The AngloGold Ashanti Obuasi Mine project is located in the Ashanti region, approx. 280km north of Accra the capital of Ghana.

The Kakula mine circular shaft is to be used for the ventilation of the extension of the Obuasi underground gold mine.

The 5.5m diameter circular shaft was executed with piles with a max. depth of 37m. The embedment depth of the piles into the rock was between 0.5m and 1.5m.

Geology:

Lateritic sediment for the top 20m, then Reddish-brown greywacke, high to moderately weathered with fractured quartz into the fresh greywacke schist.

Fresh greywacke is up to 35Mpa

Scope of works:

• Guide wall for the secant pile wall
• 30 nos secant piles dia. 880 mm, 37 m deep for one circular ventilation shaft.
• 4 nos foundation piles dia. 1180 mm, 37 m deep for the support of the vertical drilling system
• 1 nos, center pile for the pilot hole drilling of the Raise bore rig, dia 1180mm,37 m deep.

Miscellaneous:

The center pile and support piles were installed using 1180/1060mm diameter drilling tools. The embedment depth into the rock length was varying depending on the in-situ geological ground conditions. And approx. 15m to 16m of temporary casing were installed during the drilling. The secant pile wall was executed as “hard / soft” pile wall with sufficient pile overcut to ensure the technical design requirements. In addition, the secondary piles had to be reinforced in their full length.

INFO

Construction Methods:           Secant pile wall

Construction Materials:          Concrete, steel

Main Equipment:                    BAUER BG 28

Construction Period:              Sept. 2019 - Nov 2019