Appendix B - Geotechnical Investigation Report

Classification of Material Weathering
 Term                                              Abbreviation           Definition

                                                                          Material is weathered to such an extent that it has soil properties. Mass
 Residual Soil                                             RS             structure and material texture and fabric of original rock are no longer visible,
                                                                          but the soil has not been significantly transported.

                                                                          Material is weathered to such an extent that it has soil properties. Mass
 Extremely Weathered                                       XW
                                                                          structure and material texture and fabric of original rock are still visible.
                                                                          The whole of the rock material is discoloured, usually by iron staining or
                                                                          bleaching to the extent that the colour of the original rock is not recognisable.
 Highly Weathered                                  HW                     Rock strength is significantly changed by weathering. Some primary minerals
                                  Distinctly                              have weathered to clay minerals. Porosity may be increased by leaching, or
                                 Weathered                      DW        may be decreased due to deposition of weathering products in pores.
                                  (Note 1)
                                                                          The whole of the rock material is discoloured, usually by iron staining or
 Moderately Weathered                             MW                      bleaching to the extent that the colour of the original rock is not recognisable,
                                                                          but shows little or no change of strength from fresh rock.
                                                                          Rock is partially discoloured with staining or bleaching along joints but shows
 Slightly Weathered                                        SW
                                                                          little or no change of strength from fresh rock.

 Fresh                                                     FR             Rock shows no sign of decomposition of individual minerals or colour changes.

NOTE 1: The term ‘Distinctly Weathered’ is used where it is not practicable to distinguish between ‘Highly Weathered’ and ‘Moderately Weathered’ rock.
‘Distinctly Weathered’ is defined as follows: ‘Rock strength usually changed by weathering. The rock may be highly discoloured, usually by iron staining.
Porosity may be increased by leaching, or may be decreased due to deposition of weathering products in pores’. There is some change in rock strength.




Rock Material Strength Classification
                                                                                                    Guide to Strength

                                              Uniaxial              Point Load
                                           Compressive            Strength Index
 Term                  Abbreviation       Strength (MPa)            Is(50) (MPa)        Field Assessment

 Very Low                   VL                 0.6 to 2              0.03 to 0.1        Material crumbles under firm blows with sharp end of pick;
 Strength                                                                               can be peeled with knife; too hard to cut a triaxial sample by
                                                                                        hand. Pieces up to 30mm thick can be broken by finger
                                                                                        pressure.

 Low Strength                L                  2 to 6               0.1 to 0.3         Easily scored with a knife; indentations 1mm to 3mm show
                                                                                        in the specimen with firm blows of the pick point; has dull
                                                                                        sound under hammer. A piece of core 150mm long by 50mm
                                                                                        diameter may be broken by hand. Sharp edges of core may
                                                                                        be friable and break during handling.
 Medium                     M                   6 to 20               0.3 to 1          Scored with a knife; a piece of core 150mm long by 50mm
 Strength                                                                               diameter can be broken by hand with difficulty.

 High Strength               H                 20 to 60                1 to 3           A piece of core 150mm long by 50mm diameter cannot be
                                                                                        broken by hand but can be broken by a pick with a single
                                                                                        firm blow; rock rings under hammer.

 Very High                  VH                 60 to 200              3 to 10           Hand specimen breaks with pick after more than one blow;
 Strength                                                                               rock rings under hammer.
 Extremely                  EH                  > 200                     > 10          Specimen requires many blows with geological pick to break
 High Strength                                                                          through intact material; rock rings under hammer.




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