Application of True 3D Data in Expressway

Under the background of the new normal of rapid economic development, the reconstruction and expansion of existing expressways is gradually becoming one of the focuses in the field of infrastructure construction. Because the expressway reconstruction and expansion will be affected by the existing traffic flow, safety, traffic security, progress and other factors need to be considered, so there are high requirements for construction technology and management level.

Tilt photography technology of UAV is a technology that uses UAV to carry one or more sensors to collect images from vertical and oblique directions and angles to obtain ground information. Through data acquisition and post-processing, a high-precision three-dimensional model of the ground scene can be obtained, which has the characteristics of flexibility, low cost and high efficiency. At present, tilt photography technology has benefited from the development of computer and UAV technology and has been widely used in various industries. Practical research has been carried out, including highway geological disaster investigation, highway survey and design, urban planning, urban three-dimensional modeling, open-pit mine engineering calculation, mine monitoring and so on, and rich research results have been obtained in three-dimensional modeling and precision analysis of tilt photography.

Taking an expressway expansion project in Xichang as an example, the landform units along the line gradually transition from plain to mountain, and there are many high-filling and deep-digging sites. The route widening scheme is complicated, the traffic pressure is high, and the construction is difficult. According to the characteristics of the above-mentioned projects, the UAV tilt photography technology is applied in the construction.

Excavation of earth and stone for high filling and deep excavation subgrade is one of the important construction contents of reconstruction and expansion project. Because the existing road traffic cannot be interrupted during the construction process, the existing slope is steep, and it is difficult to measure, and it is difficult to collect local measured elevation points, resulting in unsatisfactory measurement results and large error in earthwork calculation.

Through tilt photography technology, the current ground information of the work site area can be collected quickly and flexibly. After reconstructing the real model, the total earthwork volume, monthly earthwork excavation volume and earthwork proportion data can be calculated.

After calculation, the plane median error and elevation median error of directional points and inspection points in the flight area meet the national standard 1:500. Through the three-dimensional data of the real scene, the earthwork can be calculated more efficiently and accurately.

High-precision real-life models are obtained by close-range photography of unmanned aerial vehicles, slope and important features are monitored regularly, and deformation and overall trend are obtained by comparing the data of multiple real-life models. It is convenient for maintenance personnel to make treatment plans as soon as possible to avoid major safety accidents.

Using UAV to collect oblique photographic data on the construction status of high fill and deep excavation site at a certain time node, and intuitively obtain information such as construction progress, standardization of temporary protection, number of mechanical personnel involved, and timely protection construction through aerial photos and real-life models, which is a "blind spot" that is prone to problems and difficult to effectively manage in traditional construction management.

Taking a construction site in the project as an example, the ground real-life model from June to September can be reconstructed through drone tilt photography, and the monthly construction progress can be intuitively seen. Through the calculation of earthwork volume, we can know the total excavation volume and the earthwork volume that has not been cleared in time every month, which reflects the organization and investment of construction machinery. Calculate the cumulative excavation amount and get the construction progress. In addition, there are still problems such as untimely protective measures and irregular temporary protection in this site. In view of these problems, the rectification measures are put forward, and the periodic digital construction records are finally formed by combining the three-dimensional real-life model, which effectively reduces the construction safety risks and improves the engineering quality.

In the reconstruction and expansion project, traffic diversion is a difficult point. In this project, an auxiliary scheme is designed for the improvement of traffic diversion in the beam-erecting construction of the reconstruction and expansion of the unilateral framing bridge. Through oblique photography technology, the traffic induced transformation area is modeled, and timely DEM, DOM and DSM data are obtained, which provides rich and accurate basic data for the formulation of traffic induced transformation scheme. In addition, the traffic flow in the survey area can be recorded and collected by drones, which provides data support for the traffic situation calculation before and after the traffic guidance reform. On the one hand, the real-life model obtained from oblique photography three-dimensional reconstruction increases the rationality and readability of the design scheme of traffic induced transformation, and at the same time, it also enables experts or decision makers to have a better grasp of the scheme and make judgments faster.

By combining CAD design data with three-dimensional model, designers can more clearly and intuitively understand the current situation of the site geographical environment, and construction managers can more clearly understand the progress of the site construction work.

It is more convenient and intuitive to report the project work and show the design results. Practice the concept of "clear water and green mountains are priceless", promote the combination of human beings and the ecological environment, and reduce the damage to the ecological environment.