Geotechnical investigation
is important for construction of building as owner or his authorized agent have
to submit this document to building official during submission of approval requirement
and for design suitable foundation system.
The geotechnical report
should include at least following information:
a. A drawing of site showing location of
bore holes for subsurface investigations.
b.
An entire record of soil boring, log of penetration test and also soil samples should
be provided in report which facilitates foundation engineer to determine variation
in bearing capacity and settlement.
c. A complete record of soil profile.
d. In case of water table encountered in
project site, the elevation of ground water table should be included. We have
published post about determination of ground water level in our previous post.
e. Recommendations regarding
- Foundation type
- Design criteria which should include at least:
- Bearing capacity of compacted or natural soil
- Mitigation measures for expansive soils with authentic reference
- Mitigation measures for liquefaction where liquefaction susceptibility soil and seismic activity are encountered.
- Differential settlement
- Variation of soil strength
- Any possible influences of loads arrived from surrounding structures.
f. Desired total settlement and differentials settlement
g. Special provision for design and also for
construction for foundation supported on soils having expansive nature when
required.
h.
Installed capacity of deep foundation.
i. Recommended spacing of foundation
elements (say piles or piers) measure by center to center distance.
j.
Installation procedure of deep
foundation element
k.
Driving criteria including drilling
techniques, drilling fluids, sequences and also special measures for critical
conditions
l.
Reporting and inspection procedures
which facilitates to determine imstalled capacity of foundation elements.
m. Requirements for load test; we will
learn the topics as per IBC.
n. Durability aspects of foundation
elements considering surrounding environment.
o. Group action of foundation elements;
usually reducing while action, if applicable.
p. When shallow foundation is supported on
compacted fill, the following specification should include
- Site preparation prior test
- Material
- Test method (MDD, OMC)
- Allowable thickness
- Test method in filed
- Frequency of testing and reference of dry density
q. Specification for controlled low-strength material; the specification required
- Site preparation prior test
- Material
- Test method (MDD, OMC)
- Allowable thickness
- Test method in filed
- Frequency of testing and reference of dry density