At worst, petrographic analysis is purely descriptive and is seen simply as a means of assigning a name to a rock.  Petrographic reports, while often excellent in terms of petrological content, may lack the engineering content required by tunnelling machine specifiers.

To correct this situation, SubTerra Engineering is pleased to announce a new service in Engineering Petrography.  In addition to a normal petrographic description, our reports will include some or all of the following, as appropriate;

• Modal Analysis to quantify all significantly abrasive minerals in the rock

• Petrofabric Analysis to assess grain-size, angularity and microstructure

• Identification of Critical Fabrics such as grain-suturing

• Rosiwal Hardness Analysis

• Calculation of Schimazek's Wear Factor (F)

• Calculation of the Hardness Contrast between the rock and machine components

• Assessment of Cementation Coefficient

The assessment of rock abrasivity during a project is also important, especially where the envisaged life of cutting tools is not being realised.  As a result of abrasivity testing revised estimations of tool efficiency and consumption can be made.  When test results are incorporated into our TBM and Roadheader prediction models, progress rates and expected delays can be estimated.  This enables the direct calculation not only of consumables but delay due to reduced production. 

SubTerra Engineering can manage all of your rock testing requirements throughout the duration of a project, ensuring that representative samples are obtained and tested in accordance with internationally recognised standards.

For further information on how petrographic analysis can help in the selection of excavation equipment,  and control the cost of consumables, please contact us.