for machine control to operate within acceptable tolerance. In this case, the Trimble team recommended improvements to the existing design model to make it easier for the contractor to use this data in their machine control solutions. When the study was complete, NMDOT met with their contractor, FNF Construction, Inc., to ask if it would derive benefit by making recommended adjustments to the design model. FNF said yes, and the edits were made. Benavides said, “It is my personal goal to move all of our projects towards this future through e-construction.” Similarly, leaders at the California Department of Transportation (Caltrans) in Sacramento have worked closely with its contractors to provide comprehensive civil 3D models. What used to be simple finished surface models with alignments and as-built conditions from a drone survey, are now becoming comprehensive 3D site models. The contractor no longer has to build all the base layers and add utilities to prepare for construction. For DOTs, the ability to deliver constructible models and digital as- builts to contractors reduces risks and improves project transparency. Accurate data eliminates many cost and schedule risks for the transpor- tation agency and the project team. It further provides DOTs and own- ers with more transparency into everything from bidding to handover. Digital Roads to Digital Operations and Maintenance The ability to share data and drive improved workflows in today’s environment is much easier than even just five years ago. MaineDOT recently transitioned to laser scanners to complete as-built surveys faster and cheaper. A team of three surveyors used the Trimble SX10 and a Trimble R8 to scan and survey a damaged 100-year old I-95 overpass, process the LIDAR data, create true 3D models—and ex- tract precise data to deliver clearance reports—all in two days. That’s a job that would have taken two survey crews a full week to survey and several more expensive pieces of survey gear. This type of tech- nology provides the DOT with a digital twin asset that now can be tracked as it changes over time, allowing for optimized maintenance and inspection activities. Contractors can also contribute and benefit from the process. Heavy civil contractor, Zak Dirt recently completed the $31 million Colorado 119 Boulder Canyon Improvements project, which involves the repair of a 15-mile stretch of flood-damaged Colorado Highway 119 between Boulder and Nederland for the Colorado Department of Transporta- tion. The one-year project required the tracking of approximately 41,000 cubic yards of material among other tasks. The team needed topo maps to help track progress and calculate vol- ume quantities, but conventional survey methods in the steep canyon terrain were too dangerous and difficult. With drone data, the project team was able to track quantities, compare cross-sections with design intent, and measure and revise blast slopes as needed. The data from the platform was shared among project managers, surveyors, superin- tendents, engineers, and others within Zak Dirt. Just as importantly, the project team was able to provide the Colorado Department of Transportation project updates and relay progress reports to owners
Other pioneering transportation agencies are following suit. Advancing the use of Digital Construction Technologies With an eye on redefining its business model and achieving full trans- parency with its contracting partners, the New Mexico Department of Transportation (NMDOT) implemented a pilot project built as part of the Federal Highway Administration’s (FHWA) Every Day Counts (EDC) e-construction initiative. NMDOT defines e-construction as the collection, review, approval, and distribution of highway construction contract documents in a paperless environment, which helps meet the goal of making the data flow from the design side to the contractor for machine control and survey. “Our goal is to assist our contractor partners in working towards one common goal of quality project completion,” said Priscilla Benavides, Central Region Design Manager for NMDOT. Today, she is helping to deliver the state’s first e-construction project for the reconstruction of I-40. As part of the pilot program, NMDOT had Trimble perform a digital design review of the data with a focus on suitability for construction model purposes against the typical needs of a contractor for earthmoving, grading, and paving purposes. The study also identified potential improvements that could be made within the design model to reduce the time needed to bring the model into the contractor’s field technology. For instance, the study found that the NMDOT design model didn’t contain superelevation data, which is data needed by the contractor in order to build accurate paving mod- els. Bold leadership recognizes the role of technology to effectively streamline the delivery process. Another challenge faced was the discrepancy between design standards and field requirements for linework. 3D linework, for example, should be provided with defined intervals that meet the minimum require- ments to develop a purpose-built surface model. For instance, design data might provide stations every 100 feet, but the contractor has to re-build that model to every 20 feet to meet contractual and technical requirements for use of machine control. In order to meet the specifi- cations for a surface with 0.05’ accuracy, the model data provided has to be better than that by at least 50 percent, if not 75 percent, in order Colorado contractor Zak Dirt relied on drone data to track progress and share updates with the Colorado Department of Transportation for a recent highway improvement project.
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csengineermag.com
may 2021
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