Client name: BHP Billiton

Duration: 2013

Location: Mining Area C, Pilbara, Western Australia, Australia

Coffey conducted a slope stability analysis which resulted in slope angles between 8 and 10° steeper than originally proposed. We used strength models which incorporated upgraded bedding plane strengths through the assessment of small scale waviness from down-hole data. 


Mining Area C is one of BHP Billiton‘s major iron ore mining hubs in Western Australia.

They were looking for industry best practice to be applied in slope design to a series of deposits in Mining Area C. On another of their projects, Coffey had applied an innovative methodology for incorporating small scale waviness within design shear strengths.


Interpretation of optical and acoustic televiewer surveys was undertaken in order to ascertain the degree of small scale waviness within the deposit.

Once quantified, the waviness upgrade value was incorporated into the defect plane shear strength model to provide upgraded design strengths. These were incorporated into the slope stability modelling within anisotropic strength models.


A series of analyses were undertaken to provide a slope design that met both deterministic and probabilistic acceptance criteria.

Our revised slope design resulted in increased slope angles in the order of 8 to 10° over a 150m high slope.

With a strike of over a kilometre, this resulted in the potential for increased ore recovery and significant savings in terms of reduced waste movement, and the associated costs.