Reference Document - MCU24/0002 [As Published]

                              www.awgeotechnics.com.au



                                                                   SITE SPECIFIC NOTES

                            We have classified the site as Class P in accordance with AS2870-2011.
                            Abnormal Moisture Conditions
                            Using the guidelines in AS 2870-2011 we have derived a normal ys in excess of 20 mm (refer front
                            page), which is a measure of the potential of the strata to change volume with changes in soil moisture
                            (generated by seasonal moisture variations).
                            During the site visit, we also noted features (see front page) within the zone of influence of the
                            proposed building footprint, which are specifically mentioned in Clause 1.3.3 of AS 2870-2011 as
                            contributing to abnormal moisture conditions (AMC). Clause 2.1.2 specifically notes that AMC sites
                            require a “P” classification and AS 2870-2011 offers the following advice to the footing designer on
                            the impact of AMC conditions.
                            Clause 1.3.3 (in part) “Buildings constructed on sites subject to AMC have a higher probability of
                            damage than that given in Clause 1.3.1”
                            Clause 1.4.1 General The design conditions specified in Clauses 1.4.2 and 1.4.3 for beams and slabs
                            supported by the foundation on normal sites shall apply.
                            For other than normal sites, the design of the footing system shall be by engineering principles to
                            ensure the footings perform in accordance with Clause 1.3. Design considerations that are particular
                            to the site shall be considered.
                            Clause 1.4.3(b) “Past satisfactory performance of similar footings on similar sites”
                            As the above quoted normal ys does not take into account ground movements generated by the
                            abnormal conditions, the design engineer must use his/her experience and judgment to ensure that
                            the design provides acceptable performance. In doing this, the following must be considered:
                                 •     How the proposed development will change the existing equilibrium of the soil moistures.

                                 •     The long term impact on the soil moisture equilibrium of existing and future vegetation and
                                       structures.

                                 •     Appendix H and/or CH of AS2870-2011.

                                 •     Effective site drainage.

                                 •     Past satisfactory performance of similar footings on similar sites.
                            As the above quoted “normal” ys does not take into account the additional ground movements
                            generated by the “abnormal” conditions, the design engineer must use his/her experience and
                            judgment to ensure that the design provides acceptable performance. In doing this, the following
                            must be considered-
                                 •     How the proposed development will change the existing equilibrium of the soil moistures.
                                 •     The long-term impact on the soil moisture equilibrium of existing and future vegetation and
                                       structures.
                            Where vegetation exists within the zone of influence of the proposed footing system, the design
                            engineer shall consult Appendix H and/or Appendix CH of AS2870 in order to provide a suitable
                            structural design.
                            Although we are not arborists nor have we been provided with a site feature survey showing the
                            location, height and tree canopy information, we have provided an initial estimate of the maximum
                            potential surface movement due to the tree-induced suction change in addition to the normal design
                            suction change “ytmax” below;
                                                    Normal ys                 ytmax          Estimated Design Class

                                                    31 - 40 mm               16 mm                  Class H1

                            Once a site feature survey is completed and the relevant tree information provided, we can provide
                            a specific surface movement suction change calculation “yt” to aid the design engineer.




                            AWT 77775 Site Classification Report
                                                                                                                        Page 3 of 17


Document Set ID: 22750694
Version: 1, Version Date: 03/01/2024