COLLARS AND LINERS
With over 20 years' experience in shaft construction and ancillary activities, Mancala is able to provide its clients with:
Geotechnical appraisal of the proposed shaft site;
Design and construction of surface infrastructure which can combine the requirements of both the raise boring activity and the final shaft use (e.g. fan, evasse or GAG installations);
Pre or post sinking in near surface lithologies using a variety of methods and
Non-entry shaft support using either sprayed fibrecrete or steel liners.
Over recent years Mancala has seen an increasing requirement for shaft support which incorporates speed of installation, structural certification and flexibility. As a consequence Mancala has adapted and improved the process of using galvanised steel liners as a non-entry method of ground control for vertical raise bored shafts.
The concept uses modular liner segments which are assembled as the installation is lowered into the shaft immediately following the raise boring activity. The method which can incorporate grouting of the shaft/liner annulus has been used on shafts up to 5.5m in diameter and in excess of 100m depth.
Off site fabrication and on site assembly during raise boring allows installation rates of up to 40 metres per day. Adaption of the liner design to incorporate ladderways for second egress or service lines are available.