At the heavy-duty end of the thin liners is the company’s Tunnel Guard liner that has made the transition from hard-rock to coal while the Castonite liner offers a lower strength product.

TSLs are typically applied at a thickness of 1/8in to 1/4in, compared to traditional shotcrete which is applied at a thickness of 1in to 3in, resulting in materials savings of over 90%.

There is less wasted through rebound. For instance; dry shotcrete has a rebound of between 20% and 40% and wet shotcrete between 10% and 20%. Thin Support Liners have a rebound of less than 2%.

TSL’s can be used in a range of applications such as support between rock anchors; replacing mesh/screen; reinforcing pillars; assisting with coal longwall change-overs (moves and set-ups); ventilation seals and gas ingress (from the rock).

Used mostly in hard rock applications, Tunnel Guard was introduced in 2002 into a South African gold mine as a cost effective alternative to shotcrete.

Tunnel Guard is a two component product, containing a cementitious powder with fibers and a liquid polymer. One advantage is a significant reduction in the amount of materials handled compared with other liners such as shotcrete.

Tunnelguard has become one of Strata Products’ largest selling thin support liners with large sales in South Africa, a growing market in Australia and a new test market in North America. Underground testing in the US was recently completed.

Tunnel Guard has a bond strength of +4000 psi and a tensile strength of 360psi. Described as being similar to gunnite, the product is however, said to be around ten times more effective.

Tunnel Guard is being offered fully applied by Strata Products subsidiary, Strata Mine Services in the U.S. market.

Another recently developed TSL product is Castonite, a weatherproofing product described as reactive. This means it reacts quickly and sets faster than other similar products, and is rigid, not flexible. It is suitable for applications where structural strength is not required.

The product was used at a new coal mine in the US to stop weathering and provide support in the area around the bottom of the new up-cast shaft where the ventilation velocity was high and the air humid. Clearly this could cause the coal to weather and collapse over time requiring rehabilitation that would be disruptive and costly.

The Castonite effectively sealed the coal and offered some confinement to the rib pillars and roof in the various nearby excavations.

It was also used to stop weathering and improve illumination in a wash bay and adjacent area that was part of an underground workshop complex. While Castonite’s properties are similar to weather proofing sealants, it develops full properties in a matter of seconds. Castonite has a bond strength of 260psi and a tensile strength of 500psi.

Castonite has been sold to approximately six different operations in the US.