Page 18 - Building Regulation and Design Guidelines - Structural (Grey Code)

SECTION: 1 GEOTECHNICAL GUIDELINES & REGULATIONS SECTION: 1 GEOTECHNICAL GUIDELINES & REGULATIONS
1.3.6 SHALLOW FOUNDATIONS
- The foundation level should be in compliance with the architectural
requirements.
- Net allowable bearing pressure to be determined considering
shallow foundations at the foundation level using practical
experience and the results obtained from the field standard
penetrations tests, the empirical equations developed by Terzhagi
- Peck/Merehof and modified by Bowles considering a proper FOS
against shear failure of the soil.
- Using the calculated allowable bearing pressure value, the total
settlement for isolated/strip footing and raft foundation shall be
within 25mm & 50mm respectively. The differential settlements
should be indicated.
- The proposed foundation recommendations must ensure that an
adequate safety factor against likely uplift pressure established
based on selected Design GW level is satisfactory to local authority
and / or project requirements particularly when basement floor(s)
exist.
- Modulus of sub-grade reaction ks (kN/m3) shall be indicated in the
soil report when the raft foundation is recommended.
- The foundation ground must be proof rolled with vibratory
compactor to confirm that any loose materials are compacted to not
less than 95% of the maximum dry density obtained by performing
modified Procktor test.
- The specialist should confirm in writing that the undesirable
materials have been removed, the foundation ground has been
inspected and the recommended bearing capacity corresponding to
the foundation depth is properly achieved.
1.3.7 PILE FOUNDATIONS
- The soil report should propose the suitable type of pile to be
used, the allowable working loads in compression and tension
considering minimum factor of safety of 2.5. Piles spacing should
be recommended in the piling recommendations Minimum 2.5 the
pile diameter, Fig. (1.15). It should be noted that the minimum pile
toe level should be at least at depth of two times the diameter of
pile socketed in the hard strata in order to consider this strata in
the design.
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1 PILE 2 PILE 3 PILE 4 PILE 5 PILE 6 PILE
7 PILE 8 PILE 9 PILE 10 PILE
11 PILE 12 PILE 13 PILE
14 PILE 15 PILE 16 PILE
Fig. (1.15): Piles Distribution
- The geotechnical report shall include an estimate of single pile vertical
and lateral stiffness for the adopted pile cut off levels and penetration
depths. Lateral stiffness shall be based on cyclic conditions. The
assessment of pile group effects on vertical and lateral stiffness shall
be performed by the foundation design Engineer.
- For bored cast-in-situ piles, settlements of the order of 1% of the pile
diameter is normally required to mobilize full skin friction whereas
full bearing is developed at much higher settlements (usually at 10%
of pile diameter). Therefore, it is recommended that the pile capacity
shall be based on full skin friction and partial end bearing.
- Where the borehole depth is not satisfactory for the design,
additional boreholes should be carried out to the required depth to
reconfirm the continuity of the strata. Fig. (1.15): Piles Distribution
1.3.8 FOUNDATION CONCRETE
Concrete mix design should consider strictly the chemical analysis data
for both soil and water and to be in line with Trakhees Construction
Materials Quality Control Guidelines.
1.3.9 LIQUIFACTION:
The likely liquefaction induced effects are:
- Settlement.
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