In 2020, the Arkansas Department of Transportation (ARDOT) implemented Advanced Geotechnical Methods in Exploration (A-GaME), a technology that provides real-time, continuous monitoring and recording of information during the drilling process. The agency used A-GaME to repair slope stability issues northwest of Ozark.
The department has also developed a network of Global Navigation Satellite System (GNSS) Continuously Operating Reference Stations (CORS) to create accurate positioning for the planning and construction of highway projects. Data from these stations is available to infrastructure personnel, government officials and the general public.
ARDOT’s Implementation of A-GaME Approaches
The Arkansas Department of Transportation (ARDOT) put into effect numerous geophysical methods to resolve slope stability issues near a roadway outside of Ozark. During the repair process, ARDOT also implemented complementary approaches known as Advanced Geotechnical Methods in Exploration (A-GaME), a site exploration technique that allows for continuous monitoring of geotechnical drilling operations.
For the past 40 years, one portion of an Arkansas highway has experienced severe stability and settlement issues. Despite recurring restoration efforts involving alterations in the drainage system and material replacement at the landslide toe, the instability persisted. In 2018, a $2.3 million stabilization effort that included the installation of 100 soil/rock anchors and horizontal drainage toward the top of the landslide was conducted. However, further cracking of the slope and pavement was reported just one year after the restoration.
In the past, drilling, sampling and other boring methods were not enough to provide the agency with a clear picture of the subsurface conditions causing the landslide. These efforts alone only provided ARDOT with limited point-specific data. To combat this issue, ARDOT used multiple A-GaME approaches to conduct investigations including electrical resistivity testing, microtremor horizontal to vertical spectral ratio (MHVSR) measurements and multichannel analysis of surface wave (MASW)/P-wave seismic refraction measurements.
The measurements from the investigations revealed bowl-like qualities within the impermeable rock at the toe of the landslide, and that the water trapped within these bowls was the leading cause in the slope’s instability. The bedrock depressions coincided with multiple spring locations that were detected throughout field measurements. This discovery further proved that the slope instability could be due to groundwater and draining impedance.
ArCORS: Real-time Construction Data for All
In 2021, ARDOT developed a network of Global Navigation Satellite System (GNSS) Continuously Operating Reference Stations (CORS). This e-construction method is used to produce accurate positioning for the planning, development and construction of highway projects. The GNSS network provides real-time corrections that are broadcast in Radio Technical Commission for Maritime Services (RTCM) format and Compact Measurement Record (CMR) format to GNSS receivers with internet connections.
Arkansas’ Continuously Operating Reference Station (ArCORS) is accessible to government personnel and the general public. As an act of public service, the agency has provisions in place to ensure that the real-time information is both accurate and accessible. The department provides the basic information necessary for users to connect to the system. However, the agency does not provide the software necessary to make the connection and detailed configuration for the specific software used to connect to the ARCOS system is the responsibility of the user.
The public can retrieve both RTCM and CMR messages instantaneously and download information for post processing. The program uses administrative monitoring of its users and their activity. ARDOT regularly monitors the program but encourages users to report inaccurate information so that it can be corrected or removed.
For the general public to gain access to the ArCOS network, users must provide their name, contact information, equipment information and more to ARDOT. After a user’s request is successfully processed, the agency provides them with a username and password that allows them to access the ArCOS system free of charge.