ENABLING SURFACE STABILISATON
BETWEEN ROCK BOLTS
Rock bolts are used to stabilise rock excavations in mining, tunneling and civil engineering operations such as concrete dam reinforcements, road cuts and bridge abutments. A critical element to excavations of this kind is the surface stabilisation between rock bolts to hold unstable or fractured rock masses together. This stability is achieved by using CMA non-producer member Technicrete’s Thin Skin Liner (TSL), a modified, polymer-based, fibre-reinforced, thin sprayed liner. Wherever precast stabilisation is not an option, the easyto-use kits can be used. They consist of a special liquid which is a blend of powder chemicals and graded silica sand with polypropylene fibres. The contents of the kit are simply emptied into a suitable mixer or pump with a positive displacement-type pump arrangement, then sprayed onto the cleaned rock face and into open joints and fissures covering all surfaces needing to be supported. Maximum penetration is obtained by spraying directly into any open joints. Compressed air is added at the nozzle to spray the fresh mix, while a 7m delivery hose provides the best effect. The bonding properties of Technicrete TSL bind the rock faces inside the fissures to provide a more stabilised rock surface and minimise the unravelling of rock mass. The tensile properties of Technicrete TSL spanning across joints and cracks resist shear and direct tensile movement, adding to back pressure in the rock mass for added stabilisation. In low-stress environments, the bonding and tensile strengths assist in preventing block movements while keeping the rock “beam” intact. Benefits of Technicrete TSL • It can be rapidly deployed in underground environments, as equipment is easy to handle in confined areas. • The sprayed-on support is quick to mix and hardens rapidly. • It can be used as rock support for areal stabilisation of rock surfaces. • It stabilises friable ground. • It seals sensitive rock types such as smectite, shale and soft shales against water and humidity. • It prevents unravelling of fractured ground by holding key blocks in place. • It seals dams, sumps and drains. • It provides temporary areal support prior to overcoating with shotcrete, which has a strong adhesion to Technicrete TSL. • It can be safely applied to damp substrates (but not onto surfaces covered in running water). Specifications Technicrete TSL has a shear strength of >0,25MPa after 24 hours, a tensile strength of >2MPa after seven days, an ultimate bond of shear 1,0MPa and a bond strength of 1,0Mpa.
PRECAST | ISSUE TWO | 2021
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