A Case History of the Use of Geofoam for Bridge Approach Fills

A new bridge replaced the Route 85 Bridge over Normans Kill Creek in Albany, NY in 2001. The old bridge was a double span steel truss bridge with pile-supported abutments and a mid pier in the creek channel. The replacement is a single span concrete girder bridge and was constructed adjacent to the old bridge to minimize the extent of realignment of the roadway centerline. The soil stratigraphy along the creek bank consists of weak and compressible lacustrine deposits. During construction of the new bridge, the old bridge had to remain in operation. EPS geofoam was used as a lightweight substitute for soil to construct the approach fills for the new bridge to assure stability and minimize settlements. Extensometers and earth pressure cells were installed to monitor the performance of the approach fills. The roadway profile has been surveyed periodically to develop the settlement profile over time. In addition to improving stability and reducing settlements, the use of geofoam for the bridge approaches has resulted in additional benefits. The construction was quick and took place in winter. Lateral pressures against the abutments and wing walls are low. Results of the field monitoring are presented and compared with computer modeling of a representative section

Reliability-based serviceability limit state design for immediate settlement of spread footings on clay

AbstractWhile many spread footings constructed on clayey soils are designed using consolidation settlement analyses for the serviceability limit state (SLS), immediate settlement, or undrained displacement, of the footing may also contribute a significant portion of the total and/or differential settlement. Owing to possible magnitudes in immediate settlement, and with regard to stress history, assessment of the contribution of immediate settlement comprises an essential task for the understanding of the performance of a foundation system. This study proposes a simple reliability-based design (RBD) procedure for assessing the allowable immediate displacement of a spread footing supported on clay in consideration of a desired serviceability limit state. A relationship between the traditional spread footing bearing capacity equation and slope tangent capacity is established, then incorporated into a bivariate normalized bearing pressure–displacement model to estimate the mobilized resistance associated with a given displacement. The model was calibrated using a high quality database of full-scale loading tests compiled from various sources. The loading test data was used to characterize the uncertainty associated with the model and incorporated into an appropriate reliability-based performance function. Monte Carlo simulations were then used to calibrate a resistance factor with consideration of the uncertainty in the bearing pressure–displacement model, bearing capacity, applied bearing pressure, allowable displacement, and footing width. An example is provided to illustrate the application of the proposed procedure to estimate the bearing pressure for an allowable immediate displacement of a footing at the targeted probability and serviceability limit state

Tension and Compression Micropile Load Tests in Gravelly Sand

Micropiles were selected for several upgrades to a paper machine at the Nippon Paper Industries USA Company in Port Angeles, Washington. This paper presents several aspects of the micropile design and subsequent load test performance for two separate upgrades at the paper mill. The micropile load tests, performed in tension and compression, provide a reference for micropile performance in medium dense to dense, gravelly sand. Comparison of the load test performance suggests that the common assumption of neglecting the contribution of end-bearing resistance does not adequately model micropile behavior. Additionally, evidence is presented for load transfer through the micropile casing. The load test performance is interpreted in the framework of a simple, global stiffness degradation technique, which provides an estimate of bond stresses. The analyses suggest that the mode of loading (e.g., tension or compression) influences the load transfer properties for the small diameter micropiles

Effect of Particle Shape on Stress-Dilatancy Responses of Medium-Dense Sands

The effect of particle shape on the strength, dilatancy, and stress-dilatancy relationship was systematically investigated through a series of drained triaxial compression tests on sands mixed with angular and rounded glass beads of different proportions (0%, 25%, 50%, 75%, and 100%). A distinct overall regularity parameter was used to define the particle shape of these mixtures, which ranged from 0.844 to 0.971. The test results showed that all of the samples at an initial relative density of 0.6 exhibited strain-softening and volume-expansion behavior. It was found that the peak-state deviatoric stress, peak-state axial strain, and peak-state friction angle at a given confining pressure decreased with increasing overall regularity. The maximum differences in the peak-state deviator stress, peak-state axial strain, peak-state friction angle, excess friction angle, and maximum dilation angle due to changes in particle shape could be as much as 0.61MPa, 5.4%, 8.6, 1.5, and 3 degrees at a given confining pressure of 0.4MPa. In addition, it was found that the slope of the relationship between the peak-state friction angle and maximum dilation angle was independent of the particle shape, whereas the intercept (i.e.,the critical-state friction angle) was significantly influenced by the particle shape. A stress-dilatancy equation incorporating the effect of overall regularity was proposed and provided a good estimate of the observed response accounting for the different particle shapes investigated

Development and Implementation of a High-Pressure, Double-Acting, Bi-Directional Loading Cell for Drilled Shafts

Drilled shaft foundation elements provide a cost-effective foundation alternative for the support of building and bridge superstructure loads. Bi-directional pile loading tests (BDPLTs) to evaluate the capacity of drilled shafts have become popular owing to their capacity to save time and effort as compared to the use of top-down loading tests. However, the use of BDPLTs requires that production shafts be post-grouted following testing in order to assure appropriate in-service performance. Commonly used single-acting loading cells and/or loading cell construction details can pose the potential for the development of voids following post-grouting due to their monotonic jacking action and large footprint. This paper described the development and use of high pressure bi-directional loading cells intended to minimize the possibility of post-test construction defects. First, a comparison was made between the single-acting and double-acting loading cells. Second, the results of laboratory calibrations on the pressurized loading cells were performed, as were component testing of the pumps, hoses, and hydraulic fluid synchronization lines. Then, the use of the new high pressure double-acting loading cells in production testing of instrumented shafts was described, and the efficacy of the new loading cells was illustrated. The new loading cells provided the profession with a load cell alternative for conducting BDLTs and should serve to help reduce the risk of post-test grouting defects in drilled shaft foundations.Keywords: field testing, cementing/grouting, deep foundations, site infrastructure and constructio

Dynamic, In-situ, Nonlinear-Inelastic Response and Post-Cyclic Strength of a Plastic Silt Deposit

This study presents the use of controlled blasting as a source of seismic energy to obtain the coupled, dynamic, linear-elastic to nonlinear-inelastic response of a plastic silt deposit. Characterization of blast-induced ground motions indicate that the shear strain and corresponding residual excess pore pressures (EPPs) are associated with low frequency near- and far-field shear waves that are within the range of earthquake frequencies, whereas the effect of high frequency P-waves are negligible. Three blasting programs were used to develop the initial and pre-strained relationships between shear strain, EPP, and nonlinear shear modulus degradation. The initial threshold shear strain to initiate soil nonlinearity and to trigger generation of residual EPP ranging from 0.002 to 0.003% and 0.008 to 0.012%, respectively, where the latter corresponded to ~30% of Gmax. Following pre-straining and dissipation of EPPs within the silt deposit, the shear strain necessary to trigger residual excess pore pressure increased two-fold. Greater excess pore pressures were observed in-situ compared to that of intact direct simple shear (DSS) test specimens at a given shear strain amplitude. The reduction of in-situ undrained shear strength within the blast-induced EPP field measured using vane shear tests compared favorably with that of DSS test specimens.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Effect of correlation structure model on geotechnical reliability-based serviceability limit state simulations

Reliability-based serviceability limit state (SLS) models for foundation elements commonly employ a two-parameter load-displacement model to relate imposed displacements to a particular load or vice versa. Numerous studies have shown that the load-displacement model parameters tend to be correlated; subsequently, considerable effort is required to appropriately model the correlation structure for Monte Carlo-based reliability simulations. This paper uses copula theory, a database of high quality full-scale loading tests of spread footings on aggregate pier (i.e., stone column) reinforced clay, and a recently developed ultimate limit state (ULS) model to investigate the effect of various correlation structures on the probability of exceeding the SLS. “Lumped” load and resistance factors, which conveniently relate the portion of mobilized resistance to a given footing displacement, accounting for uncertainty in the applied load, ULS resistance of the clay subgrade, allowable displacement, and footing size, generated using various assumed correlation structure models are compared. Additionally, the penalty in reliability associated with ignoring the bivariate correlation is explored for comparison. This study demonstrates that selection of the appropriate copula represents a critical task in the development of calibrated reliability-based geotechnical SLS design approaches.Non UBCUnreviewedThis collection contains the proceedings of ICASP12, the 12th International Conference on Applications of Statistics and Probability in Civil Engineering held in Vancouver, Canada on July 12-15, 2015. Abstracts were peer-reviewed and authors of accepted abstracts were invited to submit full papers. Also full papers were peer reviewed. The editor for this collection is Professor Terje Haukaas, Department of Civil Engineering, UBC Vancouver.FacultyOthe

ULTIMATE LIMIT STATE RELIABILITY-BASED DESIGN OF AUGERED CAST-IN-PLACE PILES CONSIDERING LOWER-BOUND CAPACITIES

The use of augered cast-in-place (ACIP) piles for transportation infrastructure requires an appropriate reliability-based design (RBD) procedure. In an effort to improve the accuracy of an existing design model and calibrate appropriate resistance factors, this study presents a significantly revised RBD methodology for estimating the shaft and toe bearing capacity of ACIP piles using a large database consisting of static loading tests in predominately granular soils. Resistance factors are calibrated at the strength or ultimate limit state (ULS) for ACIP piles loaded in compression and tension in consideration of lower bound limits. The inclusion of the lower-bound limits resulted in a 24 to 50 percent increase in the calibrated uplift resistance factors, and a 20 to 150 percent increase in the calibrated compressive resistance factors. Although the impact of lower bound limits on resistance factors depends on the degree of uncertainty in the distribution of resistance, this effect is outweighed by the type of distribution selected (i.e. normal, lognormal) at more stringent target probabilities of failure due to differences in distribution shape at the location of the lower bound limit. A companion paper explores the use of the revised ULS in a reliability-based serviceability limit state (SLS) design framework.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

SERVICEABILITY LIMIT STATE RELIABILITY-BASED DESIGN OF AUGERED CAST-IN-PLACE PILES IN GRANULAR SOILS

This study proposes a reliability-based design (RBD) procedure to evaluate the allowable load for augered cast-in-place (ACIP) piles installed in predominately granular soils based on a prescribed level of reliability at the serviceability limit state (SLS). The ultimate limit state (ULS) ACIP pile-specific design model proposed in the companion paper is incorporated into a bivariate hyperbolic load-displacement model capable of describing the variability in the load-displacement relationship for a wide range of pile displacements. Following the approach outlined in the companion paper, distributions with truncated lower-bound capacities were incorporated into the reliability analyses. A lumped load- and resistance factor is calibrated using a suitable performance function and Monte Carlo simulations. The average and conservative 95 percent lower-bound prediction intervals for the calibrated load- and resistance factor resulting from the simulations are provided. Although unaccounted for in past studies, the slenderness ratio was shown to have significant influence on foundation reliability. Because of the low uncertainty in the proposed ULS pile capacity prediction model, the use of a truncated distribution had moderate influence on foundation reliability.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Characterization of Frictional Interference in Closely-Spaced Reinforcement in MSE Walls

This research addresses one of several knowledge gaps in the understanding of tall MSE wall behavior: prediction of reinforcement loads impacted by frictional interference of closely-spaced reinforcements associated with tall walls.Pacific Northwest Transportation Consortiu