DULLES TOLL ROAD
Loudon County, VA
The Robert B. Balter Company (Balter) provided a geotechnical pavement evaluation on the Dulles Toll Road (Virginia Route 267). The project includes the westbound lanes of the Toll road between the I-495 interchange and the main Toll Plaza, located about 1.2 miles west.
The Dulles Toll Road (DTR) was originally constructed in 1984 and consisted of only two lanes, with the additional two lanes constructed in the years following. A rehabilitation of the pavement was performed along the subject stretch of road approximately 4 years ago. The rehabilitation consisted of a mill and overlay program. Since the rehabilitation project was completed, the roadway has been subject to severe distress, including alligator cracking, block cracking, and raveling. The purpose of this evaluation was to assess the existing pavement conditions and to provide recommendations for repair of the damaged pavements.
The main challenge to performing the work along the DTR was the coordination effort involved to obtain permission to access the road. The DTR is a heavily traveled roadway located in the DC area and traffic volumes are extremely high during the rush hour periods and throughout the day. Significant coordination was required with both the Metropolitan Washington Airports Authority (MWAA) and DTR personnel. Because of personnel safety issues, MWAA would only permit the work to be performed in the two outside lanes. To complete the work, a mobile roadway closure was performed by a subcontractor using an approved Virginia Department of Transportation (VDOT) Typical Traffic Control (TTC) plan. Once the traffic control and lane closure permits were approved by MWAA work began.
The field evaluation consisted of two parts, an observation program and a coring program. The observation program consisted of walking the DTR to visually observe the existing pavement conditions. This was accomplished using the mobile lane closure in the right-most lane. This allowed for Balter’s personnel to walk the shoulder and right lane. During this program, station numbers were marked out on the shoulder in 25 foot increments. To detail the conditions of the pavement, a rating system was developed to allow for simple descriptions of the distress and recommended repairs. The rating system was used for each lane at the 25-foot stations. The rating system also allowed for a faster evaluation of the pavement. In addition, all 4 lanes were visible from the right lane, which allowed for the need of only one day of observations.
The coring program was performed on the second day at locations selected and marked in the field during the observation program. A total of 8 pavement cores were collected from the DTR. The cores were removed and returned to the laboratory for proper documentation. A hand auger boring was advanced through the aggregate base layer and into the underlying soil subgrade. Samples of both the aggregate base and the underlying soil subgrade were collected for laboratory testing.
The collected soil samples were submitted to our AASHTO accredited and Corps of Engineers validated laboratory for standard index testing, including Natural Moistures, Atterberg limits, and Sieve gradations.
Using the collected field and laboratory data, recommendations for repair of the pavement were developed. The collected information indicated that the best performing sections of the roadway consisted of the thickest pavement section, whereas those area performing poorly either correlated to thin pavement sections, or poor quality soils. Because of the limited testing the recommendations were based on the visual observations made during the field evaluation. A detailed geotechnical report was prepared which described the various recommendations, which ranged from filling cracks to complete reconstruction of the pavement and soil subgrade. Numerous iterations of the report were prepared for each percent design period, which also resulted in design meetings. Balter also assisted in the development of the specifications for the geotechnical aspects of the project.