Response to Information Request - MCU12/0184

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Rock Description Explanation Sheet (2of 2)



COMMON DEFECTS IN                                            Diagram                       Map           Graphic Log DEFECT SHAPE                 TERMS
ROCK MASSES                                                                               Symbol          (Note 1)      Planar           The defect does not vary in

   Term           Definition                                                                                                             orientation


             A surface or crack across which the                                                                        Curved           The defect has a gradual
Parting
              rock has little or no tensile strength.                                     20                                             change in orientation
              Parallel or sub parallel to layering
             (eg bedding) or a planar anisotropy
                                                            @. ~Bedding \.9
                                                             .... ’..4  ~::il                                           Undulating       The defect has a wavy surface

             in the rock substance (eg,cleavage).
                                                                                           YCleaVage (Note2)
                                                                                                                        Stepped          The defect has one or more
             May be open or closed.
                                                                                                                                          well defined steps


Joint         A surface or crack across which the                                                                       Irregular        The defect has many sharp

              rock has little or no tensile strength.                                                                                     changes of orientation
              but which is not parallel or sub
              parallel to layering or planar
              anisotropy in the rock substance.
                                                           -_

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                                                                                               ,,\0           ~I       Note: The assessment of defect shape is partly
                                                                                                                              influenced by the scale of the observation.
                                                                                                            (Note 2)
              May be open or closed.
                                                                                                                       ROUGHNESS TERMS
                                                                                                                        Slickensided     Grooved or striated surface,
                                                                                                                                         usually polished
Sheared       Zone of rock substance with roughly
Zone
              parallel near planar, curved or                                                                           Polished         Shiny smooth surface
(Note 3)      undulating boundaries cut by
                                                                                                                        Smooth            Smooth to touch. Few or no
              closely spaced joints, sheared
              surfaces or other defects. Some of
              the defects are usually curved and
              intersect to divide the mass into
                                                                                            3y ’"
                                                                                                              fj        Rough
                                                                                                                                          surface irregularities


                                                                                                                                         Many small surface irregularities
              lenticular or wedge shaped blocks.                                                                                         (amplitudegenerally less than
                                                                                                                                         1 mm). Feels like fine to coarse
                                                                                                                                         sand paper.


Sheared       A near planar, curved or undulating                                              40
                                                                                                                        Very Rough       Many large surface
Surface
(Note 3)
              surface which is usually smooth,
              polished or slickensided.
                                                             df5                                y"
                                                                                                r
                                                                                                               I~~                       irregularities (amplitude
                                                                                                                                         generally more than 1 mm).
                                                                                                                                          Feels like, or coarser than very
                                                                                                                                         coarse sand paper.



Crushed       Seam with roughly parallel almost                                                                        COATING TERMS
Seam                                                                                                                    Clean             No visible coating
              planar boundaries, composed of                                          :
(Note 3)      disoriented, usually angular
              fragments of the host rock
              substance which may be more
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                                                                                                ~ I~                    Stained           No visible coating but
                                                                                                                                         surfaces are discoloured

              weathered than the host rock. The
                                                                                                                        Veneer            A visible coating of soil or
              seam has soil    properties.
                                                                                                                                          mineral, too thin to measure;
                                                                                                                                          may be patchy


              Seam of soil substance usually with                                                                       Coating           A visible coating up to 1 mm
Infilled
Seam          distinct roughly parallel boundaries                                                                                        thick. Thicker soil material is

              formed by the migration of soil into                                                                                        usually described using
              an open   cavity or joint, infilled
              seams less than 1 mm thick may be

              described as veneer or coating on
                                                                                                ~65             ~
                                                                                                                                          appropriate defect terms (eg,
                                                                                                                                          infilled seam). Thicker rock
                                                                                                                                          strength material is usually
                                                                                                                                          described as a vein.
              joint surface.

                                                                                                                       BLOCK SHAPE TERMS
                                                                                                                         Blocky           Approximately
Extremely     Seam of soil substance, often with                                                                                          equidimensional
                                                                                                    32
Weathered
              gradational boundaries. Formad by
Seam
              weathering of the rock substance in
              place.
                                                              ~ y "’-                                            ~
                                                                                                                        Tabular           Thickness much less than
                                                                                                                                          length or width
                                                                          Seam
                                                                                                                        Columnar          Height much greate than
                                                                                                                                          cross section




 Notes on Defects:
                                                                                                                                                                             ~
     1. Usually borehole logs show the true dip of defects and face sketches and sections the apparent dip.
                                                                                                                                                                             ::;
     2. Partings and joints are not usually shown on the graphic log unless considered significant.                                                                          ....

                                                                                                                                                                             o
     3. Sheared zones, sheared surfaces and crushed seams are faults in geological terms.
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