Microtrenching is a minimally invasive and less time consuming installation method for underground ducts that is best suited for high traffic areas especially under a highly compact material like a concrete or asphalt roadway, curb, or sidewalk. Microtrenching has a low environmental impact and offers minimal disruption to traffic.
With microtrenching, a relatively narrow and shallow trench is excavated using a special trenching machine with a large saw blade capable of cutting through concrete and asphalt.
The width of the trench will only need to be a few millimeters wider than the maximum width of the duct. Keep in mind that all ducts have a slight tolerance (+/-) from the listed diameter, so plan on using the maximum tolerance and then choosing the next size up when selecting a blade.
The typical depth of a micro trench is only 10cm because of the high strength and temperature regulating properties of the trench wall and fill material, a deeper drench is not needed. Traditional round microduct assemblies will easily fit into a 10cm microtrench with room to spare for fill material, however flat or link style ducts may require a deeper trench up to 25cm. A good rule of thumb for these styles of duct is to take the longest dimension and add 8cm.
With the microduct in place make sure that no ducts are kinked or bent by blowing a small sponge or BB through each duct to make sure it comes out the other side so that any issues can be addressed before the trench is sealed.
With the duct integrity verified, it’s time to re-seal the trench hot polymer, elasto-polymer or grout to restore the surface. Best practices call for a rubber strip placed between the duct and the fill material for protection in the event that the trench ever needs to be re-entered.