Excavating of trenches true to profile especially in harder material always is a challenge for a construction company. If the material has to be blasting the result very often is an oversized profile with unstable walls.
Here WIRTGEN Surface Miners have proven their ability yo cut trenches true to profile.
To improve the watersupply for the city of Benghazi, Libya, a 50 km long pipeline shall be connected to a water reservior. In urbanic areas and some suburbs of Benghazi this pipeline trench has to be built in rock formations covered by hard caprock. The carbonate stone has a compressive strength of appr. 10 MPa and the caprock of 40 MPa.
The very tenacious material is very difficult to be loosened.
Due to expected damaged to nearby buildings, blasting was prohibited respectively possible only under restrictions. Therefore the responsible construction company decided to use WIRTGEN Surface Miners in this difficult 6.7 km long section.
WIRTGEN had to build a trench appr. 4.5 m in depth, width at the bottom 3.4 m. With a slope of 2:1 appr. 8 m width at the surface have been necessary.
The responible construction company purchased a WIRTGEN Surface Miner 2100 SM. This is a road milling machine specially reinforced and prepared for this purpose.
The close time schedule required immediate start of the job. So it was decided to start the first section using a commom WIRTGEN Milling Machine 2100 DC. After some modifucations and providing the machine with suitable cutting tools this machine started the job on March 29, 1993. On May 5, 1993 the first 665 m long section has been completed.
After checking the profile when reaching appr. 4.2 to 4.3 m depth, it was found out that width at the bottom was 5.4 to 5.6 m instead of the minimum of 3.4 m. That means that a much steeper sideslope has been achieved than expected.
This was a benefit since the starting width at the surface could be reduced and therefore the amount of material to be cut.
Depending on the hardness of material a cutting performance of 40 to 90 m3/h has been reached. So within 34 working days a volume of 18,800 m3 has been cut. The cut material has been loaded to trucks directly. The trucks transport the material to a dump.
This material will be used for filling purpose after laying the pipeline. Due to the small particle size reached during cutting, the material can be used directly for this purpose without any further processing.
In this case a construction company used the benefit offered by WIRTGEN Surface Miners. They were able to cut trenchs true to the required profile with stable and clean level bottom. Furthermore the cut material could be used for other purposes without any further processing.