bending moments developed in the individual piles, and the distributions of the lateral loads in each pile row, which were all in good agreement with the measured results.

The precise cause for concrete damage observed in the vicinity of parked B-1 and F/A-18 aircraft has been determined. The combination of downward- directed auxiliary power unit (APU) blast and spilled aircraft oils are responsible for the scaling observed at these sites. Laboratory tests confirmed that ester-based lubricating oils and hydraulic fluids are chemically reacting with the calcium hydroxide in the concrete and destroying the mortar-aggregate bonds. The cyclic heating of the pavement by the APU greatly accelerates the reaction and facilitates the mixing and refluxing of aircraft fluids with the aqueous calcium hydroxide present. A variety of sophisticated tests were conducted to verify these findings, including X-ray diffraction and mass spectroscopy. In addition, the damage observed at military installations was duplicated under controlled laboratory conditions. After five weeks of subjecting a test slab to cyclic heat and jet oils, damage similar to that observed in the field was produced.

This study was an analytical an experimental investigation into the influences of material anisotropy and principal plane rotation on the stress-strain and strength behavior of granular soil (Reid-Bedford Sand). The laboratory investigation entailed the performance of approximately fifteen triaxial tests under conventional compression and extension loading, and five through initial shear, followed by hydrostatic compression. The initial tests with an additional fifteen experiments were used in characterizing the influence of inherent anisotropy and principal plane rotations on material response. The latter were employed to delineate the affects of stress-induced anisotropy. A review of existing elasto-plastic theory as related to soil mechanics showed only a few models of a phenomenological nature which of the multi-surface isotropic/kinematic hardening characterizations, Prevost's pressure sensitive model, was used in the prediction of the hollow cylinder tests. Although the model reasonably reproduced the response along its calibration path, it did not quantitatively or qualitatively predict the laboratory results along other stress paths which involved principal plane rotations. The report concludes with a discussion on the significant influence of anisotropy on the stiffness, strength, and plastic flow rate direction of granular media, and the need for improved analytical representation.

BDV31-977-29, Florida geology with its non-uniform rock and soil layers, variable deposits of poor soils (clay, organics, etc.), and weathered (and possibly voided) limestone is a major concern for design engineers, contractors, and maintenance personnel. However, determining the makeup and integrity of the underlying soil layering can be challenging. A better and more thorough means of assessing and understanding a larger area of the subsurface at construction sites would help to determine the exact needs of a project or to efficiently maintain existing infrastructure., Research Objectives, Previously, the researchers developed a nondestructive surface test that uses seismic waves to yield useful information about subsurface conditions, showing its effectiveness at identifying and locating voids and anomalies (FDOT project BDK75-977-66). In this project, they further developed the method’s software and tested a field-deployable version.

BD-545, RPWO #59, Florida bridges in recent years have increasingly been supported by large drilled shafts that are 8-12 feet in diameter. The use of large diameter shafts reduces the number of piles needed to support the structure, which in turn can lower construction costs and aid noise abatement efforts. The large shafts are also more resistant to lateral pressures like those resulting from hurricane forces or vessel impacts.

BD-545, RPWO #59, The study investigated the behavior of large diameter drilled shafts embedded short distances in Florida Limestone (i.e. L/D=1 &3). The work was performed via laboratory (centrifuge) tests and at two field sites (17th Street and Fuller Warren Bridges). The work focused on the modeling the axial, shear and moment response of shafts subject to combined axial and lateral loading in uniform and variable strength/modulus limestone. The study found that that O'Neill's method of assessing tip resistance vs. displacement was accurate if the Harmonic or Geometric Mass Modulus of the rock is assessed within three diameters below the shaft's tip. In the case of tip shear, it was found that a bilinear elastic plastic model with failure assessed from Mohr-Coulomb provided good results. For tip rotation, the model proposed by Bell (1991) gave very reasonable results even though it requires assessment of tip shear and lateral tip displacement.

BDV31-977-29, A new 2-D Full Waveform Inversion (FWI) software code was developed to characterize layering and anomalies beneath the ground surface using seismic testing. The software is capable of assessing the shear and compression wave velocities (Vs and Vp) for 1,200 cells (0.75 x 0.75 m resolution) in an 18 x 36 m (60 x 120 ft) region in 20 to 30 min on a standard laptop computer. The software, which includes a graphical software interface, allows the user to setup the test line (spacing, number of shots, and receiver), view the raw data, condition the data (filter, window, remove poor channels), preprocess the data (identify initial velocity profile), and analyze (invert) the conditioned data to obtain independent Vs and Vp results graphically or in file format (PDF)., Next, a synthetic study was undertaken with the 2-D FWI software to investigate its capability of identifying 3-D voids (size, shape, and depth). Synthetic waveform data sets were generated using a 3-D finite difference model of a domain with a void of various sizes and depths, and surface-based test lines were both on the top of the void and away from the void. The synthetic waveform data sets were then analyzed by the 2-D FWI software as if they were collected from field experiments. The FWI results revealed that if the test line is on the top of a void, the maximum embedded depth at which the void can be detected is about three void diameters. In the case of test lines that are away from the void, the void can still be identified in inverted profile if the test line is near the void edge; however, the void becomes distorted and non-existent if the test line is at least one diameter from the void., The 2-D FWI software was then tested at five FDOT sites with unknown soil/rock layering and both known and unknown voids at time of seismic testing. Subsequent invasive testing (SPT and CPT) was performed near or at the anomaly for validation. A comparison of the seismic results with the SPT/CPT results revealed that FWI did an excellent job of identifying soil and rock layering (e.g., soil and limestone depths at Kanapaha and Newberry, FL), identifying unknown voids (Newberry and Tallahassee, FL), and the extent of existing voids (US 441 and Gainesville, FL). As with the synthetic study, field seismic results from test lines one diameter from the void did show void distortion, but it was not present further away., Finally, the software was demonstrated and used by FDOT field personnel on a test site. The seismic equipment used for this project included both a 24-channel coupled geophone array with sledge hammer point source,a new 24-channel land-streamer, and a propelled energy generator (PEG). The land streamer and PEG may be towed behind a vehicle and used to investigate the subsurface profiles beneath a roadway (e.g., US 441).

FDOT Contract No. BDV31-977-20, UF Contract No. 00, The research focused on evaluation of Florida limestone’s unconfined compressive strength, qu, through, drilling parameters – crowd, torque, penetration rate, rotational speed, and bit diameter – in both the, laboratory and field for assessing a shaft’s side shear. Synthetic homogeneous limestone blocks of, various strengths were cast in the laboratory and allowed to cure for 14 days; The blocks were then, drilled with rock augers of two different diameters at multiple penetration rates and drilling rotational, speeds. Both crowd and torque were measured in real time. Estimation of rock strength, qu from drilling, relationships developed by Karasawa (2002a) and Teale (1965) were evaluated. It was found that, Teale’s specific energy approach could estimate rock strength, qu using the multiple diameter drill bits, expected in field drilled shaft construction., In the field, shaft installation was monitored (crowd, torque, penetration rate, etc.) at three sites (Little, River, Overland, and Kanapaha) from which rock strength, qu was estimated along with shaft side shear., For side shear, FDOT’s design equation in limestone was used with split tension strength initially, estimated from qt/qu ratio established by field cores; subsequently, Johnston’s qu vs. qt/qu relationship, was used. The estimated unit skin friction in multiple rock formations and segments was compared by, instrumented segment during Osterberg, Statnamic, and top-down static load testing. The mean bias, (measured/predicted) unit side shear in limestone was 1.00, and the coefficient of variation, CV, was, 0.07. The results suggest that estimating rock strength and shaft side shear using drilling parameters is, viable, especially considering the currently available rig monitoring equipment (Jean Lutz, Bauer, etc.).