Appendix E - Geotechnical site classification report · MCU25/0022

PROJECT NO.: 23/8894                                                            19th JULY 2023

2.      SUB-SURFACE INVESTIGATIONS: Boreholes carried out revealed silty clay
        topsoils of medium to high plasticity overlying layered and fractured siltstone of Kin Kin
        Beds Geological origin. The soils are classified as “CI-CH” and “XW” respectively in
        accordance with Table A1 of A.S. 1726 “Geotechnical Site Investigations”. No ground water
        was encountered. Detailed borelogs are attached.
        Testing was carried out to determine soil-bearing capacities using a 9-kg Dynamic Cone
        Penetrometer (DCP) at borehole location 2 and 3. The results of these tests are attached. The
        consistency of the soil was found to be firm to stiff silty clays over dense highly weathered
        siltstone. Soil bearing capacities of 100 KPa were encountered below 0.3 metres depth at the
        test sites.

        A sample of the Silty Clay was taken and tested in the laboratory.
        The results showed a Liquid Limit of 38.5% and a Linear Shrinkage of 14.5%. These clays
        were assessed to be moderately to highly reactive to soil moisture variations and therefore
        ground movements (Ys) of between 20mm to 40mm are likely.

3.      SITE CLASSIFICATION: From the test results viewed, we would classify the site as
        equivalent to: -  CLASS “M”
        -in terms of The Australian Standard 2870, “Residential Slabs and Footings”.
        Should site earthworks substantially alter the subgrade from that shown on the
        attached borelogs, this classification may vary.

4.      FOUNDATION RECOMMENDATIONS:
        All site earthworks carried out must comply with A.S.3798 “Guidelines on Earthworks for
        Commercial and Residential Development”, to validate this site classification.
        All topsoils containing grass, tree roots and other organic material shall be removed from the
        building footprint prior to construction commencing.
        Structural Filling should be placed and compacted to a minimum dry density ratio of 95%
        Standard. Field density testing should be carried out to assess the standard of compaction
        achieved to be considered as “Controlled Fill” as specified in AS2870. Any filling should be
        keyed into the natural slope (by benched key interface) and battered no steeper than 2.5H:1V
        unless filling is supported by an engineer designed Retaining Structure.

        Foundations for construction on isolated columns should be supported on mass concrete
        bored piers taken into underlying highly weathered siltstone having a minimum bearing
        pressure of 100KPa. Depths should also be adequate for the resistance to uplift and racking
        forces.
        For a proposed lightweight structure with slab on ground construction, we recommend
        foundations and slab be designed as a stiffened raft slab designed in accordance with Figure
        3.1 of A.S. 2870 for a Class M site. All footings shall be founded through any fill into
        underlying dense weathered siltstone.




8894-193 Sankeys Rd-FEDERAL               Page 3 of 15                                19/07/2023