A-GaME: Avoiding Unforeseen Costs on Transportation Projects Through Early Detection of Subterranean Obstacles

The Federal Highway Administration is encouraging State Departments of Transportation to utilize A-GaME, one of the agency’s Every Day Counts (EDC-5) innovations, to mitigate risks and improve reliability of geotechnical site characterization with proven, effective exploration methods and practices.

NJDOT used a drone to safely photograph the full extent of the soil erosion

NJDOT used a drone to safely photograph the full extent of the soil erosion

This article is a summary of an interview with New Jersey Department of Transportation (NJDOT) employees with expertise in engineering and geology from Geotechnical Engineering and Engineering Geology. The interview was held with Kim Sharp (Supervising Engineer, Geotechnical Engineering), John Jamerson (Project Engineer, Engineering Geology), and Amanda McElwain (Principal Engineer, Engineering Geology) to discuss how NJDOT utilizes A-GaME methods for its projects and the benefits these methods provide.

Q:  What is A-GaME?

A-GaME is an acronym for “Advanced Geotechnical Methods of Exploration” that encompasses a relatively new set of techniques for subsurface exploration that provides a more complete understanding of an area’s geotechnical and geological properties. In short, these techniques allow engineers to “see” what’s underground during a project’s design phase.

A-GaME techniques include the following processes:

Tools of the trade: sledgehammer, striking plate, and sensors are used to measure seismic vibrations through soil

Transportation projects typically use soil borings to collect soil samples, which are then tested in labs to determine the soil properties (e.g., water content, water depth, soil type, etc.) that will inform project design and construction. A-GaME techniques supplement soil borings and can more accurately identify obstructions, bedrock, and other soil conditions that could cause construction delays. They can also detect more subtle changes in soil conditions than conventional bore holes or penetration tests.

Q: Which of these methods has NJDOT used? Have they been successful?

Each A-GaME method yields benefits. The key is to find the right method for each project. NJDOT has utilized A-GaME methods in the preliminary design and design phases of several projects. In these projects, the results of the exploration have benefited project design and construction. Some of the more prominent examples of NJDOT’s use of A-GaME include:

  • Seismic Piezocone and P-S seismic logging techniques for the Pulaski Skyway seismic retrofitting of foundations. Consultants used these techniques in their site-specific seismic response analyses to derive shear wave velocity correlations and discover the various layers and depths of fill, organics, sands, clays, glacial till, and bedrock composition. This information allowed the engineers to determine how to retrofit each foundation to withstand a seismic event.
  • Mapping talus deposits – that is, collected rockfall piles – over bedrock on Route 80.
  • Microgravity surveys have been used in mine investigations. Northern New Jersey has several abandoned mines, and these surveys have provided safer and more complete methods to map and assess the structural integrity of these mines and inform remedial strategies.
  • Seismic methods were also used on another project near the Delaware Water Basin to measure the depth of talus deposits. Seismic activity was monitored from the road vibrations and the waves were measured at various points around the deposit to determine the locations of voids and the pile’s overall depth.
  • Mapping of rock joints for bridge foundation design along Route 4. Mapping the locations of the fractures in the rock allowed the design team to place the bridge foundations in structurally sound locations based on the competency of the rock mass. The process assisted in determining the long-term stability of the rock mass, the rippability (ease of excavation) and constructability of the mass, possible excavation angles, and the potential need for additional support.
  • Bathymetry Survey has been used in waterways upstream and downstream of structures on navigable waterways to provide river bottom elevation cross sections. This technique was used on the Pulaski Skyway project to reveal images of debris that had fallen off ships into the Hackensack River and could present issues during construction of the proposed foundation seismic retrofitting. The information saves time and money in the construction phase by alerting contractors to obstructions that will need to be removed.
  • Geophysical explorations have been used for finding shallow surface and river bottom debris, utility installations, and mapping existing bridge footing configurations underwater.
  • LiDAR survey has been used for site investigation on rock faces on a few projects during design.
  • Optical and acoustic tele-viewers have been used some down hole in soil borings to characterization of rock and any open voids.
  • Single Station Passive Seismic Survey (SSPSS) has been used to differentiate weathered rock from bedrock using ambient vibrations. Determining the interface between weathered rock and competent bedrock is essential, whether it is for rock slope stability, excavation concerns (mechanical or blasting), or foundations. SSPSS helped determine if the top layer was comprised of weathered rock, or if the top layer was comprised of loose boulders with lots of air-space in between.
  • Drones have been used in emergency situations to investigate large slope failures and to inform design on rockfall mitigation projects. On I-287, a drone equipped with a high-resolution camera was able to take photographs and videos revealing a broken drainage pipe that was contributing to erosion that required immediate remediation. This was safer and more cost effective than utilizing a team of workers to investigate. On I-280 and I-287, drones have also been used for rockface mapping and early site characterization as a design tool.
The source driver impacts the source, like a hammer striking a nail, and generates a wave. The pressure waves and seismic waves are recorded by the geophones as they travel through the fluid and soil walls.

The source driver impacts the source, like a hammer striking a nail, and generates a wave. The pressure waves and seismic waves are recorded by the geophones as they travel through the fluid and soil walls.

Q: Who determines which method to use, and who does the exploration?

Our office, in collaboration with design consulting firms, determines the most appropriate new technology methods for each project. The right method is largely determined by the type of project and its location. For example, projects that cross rivers may rely on sonar, LiDAR, or tomography to assess the conditions under the water and on the river’s slopes. On the other hand, a project in the mountains may require seismic methods of subsurface exploration because the steep slopes and rocky terrain make conventional testing impossible.

NJDOT often utilizes these methods during a project’s design phase to be proactive in reducing the risks and costs associated with underground soil conditions during construction. Some of these methods are also useful in emergency situations.

NJDOT sources A-GaME work to a small group of contractors that have knowledge on how to use the highly specialized and expensive equipment required to perform the tests, and the skilled, specialty trained personnel to conduct the tests and interpret the data. NJDOT and local governments rely upon private industry contractors to perform these specialized services; in fact, the geophysical firms themselves may not own the specialty equipment (e.g., seismographs, etc.), but will rent it out as needed due to the high costs of ownership. When we develop the boring program, the prime design consultant firm will often contract with a specialty geophysical firm. Sometimes the geophysical firm will be hired by the drilling contractor.

Q: You just said that these methods can be expensive, but isn’t an important benefit of these methods to save money?

A-GaME techniques tend to have a higher up-front cost, but these methods save money over the life of a project through risk reduction. When designers, DOTs, and contractors have a better understanding of the issues that could arise due to subterranean conditions (e.g., bedrock, air voids, old storage containers, abandoned mines), the project can account for these conditions rather than discovering them during the construction phase.

In the design phase, A-GaME methods can provide information to ensure that foundations are not overdesigned, or are appropriate for rocky terrain, and can improve constructability over the life of the project – which can deliver cost savings.  Overall, these techniques reduce costs associated with construction delays, change orders, and litigation.

In some environments, projects on mountainous terrain for example, the cost of soil borings can be very high to mobilize equipment, so supplementing borings with geophysical techniques brings the project cost down.

The information about soil known by traditional boring methods. Source: Minnesota DOT

The information about soil known by traditional boring methods. Source: Minnesota DOT

Q: What knowledge, skills, and abilities are needed to advance the use of A-GaME at NJDOT?

Delivering the specialized equipment, skills, and education needed for A-GaME are currently outside the capabilities and day-to-day responsibilities of NJDOT’s Geotechnical Engineering Department. Testing methods are complicated, and the resulting data often require the analyst to have a PhD in Geology.  The degree of specialization warrants the need for outsourcing the work to specialty contractors who would regularly perform these functions and hone their expertise.  Engineers entering the profession would not necessarily have had sufficient exposure to these techniques at the undergraduate level.

However, NJDOT staff have been going on-site when the specialty contractors perform work on NJDOT projects to learn more about these methods and climb the learning curve. When DOT staff have more knowledge about the methods, the odds of advancing their use in future projects increases.

Q:  What are some challenges to A-GaME’s deployment?

From an engineering perspective, all of the design firms need to become aware that there are lots of methodologies available to analyze and obtain soil and rock properties for better, and sometimes more efficient and cost-effective, designs of our foundations and rock slopes.  We work with firms of varying capacities including some less experienced firms with little awareness of the methods.  There are also some firms that would be interested in implementing these services on select projects, but until recently were not sure that NJDOT was open to their use, such as for rock work.

Information provided by ERI imaging is much more thorough. Source: Minnesota DOT

Information provided by ERI imaging is much more thorough. Source: Minnesota DOT

NJDOT project management teams also can be resistant to spending the extra up-front money for this type of testing and analysis. Soil boring drilling contractors do not want to work in tandem with geophysical firms because they have to wait for the firms to get out there and complete their work; for example, there are peripheral costs and scheduling uncertainties related to use of optical or acoustical televiewer work. The drilling contractors do not want to be idle while the geophysical work is being performed.  They want reliability as to when work will be completed so they can quickly move on to the next job.  So, we have found that fewer drilling contractors may actually bid on the job if they have to work in tandem or accommodate the geophysical firm services.  This can drive the bid costs up.

Q:  What are the next steps for A-GaME?

NJDOT and most other DOTs are still learning about A-GaME methods and their applications. The next step for NJDOT’s adoption of A-GaME is to continue to spread knowledge of these methods and encourage their use to supplement traditional boring techniques.

NJDOT’s Bridges and Structures Design Manual is being updated and, as part of the revision process, Geophysical Testing has been added to the new Sections 25 and 26.  While FHWA still must review these and other revisions to the Manual before it is made available to the public, the inclusion of A-GaME in the manual should eventually increase the awareness and use of these innovative methods among consultants. New innovative techniques are being added in the subsurface contract language as well.

Knowing where you will encounter bedrock is very helpful for excavation or drilling. You cannot get a complete picture such as this from bore samples. Courtesy of Jeff Reid, Hager-Richter Geoscience, Inc.

Knowing where you will encounter bedrock is very helpful for excavation or drilling. You cannot get a complete picture such as this from bore samples. Courtesy of Jeff Reid, Hager-Richter Geoscience, Inc.

NJDOT is encouraging designers to learn more about these methods and to seek approval for their use when designing NJDOT projects. NJDOT’s geotechnical team anticipates that, with familiarity, project managers will support additional funding for A-GaME during the design phase and use within the industry will grow.

Q:  Is there any other information you would like us to know about implementing the A-GaME?

These methodologies provide a wealth of information regarding soil and rock that soil borings and visual observations alone cannot provide us.  These methodologies better assist NJDOT in subsurface exploration for our highway structures and rockfall mitigation projects, as well as aid in determining pre-construction constructability issues on our heavily traveled waterways.

Resources

FHWA. (n.d.) Advanced Geotechnical Methods in Exploration (A-GaME). Retrieved from: https://www.fhwa.dot.gov/innovation/everydaycounts/edc_5/geotech_methods.cfm

Kelley V.C. (1987) Joints and fractures. In: Structural Geology and Tectonics. Encyclopedia of Earth Science. Springer, Berlin, Heidelberg. Retrieved from:  https://doi.org/10.1007/3-540-31080-0_56

NJDOT (n.d.). Innovative Initiative: What are Advanced Geotechnical Methods in Exploration? Retrieved from:  https://www.njdottechtransfer.net/advanced-geotechnical-exploration-methods/

Palmström A. (2001). Measurement and Characterization of Rock Mass Jointing, Chapter 2, In-Situ Characterization of Rocks. Editors: V.M. Sharma and K.R. Saxen. Retrieved from:   http://rockmass.net/ap/69_Palmstrom_on_Jointing_measurements.pdf

United States Geological Survey (n.d.) Geologic Units Containing Talus. Retrieved from: https://mrdata.usgs.gov/geology/state/sgmc-lith.php?code=1.5.5

 

Figure 3. Routes 55 & 47 were surveyed using a mobile unit which produces an enormous number of accurate and precise points (approximately ¼” inches apart for about 2 miles) for this bridge replacement project.

NJDOT Tech Transfer Innovation Interview: 3D Reality Modeling

In prior rounds of the Every Day Counts (EDC) program, the Federal Highway Administration (FHWA) sought to raise awareness and encourage the general education of transportation professionals in the uses of 3D models in all phases of project delivery, including the areas of planning, data collection and management, design, construction, operations and maintenance of highway facilities.  EDC-2 emphasized 3D engineered models for design and construction, while EDC-3 promoted the broader use of 3D models and digital data to further advance other application areas.

To find out a little more on what NJDOT has been doing to advance 3D modeling, we conducted an interview with Jim Coyle, a Geodetic Survey SME at NJDOT.  He is the supervisor of a relatively new unit, the Bureau of Survey Support that is working to deploy new technologies including the in-house integration of Lidar and software to create surveys from point clouds. The 3D modeling group within Survey Support is staffed with four individuals.  Below is an edited summary of our interview and follow-up discussion.

Q. What is meant by 3D Reality Modeling?

Reality modeling is the process of capturing the physical reality of an infrastructure asset, creating a representation of it, and maintaining it through surveys. Reality modeling gathers existing conditions in 3D using one or more devices—for example, cameras on drones, handheld camera, laser scanner, phones—to support mapping, design, construction, inspection and asset management.

At the foundational level, we start by establishing a 3D topographic map of the “existing world.” Other disciplines create their models, often using the 3D topo as a starting point or “designed-on-this-backdrop” model.

It’s handy to keep in mind that there are different definitions, references and standards in the usage of the term “modeling.” It depends on the discipline and who is supposed to make what deliverable or standard file type, but the backbone definition is obvious: an image speaks a thousand words.

Q. What is being done at NJDOT with 3-D reality modeling? What are typical use cases at NJDOT?

NJDOT is ahead of the curve in the use of mass data collection systems to create a visual model of existing conditions that planners can work within. We create this world using Lidar or reality capture through photogrammetry.

Photogrammetry is the process of capturing images of an object from many different angles and using these images to create three dimensional models, indexing and matching common features in each image. It is the science of making measurements from photographs. Lidar, or light detection and ranging, is a process whereby laser scanning produces accurate three-dimensional representations of elevations.

At NJDOT, we have used ContextCapture, a reality modeling software to create a 3D reality mesh. A reality mesh is a 3D model of real-world conditions that contains large amounts of triangles and image data that can be geospatially referenced. We coordinated with our Bureau of Aeronautics to fly a drone with a camera to do the data capture. Basically, the drone flies in a grid pattern taking a large number of overlapping pictures which can be plugged into software to create a 3D reality model. We used it to estimate the amount of dredging material for a project in Cape May as well as for a project at Route 29 and Duck Island (see Figures 1 and 2).

Figure 1. Route 29 & Duck Island Landfill. Requested by Environmental for 2D topographical purposes. The most cost-efficient method to fulfill the original 50+ acre objective was to fly the area with a photographic drone and create a model from the photos (Flown by the NJDOT Aeronautics Unit). Shown above are 2 views of the resulting 3D model.

Figure 1. ROUTE 29 & DUCK ISLAND LANDFILL. Requested by Environmental for 2D topographical purposes. The most cost-efficient method to fulfill the original 50+ acre objective was to fly the area with a photographic drone and create a model from the photos (Flown by the NJDOT Aeronautics Unit). Shown above are 2 views of the resulting 3D model.

There are different ways to collect laser scanning data such as through a drone, on a vehicle, or from the side of the road. NJDOT has purchased a static laser scanner that can be placed on the side of the road to collect point cloud data. It works a lot like a typical survey unit with control targets. We have used software, TopoDot, that puts in lines and features that creates the topographic layer and the digital terrain model, or DTM, surface file. We have done multiple projects with our static laser scanner.

Figure 2. Route 29 & Duck Island Landfill. Shown here is a contoured elevation heatmap. The model that was created is 3D by default, so creating this view is extremely easy to do. The model shows little erosion along the top and steep sides. Inasmuch as the model is both precise and accurately geo-located, future surveyed models of this ecologically sensitive area can easily be compared to this model.

Figure 2. ROUTE 29 & DUCK ISLAND LANDFILL. Shown here is a contoured elevation heatmap. The model that was created is 3D by default, so creating this view is extremely easy to do. The model shows little erosion along the top and steep sides. Inasmuch as the model is both precise and accurately geo-located, future surveyed models of this ecologically sensitive area can easily be compared to this model.

For larger projects, such as for roadway segments of two or three miles, a mobile scanner is needed. At present, NJDOT lacks a mobile scanner so this work has been outsourced to consultants. NJDOT has piloted the mobile scanning process, and we just used it for a bridge replacement project for the Route 55 Bridge over Route 47. The survey resulting from this mobile scanning is being used to support the design phase (see Figures 3 through 6).

The good thing about doing a laser scanner survey is that we get information from the surface all the way up—from signal heads to overhead wires. Normally, you do not deliver that for the survey work, but if the engineer later needs additional information you do not need to go back into the field with supplemental surveys. You can see that this can offer benefits in terms of safety, cost-savings and other efficiencies.

Traditionally, NJDOT did not have staff of photogrammetrists so the agency had to outsource to consultants all of its mapping. Now with this LIDAR technology, NJDOT is able to use the raw point cloud data (still collected by the consultant in the case of mobile scanning) to do the survey mapping in-house which appears to offer cost-savings.

Figure 3. Routes 55 & 47 were surveyed using a mobile unit which produces an enormous number of accurate and precise points (approximately ¼” inches apart for about 2 miles) for this bridge replacement project.

Figure 3. ROUTES 55 & 47 POINT CLOUD MODEL. Routes 55 & 47 were surveyed using a mobile unit which produces an enormous number of accurate and precise points (approximately ¼” inches apart for about 2 miles) for this bridge replacement project.

Q. Who will make use of 3-D Modeling in the future?

Everybody, but for this discussion we will focus on transportation, including planning, construction and maintenance of transportation systems.

3D models of transportation systems will enable planners to get a real world, spatially accurate, view of preexisting roadway features. 3D models are the foundation for 4D simulation models. For example, proposed traffic patterns and sight distances can be simulated visually. It is possible to lay down concept plans within this visual model essentially bringing the real world into your computer.

Designing in 3D is really a new paradigm. The combination of 3D modeling and Global Positioning Systems (GPS) will allow construction crews to use Automated Machine Guidance (AMG) to complete projects faster and with improved quality and safety. GPS-enabled construction equipment can run virtually non-stop with guidance from 3D model data and achieve precise grades on the first pass. GPS rovers can be used to spot check elevations and horizontal offsets. Traditional 2D methods rely on grade stakes and 2D paper plan sheets.

Figure 4. Switching the “view mode” of a point cloud is just a click. These views show the point cloud in contour mode (0.1 contours) and deviation from a plane mode.

Figure 4. ROUTES 55 & 47 POINT CLOUD MODEL. Switching the “view mode” of a point cloud is just a click. These views show the point cloud in contour mode (0.1 contours) and deviation from a plane mode.

The 3D model can be updated with as-built location data throughout the construction process. After construction, the 3D model becomes the record drawing. The 3D model will have useful benefits as a base map for future maintenance and can be stored in a GIS database for asset management.

Q. How does 3D reality modeling benefit the agency’s various operations?

Having all design elements in 3D improves accuracy and decreases unintended occurrences. Design conflicts become much more apparent.

It is also easier for each discipline to identify how they fit into the project as a whole. This understanding allows for efficient conflict resolution during design and an improved product that should be much easier to construct.

Figure 5. Low Cost As-Builts. In this view (RGB/real color mode) of the Route 55NB to Route 47 NB Ramp nose, assets such as signs, inlets, junction boxes, guide rail and post, striping, etc. are documented with true mapping grade 3D coordinates. The density of point cloud (approx. 4 to 5 mm apart) can be seen near the inlet/curb in the lower left.

Figure 5. ROUTES 55 & 47 POINT CLOUD MODEL. Low Cost As-Builts. In this view (RGB/real color mode) of the Route 55NB to Route 47 NB Ramp nose, assets such as signs, inlets, junction boxes, guide rail and post, striping, etc. are documented with true mapping grade 3D coordinates. The density of point cloud (approx. 4 to 5 mm apart) can be seen near the inlet/curb in the lower left.

With an engineered 3D model, everyone can see a lifelike representation of what the finished project will look like. These 3D project files can be uploaded anywhere, which means everyone—even those without a technical background—can quickly get up to speed around a project’s concept. The emphasis on 3D-driven design offers new ways of easily communicating information with clients and the public; from 3D KMZ files that can be viewed in Google Earth to full virtual reality (VR) tours of a virtual corridor; the final product has never been easier to visualize.

When a project is presented to the public in 3D, stakeholders quickly have a comprehensive understanding of what is occurring by seeing the depth and details they will ultimately see once the project is constructed.

Figure 6. Measuring and calculating bridge clearances takes seconds when using a 3D point cloud model, and no one had to step into the road to do it.

Figure 6. ROUTES 55 & 47 POINT CLOUD MODEL. Measuring and calculating bridge clearances takes seconds when using a 3D point cloud model, and no one had to step into the road to do it.

Q. What skills, knowledge and abilities are needed to advance the use of 3D reality modeling at NJDOT?

The skills required include an understanding of surveying general principles. There is a need for surveyors and technicians with the ability to interpret and render 3D data including data capture, registering, and creating the point cloud, and familiarity with MicroStation/CADD and TopoDOT software. Folks need to be comfortable working with computers and CADD.

Q. What tools, equipment, or techniques are being used by the agency to advance modeling?

The Bureau of Survey Support is currently working with Static/Mobile Lidar scanners, cameras, drones as well as traditional survey equipment and various software (Bentley/Leica Suite products). As I’ve mentioned, we are exploring how to use these products for projects in-house and in collaboration with our consultants where we may not have the scanning equipment.

The future is in 3D design. NJDOT Design is in the process of upgrading the Bentley CAD suite of software including OpenRoads Designer and OpenBridge Designer. NJDOT should have the tools within six months or a year. Following training, I anticipate that NJDOT will be designing with 3D within two to three years.

Resources

FHWA. (2017). 3D Engineered Models. Retrieved from: https://www.fhwa.dot.gov/construction/3d/