1.1.1                            GENERAL DESIGN RULES

• Unless recommended otherwise, the lowest floor slabs of a building should not be designed as on-grade slabs.
  • Floor slabs directly above a raft-type pile cap may be designed as on-grade.
  • The following structures may also be designed as on-grade structures provided that they can be readily repaired or replaced if damaged by settlement:
    • fence walls, landscaping structures and lightweight covered walkway; and
    • floor slabs used for car parking, loading and unloading, vehicular ramp or pedestrian pavement.
  • For structures such as transformer rooms and pump houses, the foundations should be carried down through the reclaimed materials to a firm stratum with the lowest floor slabs designed as suspended.
  • Underground utilities and drainage underneath a building should be supported by suspended floor slabs or pile caps. The pipe connection at the interface between the structurally supported portion and the on-grade portion of pipes should be designed to accommodate differential settlement due to the subsidence of the latter.
  • Where significant settlement due to long-term consolidation of the ground is anticipated, measures should be provided in the pile cap design to mitigate the migration of soil into any void that may be formed underneath the pile cap due to consolidation of the ground below.
  • The effect of negative skin friction on pile elements should be duly assessed.