Underground Construction

RIX’s Construction Teams are highly motivated and multi-skilled, which allows a variety of specialised tasks to be completed safely and economically by one contractor. We have successfully completed some very challenging concrete structures, often in very limited or difficult access areas. Examples include:


Excavation for a new hydro plant underground in Sydney’s North Head Sewerage treatment plant. Below a 60m deep shaft, RIX teams carried out staged excavation and ground support, including installing rock bolts, mesh, drainage and shotcrete to the roof and walls of a new cavern area. Work also required form up irregular walls, a new floor and support for the new plant, and the installation of all new flanges to the existing Sewer outlet.

CROSS CITY TUNNEL – Arch Form construction

Perhaps the most challenging of our construction projects was underground the arch forms in Sydney’s Cross-City Tunnel. The 4.8m high, 2.1km long tunnel has two lanes of traffic in both directions. This enables commuters to bypass 18 sets of traffic lights and other slow moving traffic in the CBD of Sydney. The self-propelled arch form for this tunnel was used to construct three 1m thick sections of reinforced concrete, each 50 meters long.

RIX’s Construction Team partnered with the client to devise a successful time saving methodology for installing the reinforcing steel bars required within the concrete structure. With the arch form safely and swiftly completed, our team was able to complete many other concreting, shotcreting, excavation, steel fabrication, drilling and rock bolting tasks during the following 18 months they remained on the project until its completion.

AIRPORT LINK TUNNEL BRISBANE – Limited access demolition

RIX employed specialised, staged demolition techniques including hydro demolition, rock drilling, hydraulic concrete splitting, concrete rope/saw cutting, hand jackhammering and robotic jackhammering to remove temporary 900mm diameter piles and overhead capping beams through the main tunnel and in limited access and air plenum areas. These dangerous works were safely completed by our expert team over a three-month period, working night and day without interruption to the adjacent tunnel construction teams.

Centre: One 50m section of three completed concrete arch forms.

Left: RIX’s specially designed, built and certified ‘Reo Cage Cradle,” which made the installation of the overhead reinforcement cages safely possible.

Right: The reinforcement cages held in place attached to the roof and sides of the excavated tunnel faces by chemical rock bolts, also installed by our crews. The arch form in the background on rails is about to be brought into place to form up the first 7m section, ready for pumping the concrete into place. The arch form is self-propelled on its own rails and allows passing traffic to continue along the confined tunnel while the arch form construction continues.