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A study was performed to investigate the factors that affect the accuracy of the procedures used by the Virginia Department of Transportation for design of drilled shaft sound wall foundations. Field load tests were performed on eight inch and nine inch diameter drilled shafts, and the results were compared to theoretical solutions for ultimate lateral load capacity. Standard Penetration Tests were run in the field and laboratory strength tests were performed on the soils from the test sites. It was found that published correlations between blow count and friction angle for sands and gravels can be used to estimate friction angles for the partly saturated silty and clayey soils encountered at the test sites. A spreadsheet program was developed to automate the process of determining design lengths for drilled shaft sound wall foundations. The spreadsheet was used to investigate the effects of different analysis procedures and parameter values on the design lengths of drilled shaft sound wall foundation. / Master of Science

In this dissertation, we investigate the macroscopic magnetic properties of bulk high-temperature superconductors (HTS) containing an array of artificial holes in view of enhancing their performances. The study involves a numerical modelling part and an experimental characterization part. In each part, novel concepts are highlighted and detailed. In particular, we develop a three-dimensional finite-element method (FEM) for calculating the magnetic field penetration in HTS where a single time-step is used in the case of a linearly varying applied magnetic field, and we probe the magnetic field in the volume of drilled samples with the help of microcoils inserted inside the holes. The thesis starts with an introductory chapter that describes the general concept of high-temperature superconductivity and particularly draws the attention on the interests and on the synthesis of drilled structures. Then, we detail the modelling tools that are used for evaluating the magnetic properties of drilled samples. Three models are taken into account: (1) the numerical Bean model which is a generalization of the Bean model for arbitrary cross sections where the samples are assumed to have an infinite height; (2) a 2D finite element model implemented in the open source solver GetDP for samples with an infinite height and assuming a power law relationship, that is characterized by a critical exponent n, between the electric field, E, and the current density, J; (3) a 3D finite element model with the same equations as those of model (2), but where these are solved in a three-dimensional sample with a finite height. For large values of n, both FEM models use the properties of a slow magnetic diffusion to reduce the number of time steps. In particular, the trapped flux can be calculated with only two time-steps: during the first step, the applied magnetic flux density is increased with a constant sweep rate to a maximum value, it then decreases to zero with the same sweep rate during the second step. The models are first used in simple geometries where they are compared to other available techniques. These are next applied to drilled samples. A systematic numerical study of the influence of the holes on the magnetic properties of the sample is reported. A single hole perturbs the critical current flow over an extended region that is bounded by a discontinuity line, where the direction of the current density changes abruptly. In samples with several holes and a given critical current density, we demonstrate that the trapped magnetic flux is maximized when the centre of each hole is positioned on one of the discontinuity lines produced by the neighbouring holes. For a cylindrical sample, we construct a polar triangular hole pattern that exploits this principle; in such a lattice, the trapped field is 20% higher than in a squared lattice, for which the holes do not lie on discontinuity lines. These results are experimentally validated. Two parallelepipedic samples are drilled with two different hole lattices. The trapped magnetic flux density of these samples is characterized by a Hall probe mapping before and after drilling holes. The sample in which the holes are aligned on the discontinuity lines exhibits the smallest magnetization drop that results from the hole drilling. Then, we resort to a novel experimental technique using microcoils inside the holes to characterize the local magnetic properties in the volume of drilled samples. In a given hole, three different penetration regimes can be observed when the sample is subjected to an AC magnetic field: (i) the shielded regime, where no magnetic flux threads the hole; (ii) the gradual penetration regime, where the amplitude of the magnetic field scales with the applied field; and (iii) the flux concentration regime, where the magnetic field exceeds that of the applied field. A comparison of the measurements with simple models assuming an infinite height shows that the holes may serve as a return path for the demagnetizing field lines. In the case of a pulsed field excitation, that measurement technique also allows us to estimate the trapped magnetic flux density in the volume of the sample and compare it with that on the surfaces. Moreover, the penetration of a magnetic pulse from hole to hole is described in the median plane and on the surface and the differences of penetration speeds are explained. Finally, we investigate the magnetic properties of drilled samples whose holes are filled with a ferromagnetic powder. To this aim, we use experimental techniques (Hall probe mapping techniques, together with measurements of the volume magnetization and of the levitation force between the HTS sample and a permanent magnet) and a numerical model (3D FEM) to characterize the modification of the magnetic properties resulting from the impregnation of the holes with AISI 410 ferromagnetic powder. Numerical results support the experimental observations and give clues to understand the mutual interaction between the HTS sample and the ferromagnetic powder inserted in its holes. In particular, the Hall probe mappings of the distribution of the trapped flux above the non-impregnated and impregnated samples reveal an increase of trapped flux after impregnation that is confirmed by simulations.

Estimating the earth pressures applied on drilled shaft retaining walls in expansive clays is challenging due to the soil's tendency to shrink and swell under cycles of moisture fluctuation. While empirical suggestions do exist, significant uncertainty exists regarding the effect of volumetric changes of the soil on the earth pressures. In order to investigate this uncertainty, a fully instrumented drilled shaft retaining wall named in the honor of Lymon C. Reese, was constructed in the highly expansive clay of the Taylor formation. Inclinometers and optical fiber strain gauges were installed in three instrumented shafts and time domain reflectrometry sensors were placed within the soil to measure changes in the moisture content. Nearly two years of monitoring data have been obtained which are used to estimate the earth pressure distribution at different moisture conditions. Processing of the raw strain data was required to eliminate the effects of tension cracks and other microscale factors that caused significant variation in the results. Good agreement was obtained between the processed strain and inclinometer data as the deflected shapes predicted from both monitoring elements were similar. Finally, the earth pressure distribution for six dates that represent different moisture conditions of the Taylor clay were plotted and the results of the strain gauge and inclinometer analysis were consistent. A p-y analysis was also conducted to estimate the range of earth pressures applied on the wall. A triangular earth pressure diagram was used as external load above the excavation level and the equivalent fluid pressure was evaluated by matching the deflected shapes generated from the inclinometer data to those predicted by the p-y model. The results were compared to the empirical values that TxDOT uses for design of similar type of walls in expansive clay. Finally, the side shear and temperature effects on the lateral response of the wall were quantified. A differential linear thermal model was used to evaluate the temperature effects and a t-z analysis was conducted to account for the side shear applied on the wall due to volumetric changes of the soil. It is recommended that their combined effect be considered in the design. / text

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Master of Science / Department of Architectural Engineering and Construction Science / Kimberly W. Kramer / Soils conditions vary throughout the United States and effect the behavior of the foundation system for building structures. The structural engineer needs to design a foundation system for a superstructure that is compatible with the soil conditions present at the site. Foundation systems can be classified as shallow and deep, and behave differently with different soils. Shallow foundation systems are typically used on sites with stiff soils, such as compacted sands or firm silts. Deep foundation systems are typically used on sites with soft soils, such as loose sands and expansive clays. A parametric study is performed within this report analyzing tilt-up concrete structures in Dallas, Texas, Denver, Colorado, and Kansas City, Missouri to determine the most economical tilt-up wall panel and foundation support system. These three locations represent a broad region within the Midwest of low-seismic activity, enabling the use of Ordinary Precast Wall Panels for the lateral force resisting system. Tilt-up wall panels are slender load-bearing walls constructed of reinforced concrete, cast on site, and lifted into their final position. Both a 32 ft (9.75 m) and 40 ft (12 m) tilt-up wall panel height are designed on three foundation systems: spread footings, continuous footings, and drilled piers. These two wall heights are typical for single-story or two-story structures and industrial warehouse projects. Spread footings and continuous footings are shallow foundation systems and drilled piers are a deep foundation system. Dallas and Denver both have vast presence of expansive soils while Kansas City has more abundant stiff soils. The analysis procedure used for the design of the tilt-up wall panels is the Alternative Design of Slender Walls in the American Concrete Institute standard ACI 318-05 Building Code and Commentary Section 14.8. Tilt-up wall panel design is typically controlled by lateral instability as a result from lateral loads combining with the axial loads to produce secondary moments. The provisions in the Alternative Design of Slender Walls consider progressive collapse of the wall panel from the increased deflection resulting from the secondary moments. Each tilt-up wall panel type studied is designed in each of the three locations on each foundation system type and the most economical section is recommended.

The soil-structure interaction models associated with laterally loaded deep foundations have typically been based on load tests involving relatively small diameter foundations. The lateral soil resistance for larger diameter foundations has been assumed to increase linearly with diameter; however, few, if any load tests have been performed to confirm this relationship. To better understand the lateral resistance of large diameter deep foundations in sand, a series of full scale, cyclic, lateral load tests were performed on two 1.2 m diameter drilled shafts and a 0.324 m diameter steel pipe pile in sand. Although the tests involve two different foundation types, the upper 2.4 m of the profile, which provides the majority of the lateral resistance, consists of sand compacted around both foundation types. Therefore, these test results make it possible to evaluate the effect of foundation diameter on lateral soil resistance. The drilled shafts were first loaded in one direction by reacting against a fifteen-pile group. Subsequently a load test was performed in the opposite direction by reacting against a 9-pile group. The soil profile below the 2.4 m-thick layer of compacted sand consisted of interbedded layers of sand and fine-grained soil. For the drilled shaft load tests, pile head deflection and applied load were measured by string potentiometers and load cells, respectively. Tilt was also measured as a function of depth with an inclinometer which was then used to calculate deflection and bending moment as a function of depth. For the pipe pile, deflection and applied load were also measured; however, bending moment was computed based on strain gauges readings along the length of the pile. The lateral response of the drilled shafts and pipe pile were modeled using the computer programs LPILE (Reese et al., 2000), SWM6.0 (Ashour et al., 2002), and FB-MultiPier Version 4.06 (Hoit et al., 2000). Comparisons were made between the measured and computed load-deflection curves as well as bending moment versus depth curves. Soil parameters in the computer programs were iteratively adjusted until a good match between measured and computed response of the 0.324 m pipe pile was obtained. This refined soil profile was then used to model the drilled shaft response. User-defined p-multipliers were selected to match the measured results with the calculated results. On average very good agreement was obtained between measured and computed response without resorting to p-multipliers greater than 1.0. These results suggest that a linear increase in lateral resistance with foundation diameter is appropriate. LPILE typically produced the best agreement with measured response although the other programs usually gave reasonable results as well. Cyclic loading generally reduced the lateral resistance of the drilled shafts and pile foundation by about 20%.

Deep foundations like auger-cast piles and drilled shafts frequently extend through liquefiable sand layers and bear on non-liquefiable layers at depth. When liquefaction occurs, the skin friction on the shaft decreases to zero, and then increases again as the pore water pressure dissipates and the layer begins to settle, or compact. As the effective stress increases and the liquefiable layer settles, along with the overlaying layers, negative skin from the soil acts on the shaft. To investigate the loss of skin friction and the development of negative skin friction, soil-induced load was measured in three instrumented, full-scale auger-cast piles after blast-induced liquefaction at a site near Christchurch, New Zealand. The test piles were installed to depths of 8.5 m, 12 m, and 14 m to investigate the influence of pile depth on response to liquefaction. The 8.5 m pile terminated within the liquefied layer while the 12 m and 14 m piles penetrated the liquefied sand and were supported on denser sands. Following the first blast, where no load was applied to the piles, liquefaction developed throughout a 9-m thick layer. As the liquefied sand reconsolidated, the sand settled about 30 mm (0.3% volumetric strain) while pile settlements were limited to a range of 14 to 21 mm (0.54 to 0.84 in). Because the ground settled relative to the piles, negative skin friction developed with a magnitude equal to about 50% of the positive skin friction measured in a static pile load test. Following the second blast, where significant load was applied to the piles, liquefaction developed throughout a 6-m thick layer. During reconsolidation, the liquefied sand settled a maximum of 80 mm (1.1% volumetric strain) while pile settlements ranged from 71 to 104 mm (2.8 to 4.1 in). The reduced side friction in the liquefied sand led to full mobilization of side friction and end-bearing resistance for all test piles below the liquefied layer and significant pile settlement. Because the piles generally settled relative to the surrounding ground, positive skin friction developed as the liquefied sand reconsolidated. Once again, skin friction during reconsolidation of the liquefied sand was equal to about 50% of the positive skin friction obtained from a static load test before liquefaction.

In the field of civil engineering, particularly structural foundations, low-cost options and time saving construction methods are important because both can be a burden on the public. Drilled shafts have proven to both lower cost and shorten construction time for large-scale projects. However, their integrity as load-carrying foundations has been questioned. The statnamic load test was conceived in the 1980s as an alternative method of testing these larger, deeper foundation elements. Performing a load test verifies that the load carrying capacity of a foundation is agreeable with the estimated capacity during the design phase and that no significant anomalies occurred during construction. The statnamic test, however, is classified as a rapid load test and requires special data regression techniques. The outcome of available regression techniques is directly related to the available instrumentation on the test shaft. Generally, the more instrumentation available, the more complete results the regression method will produce. This thesis will show that a proposed method requiring only basic instrumentation can produce more complete results using a predictive model for side shear development with displacement during the statnamic test. A driven pile or drilled shaft can be discretized into segments based on the load shed distribution model. Each segment can be analyzed as a rigid body. The total static capacity is then the summation of each segments’ contribution. Further, a weighted acceleration can be generated and used to perform an unloading point analysis.

There are over 602,000 bridges in the United States, of which 12.5% are classified as functionally obsolete and 11.2% are structurally deficient. The functionally obsolete bridges will require expansion or replacement to increase the service capacity of the bridge. The structurally deficient bridges will either need remediation of the load carrying elements which are damaged or deteriorated or will need to be replaced completely. Replacement of the bridges means new construction; new construction means better design and quality assurance to meet the 100+ year service life requirement in place now. Rehabilitation of bridges will require better design and quality assurance to increase the current service life of the structure. This dissertation presents new design, testing, and repair methods developed to extend the life of new and existing bridges through pressure grouting, thermal integrity testing of drilled shafts, and the bond enhancement of fiber reinforced polymer (FRP) repair materials bonded to concrete with vacuum bagging and pressure bagging, respectively. Pressure grouting of drilled shaft tips has been used for over five decades to improve the end bearing capacity, but no rational design procedure had ever been published until this study. The research outlined in this dissertation analyzed nine grouted shafts and compared them to standard design procedures to determine the improvement in end bearing. Improvements ranged from 60% to 709% increase in end bearing capacity. From these improvements, a design procedure was developed for pressure grouted drilled shafts. Post construction inspection of drilled shafts relies largely on non-visual techniques dealing with measured concrete quantities, acoustic wave speed or frequency, gamma radiation attenuation and now the internal temperature of the curing concrete. Thermal Integrity Profiling (TIP), developed at USF, utilizes the heat of hydration of curing concrete to evaluate the concrete cover, foundation shape, cage alignment, and concrete mix design performance. This research developed standard test equipment and procedures for thermal integrity testing. Comparing the results of the different types of integrity tests is difficult due to the varied nature of the different tests. The dissertation looked at various shafts constructed across the nation which were tested with thermal and at least one other integrity test method. When compared to acoustic and gamma radiation test results, TIP agreed with 4 of 6 cases for acoustic and 2 of 5 cases using gamma radiation. In the one case were both sonic caliper and inclination data were available, TIP showed good agreement. Vacuum bagging and pressure bagging are techniques for improving the FRP-concrete bond in the repair of partially submerged piles. Prototype vacuum bagging and pressure bagging systems were developed and bond improvement assessed from results of pullout tests on full size piles repaired under simulated tidal exposures in the laboratory. Pressure bagging gave better bond and was found to be simpler because it did not require an airtight seal. A field demonstration project was conducted in which pressure bagging was used in combination with two different glass FRP systems to repair two corroding piles supporting the Friendship Trails Bridge across Tampa Bay. Inspection of the post-cured wrap showed no evidence of air voids.