Geosynthetic Stabilization of Weak Subgrade

Primary Investigator Contact Information

Eli Cuelho
Western Transportation Institute
PO Box 174250
Bozeman, Montana 59717
406-994-7886
elic@coe.montana.edu

External Project Contact(s)

Kent von Maubeuge
NAUE GmbH & Co. KG
GewerbestraBe 2
, NULL
+49 (5743) 41 2
kvmaubeuge@naue.com

Report(s)

There are no reports associated with this project.

Project Objective

This project aims to construct test sections in the field to investigate the relative benefit of various geosynthetics available on the market to an unpaved road.

Project Abstract

The use of stiff geosynthetics in unpaved roads on soft subgrade is known to provide a reinforcing benefit to the road, allowing better distribution of applied loads and increased bearing capacity. However, there is not yet an accepted standard design technique that incorporates the material properties of the geosynthetic in the design to account for the reinforcement it provides. Therefore, design of a geosynthetic unpaved road should take into consideration the results of preceding laboratory and field investigations. This project aims to construct test sections in the field to investigate the relative benefit of various geosynthetics available on the market to an unpaved road. The location of the test sections is in Lewistown, Montana at the TRANSCEND research facility operated by the Western Transportation Institute. A prepared and placed subgrade will provide equivalent conditions for each test section; likewise the gravel surfacing along the entire test bed will be uniform. Controlled traffic loading with frequent rut profile measurements will indicate performance benefits of each geosynthetic in the test sections. Additionally, post-traffic examination of the geosynthetic will provide invaluable information regarding the performance and installation survivability of the geosynthetics. This effort is jointly sponsored by the Montana Department of Transportation (MDT); NAUE GmbH & Co. KG, a geosynthetic manufacturer based in Germany; and the University Transportation Center (UTC) program (part of the Research and Innovative Technologies Administration of the USDOT). NAUE is sponsoring the construction and monitoring of four test sections; while MDT is sponsoring the construction and monitoring of an additional seven test sections. The UTC program will provide support to the overall effort. Data collected and conclusions drawn from these parallel projects will be summarized in an integrated final report. This project represents the NAUE portion of the overall effort.

Task Descriptions

Design and Construction of Test Sections
1. Researchers will design and construct eleven geosynthetic-stabilized test sections and two control sections. Each test section containing geosynthetics will be 15 m long and the control sections will be 20 m long. Construction activities basically include the excavation and placement of the subgrade, geosynthetic, instrumentation and gravel surface.
Soil Testing and Instrumentation
1. Researchers will test soil subgrade properties, including water content, Atterberg limits, and particle size distribution to determine soil classification. Subgrade soil strength will be measured during construction using a dynamic cone penetrometer, a hand held vane shear, a nuclear densometer and moisture content. Electronic instrumentation will be installed to collect displacement and pore water pressure data during the traffic loading.
Vehicle Loading and Data Collection
1. Researchers will conduct controlled vehicle loading using a three-axle dump truck; the vehicle will travel over the test bed in one direction for up to 1000 passes or until ten centimeters of rutting occurs in all test sections. Once loading is complete, gravel will be removed to allow detailed measurement of the rut bowl at the level of the subgrade, thorough inspection of the geosynthetic materials, investigation of installation damage, and evaluation of junction survivability.
Analysis
1. The research analysis will be based on a cumulative examination of all data, including subgrade, geosynthetic, and gravel properties; road performance; and physical post-testing examination of the geosynthetic and subgrade. The analysis will be the basis for a comprehensive explanation of the results indicating the performance of each geosynthetic, relative to other geosynthetics and the control section.
Reporting
1. A final report will be prepared to summarize detailed construction information and performance results for each test section.