The expansion of the busy A1 motorway is one of the most urgent motorway expansion projects in Germany. In order to solve the challenges of the complex terrain and plan specifications intelligently and economically, ARGE A1 Hamburg - Bremen relies on the use of advanced technology. The new technology of profile milling with the help of a 3D machine control from Trimble makes a significant contribution to cost-effectiveness and time savings.

Achim Hübschmann, floor coordinator of ARGE A1 explains the milling plan

The extension of the heavily used A1 is one of four pilot projects of the federal government for the expansion of motorways (A models). These A-model projects are long-term partnerships between the public and private sectors to provide public infrastructure. On behalf of the public sector, private companies provide and finance a wide range of services for the expansion of a route as well as its operation and maintenance within the framework of a 30-year concession contract. In return, they receive a monthly share of the truck toll that applies to the motorway section. The investment volume for the expansion of the A1 is approx. 650 million euros.

The contractor is the private project company A1 mobil. The shareholders of A1 mobil are Bilfinger Berger Project Investments GmbH, the British infrastructure developer and operator John Laing Infrastructure Ltd. as well as the Johann Bunte Bauunternehmung GmbH Co. KG, which in turn has commissioned the A1 Hamburg-Bremen consortium with the planning and construction work as a subcontractor. The Federal Republic of Germany, represented by the State of Lower Saxony, is the client of the concession project.

ABS machine operator Sven Ungnade controls the milling result and was even able to take over the stationing himself because of the user-friendliness of the Trimble SPS930 universal total station.

The concession project “Operator model federal motorway A1 (A model) Hamburg - Bremen” started in August 2008. As part of this project, the A1 motorway between the Buchholzer Dreieck and the Bremer Kreuz will be expanded from currently four to six lanes in the future. The completion of the expansion work is scheduled for the end of December 2012.

Sven Ungnade stationed the SPS930 universal total station.

For the expansion, the 73-kilometer route was divided into 26 construction sections, all of which are approximately six kilometers long. The expansion of neighboring sections is staggered in time. There is always a construction site-free zone at least six kilometers long between two sections that are under construction at the same time. This avoids long construction sites and increases road safety.

Various specifications and conditions (noise protection, existing structures, etc.) in the plan approval procedure make it necessary to create the new roadway using a combination of asphalt and concrete. The wear layer of the carriageway at a height of 4 cm must be removed over the entire route. In addition, a gradient optimization must be carried out on the entire route and the cross-section must be adapted to the regulations with a gradient of at least 2.5%. In-depth soil investigations showed, however, that large parts of the existing substructure are still stable and can remain.

The question that ARGE A1 now asked itself was: do we completely dismantle the road and reinstall it, or do we use the parts of the substructure that are still stable? Is it economically and technically feasible to continue using the stable substructure?

ABS Managing Director Wolfgang Schmidt-Legahn is proud of his team, which flawlessly converts the complicated milling plan into reality with the new 3D control from Trimble.

“The decision was made in favor of reuse in order to save expensive, new material and to remove less old material that has to be recycled and reused or stored. The time saved through less dismantling and installation work was of course also an important factor, ”said ARGE A1 floor coordinator Achim Hübschmann.

The challenge that had to be solved in order to make this decision a reality was to flexibly adapt the milling depth to the various subsurface conditions and profile changes. The prerequisite for this was the calculation of a detailed milling plan. The ARGE A1 surveying team went straight after the traffic was reassigned and completely re-measured the roadway with 3 points in a 10 meter grid. The measured points were read into CAD software and output in Microsoft Excel. The file shows the milling depths of the entire carriageway in five centimeter steps in numbers and colors.

The next question was how do we make sure that the milling machine realizes the milling plan exactly? Do we do it in the conventional way by spraying the values ​​on the route every 5 meters? The measurement effort would be gigantic and the manual transfer of the values ​​to the milling machine would be fraught with sources of error. A more intelligent solution was therefore sought.

Profile milling with the Trimble 3D control when expanding the A1.

This is where ABS Asphalt Beton Service GmbH Co. KG came into play as a subcontractor for the milling work. Mr. Wolfgang Schmidt-Legahn, managing director of ABS decided to equip his Wirtgen W2100 milling machine with an automatic, three-dimensional control. With the help of this advanced technology, the design data is transferred from the office directly to the computer on board the milling machine, so that the two machine operators can automatically implement the complex milling plan without strings, stakes or road markings. In order to test the new technology in practice, Schmidt-Legahn decided to first use the system on a rental basis. Systems from three manufacturers were tested. Only the Trimble® GCS900 3D control with SPS930 universal total station could meet the high expectations.

With the selected Trimble solution, the calculation and transmission of the actual data is carried out by the SPS930 universal total station. The UTS automatically tracks a target attached to the milling drum, continuously measures the actual position of the target and transmits this data to the CB430 computer, which is attached to the outside of the milling machine. The computer compares the actual data with the data from the milling plan, calculates the necessary milling depth and controls the hydraulic valves accordingly so that the milling process takes place automatically according to the milling plan that has been read. The job of the machine operator in the cabin is to control the direction, the second machine operator controls the milling result with another measuring station. Markings on the road are therefore completely unnecessary. The milling machine works exactly according to the specified milling plan. The milling speed with this new technology is 15 meters per minute - and that with millimeter precision. The milling performance per day is on average 5000-6500 m2 with a milling depth fluctuating between 4 and 30 cm.

Thanks to the professional instruction of the two machine operators Mark Reinecke and Sven Ungnade by the local Trimble sales partner Eilers Droste, the new technology worked wonderfully from the start. Hans-Hermann Roblick, the responsible construction manager at ABS, describes it aptly with a single sentence: “How simple it is with Trimble.” He adds: “The milling machine works automatically, we only check the result, and that's in the Tolerance range of +/- 5mm. "

The machine operator Sven Ungnade continuously checks the milling depth with the measuring system and confirms the accuracy. He is particularly pleased with the ease of use of the Trimble system. “Right from the start, I even took on the stationing of the total stations myself, and it runs smoothly. Because the milling result is checked every day by an independent surveyor. "

ARGE A1 Hamburg-Bremen and the subcontractor ABS agree that profile milling with an automatic 3D control from Trimble is the most economical, fastest, simplest and safest solution for realizing different milling depths in transverse and longitudinal profiles according to plan, so that the existing stable Substructure of the road can be obtained. The cost of calculating the milling plan and the acquisition of the 3D control is quickly amortized by saving approx. 7000 tons of compensation material per construction phase, which is calculated at a price of 50 € per ton for material including installation.

A project of this size, which is carried out under difficult conditions, benefits enormously from the use of the most modern construction technology.