This code provides guidelines for ensuring the structural safety of buildings founded on shallow foundations resting on rock. It covers site investigation, determination of rock properties, and methods for calculating bearing capacity and permissible settlement. The code addresses both intact and jointed rock masses, offering presumptive values and analytical methods for foundation design.
Code of practice for the structural safety of buildings on shallow foundations on rocks
Quick Reference Values
Shallow foundation definition (Df/B)<= 1
General Factor of Safety for bearing capacity3
Permissible total settlement for isolated footings on rock12 mm
Permissible total settlement for raft foundations on rock20 mm
Permissible differential settlement for rock foundations0.0015L
Presumptive SBC for Hard Rock (e.g., Granite)3240 kN/m²
Key Formulas
q_ult = c’Nc + qNq + 0.5γBNγ — General bearing capacity of rock
Practical Notes
Presumptive bearing capacity values from Table 2 are for preliminary design only and must be confirmed by site-specific investigation.
The presence, orientation, and condition of joints and discontinuities in the rock mass are critical and can govern the foundation's stability over the intact rock strength.
Accurate assessment of settlement, especially differential settlement, is as important as checking the bearing capacity for safety and serviceability.