Expando Articles

Tunnelling a horizontal shaft through Sydney Sandstone

John Rothwell Director of No Blast Pty Ltd - Monday, October 31, 2011

We are now involved in a small residential tunneling project in North Sydney. The owner is in his early 70s and knows that in the future the 38 steps from his gate to his door are going to become a really big obstacle. The project is to cut a tunnel through the rear of the garage under the front lawn and then under the existing lounge room, where a small elevator shaft will connect the vertical shaft to the horizontal tunnel under the front lawn. The project has been a hobby for the former mining engineer.

Due to the cost and time taken to excavate the first five meters of the tunnel we have been engaged to help. The challenge has been to fill horizontal and vertical holes using the chemical Expando. We initially used a grout pump to fill the horizontal holes but the cost of hiring was too expensive for this residential job so we came up with an alternative method.

We have been filling long skinny bags with the chemical Expando and forcing the bags into the horizontal holes using a PBC pipe and Timber ream it has had the same effect as if we had poured it into the holes from the top.

We are now far enough under the house that we can start cutting in the vertical shaft .Holes have been drilled up from the lower tunnel and as we remove the rock from the top we can simply drop it down the hole to be cleaned out through the garage. 

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There's No Such Thing As A Good Vibration

John Rothwell Director of No Blast Pty Ltd - Tuesday, September 20, 2011

Case Study At Liney Point

Expando at Liney Point Case Study

Difficult sites and issues with vibrations are now a thing of the past thanks to an innovative product that’s been tried and tested overseas now it’s finally come to Australia. Expando – a non explosive demolition agent, is suitable for difficult sites where vibrations and noise are an issue and those with a high concentration of rock or for confined spaces.

Expando, owned by a local Australian company, No Blast, is currently being used to excavate a site in Linley Point that will eventually become one of Sydney’s largest and most innovative homes. 

The development began with the demolition of two neighbouring waterfront homes that were situated on a steep precipice of rock descending to the waterline at the southern point of the bay. The terrain the houses were built on and the sheer size of the development meant the removal of a momentous amount of rock. Excavation has already been underway for nine weeks and there’s still another six weeks to go before it is cleared, leveled and ready for phase two. 

So with a project of this magnitude, where do you start? Stephen Johnson, owner of SJ Constructions, who has taken on the planning, design and development of the home, begins ‘For the first few weeks we went about the dig in the traditional way using an excavator but the noise and vibrations from the continuous thump of the excavator was affecting neighbouring properties so we stopped the dig and went about finding a less intrusive excavation method.’ 
‘When water freezes, it expands that’s why when water that collects in road cracks turns to ice in winter it enlarges those crevices into gaping potholes.’ I knew there had to be a man made solution out there that behaved in a similar way so I started a Google search and found a non explosive expansive mortar called ‘Expando’ from a local Australian supplier.’  

‘The owner of Expando, John Rothwell delivered the first load and demonstrated how to use it. It’s idiot proof really, easy to mix, non toxic so there’s no license requirement for careful handling and no OH&S issues.’ 

‘Because of the enormous scale of the project we wanted to make sure we had the best and most cost effective technique before we commenced, so we began experimenting with the size and spacing of the holes before we were satisfied we had the best method down pat.’
‘We start by drilling the holes and then we fill them at different times of the day so the rock cracks in sequence. We fill the holes at the face of the rock in the morning and work our way backward. The face cracks and falls, then the next level back goes and so on. We then use an excavator once a day for final removal offsite, this reduces the impact noise and vibrations have on the neighbours and allows us to continue working on the dig throughout the day.’ 

‘We use 20kgs of Expando per seven 1.6 metre holes, 38 millimeters in diameter – that’s 2.3 cubic metres of rock removed per 20kg box.’ 

Now you have discovered Expando, would you use it on other projects? ‘Definitely, it’s perfect for confined spaces such as drilling under a house, or whenever vibrations or noise is an issue. It’s also great having a local supplier that you can call upon. The site can only store a small amount of material so John makes regular trips to deliver more Expando’.  

So what will the development eventually look like? ‘We are still planning the finishing touches but eventually this will be a 3000sq metre home which comes complete with a ballroom, 20 seat home theatre, indoor / outdoor swimming pool, a bowling alley, 120,000 litre fish tank, and a badmington court. It will take two years to construct and we are aiming for a 7 star rating BASIX rating’. 

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