Diavik Diamond Mine A21 Project

North West Territories, Canada

The Diavik mine is operated by Diavik Diamond Mines Inc., a member of the Rio Tinto Group, and is located approximately 220 kilometers south of the Arctic Circle and 300 kilometers by air from Yellowknife, the territorial capital.

A deep cut-off wall was required for the 2.2 km perimeter dike so that the fourth kimberlite pipe, designated A21 and located under the waters of Lac de Gras, can be open-pit mined. A combination of different foundation engineering techniques was required to construct the proposed cut-off wall structure safely, efficiently, and within environmental regulatory limits.

The works on the cut-off wall were completed with jet grouting (pre-drilling and jetting) to safely close the gap between the bottom of the already installed CSM element and the installed lower grout curtain. Quality control provisions included standard material testing and verification drilling to prove the quality and integrity of the installed cut-off wall. The latter one was also surveyed and as-built drawings were produced to provide the necessary documentation and proof to our client. During the subsequent dewatering process, various survey systems and geological instrumentation are in place to monitor the status of the dewatering and the dike structure itself. These allow the client not only to have important live information such as the in-pond water level, the amount of water pumped, wall inclination and defl ection but also provides information on the sealing effect of the installed cut-off wall. In this regard, the feedback provided by the client was very positive.