Response to Information Request - MCU12/0184

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       coffey.)

       Rock Description Explanation Sheet (1 of 2)


       The descriptive terms used by Coffey are given below. They are broadly consistent with Australian Standard AS1726-1993.

       DEFINITIONS:         Rock substance, defect and mass are defined as follows:

        Rock Substance In engineering terms roch substance is any naturally occurring aggregate of minerals and organic material which cannot be
                       disintegrated or remoulded by hand in air or water. Other material is described using soil descriptive terms. Effectively
                            homogenous material, may be isotropic or anisotropic.
        Defect              Discontinuity or break in the continuity of a substance or substances.
        Mass                Any body of material which is not effectively homogeneous. It can consist of two or more substances without defects, or one or
                            more substances with one or more defects.



       SUBSTANCE DESCRIPTIVE TERMS:                                                           ROCK SUBSTANCE STRENGTH TERMS

       ROCK NAME            Simple rock names are used rather than precise                    Term        Abbrev-     Point Load           Field Guide
                            geological classification.                                                    iation      Index, Is50
                                                                                                                         (Mpa)

       PARTICLE SIZE        Grain size tenns for sandstone are:
        Coarse grained      Mainly 0.6mm to 2mm
                                                                                              Very Low       VL      Less than 0.1      Material crumbles under firm
        Medium grained      Mainly O.2mm to 0.6mm
                                                                                                                                        blows with sharp end of pick;
        Fine grained        Mainly O.06mm Oust visible) to 0.2mm
                                                                                                                                        can be peeled with a knife;
                                                                                                                                        pieces up to 30mm thick can
       FABRIC               Terms for layering of penetrative fabric (eg.bedding,                                                       be broken by finger pressure.
                                                               .




                            cleavage etc. )are:

        Massive             No layering or penetrative fabric.
                                                                                              Low             L         0.1 to 0.3      Easily scored with a knife;
        Indistinct          I...ayeIing or fabricjust visible. little effect on properties.                                             indentations 1 mm to 3mm
                                                                                                                                        show with firm bows of a
        Distinct            Layering or fabric is easily visible. Rock breaks more                                                      pick point; has a dull sound
                            easily parallel to layering of fabric.                                                                      under hammer. Pieces of
                                                                                                                                        core 150mm     long by 50mm
       CLASSIFICATION OF WEATHERING PRODUCTS                                                                                            diameter may be broken by

         Term        Abbreviation                        Definition                                                                     hand. Sharp edges of core

                                                                                                                                        may be friable and break
        Residual         RS           Soil derived from the weathering of rock; the                                                     during handling.
        Soil                          mass structure and substance fabric are no

                                     longer evident; there is a large change in
                                     volume but the soil has not been significantly           Medium          M         0.3to 1.0       Readily scored with a knife; a
                                     transported.                                                                                       piece of core 150mm long by
                                                                                                                                        50mm diameter can be
                         XW           Material is weathered to such an extent that it                                                   broken by hand with difficulty.
        Extremely
        Weathered                    has soil properties, ie, it either disintegrates or
        Material                     can be remoulded in water. Original rock fabric

                                     still visible.                                           High            H           1 to 3        A piece of core 150mm long
                                                                                                                                        by 50mm can not be broken
        Highly           HW           Rock strength is changed by weathering. The                                                       by hand but can be broken
        Weathered                     whole of the rock substance is discoloured,                                                       by a pick with a single firm
                                      usually by iron staining or bleaching to the                                                      blow; rock rings under
        Rock
                                      extent that the colour of the original rock is not                                                hammer.

                                     recognisable. Some minerals are decomposed
                                     to clay minerals. Porosity may be increased by
                                                                                              Very High VH               3to 10         Hand specimen breaks after
                                     leaching or may be decreased due to the
                                                                                                                                        more than one blow of a
                                     deposition of minerals in pores.
                                                                                                                                        pick; rock rings under
                         MW          The whole of the rock substance is discoloured,                                                    hammer.
        Moderately
        Weathered                    usually by iron staining or bleaching, to the
        Rock                          extent that the colour of the fresh rock is no
                                                                                              Extremely EH            More than 10 Specimen requires many
                                      longer recognisable.
                                                                                              High                                      blows with geological pick to

        Slightly         SW           Rock substance affected by weathering to the                                                      break; rock rings under
                                      extent that partial staining or partial                                                           hammer.
        Weathered
        Rock                          discolouration of the rock substance (usually by
                                      limonite) has taken place. The colour and
                                      texture of the fresh rock is recognisable;
                                      strength properties are essentially those of the        Notes on Rock Substance Strength:
                                     fresh rock substance.                                    1. In anisotropic rocks the field guide to strength applies to the strength
                                                                                                perpendicular to the anisotropy. High strength anisotropic rocks may
        Fresh Rock        FR          Rock substance unaffected by weathering.                  break readily parallel to the planar anisotropy.
                                                                                              2. The term ’extremely low" is not used as a rock substance strength
       Notes on Weathering:                                                                     term. While the term is used in AS1726-1993, the field guide therein
       1. AS1726 suggests the term "Distinctly Weathered" (DW)to cover the range of              makes it clear that materials in that strength range are soils in
         substance weathering conditions between XW and Sw. For projects where it is             engineering terms.
          not practical to delineate between HW and MW or it is judged that there is no       3. The unconfined compressive strength for isotropic rocks (and

          advantage in making such a distinction. DW may be used with the definition             anisotropic rocks which fall across the planar anisotropy) is typically
          given in AS1726.                                                                       10 to 25 times the point load index (ls50). The ratio may vary for
       2. Where physical and chemical changes were caused by hot gasses and liquids              different rock types. Lower strength rocks often have lower ratios
         associated with igneous rocks, the term ’altered" may be substituted for                than higher strength rocks.

         ’weathering’ to give the abbreviations XA, HA, MA, SA and DA.