Microtunnelling is an efficient and environmentally friendly alternative to open-trench construction. TPMD operates a range of microtunnelling Tunnel Boring Machines (TBMs), which are able to work in even the most challenging of ground conditions.
This trenchless technique offers precise line and level installations in various ground conditions including rock.
Most of the functions of the microtunnelling operation are computer controlled or assisted. As such the workforce does not routinely work in the tunnel. It is accurate to industry standard tolerances (British Tunnelling Society) and thus is suitable for gravity sewer installations. The machines can be operated from either shafts or cofferdams. Microtunnelling is particularly suited to the urban environment where it minimises disruption to businesses, residents and traffic.
The majority of microtunnelling work is carried out using slurry TBMs . These offer the ability to work below the water table, using the slurry as a transport medium for the excavation arisings and to balance the groundwater pressure. Excavated material is separated from the liquid by a specialised plant situated at ground level. The liquid is then recycled, being sent back to the TBM and forming a closed loop system. This method of excavation also enables construction of pipelines within challenging ground conditions without any type of pre-treatment or ground water control. This type of TBM can also be configured to work in rock.
Another of the advantages provided by microtunnelling is the minimal ground movement caused during installation.