ENG464
ENG 464 Assignment 2 1
ENG464 Geotechnical Engineering
Assignment 2
Analysis of group-pile foundations
A pile group consisting of 8 x 8 cylindrical bored and cast in situ piles at 2.4 m centres, each with a
diameter of 600 mm and extending from 3 m depth to 18 m depth is constructed in a 28 m deep
stratum of stiff clay overlying bedrock. The undrained shear strength of the clay at a depth of 18 m
is 100 kPa and an average value over the length of the piles is 50 kPa. The undrained elastic
modulus Eu of the clay is approximately 20 MPa.
(a) If the pile group supports a fully-factored load of 33 MN, determine the global factor
of safety.
(19)
(b) Estimate the immediate pile head settlement and comment upon the practical effects
of its magnitude and likely accuracy.
(6)
Coefficients for vertical displacement are given below in Figure 1.
Christian J.T. & Ca
ier W.D XXXXXXXXXXJanbu, Bje
um and Kjærnsli’s chart reinterpreted. Canadian Geotech. J XXXXXXXXXX.
Janbu N., Bje
um L. & Kjærnsli B XXXXXXXXXXVeiledning ved løsning av fundamenteringsoppgaver. (Soil mechanics applied to some engineering
problems), Norwegian Geotech. Inst. Publ. 16, Oslo, Norway.
Figure 1 Coefficients for vertical displacement
(Total marks 25)
ENG 464 Assignment 2 2
The small print
This is not a task which can be completed simply by looking at the InterNet. Original thinking is
equired, demonstrating sound reasoning and rational argument (including diagrams, calculations,
and spreadsheets developed as appropriate) to support your conclusions.
Students’ attention is drawn to the University’s policy on plagiarism.
The report must be set out as a formal technical submission/calculation sheet.
This report is worth 10 % of the marks for this unit.
Submissions are due by 1630 (ACST) on the Thursday of Week 7 (see Learnline for details).