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In this paper, a constitutive model is presented to model the behavior of various soils (sand and clay) in different loading conditions and the minimum required parameters are obtained. Although some practical features (concepts) of the bounding surface framework and modified Cam-Clay have been employed in its formulations, the model is developed mainly based on the generalized plasticity framework. Moreover, some concepts such as dilatancy relation and loading history surface are redefined. Finally, the proposed constitutive model is evaluated using the experimental data related to two different sandy soils and three different clays under different loading conditions. Finally, it is concluded that the proposed constitutive model can easily be calibrated for various clayey and sandy soils. It can depict different behavioral aspects of these soils under different monotonic and cyclic loading conditions. [ABSTRACT FROM AUTHOR]

Rapid load pile testing (RLT) techniques such as Statnamic were developed as an alternative to more frequently adopted static and dynamic tests. The existing unloading point method (UPM) for deriving equivalent static load-settlement behavior from rapid load tests seems to be adequate in coarse-grained soils but may result in poor prediction in clays and silts. To address these shortcomings, the UPM has been improved to reflect soil type, and new analysis techniques have been developed. To test the performance of the improved UPM and new analysis techniques, pile tests from two clay sites were analyzed. The first case study site was underlain by very to extremely high-plasticity Quaternary London clay, and the second site was underlain by low- to intermediate-plasticity matrix dominant glacial till. The best predictions of static equivalent load-settlement behavior for very-high-plasticity clay were obtained from a new analysis technique that incorporated a soil-specific rate effect parameter (selected on the basis of the clays' plasticity index) that varied with pile settlement. In general, the UPM performed better for tests undertaken in the low- to intermediate-plasticity glacial till, as there is greater experience of RLT in these soils. The results of the study suggest that the development of analysis techniques would benefit greatly from tests in a wider variety of soil types. On the basis of the findings of this study, improvements to the UPM and Schmuker techniques are presented, which include pile settlement-dependent variation of the damping and rate effect parameters. [ABSTRACT FROM AUTHOR]

The purpose of this study is to evaluate the adequacy of the 100-year discharge along with the Froehlich bridge abutment scour equation adopted by the U.S. Federal Highway Administration (FHwA) in predicting abutment scour for bridge design purposes in South Carolina streams. The analysis utilized bridge properties, stream cross-sectional and hydraulic data, local flood frequency equations, a one-dimensional steady river flow computer model (WSPRO), and procedures recommended by the FHwA for predicting abutment scour. A method was developed to identify the single stream-discharge at each bridge that can cause the abutment scour that was observed at 73 bridge abutments. Analysis of the results revealed that for one-third of the abutments in the sandy soil region of South Carolina, the flow rates required to produce the observed scour depths had return periods greater than 100 years. Although for bridges in the region dominated by clay soil, the return periods were significantly smaller than 100 years. [ABSTRACT FROM AUTHOR]