Volume 6 – Geotechnical Manual, Site Investigation and Engineering ...

Chapter 2 GEOTECHNICAL DESIGN PROCESS
Site
Investigation/
laboratory
Testing
Established
Theory
Experience
and Judgment
Figure 2.3 Combination of Sources of Information in Geotechnical Design
2.2.4 Designer’s Analysis and Design
Some the common geotechnical analysis and design carried out by the Department include
evaluation and determination of the soil bearing capacity, settlement, seepage forces; and stability
of slope, earth retaining structures as well as the selection of effective soil and geosynthetic filter in
sub-soil drainage.
In carrying out the analysis and design, sound engineering by experience geotechnical engineer
should be incorporated to compensate for the many uncertainties in actual soil behavior, which
should take into consideration the following factors:
• Required reliability or acceptable probability of failure
• Consequence of failure
• Degree of uncertainties in soil properties and applied loads
• Compromise between cost and reliability
• Degree of ignorance of the structure behaviour
2.2.5 Check Compliance and Need for Modification during Construction
During construction, site operation shall be checked for compliance with the method of construction
assumed in the design. Also, observation and measurements of the structure and its surrounding
may necessitate some remedial measures or alterations to the construction sequence, for example
the unexpected excessive settlement of the embankment under construction would warrant the
review of the design and proposed sequence of construction. In fact, a great deal of geotechnical
information can be gathered during construction phase of a project, particularly those involving
huge volume of earth excavation or exposure where the actual ground conditions can be identified.
These information should then be used to validate the geotechnical design assumptions or soil
parameters and if necessary, to revise and modify the design accordingly.
2-6 March 2009