Page 29 - Demo

As indicated in Section 5.3 above, a lightweight house on poles, with a non-habitable space below is proposed. The house shall be supported on shallow ground beams running perpendicular to the shore. The ground beams shall not extend more than 300mm below the top of the platform level. They shall be designed to span over a 4m x 4m void and a 2m cantilever at the ends. The ground beams shall be designed assuming an Ultimate Geotechnical Bearing Capacity of 300kPa. Ultimate loads and a Strength Reduction Factor of 0.5 shall be used with this value.
6 Conclusions & Recommendations
The site is considered to be suitable for subdivision, however it should be appreciated that significant development works are required to achieve access and to create a viable house site. These matters are discussed in Section 5 above.
The site is vulnerable to liquefaction and lateral spreading. It also has a high water table and up to 1.2m of topsoil/fill. A light weight house on poles, with a non-habitable car turning area at the lower floor is proposed. A geogrid reinforced granular raft with a surface at RL3m is required at the proposed house location. Undercutting of unsuitable soils below the level of the raft, dewatering and replacement with compacted hardfill placed on a geotextile will be required. In addition, extensive earthworks (including undercutting of unsuitable soils) are required to create site access.
The potential for flooding has been addressed by filing to RL3m and constructing a house on poles with a non-habitable undercroft. Approval from the district council will be required for this proposal. It should be appreciated that, because of the excessive settlement which would occur due to liquefaction, significantly raising the level of the proposed platform is unlikely to be allowed.
The proposed earthworks and foundation proposals shall be developed with input from a geotechnical engineer. In addition, all foundation works and earthworks shall be undertaken under the direction of a geotechnical engineer.
6c Myrtle Drive, Omokoroa O’Brien Geotech Ltd Project 533 February 2017
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