Preliminary experimental and analytical investigations were conducted to evaluate the performance of pavements with and without geotextile or geogrid reinforcement materials. Four pavement sections were tested: one unreinforced section that served as a control and three sections reinforced with either one of two geotextiles or a geogrid. The pavement sections were constructed to model a typical secondary road in Virginia built over a weak granular (silty sand) subgrade material. Loading of the pavement sections was accomplished through the use of a computer-controlled pneumatic system that delivered approximately 55 kPa through a 30-cm rigid plate at a frequency of 0.5 Hz. The resulting displacement of the pavement surface was monitored by an array of linear variable displacement transformers. The performance of each pavement section was evaluated as a function of the applied number of cycles, the resulting surface deflection profile, and the layer deflection profile. It was concluded that geosynthetics can substantially improve the performance of a pavement section constructed on a subgrade soil with a low California bearing ratio. Also the reinforcing mechanisms of geogrids and geotextiles are different.

Laboratory evaluation of geosynthetic-reinforced pavement sections

Limitations The information contained in this document is the result of original research and is made available solely as a contribution to the general state of civil engineering knowledge. As such, this document does not constitute a design manual or standard, and should not be interpreted, used or referred to as such. The author assumes no liability for the performance of any structure constructed using the methodologies discussed in this document. In addition, any reference, either direct or indirect, to a specific geosynthetic material or product is made solely for the purposes of the study documented in this report and does not constitute an endorsement or promotion of that material or product by the author. Distribution and Use Authorization is hereby granted to copy, distribute and print this document without restriction provided that this document is copied, distributed and printed in its entirety, at no cost and used for individual reference purposes only. This document may not be sold or used in whole or in part in any manner for commercial purposes of any type, including manufacturer's product or marketing literature, without prior written consent of the copyright holder. Printing Those wishing to make a paper copy of this document are advised that it is formatted for double-sided printing. A gutter has been provided in the page formatting to allow space for binding along the side if desired. It is suggested that the printer settings in Adobe Acrobat be set to "Print as image" for optimum readability.

Integral-Abutment Bridges: Problems and Innovative Solutions Using EPS Geofoam and Other Geosynthetics

Column-supported embankments with or without basal geosynthetic reinforcement can be used in soft ground conditions to reduce settlement by transferring the embankment load to the columns through stress redistribution above and below the foundation subgrade level. Column-supported embankments are typically used to accelerate construction and/or protect adjacent facilities from additional settlement. The column elements consist of driven piles or formed-in-place columns that are installed in an array to support a bridging layer or load transfer platform. The bridging layer is constructed to enhance load transfer using several feet of compacted sand or sand and gravel that may include one or more layers of high-strength geotextile or geogrid reinforcement. Mobilization of the mechanisms of load transfer in a column-supported embankment requires some amount of differential settlement between the columns and the embankment as well as between the columns and the foundation soil. When the embankment height is low relative to the clear spacing between columns, there is the risk of poor ride quality due to the reflection of the differential foundation settlement at the surface of the embankment. The minimum embankment height where differential surface settlement does not occur for a particular width and spacing of column is the critical height. The conventional approach is to express critical height as a fixed ratio of the clear span between adjacent columns; however, there is no consensus on what ratio to use and whether a single ratio is applicable to all realistic column arrangements. The primary objective of this research is to improve the understanding of how columnsupported embankments deform in response to differential foundation settlement. A bench-scale experimental apparatus was constructed and the equipment, materials, instrumentation, and test procedures are described. The apparatus was able to precisely measure the deformation occurring at the sample surface in response to differential settlement at the base of the sample. Critical heights were determined for five combinations of column diameter and spacing representing a wide range of possible column arrangements. In addition, tests were performed using four different column diameters in a single column configuration with ability to measure the load

Critical height and surface deformation of column-supported embankments

Wastes generated due to human activities pose a threat to the environment, and their safe and economical disposal is warranted. Landfilling of these wastes is still the most widely practised and viable alternative for their disposal. This is usually accomplished by using engineered waste containment systems in which compacted liners of predominantly clay soils are employed between waste and natural ground to act as barrier to chemical leaching. It follows that the design hydraulic conductivity of the clay is a governing parameter and many environmental regulations require this parameter to be less than 1x10"' m/s. Therefore, the precise assessment of hydraulic conductivity and the compatibility of the liner material with the permeant or leachate encountered, is paramount to ensure the effective performance of the clay liner. This thesis reports the test results of the compatibility and hydraulic conductivity of some Victorian soils used for liner construction.

Hydraulic conductivity and chemical compatibility of some Victorian soils used as liners for waste containment

: Soil-Structure Interaction (SSI) analyses have proven to be powerful tools for use in analyzing, designing, and monitoring geotechnical structures. SSI analyses are particularly useful in problems of complex geometry and loading conditions such as lock walls. Several SSI analyses of Corps of Engineers lock walls have shown that the behavior of the soil-structure interface has a significant influence on the magnitudes of the loads acting against a lock wall. They have also illustrated that the pre- and post-construction field stress paths followed by interface elements often involve simultaneous changes in normal and shear stresses, as well as shear stress reversals. The hyperbolic formulation for interfaces, used commonly in SSI analyses, models interface behavior in the primary loading stage very closely. However, it has not been extended to accurately model simultaneous changes in shear and normal stresses, reduction of shear stress, reversals in the direction of shear, or unload-reload cycles at the interface. The purpose of this research is to develop an interface model capable of giving accurate predictions of the interface response under field loading conditions. In order to develop the necessary test data, the Large Displacement Shear Box (LDSB) at Virginia Polytechnic Institute and State University, Blacksburg, VA, was modified to permit soil-to-concrete interface testing. A. concrete specimen for interface testing was prepared with a surface texture similar to that of concrete retaining walls in service. A number of tests were performed on the interface between this concrete specimen and a uniform dense sand: initial loading, shear reversals, staged shear, and unloading-reloading of the interface. This research is being conducted in two phases. This report presents the results of the testing performed for the Phase I research.

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George Michael Filz

Papers

An experimental and analytic study of earth loads on rigid retaining walls