Approved Plan - EXE230029

            Stockpiles of construction materials, excavated materials, existing footings, etc. should be kept well clear of
            the batter crests to avoid surcharging the slopes.

            We expect that retaining walls will be constructed within the temporary batters, temporarily propped,
            backfilled and permanently supported by the structure.



            6.5     Retention Design Parameters
            The following characteristic earth pressure coefficients and subsoil parameters may be adopted for the
            design of retaining walls that will be propped by the structure and any landscape retaining walls:
                 For retaining walls that will be temporarily propped, backfilled and permanently restrained by the
                  structure, we recommend the use of a triangular lateral earth pressure distribution with an ‘at rest’ earth
                  pressure coefficient (ko) of 0.6 for the soil profile, assuming a horizontal backfill surface.
                 For landscape retaining walls, where we assume minor movements will be able to be tolerated, we
                  recommend the use of a triangular lateral earth pressure distribution with an ‘active’ earth pressure
                  coefficient (ka) of 0.4 for the soil profile, assuming a horizontal backfill surface.
                 A bulk unit weight of 20kN/m3 should be adopted for the retained profile.
                 Any surcharge affecting the walls (e.g. nearby footings, compaction stresses, sloping retained surfaces,
                  construction loads etc) should be allowed for in the design using the appropriate above earth pressure
                  coefficient.
                 Conventional retaining walls should be designed as drained and provision made for permanent and
                  effective drainage of the ground behind the walls. Subsurface drains should incorporate a non-woven
                  geotextile fabric, such as Bidim A34, to act as a filter against subsoil erosion. The subsoil drains should
                  discharge into the stormwater system.
                 Lateral restraint of retaining walls founded in the soil profile below bulk excavation level or adjacent
                  surface levels may be provided by the passive pressure of the soil below these levels. A ‘passive’ earth
                  pressure coefficient, Kp, of 3 may be adopted, provided a Factor of Safety of at least 2 is used in order to
                  reduce the high deflections that are associated with achieving a full passive case. Localised excavations
                  in front of the walls e.g. for buried services etc must also be taken into account when checking the
                  embedment depth design. We note that where the ground surface on the low side of the wall slopes
                  away from the wall, the lowest ground level within 5m of the wall should be adopted for assessing the
                  level at which passive resistance will be effective.
                 Friction between the base of a retaining walls and the underlying bedrock can be calculated using a
                  friction angle of 35°, provided the base is clean, rough and dry when the retaining wall footing is poured.



            6.6     Footing Design
            The ASI report has assessed the residual clays to have a high potential for shrink/swell reactivity with changes
            in moisture content. However, considering the limited thickness of reactive residual clays and clay fill,
            characteristic surface movements in the range for a Class S to Class M site are expected and are likely to be
            differential across the proposed house. However, we expect trees to be removed as part of the work and so

            35891URrpt Rev1                                      10
Document Set ID: 22532435
Version: 1, Version Date: 07/08/2023