Cut-and-Cover Trenching

Definition - What does Cut-and-Cover Trenching mean?

Cut-and-cover trenching is a form of open trench installation. It begins with a trench. Small projects may be completed entirely from the surface with a microtrencher. Larger projects may involve heavy equipment, such as a backhoe. Depending on the depth of the trench required by the project, cranes and backhoes may be lowered into the trench, which is finished as the work progresses to the required depth. When the trench is finished, it's backfilled.and the surface of the ground is restored to its original condition.

Trenchlesspedia explains Cut-and-Cover Trenching

Many cut-and-cover trenching projects can be as simple as digging a trench, dropping a length of pipe into the trench and backfilling the trench with the dirt removed from the trench. Other, more complex projects, such as the preparation of a tunnel or conduit beneath existing infrastructure, require significant planning. After the planning phase, cut-and-cover has six essential steps:

  1. Narrow retaining wall trenches are dug on each side of and as deep as the bottom of the planned excavation. These trenches are filled with bentonite mud until a permanent retaining wall material, such as reinforced concrete, can replace the mud.
  2. Excavation of the main trench between the retaining wall trenches begins. The depth of the initial excavation of the main trench is only deep enough to allow for the installation of steel struts between the retaining walls and the upper cover of the tunnel or conduit.
  3. A roof slab is installed over the trench. Depending on planning, decking that supports the surface over the roof slab may be installed as well. If a roof slab is installed, it will include an opening to allow digging machinery to be lowered into the trench. Additional struts may be added between the retaining walls as needed to support the walls while excavation continues.
  4. Excavation and the installation of supporting slabs continues until the base level of the trench is reached.
  5. The side walls of the trench are installed and the trench's slab base is put in place.
  6. The ground is restored to its original condition.


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