The Southern African Institute of Mining and Metallurgy (SAIMM) Johannesburg branch held its monthly technical presentation at Worley Parsons in Johannesburg last Thursday, 19th of January 2017.

SAIMM Johannesburg branch chairperson John Arthur Luckmann formally introduced presentation speaker Lawrence Schultz from the Redpath Mining (Pty) Ltd to the audience. John in few words explained purpose of presentation entitled “ Ghaghoo Decline Tunneling Through Sand ” and importance of the “Ghaghoo decline tunnelling through sand” for mining and metallurgy professionals working in Southern African mining industry.

The presenter stated that the GEM Diamonds who wholly owns the Ghaghoo mine commissioned Redpath Mining (South Africa) in June 2011 to find an innovative way to develop a tunnel at -8° to the horizontal through poorly consolidated ground in order to gain access to the ore body at their Ghaghoo mining operation.

Lawrence depicted holistically how ore body does not manifest itself on surface but is overlain by 85 metres of Kalahari Desert sand and layers of calcrete. Speaker revealed to the audience that the project is situated in the Ghaghoo mine which is located in the South-East portion of the Central Kalahari Game Reserve 325 km North-West of Gaborone, Botswana.

Mr Schultz indicated that the decline tunnelling method utilising an Open Face Tunnel Shield (OFTS) was selected to execute the project, which Redpath Mining management believe to be a ‘World First’. Speaker lucidly described the challenges encountered and the steps taken to mitigate the risks, just to explain daily conditions he gave an example like temperature can onerously impact life of humans on project site. For example the miners working on the site of project can be exposed to temperature of 49°C at lunchtime and to minus 4°C during the night.

Lawrence revealed that the rapid changes in temperature created great difficulties for all employees being working on project site - practically those workers could not properly sleep nor efficiently work in such high temperature. Lawrence also expanded on challenge in dealing with safety aspects particularly with unsafe ground particularly when intersecting the thick calcrete layer in the tunnel, alternative means of excavation were required, as the calcrete had a UCS in excess of 180Mpa.The impact breakers had to be used to break up the calcrete in order to load such onto the belt. The vibration from the impact breakers caused movement of the sand and increased the span above the OFTS to the face all of these requirements posed great safety risk.

After presentation was completed several questions from the floor were posed to the presenter by the mining professionals’ who were interested in the methodology used to deal with such harsh conditions at the project side. Following session of questions the presentation attendees were invited to the bar area for cocktails and drinks kindly sponsored by the Redpath Ming (Pty) Ltd where more questions were proffered  to Lawrence from other professionals who missed an opportunity during questions session. Please note the photos enclosed below are taken directly from the Lawrence Schultz presentation slides.