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Geotechnical holes were drilled at the box cut and decline locations to investigate the soil and rock characteristics. The program included geotechnical core logging and laboratory test samples including UCS, Triaxial Compressive Strength, Brazilian ITS, elastic modulus measurements, and Poisson Ratio measurements.

The following box cut slope angles were used with a factor of safety between 1.5 and 1.8.

• Central and North box cut: highwall height of 28.0 m and slope inclination of 63°.

The following design was used for the bench face angles and bench dimensions for the Central and North box cuts.

• The bench face angle in loose overburden is 31° from horizontal, with a maximum 4.0 m bench H and a 5.0 m bench W.

• The bench face angle in completely weathered sandstone is 45° from horizontal, with a maximum 7.0 m bench H and a 5.0 m bench W.

• The bench face angle in highly weathered sandstone is 55° from horizontal, with a maximum 7.0 m bench H and a 5.0 m bench W.

• The bench face angle in competent sandstone is 63° from horizontal, with a maximum 10 m bench H and a minimum 5.0 m bench W.

Waterberg Technical Report

The recommended Central and North Complex decline box cut slope configuration is shown in Figure 16-24.